| Summary: | 碩士 === 國立臺灣大學 === 森林學研究所 === 87 === In 1938, it was discovered that Taiwan Yuhinas (Yuhina brunneiceps), which are endemic to Taiwan, exhibited cooperative breeding behavior. To further our understanding of Taiwan Yuhinas, research on their breeding ecology was conducted at Mei-Fung, in the mountains of central Taiwan, from January 1997 to April 1999. The research focused on territorial behavior, pair relationships, dominance hierarchies, breeding cooperation, parental group formation and variation in the composition of parental groups of the 8-9 parental groups within the study area.
Taiwan Yuhinas maintained territories and lived in parental groups year-round. I observed 17 parental groups of 3 to 7 adults each. The most common parental group size was 4 (47%). Each parental group consisted of 1 to 3, communally nesting, monogamous pairs and some had a single, unmated helper. Each parental group was organized by a male dominance hierarchy in which the head, wing, and tail length of higher ranking males were greater than those of lower ranking males (Mann-Whitney U test p<0.05). Only the largest male, the alfa-male, engaged in territorial defense singing. The position of females in the dominance hierarchy was not related to their body size but to the rank of their mate. Male Yuhinas had significantly longer heads, wings and tails than females (Mann-Whitney U test p<0.05).
Each member of the parental group contributed to the rearing of the young in their communal nest. During the nest building and incubation period, the female worked harder than the male, but during the nestling feeding period the amount of work performed by males and females was more variable. Each brood required about 70 days to rear to fledging. Parental groups could rear 3 broods each breeding season. In nests used by 2 or 3 females, I observed 2 or 3 different patterns of spots on the eggs, supporting observations by other researchers that the pattern of spots on eggs is unique for each female. At Mei-Fung, new individuals joining parental groups were either male offspring from previous breeding seasons with a non-relative mate, or a non-blood-relative pair. From 24.2% to 29.6% of the Taiwan Yuhinas at Mei-Fung disappeared annually. One bird banded as adults in an earlier study have lived at least 8 years.
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