關原地區青背山雀 (Parus monticolus) 親鳥育雛食物分配之探討

Abstract

本研究藉由架設在關原地區所設置之巢箱中的小型錄影機記錄青背山雀（Parus monticolus）親鳥的餵食行為和雛鳥的乞食行為。結果顯示於青背山雀中，第一隻孵出雛鳥與最後一隻孵出雛鳥之孵出間隔相差0.963 ± 0.372天（N = 5），雛鳥體重顯著受到孵化順序所影響（P< 0.001），越早孵出之雛鳥體重越重，然孵化順序對體重的影響則隨著育雛天數的增加而逐漸減少（P = 0.038）；於育雛期間，雛鳥體重隨著育雛天數的增加而逐漸上升（P < 0.001），然體重增加率隨著育雛天數逐漸減少（P < 0.001）；不同性別、親緣關係之雛鳥在體重和孵化順序上皆無顯著差異（P > 0.05）。當親鳥啣食物回巢時，不同體重的雛鳥於乞食時，和親鳥間距離、乞食高度及張嘴乞食比例上皆無顯著差異，但在雌鳥進巢時，體重較輕的雛鳥較早張嘴乞食（P = 0.006）。在親鳥餵食方面，雄鳥餵食頻率與餵食量皆高於雌鳥（P < 0.05），且在育雛天數、雛數、雛鳥性別比及原生子代比例不同的巢中，雄鳥佔餵食趟數（或餵食量）之百分比皆無顯著差異（P > 0.05）。兩性親鳥於進巢後位置與餵食前位置皆具高度的可預測性，然而於11巢中，僅有3巢之兩性親鳥在餵食前位置有顯著差異，且夾角大於60°。當親鳥啣食物回巢時，和親鳥間距離較近、乞食高度較高及張嘴乞食比例較高的雛鳥其獲食百分比（或獲食量）較高（P < 0.05），且在雄鳥進巢時，較早張嘴乞食的雛鳥獲食百分比（或獲食量）較高（P < 0.05），但在雌鳥進巢時則否。親鳥除了依據雛鳥乞食進行餵食分配外，兩性親鳥本身亦有選擇性餵食之行為，當雄鳥進巢時，體重較重的雛鳥獲食百分比（或獲食量）較高（P< 0.05），雌鳥進巢時，體重較輕的雛鳥相對獲食百分比（或獲食量）較高，但在統計上未到達顯著（P > 0.05），然就雛鳥的總獲食次數或總獲食量而言，不同體重的雛鳥間無顯著差異（P > 0.05）。在育雛天數、雛數、雛鳥性別比、原生子代比例及雄鳥佔餵食趟數（或餵食量）之百分比不同的巢中，雄鳥佔不同體重排名雛鳥之獲食次數（或獲食量）之百分比在程度上並無顯著差異（P > 0.05）。對於兩性親鳥在不同體重之雛鳥餵食分配上差異之原因，生活史取捨假說較能給予適當的解釋，推測兩性親鳥存活率之差異造成其對於現在與未來繁殖在投資的量上並不一致，雄鳥傾向投資較多資源於未來繁殖上，雌鳥則傾向投資較多於現在繁殖上，因而造成兩性親鳥對雛鳥食物分配上之差異。Parental feeding and nestling begging behavior of Green-backed tit (Parus monticolus) were studied via video cameras set up in the nest boxes at Guan-yuan in Taroko National Park. The result showed that for Green-backed tit, the hatching spread between the first and the last nestling was 0.963 ± 0.372 day (N = 5). Nestling’s weight was affected by hatching order (P< 0.001). The earlier the nestling was hatched, the heavier it was. However, the influence of hatching order lessened as the age of brood increased (P = 0.038). During the fledging period, the nestlings gained weight by the days (P < 0.001), though the increasing rate declined with the age of the brood. Nestlings of different sexes or paternity have shown no significant differences on weight and hatching order (P > 0.05). No matter male or female parent entered nest, there were no significant differences among the distance from parents, begging height, and begging percentage between nestlings of different weight, but when female parent entered nest, lighter nestling beg for food earlier (P = 0.006). On parental feeding of nestling, male had higher feeding rates and brought back more food than that of female. The percentage of male to the whole nest in feeding trips or loading quantity has shown no significant differences in nests of different ages of brooding, brood size, nestling sex ratio and paternity (P > 0.05). The positions of parents after entering the nest and the positions before feeding were highly predictable. However, among 11 nests only 3 nests of sexual parents had significant differences in the position before feeding and the included angle greater than 60°. When parents entered nest, nestlings that were closer to the parents or extended their necks higher or begged more often had higher chance of being fed or acquiring more amount of food (P< 0.05), and when male parent entered nest, nestlings that open mouths earlier to beg had higher chance of being fed or acquiring more amount of food (P < 0.05). However, there were no difference when the female parent entered nest. Aside from allocating food based upon the begging behavior of nestlings, sexual parents have selective feeding. Male parent fed more food to heavier nestlings (P < 0.05), while female parents fed more food to lighter nestlings (P > 0.05), and the total times of beingfed or the amount of food received of the nestlings have no significant differences between nestlings of different weight (P > 0.05). In nests of different age of brooding, brood size, nestling sex ratio, paternity and the percentage of male parent to the whole nest in feeding trips or loading quantity, male parent showed no significant differences in the percentage of times of being fed or the amount of food received of the nestlings of different weight. The life history trade-off hypothesis could better explain for the reason that sexual parents make different food allocations among nestlings of different weight. It was suggested that the difference of the sexual survival rate leads to the difference of food allocations on current reproduction by female parent and future reproduction by male parent. And it also made the sexual parents have different food allocations among nestlings