Journal of the Yamashina Institute for Ornithology
Online ISSN : 1883-3659
Print ISSN : 0044-0183
ISSN-L : 0044-0183
Roosting behaviour of two species of crows in Mie prefecture
Atsushi KurataYukio Higuchi
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JOURNAL FREE ACCESS

1972 Volume 6 Issue 5-6 Pages 489-506

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Abstract

1. From 1963 through 1967, the roosting behaviour of Jungle Crow Corvus macrorhynchos and Carrion Crow C. corone was studied in Mie Prefecture.
2. Habitat segregation was observed between the two species; C. macrorhynchos from mountains to hills, and C. corone from hills to plain.
3. From feeding ground to roost, roosting flocks were formed in four processes: feeding ground pairs and flock-flight line assembly-pre-roosting assembly-roosting assembly (roost).
4. In the process of pre-roosting assembly, initial assembly place differs in the two species. Assembly place of the earliest flock tends to be the pre-roosting assembly place of the day.
5. Numbers at the pre-roosting assembly place, were correlated with the light intensity. Numbers increased remarkably under the light intensity about 100 lux.
6. Seasonal fluctuation of numbers at roosting place was at its maximum from December through February and minimum from April through August. This is caused partly by the dispersion of the roost, and partly by the fact that most of the breeding crows roost in their territories.
7. The number of roosts in the breeding season was seven in the northern part of Mie Prefecture. Roosting numbers were 200-300, most of them non breeding birds, but some breeding birds were mixed.
8. The autumnal roost was not found in the northern part of Mie Prefecture.
9. The number of winter roosts was ten in Mie Prefecture. Roosts were mainly found beside the river. The area of dispersal from the roost was from 400 to 500km2.
10. Roosts are usually found in the forest well protected from long before. In Mie Prefecture, Pinus thunbergii woods were most often used.
11. Total number of two species of crows in Mie Prefecture was estimated as about 20, 000, based on maximum roosting numbers in winter.

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