OBSERVATIONS OF GROUP-BEHAVIOR AND BREEDING BIOLOGY OF THE YELLOW-BILLED SHRIKE CORVINELLA-CORVINA
OBSERVATIONS OF GROUP-BEHAVIOR AND BREEDING BIOLOGY OF THE YELLOW-BILLED SHRIKE CORVINELLA-CORVINA
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DOI：
10.1111/j.1474-919x.1980.tb02658.x
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发表时间：
1980-01-01
期刊：
影响因子：
2.1
通讯作者：
GRIMES, LG
中科院分区：
文献类型：
--
作者：
GRIMES, LG
Yellow-billed shrikes live in groups throughout the year. Within the group, each member helped to defend the group''s territory, warn against predators and feed the breeding female, nestlings and fledglings. During the study there was little change in the location of the boundaries and in the areas of the territories occupied by the majority of the groups. The densities of the larger groups were 2-3 times that of smaller groups. Numbers within 1 group varied by .+-.24% of the average (12) during 3 yr. Progeny remained in a group for some years before dispersing, sometimes in parties of the same sex. Both sexes exchanged groups, the females moving on average further than males. During successive periods in the history of a group the representation of the sexes varied from a surplus of females to a surplus of males. In the population as a whole the sex ratio was probably parity. Only 1 female bred in a group at a particular time and she alone incubated. Eggs were laid on consecutive days. Breeding started at the height of the dry season; the 1st peak in egg laying occurred at the beginning of the rains; laying continued through the wet season and ceased usually in Aug. The most frequent clutch size was 4, and varied little within a breeding season or between seasons. The incubation period ranged from 15-18 days, the most frequently recorded being 17 days. The nestling period was 19 days. The percentage of total eggs laid that produced fledglings was 25% and yearlings 11%. Young shrikes were independent in the 7th wk, participated in group displays in their 10th wk and fed fledglings in their 14th wk. The age of 1st breeding was not discovered. Two females in their 6th yr were still helpers in a group at the end of the study.
