English Digest

Welcome to English Digest Page !!

I edit this page, English Digest to show you many new findings on Crows that were released in thirteen scientific articles.
Till the year 2006, while the first half of my study life I had published ten papers in Japanese, therefore foreign ornithologist have little chance to access my work. (Part 1 & 3)

That those articles should be written in English, I regret it now. But in those days I gave top priority to ensure the adequate time and energy for the fieldwork. In the second priority, I focused on analyzing my data objectively and demonstrating the results precisely in Japanese. Under the lack of time I could not translate my papers into English.

Recently I resigned from ornithological research and I have a chance to translate my articles into English. Even though the ten papers had English abstract, figures and tables were attached English caption, however, it is difficult to get enough information from these articles for the reader who does not understand Japanese text. I expect for many foreign readers who interest in Crows can access this English Digest and understand my new findings in a short time.

From the year 2006 to the year 2016, while the second half of my study life I have investigated crows skulls of Jungle CrowCorvus macrorynchos collected from Hokkaido and Russian Far East. I was interested in postglacial colonization and diversification of Jungle Crow. My morphological study collaborated with the molecular phylogenetic study that was conducted by Dr. Alexey Kryukov of Institute of Biology and Soil Science. I will show you our exciting report in this page. (Part 2)

Author: Sumio NAKAMURA
Postal address: 47-1 Yayoigaoka, Takatsuki-city, Osaka-pre. 569-1021 JAPAN
E mail: crowsuperstar□@gmail.com please replace □

OUTLINE OF ENGLISH DIGEST
Part 1 Roosting behaviour - seasonalroost, flight line assembly
Part 2 Breeding biology - independence of juvenile, territorial defence, nest site comparison between Carrion Crow and Jungle Crow
Part 3 Postglacial colonisation and diversification of Jungle Crow

Part 3 in preparation, it will be uploaded next issue.

 


Part 1 Roosting behaviour
Author of "Crows of the world" D. Goodwin pointed out that much new discovery would be gained if you studied Crows communal roost from its formation to its extinction continuously.
I conducted more than 300 observations for mny seasonal roosts from its begining to its ending. There is a fundamental difference in methodology between preceeding studies and mine: short term versus long term observation, one or few pieces of still images (observations)versus a lot of still images. Therefore I can draw the seasonal changes of communal roosts like an animation.
The investigation lasted for four years. Study site locates in the central part of Japan( N 35°, E136°).The two species (Carrion Crow C. corone orientalis and Jungle CrowC. macrorhynchos) gathered to the roosts. Every observation was started at two and half hours of sunset and ended at half-hour after sunset.

Chap. 1. The seasonal and annual cycle of Crow’s roost in northeastern Osaka prefecture
Strix Vol. 21, pp. 177-185, 2003
A Journal of Field Ornithology, Wild Bird Society of Japan

Starting points:
Does every seasonal roost begins/ends at fixed date? Are there any stable annual cycles?

Conclusions:
1. From the early spring to the midsummer, the number of roosts increased along with the rise of the temperature, and the distribution range expanded. And from the autumn to the early winter, a reverse process went along the fall of the temperature.
2. The patterns of the seasonal and annual changes of the roost almost maintained the same from year to year. However, the day of arising/vanishing of roost changed within the range of 0-43 days. In one case out of 30, the roost was formed in different location.
3. The arising/vanishing of roost happened abruptly and completed within one day in most cases.

Methods:
According to the frequency of observation, I classified seasonal roosts into three grades “high resolution”, “middle resolution” and “low resolution”. The “high” roost: to know a change in detail, observed 1-4 times for one week. The “middle” roost: to know an approximate change, 2 times for one month. The “low” roost: to know whether a roost is maintained or not, once for one month.
I added up the crows which gathered in the roosting area before two hours at sunset and gained the number of early arriving crows. From two hours at sunset until half an hour after sunset I recorded the time and the number of arriving and leaving out crows. I totaled them and gained the number of arriving crows and the number of leaving crows.
The roosting number is obtained by adding the number of early arriving crows to the number of arriving crows, and substracting the number of leaving crows.

Results:

Figure 1 (below) shows the study area located in northeastern part of Osaka prefecture. Stippled area denotes woodland. There were two permanent roosting sites, K and L in plains. In woodland there were nine seasonal roosting sites, M, N, O, P, Q, R, S, T and U.


Figure 2 (below) demonstrats the number of roosting crows (Y axis) and year/month (X axis). Number of roosts (foot line) means the total number of seasonal roosts that existed for more than 15 days in each month. The two permanent roosts K and L are omitted.

Phase of increase and expansion: the gray zone in Fig. 2 indicates a period when temperature rises steadily. The left edge of gray zone corresponds to the early spring, and the right edge to the midsummer. The pattern that the number of roost increased from the left to right has been repeated for three years. It is easy to understand that the distribution region of roost has expanded from plain region to woodlands district if you collate Fig. 2 with Fig. 1.
Phase of decrease and retraction: the white zone indicates a period when temperature falls steadily. The processes went in reverse for previous period. The inverted pattern that the number of roosts decreased and the distribution region of roost contracted back to two permanent roosts in plains.
In the annual cycle of Crow’s roost distribution, there were two phases that corresponded to the annual cycle of temperature.
Figure 2 looks like the repetition of a fixed pattern. However, if you watch closely you will find many changes. The first/final day of each seasonal roost varied from year to year by 0-43 days. Only in onecase, the fixed pattern had fallen into disorder. Roost M2 was lost in the autumn of 1992 (the first row of Fig. 2) and Roost Q2 appeared (the fifth row). Location of M and Q are 4 km apart.

Please pay attention to the change of roosting number at the first/final day in Table 1. The increasing/ decreasing rate were calculated by the comparison the roosting number of the first/final day with the average roosting number of each seasonal roost. At the first/final roosting day the rate varied 26-170%. The settlement/abandonment of seasonal roost occurred within one day except for the final of Roost-S.

For me, it is difficult to predict the day of settlement/abandonment of roost. But there is little difficulty to predict the location of the next seasonal roost. Table 1 shows that the process of settlement/abandonment of roost is not gradual but rapid. More than once, I made a stupid mistake. I visited some roosts to continue a series of observation. There was no early arriving crow and no crow arrived till sunset. I waited crows for more one hour after sunset. I expected a big crow stream arriving from some flight line assembly, but in vain. I confirmed the extinction of roost only. It is obvious that crows have some cue for synchronize the choice of roosting place.


Chap. 2. The settling/abandoning of seasonal Crow's Roosts relative to minimum temperatures
Strix Vol. 22, pp. 125-133, 2004
A Journal of Field Ornithology, Wild Bird Society of Japan

Starting points:
The settling/abandoning of seasonal roosts finished within one day. How did crows succeed in rapid roost change?
In late afternoon the territory holder comes to often stop on the outstanding post. Two functions can be assumed for this behavior: (1) Demonstrate to other passing crows that here is my territory. (2) Observe roosting crows for which direction they are leaving. Other crows that do not have own territory, they are gathering at the feeding place or the assembling place (Flight Line Assembly) before leaving for communal roost. Their assembly places are very conspicuous, therefore it is easy for observer and crows to find out. It is probable that crows depend on an information by sight. But the visual information is affected by the obstacle: hill, woodland, and hog, rain etc. The roosting crows are dispersed in the wide area in daytime. Except the information by sight, which signal can be spread to the wide range all at once?

Conclusions:
1. Bad weather such as a strong wind and/or strong rain causes neither settling nor abandoning of the seasonal roost.
2. In the expansion phase (see Chap. 1), the settling and abandoning of the seasonal roost occurs when the minimum temperature is in the maximum zone, however in the retraction phase, it occurs in the minimum zone.
2. The settling and abandoning of the seasonal roost does not occur like the thermostat that switching on at a certain temperature.

Methods:
The weather is the most promising stimulus to change roost because it spread over the wide range where gathering crows live. I collected weather informations from the regional meteorological observatory.
In 18 cases, I can specify the day of settlement and abandonment by high frequency observation.
There was no evidence that the settlement and abandonment of the seasonal toost happened on a bad weather: the maximum wind speed 10m/s or more and/or the precipitation 30mm or more.

On the contrary, the fluctuation of maximum or minimum tempetrature concerned with the day of settlement and abandonment a certain degree.

Fig. 1. The fluctuations of maximum (upper line)/minimum (lower line) temperature over 15 days before and after the settling/abandoning seasonal roost in the increase/expansion phase. The arrows indicate the plots of the days of settling/abandoning roosts.

Fig. 2. The fluctuations of maximum/minimum temperature over 15 days before and after the settling/abandoning crow roost in the decrease/retracsion phase. Measurements and presentations are the same as Fig. 1.

The horizontal axis shows the time (day), the vertical axis shows the temperature (℃).Both temperature lines figured with serrated wave pattern. I negrected a smaller wave, short cycle of 3-5 days. I focused on a larger wave, long cycle of 5-15 days. In each wave I classified three zones: Maximum zone; an upper 10 % of amplitude (difference of peak-bottom temperature); Minimum zone lower 10%; Midium zone.

In the phase of increase/expansion, the settlement and abandonment occurred in the maximum zone (peak of the wave) of the minimum temperature (Fig.1 and Table 1). In the phase of retraction/reduction, the settlement and abandonment occurred in the minimum zone (bottom of the wave) of the minimum temperature (Fig. 2, Table 1)

In the increase/expansion period neither settlement nor the abandonment occurred in the day of highest temperature within 30 days interval (see in M1 and P of Fig. 1). Crows overlooked the highest wave and then responded to following wave.
In the reduction/retraction period, they overlooked the wave of lowest temperature and then changed in following wave (see M2 of Fig. 2).
It is probable that the fluctuation of the maximum/minimum temperature is a cue for roost changing, but it is not the most important factor. Some social bowels would be revealed as the main cause of roost chang in some day.


Chap. 3. The seasonal chang of Crow's roosting behavior
Strix vol. 23, pp. 65-74, 2005
A Journalof Field Ornithology, Wild Bird Society of Japan

Starting points:
The constitution of member gathering in communal roost varies seasonally. Then it is natural that a way of gathering to roost area and a method of entering into roost site should be changed seasonally. How differ the roosting behaviour among seasonal roosts?

Conclusions:
1. In Spring roosts: Many crows gather in the roost area early in the afternoon, and the arrival of the crow gets into full swing during the bright time, but the final arrivals does not change with other seasons. Crows enter roost loosely one after another.
In Summer roost: The arrival to the roost area is over far before sunset, and aerial maneuver is most inactive. Crows enter roost silently without perceptible movement.
In Autumn roost: The crows gather in the roost area from early time just the same as spring roost, but the aerial maneuver is repeated lively. Crows enter roost site noisy.
2. In the newly established roost the crows behavior differ from that in old habitual roost. The aerial maneuver is observed frequently before roosting and the flight line assemblies are observed often. Crows look like cautious and uneasy.
3. Weather factors (temperature, atmospheric pressure, weather) do not influence roosting behavior.

Methods:
I performed high-frequency investigation (1-4 times/weeks) on five roosts for three years. Four indexes - % of early arrival, light intensity of 20% arrival, light intensity of 80% arrival and participation ratio in aerial maneuvers are calculated.

I collected the following data in every observation. (a) I recorded the crows for half an hour that arrived early at the roost area before two hours at sunset. The sum total which added them up is the number of early arriving crows. (b) I recorded the crows which arrived at the roost area every five minutes from two hours before sunset until 30 minutes after sunset. The sum total which added them up is the number of arriving crows. All the same way I recorded the crows which left from the roost area and gained the number of flying away crows. I recorded light intensity for every five minutes. (c) I defined the aerial maneuver: more than a one-third of the crow which gathered in the roost area whirled up all at once and jammed in the sky for a short time. I recorded the crows which participate in each aerial maneuver. The sum total which added them up is the total number of aerial maneuver.
For each observation, the four indexes were obtained by doing the following processing. (1) I divided the number of early arriving crows by *the total number of roosting crows, and then multiplied by 100. This is “% of early arrival”. (2) I drew a figure: Y-axes indicates the accumulation of arrival crows, X-axes indicate time (min.) I drew another figure: Y-axes indicates the light intensity (lux), X-axes indicates time (min.). Refering these two figures “light intensity of 20% and 80% arrival”were obtained. (3) I divided the total number of aerial maneuver by a sum of the number of early arriving crows and the number of arriving crows and then gained “participation ratio in aerial maneuvers”.

I classified gained indexes into five periods (spring/early summer/summer/ early autumn/autumn) and demonstrated in Figure 1.

Fig. 1. Seasonal difference of roosting behaviour. ( ) shows the number of days of observation. Mann-Whitney's U test, NS: no significant difference *:P < 0.05 **: P < 0.01 ***: P < 0.001.

One autumn roost was continued more than three seasons but it happened to extinct. Instead of this old roost, a new autumn roost was formed at the east of the former roost 2 km apart. This is very rare event and I got a rare chance to compare the roosting behavior between the old and the newly established roosts (Table 1).


I obtained weather data of the study area from a local meteorological observatory and examined correlation between weather factor and four indexes (Table 2).


Results and Discussion:
1. In spring roost, about half of roosting crows had arrived before two hours of the sunset. Light intensity of 20% arrival (at the time of full-swing arrival began) was in around 5000lux. This value was the highest among five seasonal roosts. However, there was no great difference between light intensity of 80% arrival (at the time of full-scale arrival was finished).
In this season, most breeding individuals roost in their own territory and almost all non-breeding individuals participate in the spring roost. During the breeding season, the most part of plains was occupied by breeding crows. They defend their territory aggressively and the activity zone of non-breeding crows in plains is narrowed. This might be the main reason why many non-breeding individuals gather in the roost area early in the afternoon.
2. In summer roost, participation ratio in aerial maneuvers was the lowest. The light intensity of 80% arrival reached the highest.
This season is the molting period, and flight ability deteriorates. Some portion of young crows born in this spring becomes to participate in summer roost, but development of their flight ability is not enough. Furthermore, summer is the hardest season for regulation of body temperature because of the highest temperature and the highest humidity. These features imply why participation ratio in aerial maneuvers was the lowest. In summer time, territorial takeover happens rarely and territorial defense activity drops to the lowest level in the year. Under these environments, some breeding individuals participate in summer roost. In general, their departure from territory is late and so their arrival to the roost would be at dusk. This contributes to lower the light intensity of 80% arrival.
3. In autumn roost, participation ratio in aerial maneuvers was the highest. The % of early arrival was high and next to the value of spring roost.
Almost all young birds born in this spring participate in autumn roost. They were wandering around the roost area from early time. This affects the % of early arrival high. The young birds develop enough flight ability and are able to participate in aerial maneuvers. But it may be prudent to keep an open mind about the reason why participation ratio in aerial maneuvers reaches highest in the autumn roost.
4. In comparison of old and new roost (the old roost M2 which was formed more than three seasons continuously), the new roost Q2 scored only a quarter of % of early arrival of M2. As for the light intensity of 20% and 80%, the new roost had nearly 3 times high to M2. The participation ratio in aerial maneuvers was more than double in the new roost. The number of crows leaving away was more than 4 times in the new roost. The old roost continued for two or three months, but the new roost became extinct within one month.
Differences of roosting behavior between old and new roost suggests that the new roost was not trusted by many crows. It is not good way, arriving to the incredible roost from early time and waiting long for other crows arrival. The best way to participate the communal roost steadily is, checking the trend of other roosting crows, flying to the roost in a group. At the pre-roosting assembly place, it seems likely that, many crows displayed their unwillingness to new roost and demonstrated active aerial maneuvers.
Aerial maneuver, it seems likely that, is a function to instigate other crows to go away from this unfamiliar roost.
5. I examined whether four indexes of roosting behavior have any correlation with meteorological 3 factors (maximum temperature/minimum temperature/atmospheric pressure). In neither season, the high correlations were gained between indexes and factors (table 2). I also examined whether indexes are influenced by weather (fine/cloudiness/rain). There was no sign which suggest some influences of weather on indexes.
The crow has the strong flight ability, and can spare surplus food. Therefore the meteorological factors influence on roosting behavior wouldl be little.



Chap. 4. The splitting of Crow's seasonal roost
Strix Vol. 24. pp. 57-67, 2006
A Journal of Field Ornithology, Wild Bird Society of Japan

Starting points:
In very rare case I observed a splitting roost: one in habitual site and another in near. The splitting roost is against every hypotheses for bird communal roost that expect the more bird roost in one site the more advantage induces.Why and how crows formed splitting roosts?

Conclusions:
1. In almost all cases the crows communal roost are formed in one habitual place. But rarely, if ever, gathering crows failed to synchronize their roosting choice and roosted in two neighboring places – splitting roost. One roost was formed in usual roosting place, another one in a extraordinary place which changed irregularly from year to year.
2. On a day of splitting roost, many crows gathered in the roosting area from early time and participated in aerial mass flights. The numbers of crows arriving to the roosting area from four/eight directions were changes markedly at the day of splitting roost. This implies that the formation of regional roosting groups have changed.

Methods:
In every observation I recorded the crows which had arrived early at the roost area befor two hours at sunset. The sum total which added them up is named the number of early arriving crows. I divide the number of early arriving crows by the total number of roosting crows, and then multiply by 100. This is ”% of early arriving”.
I defined the aerial mass flight: more than a one-third of the crow which gathered in the roost area whirled up all at once and jammed in the sky for short time. I counted the crows which participated in each aerial maneuver. The sum total which added them up is the total crows number of aerial maneuver. I divide this number by a sum of the number of early arriving crows and the number of arriving crows and then gain “participation ratio in aerial maneuvers.
I recorded the arriving crows with its number, direction and time from two hours at sunset until half hour after sunset. The sum totals which added them up in four/eight directions were plotted in radar graph. As for the roost M1 I analyzed in four directions and about the roost Q2 in eight directions.

Fig. 1(a). (upper) Study area and the distribution of intensive surveyed roosts M, P, Q and S. The spring roost M1 (Feb.-July) and the autumn roost M2 (Oct.-Dec. in 1990 and 1991) were observed in the location M. The summer roost P (Aug.-Oct.) and S (July-Oct.) were observed in the location P and S. The autumn roost (Oct.-Nov. in 1992 only) was observed in the location Q.
(b). (lowerleft) The roosting sites x, y, z in the location M. The ordinal regular roosting site was y, and the additional temporal roosting sites were x (1990 and 1991) and z (1992).
(c). (lower right) The roosting sites v, w in the location Q. The ordinal regular roosting site was v, and the additional temporal roosting site was w in the year of 1992.

Results and Discussion:
It was only 8 days among 270 observation days that I observed the splitting roost. The probability that observer encountered the event was 0.029. This low value explains the fact that nobody reported the splitting roost in Crows communal roost before. Every observer did not perform high frequency observation like me.
The habitual roost site, the extraordinary roost site and the place of PRA (Pre-roosting Assembly Place)are distributed in narrow area (within a circle radius 1 km). The distances between two splitting roost were around 1/20 from 1/10 of the average roost interval. It means that the splitting roosts were not two independent seasonal roosts, but one roost divided temporally.

The weather of the day of splitting roost was not bad- such as a strong wind / strong rain, etc. but cloudy / fine weather.
The splitting roost was not happened at the final stage of seasonal roost, but at the intermediate stage.

As for seven events in eight splitting events, PRA (Pre-Roosting Assembly) was divided in two places, and it was not unified till the last. This suggests that gathering crows were divided into two groups from the beginning. I did not observe any rapid increase the number of roosting crows at the day of splitting roost. Also, I confirmed there was no disturbance by the human being (invasion of campers/woodsmen/other workers etc) in roosting area.
At the days of splitting roost, % of early arrival and the participation ratio in aerial maneuvers were significantly high. In most cases when % of early arrival increased rapidly, some unusual events (splitting roost, temporal roost, etc) happened. The exceptional big values of participation ratio in aerial maneuvers suggest gathering crows were restless. It seemed to me that they tried to form an agreement for the roosting place by means of repeated aerial maneuvers.

Fig. 2. Radar graphs of the number of crows arriving to the roosting area from four directions are showen in the case of number 1, 2, 3, 7. In each graph the date of observation, the percentage of crows arriving early (the total number of crows gathered 2 hr before sunset divided by the total number of roosting crows) and the total number of roosting crows are given. Asterisks indicate the days of the splitting roost.

The pattern of the radar graph changed remarkably after a day of splitting roost. In general, the crows come from their territory or daily activity zone. The rapid change of the pattern in radar graph suggests that the composition of regional roosting groups had changed.

Fig. 3. Radar graphs of the number of crows arriving at the roosting area from four or eight directions are showen in the case of 4, 5, 6, 8. See Fig.2 caption for details.

 

 

Chap. 5. Dynamics of flight line assemblies of crow's in the Osaka area
Japanese Journal of Ornithology Vol. 53. pp. 77-86, 2004.
The Ornithological Society of Japan

Starting points:
How can the crow's communal roost arise/disappear abruptly within a few days? Sometimes a great many crows arrive at roosting place in a group at dusk. How can they form a big group? Why does they arrive so late?

Conclusions:
1. Almost all the crows gathering around flight line assembly (abbr., FLA) departed for one direction in big groups.
2. Every FLA formed at a distinguishable place from a distance: grassland and sand of riverbed, tree crown of a deciduous tree in a mountain ridge in winter season, sloping ground with no vegetation etc.
3. There were three types in the FLA, each had its own characteristic function corresponding to its gathering place: feeding ground, seasonal roosting location and the last turning point to the venue of old and new seasonal roosts.

Methods:
FLA were observed in eight locations in the study area but five of eight were observed only once. Intensive observations were conducted in the three locations (a, b, c) where FLA was observed repeatedly (Fig. 1).
The location a is a grassland/sand in wide riverbed and FLA was formed irregularly. Crows formed a feeding place assembly in the early hours of the afternoon.
At the location b, there were seasonal roost in spring and autumn. In the year 1992, autumn roost was not settled there but in the location Q. The location b and M are the same place. During the seasonal roost M was absent, there happened FLA b was formed irregularly (Fig. 2.).
The location c is a bare ground without vegitation and FLA was formed continuously during early summer.

Fig. 1. Study area in northeastern part of Osaka. Assembly sites a, b and their related roosting site K, L in winter (left). Assembly c and its related roosting sites M, N, O, P, Q in summer (right). Stippled area denotes woodland.

I collected the following data in every observation.
(a) I recorded the crows for half an hour that arrived early at the FLA area before two hours at sunset. The sum total which added them up is Total number of crows gathered around at 2 hr before sunset. I tried to discriminate adult and juvenile. I also gained Ratio of juvenile in the crows gathered around at 2 hr before sunset.
(b) I recorded the crows which arrived at the FLA area every five minutes from two hours before sunset until 30 minutes after sunset. They were divided into two groups: joining the assembly and passing over the FLA. The sum total of former is Total number of crows arrived at the assembly. The sum total of latter is Total number of crows passing over.All the same way I recorded the crows which left from the FLA area for main-dirction and sub-direction. The sum total for main-direction is Total number of crows departing. The sum total for sub-direction was divided by that for main-direction, and gained Ratio of birds departing for sub-direction(%).
(c)I recorded light intensity for every five minutes. I drew three figures: Y-axes indicates the accumulation of arrival crows, departing crows , passing over crows. X-axes indicate time (min.) I drew another figure: Y-axes indicates the light intensity (lux), X-axes indicates time (min.). Refering these figures I obtained Light intensity of 80% arrival, Light intensity of 20 % departing, Light intensity of 80 % departing.Light intensity of 80 % passing over.
(d) I defined the aerial maneuver: more than a one-third of the crow which gathered in the FLA area whirled up all at once and jammed in the sky for a short time. I recorded the number of crows which participate in each aerial maneuver. The sum total which added them up is the total number of aerial maneuver. I assumed that a rough number of crows gathering around FLA is a sum of Total number of crows gathered around at 2 hr before sunset and Total number ofcrows arrived at the assembly. Because in every FLA a main stream of departure begun after a main stream of arrival ended. I obtained Participation ratio to aerial evolution by dividing the total number of aerial nameuver by the rough number of crows gathering around FLA.

Results and Discussion
Fig.3 (below) demonstrated that the more crows gathered around at 2 hr before sunset the more crows joined the FLA. This result coincide with the pre-roosting gathering of Motacilla alba (Zahavi 1970).

Fig. 4 (below) denied a refutation that the more crows fly toward the communal roost then Total number of crows gathered around at 2 hr before sunset, Total number of crows arrived at the assembly and Total number of crows passing over would be more. There was no positive correlations between Total number of crows gathered around at 2 hr before sunset and Total number of crows passing over in every assembly. On the contrary, there would rather be a week negative correlation in the assembly b and c. That is, the more crows gathered around FLA, the more crows would not pass over but joined the assembly.

Ratios of birds departing for sub-direction were negligible (a: 2.0%, b: 3.9%, c: 0%) (below, Table 1).It is probable that gathering crows adjusted their roost choice and departed for common direction (main-direction).

The FLA a was originated irregularly from a feeding ground assembly in river bed and was mainly composed of juvenile crows. They scattered widely in variable groupsize, feeding, playing, bathing and resting. The gathering crows departed for the annual roost L early in the afternoon under high light intensity (Table 1). They did not wait till darkness coming when a large number of crows passed over this site for the same roost L.

The location of FLA b was the same of seasonal roost M. The FLA b accidentally became a temporal roost during two transition periods: first period;10 days after the autumn roost M vanished, second period; 10 days before the spring roost M started (below, Table 3). In the days of temporal roost, more crows gathered early around two hours before sunset and aerial evolutions were more active than the days without temporal roost. The main departure started under low light intensity with a large group size. Roosting number to the temporal roost was small, almost one third of Total number of crows gathered around at 2 hr before sunset. It seems that the temporal roost is a wreckage of unsuccessful trial of revival/foundation of seasonal roost M.

The assembly c demonstrated a clear change of Group size of departure (below, Fig. 5). Transition period was defined ten days before and after the last day (Day = 0) of spring roost M. During this critical period the group size increased rapidly, reached a peak and then decreased abruptly. Till the final day crows departed for the spring roost M, and after they changed direction. Their change of roost selection caused a fall of spring roost M and a rise of summer roost N. It is probable that a FLA formed at the turning point of roosting course would induce an abrupt arise/disappear of seasonal roost.

 

 

Chap. 6 Seasonal change of the number of crows at a feeding site
Sreix Vol. 20, pp. 149-152, 2002 (Short Communication)
A Journal of Field Ornithology, Wild Bird Society of Japan

Starting point:
I encountered a feeding site that had been maintained for a long term by an woman around 80 years old. At dawn all through the year, food was offered with fixed quantity and constitution: a scrap of garbage from kitchen and a medley of bread scrap in total 2-3 kilogram. Ccrows, doves, sparrows were regular customers. How will the number of users change seasonally?

Method:
The feeding site occured in Takatsuki city, Osaka prefecture, central Japan. There was a small area of 3.0 ha beside Meishin expressway, that consisted of a minipark, a small woodland, a small vacant land and the slope of the expressway. The site was surrounded by wide residential area. In the outskirts, a radius of less than 1 km does not have the farming ground.
The feeding site that had been maintained for a long term by an woman around 80 years old. At dawn all through the year, food was offered with fixed quantity and constitution: a scrap of garbage from kitchen and a medley of bread scrap in total 2-3 kilogram. Ccrows (Carrion CrowCorvus corone and Jungle Crow C. macrorhynchos), dovesColumba livia, sparrows Passer montanus were regular customers.
The study reached at monthly frequency for three years from January, 1990 to December, 1992. The observation started one hour before sunrise and was finished one hour after feeding.

Results and Discussion:
The old woman fed birds without being picky. When she sprinkled food, the birds which waited on neighboring electric wires, poles, trees rushed for food all at once. Roughly speaking, three rings were formed on the ground around her: inner ring by domestic pigeon, middle ring by sparrow, outside ring by Carrion Crow. Jungle Crow stayed at a distance on electric wires, poles, trees and jumped at a lump of food on the ground and escaped with it. The majority of crow which gathered were juvenile. One adult pair used the feeding site all the year because their territory included the site.
Seasonal changes of the number of crows, feral pigions, tree sparrows are showen below.

For three years, the number of crows decreased rapidly in early summer and recovered in autumn. The pattern of the increase and decrease of pigion was reversed to that of crow. In sparrow, clear seasonality was not recognized.

The rapid decrease of the number of crows in early summer might be explained by circumstantial evidences: in May, there is no chance to participate in breeding for a juvenile,; the plain is full of territories without a gap and the territorial defence activity by breeding pair is still active,; in the woodland, there is enough nutritious accessible food,; in the mountain, the number of seasonal roost increases. The activity range of juvenile (non-breeding) crows shifted from the plains to the mountains in the summer. In early autumn the situation changes and the juvenile comes back to the plains.

In the feeding site, pigions were often checked and disturbed to access food by crows. The reverse seasonal pattern of pigeons and crows implies that there was a competition between those two species.

 

Chap. 7 No effect of maximum or minimum temperature defference on roost selection by crows
Sreix Vol. 24, pp. 183-186, 2006 (Short Communication)
A Journal of Field Ornithology, Wild Bird Society of Japan

Starting point:
In the heat hot summer, it seems, a roost of the inner mountain is cooler than a roost on the outskirts of mounain. In the severe chilly winter, a roost of the plains is warmer than a roost of the outskirts of mountain. Actually, how much difference of temperature will there be? Does the difference of temperature become the main reason of the roost choice?

Methods:
The spring roost M1 settled on the outskirts of mountain became extinct in summer, and the summer roost P appeared in the inner mountain (see Chap. 1). It is probable that most of crows which used M1 changed the roost to the roost P. I installed thermometers in the inside of two roosts and measured temperature continuously (30 min.interval, 18 days). The autumn roost M2 became extinct in early winter, it is most probable, that most of crows which used M2 changed the roost to the permanent roost L in the plains. Like the summer monitor, I measured temperature (same interval, 68 days).
Protectors were attached to the instrument and prove to avoid the influence of weather and the mischief of crow.

Results and Discussion:
Comparison of temperatures between two roost sites in summer and winter are summarized in Table 1 (below), mean ± SD, range in parenthesis, result of Wilcoxon signed rank test.

In the midsummer, the roost site of P is cooler than that of M1. There was a difference of 0.31±0.49 ℃ with minimum temperature, 1.03±0.80 ℃ with maximum temperature. In the depth of winters, the roost site of L was warmer than that of M2. There was a difference of 0.35±1.11 ℃ and 0.24±+-0.71 ℃ respectively.

Because there is not a detailed study on thermo regulation of crows, I consider it in reference to a study of doves. At the high temperature range (more than 25-30 ℃), doves release the internal extra heat by panting and vasodilatation for thermo regulation. The cost increases in proportion to ambient temperature and reaches 20% of BMR at 40 ℃. In the middle temperature range (20-25℃), the mild control of heat radiation begins by shrinkage of the blood vessel and the strain of the pilomotor muscle. However, this cost is not a big sum. At the low temperature range (lower than 20℃), the heat production by quivering begins in addition to the previous two mechanisms. Regulation cost increases in proportion to ambient temperature and reaches 170% of BMR at -10 ℃.
It is effective for a cost cut of thermo regulation to participate the cooler roost site P in summer (saving 2-3% of BMR) and the warmer roost site L in winter (saving 1-2% of BMR).

According to the roost study of Jackdaws, a roost of the downtown is 4.0℃ warmer than a suburban roost (Gylin et al. 1977). It is said that a cost cut of the termo regulation by selecting warmer roost corresponds to a cost of 15 minutes flight (equivalent to 15 km flight distance).
The crows which gathered in the roost L were assumed to spend in daytime within a radius of 15-20km. The roost L is only 0.4℃ warmer than the roost M2. For almost all the crows participating the roost L, it is not the thing which profit matches.

 


Part 2 Breeding biology
In most crow species, the study of breeding biology (Part 2) and the study of roosting behaviour (Part 1) are relations complimentary and mutually, therefore I conducted two studies simultaneously. This part present three new topics to you: independence of juvenile, territorial defence, nest site comparison between Carrion Crow and Jungle Crow.

 

Chap. 8 The Development Toward Independence of the Offspring of Carrion Crow (Corvus corone)
Journal of the Yamashina Institute for Ornithology Vol. 29 pp. 57-66, 1997.
Yamashina Institute for Ornithology

Starting points:
Everybody says that the crow is clever but nobody knows how the relation between parents and their offsprings changes. It would be worth while investigating the independence process of crows chicks.

Conclusion:
1. The relation between parents and offsprings may be classified into four stages.
First stage: while their offsprings can not move freely, can not access to food, the parents feed them willingly. When chicks approach nearby, follow closely, beg food persistently, the parent behaved receptively.
Second stage: Male parent becomes to refuse for juveniles to approach. The space between male and juveniles spreads out gradually. However, Female parent is receptive as ever. The activity range of juveniles expands rapidly and begins to spend much time in the outside of parent's territory.
Third stage: Female parent also becomes intolerant of juvenile's begging food. Male behaves more and mora agressively toward juvenile's approach. Juveniles are ousted from roosting site in parent's territory and participate in a communal roost. They spend more time outside parent's territory.
Fourth stage: The dependence on parent's territory of juveniles decreased. While in the territory, juveniles stayed in a place apart from the parents not to induce a severe aggresive response. When the next breeding starts, they do not drop in at parent's territory.
2. The parents regulated the shift to the next stage referring to the growth of their juveniles.

Methods:
I observed many breeding pairs of Carrion Crow (Corvus corone orientalis) and Jungle Crow (C. macrorhynchos)in Osaka district for three years. I focused on one Carrion Crow pair among them and conducted an intensive observation: monthly 24 hours observation as amain observation and weekly short time observation as supplement.
I attached color rings for identification to the female, but failed to the male. All chicks wre banded in nestling stage. I attached a transmitter to the back of the chick in the year 1990 to detect the position of fledglings exactly.
I recorded the interaction between parents and offsprings precisely. When parent and offspring were in the short distance within 5 meters, the aggressive response of parent was recorded according to five response leveles: 0 - no aggression; 1 - light threat; 2 - threat; 3 - attack; 4 - heavy attack.

Descriptive explanation of parent's aggressive response
0. Even if begging is obstinately, parent does not behave that it seems to be annoying. 1. Parent ruffles the feather of head, neck, and besides may, belly. Parent shows a slight check and may push out a bill towards an offspring lightly.
2. Parent ruffles the head, neck and belly feather and stick out its chest and raise its head upright and approaches its offspring coercively. These behaviour are modified with flickering wing tips and pushing out its bill menacingly.
3. Parent approaches minaciously and chase away its juvenile which is far with reserve in the slightly remote place. Parent dares a threatening flight within a hairbreadth of the overhead of its juvenile from the slightly remote distance.
4. Furthermore, the degree of the approach refusal is strengthened. Parent chases its juvenile obstinately which rans away from the near by parents. This agressive response is not so severe as that to an invading individual in breeding season.

Results:
Percentage of observed time for each juvenile with parents (within 30 m) began to decrease around 100th day after fledgling. The difference of percentage between sibling grew larger after around 200th day (Fig. 1 below).

According to the change of parent's aggressive response, the development of offspring independence was divided into four stages (Fig. 2 below).

Percentage of time spent by each juvenile within 30 metres (open bars) and percentage of refusal by parents when the juvenile approached within five meters (open circles) in each stage of the development of offspring independence. During the 4th stage, the juvenile EP did not approach its parents within 30 meters and all juveniles did not appear within five meters.

Aggressive response of parent to their juvenile offspring's approach within five meters for each stage of the development of offspring independence (Table 1, below). The index of parent's aggression is defined by the mean value of the aggressiveness level for all approaches within five meters.

The details how the parenthood changes are as follows:
First stage: The locomotiveness of juvenile just after the fledgling (0-20 days, 1991's season) was undeveloped and fledglings keep still in the forest near-by the nest. Then juvenile began to follow parents gradually (20-40 days). Parents went up to their fledgling and feeded them. When chicks approach nearby, follow closely, beg food persistently, the parent behaved receptively.
Second stage: Male parent increased his aggressive response of check and threat, even though tolerant response was dominant. The space between male and juveniles spread out. However, in the first half of this stage (40-90 days), female parent was receptive as ever. In the second half (90-140 days), female parent became to show indifference to her offsprings at times. The activity range of juveniles expanded rapidly and began to spend much time in the outside of parent's territory.
Thisd stage: Female parent also became intolerant of juvenile's approach (140-200 days). Male behaves more and more agressively toward juvenile's approach. Within 30 metres, parent's aggresive response was released in most cases. Juveniles are ousted from roosting site in parent's territory and participate in a communal roost. They spent more time outside parent's territory.
Fourth stage: Juveniles decreased their dependence on parent's territory. Their stay became short and irregular, while in the territory, they spent in a place apart from the parents not to inflame aggressive reaction. When the next breeding started, they disappeared from parent's territory.

The inability state of offsprings happened in 1990's season because the falling off of the transmitter was half-done continued. Therefore the first stage was prolonged more than one month. After having completely fallen off, the parenthood shifted for the second stage.

Discussion:
Trivers hypothesized a conflict between parents and chicks. Benefit (B) is an increase in survival rate of chick by continuing taking care. Cost (C) is a decrease in survival rate of the other chicks by continuing investing it. When it became B/C<1, it is rational that the parent breaks off investment. However, as for the chick, it is rational to demand continuation of the investment until it becomes B/C<r. r is a coefficient of relatedness, r = 0.5 at the siblings born from the same parents. The conflict began in B/C<1, and was over in B/C<0.5.

According to Trivers's schema, the four stages can be interpreted as follows:
First stage corresponds to a period of B/C>1, parents are willing to continue investing. There is no conflict between parents and chicks.
Second stage agrees with a first half of 1>B/C>0.5. Male parent begins calm approach refusal for his fledglings, but female parent continues being receptive same as before. It is adaptive that there is a time gap among parents shifting to higher aggressive response. In any case, the change of aggressive response of male (not only a disregard and evasion but also a check anda threat) promote the independence process of fledglings.
Third stage coincides with a second half of 1>B/C>0.5. Juveniles are harassed with male parent's higher aggressive response. Female parents also become more indiffernt. Juveniles are considered to be a nuisance not an object of the protection. The dependence on parent's territory becomes almost zero.
Fourth stage corresponds to B/C<0.5. In winter season when juveniles face to starvation, it becomes the insurance for them that the parent's territory is available.

The care to the chiks/fledglings/juveniles of the parent changes flexibly according to the degree of growth. The aggressiveness does not escalate aoutmatically by days after fledgling.

 

 


Chap. 9 The Territorial Behaviour of the Carrion CrowsCorvus coronein Japan
Japanese Journal of Ornithology Vol.46. pp. 213-223, 1998.
The Ornithological Society of Japan

Starting points:
1. "The territory does not exist in the world of the animal. The animals share foods and habitats peacefully. Because a researcher is bound by the preconception and so he perceives the illusions of territory. Everybody can observe what he believes." Is this claim right?
2. Does the crow's couple defend their territory against a invasion by other individuals?
3. When the breeding season ends, the territory is abandoned?
4. Does the spase of home range accord with that of territory?
5. Is the defence behaviours for the heterspecific Jungle Crow different from that for conspecific crow?

Conclusions:
1. The territory was not a illusion, but a real existence. Invasions to territory were clasified into three types: At a high altitude invasion observed in the early period of breeding season; a mid/low altitude invasion; an invasion of the adjacent breeding individual.
2. The territory was defended successfuly by the couple's effort.
3. In the district where can be expected enough food through the year, the territory is maintained throughout the year.
4. The territory almost accorded with a home range. The defense action in the peripheral area of the home range decreased in the non-breeding season.
5. There was a slight difference in territorial behaviour against conspecific and heterospecific crow.

Methods:
The study site was a suburb of Takatsuki city, Osaka pref.(34°51′N,135°36′E, alt. 13m)(Fig. 1). An agricultural cultivated area, a residential area, a shrine forest were distributed over the site in a mosaic form. Six pairs of Carrion Crow and two pairs of Jungle Crow were breeding there (Fig. 2). In 1989 I captured one of the A pair(female) by a musou net(see, the picture above) and attached colorings for identification. I performed the consecutive two days investigations for monthly in the year 1990 and 1991. When the couple was observable at the same time I recorded their position and action one by one. When they were apart widely, I chased either one and recorded same way. In case I noticed that other crows appeared during observation in the study area, I recorded the reaction of the pair. I recorded species of the invasion individual, a flight course, a spot where a defense reaction was started and a spot where it was finished. Observed defense reactions were descrived as follows: a warning call, a warning take off, a interference/dismissal flight, an aerial dogfight.

Results:
A span of one year could be divided into three periods according to progression of breeding: the breeding period (March-June), from nest building to fledgling leaving the nest site; the post breeding period (July-October), juveniles became more and more independent from parent's territory; non-breeding period (November-February), juveniles rarely came back to the territory but parents stayed inside territory all day except the night(they left to a communal roost).

At the time when I lost sight of the male or the female during observation, it was 7% and 8% respectively each on the average (table 1. not shown).

The home range of the couple was almost overlaped through the year, and the distribution did not greatly change (Fig. 3). The home range of the breeding season was narrower than other periods. The male home range was wider than a female.

The territorial response to other crows which appeared in the home rang were analized (Table 2). The number of crows per hour which appeared in the home range was the highest in non-breeding period, and was the lowest in post-breeding period. On the other hand, the ratio of defense reaction scored highest in breeding period, scored lowest in non-breeding period. The defense reaction of pair A was higher against conspecific crow than heterospecific crow. Particularly, they showed defense reaction against Carrion Crow almost without exception in breeding/post-breeding period and even showed 70% in non-breeding period.

Defence responses were classified into two categories:
Type1,when other crows tried to sail across the home range, the couple A began a warning call, a checking take-off. If the invasion individuales does not change its flight course then the couple made escalation to higher aggresive reactions, an intercepting flight, an aerial dogfight.
Type 2, when neighbour crows stopped at the edge outside of home range and repeated threatening motions and calls then the couple A hurried to there. Two couples exchanged hostile actions and calls for a while. Then either withdrew from the place, the rivalry is finished. It was rare for them to make escalation to severe aggresive response.

Detail of territorial defence behaviour in each periods were as follows:
Breeding period: Defence reaction of Type 1 was started when other Carrion Crow invaded into the home range, and was stopped when the intruder left the periphery of the home range. The Type 2 reaction to neighbour couple B,D was limited to the marginal area
Post-breeding period: Against conspecific Carrion Crow, the Type 1 defense response of couple A decreased in the penumbra of the home range. Against heterospecific Jungle Crow, they did not take the defense reaction in most cases. A collision of Type 2 matched with the heterospecific adjacency individuals(pair G) inside of northwestern part of home rang, but matched against the conspecific pair B outside of southeastern part of home range.
Non-breeding period: Against Carrion Crow passage individual, the couple showed a defense reaction when the intruder try to pass the central part of home range, but did not often take the defense reaction when the intruder's course was in the penumbra of home range. The latter case was increased in this period. The rivalries with adjacent couple G, B were similar to the previous period.

Discussion:
The couple A remained within the home range throughout the year, and they never left there in the daytime. Their home range was defended against a passage individual and an adjacent individual through the year. Even though their defense response might decrease in the post/non-breeding period in its peripheral area, but it was not observed other crows sneaked into the area to feed and/or roost. This implies that The home range was used exclusively by their territorial behaviour. The territory accorded with the home range.

In many studies on Carrion Crow, the predation of eggs and/or chicks by non-breeding young crows (floater) has been discussed. The conclusive evidence does not seem to appear, but the crime of floater is definite by many circumstantial evidences. The predation would be main reason why the defense action of couple A was severe and thoroughly for all over home range in breeding periods not only conspecific crow but also heterospecific crow.

The couple A left their territory at dusk and returned at dawn in winter. It is most probable that participated in a communal roost, just like European Carrion Crow.

In the winter season of northern Europe, the environment for Carrion Crow is very severe owing to low temperature, much snow, scare of food. Carrion Crow migrate to southern country. However, the male that had territory last breeding season tends to remain in the neighbouring area if there is viable circumstance. It seems, wintering in the north becomes advantageous by earier breeding start of the next season. In the southern part of Germany and central part Highlands of Japan, crows abandone their territories at the heavy snow, and evacuate to the little snow region for a short while. I consider that Carrion Crow maintain territory throughout the year basically if environment permits it.

 

Chap.10. Nest Site Comparisons between the Carrion Crow Corvus corone and Jungle Crow Corvus macrorhynchos in Takatsuki City
Japanese Journal of Ornithology Vol.49. pp. 39-50, 2000.
The Ornithological Society of Japan

Starting points:
Two crow species, Carrion Crow and Jungle Crow breed in the neighborhood of each other in Japan. It seems that they use almost same ecological niche. There must be some segregation between them to reduce a conflict. How does they select a nest site under a coexistence environment.

Conclusion:
1. Carrion Crow nests were found in evergreen tree 52%, deciduous tree 25%, artificial structures 23%, Jungle Crow nests were found in 92%, 3& and 5% respectively.
2. Carrion Crow nests were built in sparsely wooded area, Jungle Crow nests were built in large areas of woodland.
3. The average distance between a nest and the edge of the forest was 20m for Carrion Crows and 114m in the case of Jungle Crow. It was more difficult to discover the nest of Jungle Crow than that of Carrion Crow.
4. The ratio of cropland in the area around the nest site (r<150m)was larger in Carrion Crow than in Jungle Crow. The ratio of woodland was extremely small in Carrion Crow and was variable in Jungle Crow.
5. Allmost all of the jungle Crow nests were found (81%)in evergreen trees in areas of extensive wood land. In contrast to this, 85% of Carrion Crow nests were found in another mocro-habitat, including deciduous trees, artificial structures, mediun or small areas of woodland, or small groves of trees.
6. The feeding behaviour and the preference for nest site concealment differed considerably between the two species. These differences may induce nest site segregation.

Methods:
The study was conducted in Takatsuki city, a residential suburb of Osaka metropolis during the 1991 breeding season. Study area consists of three parts: grove and woodland; farmland and grassland; commercial, industrial and residential areaa (Fig. 1). It comprises of 13 blocks of 2km square. The investigations were performed at three stages : searching for breeding nests; recomforming breeding activity; cheking fledgling from a nest on a rtificial structure.

In this district, Carrion Crow's nesting begins in mid Feburuary and aimost all fledglings leave nest in late May. The breeding of Jungle Crow proceeds later for three weeks than Carrion Crow.
I defined a possible nest tree that is suposed to be able to nest more than 6m high from ground. Because no Jungle Crow nest was found below 6m high (37 cases), only three nests of Carrion Crow were found below 6m high(172cases).

Results:
1) Nesting site
There were clear difference on nesting site choice between two species (Table 1). Jungle Crow prefered a highly concealed site in evergreen tree, esp. Pinus densiflora. On the contrary, Carrion Crow used not only highly concealed everegreen tree but also exposed sites in deciduous tree and electric pylon/pole. In the early breeding stage, all deciduous trees did not come into leaf and it is easy to find out a nest. Most nests on pylon were removed by a power company.

2) Abundance of nesting tree
Carrion Crow selected every category of nest site from C-0 with no potential nesting tree to C-4 with abundant nesting tree (Table2). Jungle Crow used mainly C-3 medium woodland and C-4 large woodland where there was a continuous canopy. In the cases of artificial structures, Jungle Crow selected a highly concealed site of substructure on the roof.

3) Nest distance

The mean of intraspecific nest distance of Jungle Crow was larger than that of Carrion Crow, more than twice(Table 4). The interspecific nest distance was smaller than the intraspecific distances.
In cases of very large woodland where crows could nest freely at any depth from the edge of woodland, Carrion Crow selected a shallow zone(20m) and Jungle Crow selected deep zone(114m).

4) Ambient surroundings of nest (r<150m)

Ratio of cropland of Carrion Crow in case of tree nesting (26.6%)was larger than that of Jungle Crow (23.0%)(U-test, 0.01<P<0.05). In the histogram a mode of Carrion Crow positioned in one block larger side than that of JungleCrow (Fig. 3).
Ratio of woodand of Carrion Crow in case of tree nesting (14.6%)was smaller than that of Jungle Crow (45.0%)(U-test, P<0.001). The histogram of Carrion Crow demonstrated a hyperbola type but that of Jungle Crow did not show any specific pattern.


Discussion:
1) Concelment degree of nest
Even though many Carrion Crow's nest were found in deciduous tree and utility pylon, this species is not negligent of nest concelement. More than half cases Carrion Crow nested in evergreen tree. Nests in deciduous tree became undetectable when deciduous tree came into leaf in early April. Nesting in a pylon, Carrion Crow selected a final top shadow corner in order to realize a high concelment degree. When comparing with Carrion Crow's nest site choice, it seems, Jungle Crow seeks a higher concelement.
It is credible that Carrion Crow have higher tolerance to low concelement degree. They even made nests in lower tree below 6 m from the ground and made nests in no/poor woodland (C-0, 1, 2). In Sakhalin Island Carrion Crow nest on ground in an exceptional case (Nechaev 1991). I suppose that the high tolerance would be useful for breeding in northern district where steppe forest and grassland is dominant.
2) Size of woodland
Thw distance from the edge of woodland (Table 4) implies a preferable size of woodland for nest. In the case of Carrion Crow, the distance 20m correspond C-1 and C-2. 76% of tree nesting were found in C-1, 2, 3. I consider that a breeding in poor/small woodland provides a benefit from efficient feeding in cropland. In breeding season they colect mainly food from surrounding cropland (Nakamura 1998). In the case of Jungle Crow, 114m correspond to C-4. Their wide intraspecific nest distance corresponds to their wide territory. Their food items suggests that they use evenly woodland and cropland for feeding.
3) Segrigation
The interspecific nest distance is shorter than the intraspecific nest distance of both species (Table 4). It is probable that there is some competition between the two species even though intraspecific competition would be more severe. Nest site comparisons demonstrated that Carrion Crow nests in a poor/small woodland surrounding cropland and Jungle Crow nests in a large woodland. The nest concelement of Carrion Crow is inferior to that of Jungle Crow. I cosider that these differences are realized as a result of segregation. Each species would use a little bit different niche from its original one because of the existence of possible pempetitive species.
In Sakhalin Island and Tsushima Island, I observed two species nests. They showed a different feature of nest site choice than that of Japanese mainland: Jungle Crow inhabit in a middle of village/small town but Carrion Crow inhabit out side of a settlement. The nests of Jungle Crow were found in a low concelement site.

 

 


Part 3. Postglacial colonisation and diversification of Jungle Crow

in preparation