Nestling sex allocation of a joint-nesting Yuhina brunneiceps population at Meifeng

• Main Authors: Shu-Wei Fu, 傅淑瑋
• Other Authors: 袁孝維
• Format: Others
• Language: en_US
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/99283626266780323945

碩士 === 國立臺灣大學 === 森林環境暨資源學研究所 === 93 === The aim of this study was to examine the nestling sex allocation of a joint-nesting population of Taiwan yuhina (Yuhina brunneiceps). Most of Taiwan Yuhina breeds with joint-nesting strategy in the study site, and the linear hierarchy relationship within group members is obvious. Dominant males had larger wing chords than subordinate males, but there was no difference of body size between dominant and subordinate females. We assumed that the condition of males was more influenced by parental investment than that of females. I conducted the study at Meifeng area during 2003-2004; field work included observing the hierarchy and pair bond of breeding group members, and taking the blood samples from adults and nestlings. I then employed molecular techniques to determine the sex and estimate parentage of nestlings. Results showed that nestling sex was associated with maternal status, and dominant females produced more sons than subordinate females. When sex ratio of broods was analyzed, I found that primary sex ratio was influenced by timing of breeding season, group size, and brood size. The proportion of sons decreased as the season progressed and when group size and brood size were larger. Secondary sex ratio was also influenced by timing of breeding season and brood size. The results supported the predictions of Trivers and Willard hypothesis, females manipulated offspring sex in relation to maternal status and sex ratio of broods was female-biased when the resources was limited in late breeding season and when brood size was larger.