栗喉蜂虎幫手對親鳥在餵食幼鳥時期之影響

Abstract

本論文分成兩章，第一章為文獻回顧，將形成合作生殖的原因、個體間的親緣關係以及群內個體可能獲得的利益（benefit）以及所需付出的代價（cost）做初步介紹；第二章為2008年於金門島進行栗喉蜂虎（Merops philippinus）合作生殖研究之探討。我們已知金門島栗喉蜂虎具合作生殖行為，又因其屬於群聚生殖的遷徙性鳥種，其合作生殖之形成與機制可能不同於其他具終年領域性的鳥種。因此為瞭解其幫手效應屬於附加性（additive）或補償性（compensatory），我記錄親鳥與幫手回巢餵食速率代表其投資程度，同時透過血液樣本確認親鳥與幫手之間的親緣關係，推測幫手可能獲得的利益。結果顯示食物資源不是影響蜂虎繁殖成功的主要因子，且無論有無幫手的親鳥在產卵數（4.94 0.24 vs 4.75 0.22顆）、幼鳥停留巢內天數（27.06 0.83 vs 28.58 0.90天）、幼鳥離巢率（0.87 0.05 vs 0.86 0.06）、幼鳥被捕食率（0.13 0.05 vs 0.14 0.06）、體重（39.67 0.54 vs 39.46 0.64 g）、胕蹠骨長（14.33 0.22 vs 15.08 1.13 mm）、尾羽長（88.97 0.66 vs 89.46 0.78 mm），或是全部（親鳥加幫手）餵食速率（次/單位時間）上皆無顯著差異，但無幫手的親鳥餵食速率卻顯著高於有幫手的親鳥（p=0.0144）。同時親鳥最佳投資量模式的預測結果也指出親鳥在幫手協助時會減少餵食速率，上述結果皆支持栗喉蜂虎的幫手效應屬於補償性，親鳥節省的能量投資可能可以增加其存活率或未來繁殖機會。幫手中確認性別的有9隻公鳥及3隻母鳥，在親鳥親緣係數方面，僅一隻公幫手為其中一隻雄性親鳥的子代，同生殖群內幫手與親鳥（公鳥）之間的親緣相關係數（r= ）並沒有顯著高於群間(r= )（p=0.474），顯示栗喉蜂虎的幫手與親鳥間並沒有特別偏向具親緣關係。另外在線性混和效應模式（GLIMMIX）中，顯示影響親鳥餵食速率的主要因子包括幫手有無、時段、幼鳥年紀以及天氣，幫手可以減輕親鳥的負擔；親鳥餵食速率以0600-0800時最低，0800-1000時最高；幼鳥羽鞘脫落後，親鳥餵食速率較之前高；而雨天時親鳥的餵食速率最低、晴時多雲時最

This thesis includes two chapters: the first one is the literature review of the causation of cooperative breeding, as well as the relatedness between each group members, and the benefits and costs of group members; the second one is the study of cooperative breeding of Blue-tailed Bee-eaters（Merops philippinus）conducted in Kinmen in 2008. This population of Blue-tailed Bee-eaters in Kinmen exhibit cooperative breeding as well as colonial breeding and migratory behavior. The reason for their cooperative breeding behavior might be different from other territorial bird species. Therefore, in order to understand whether the effects of helper were additive or compensatory, I recorded the provision rates of breeders and helpers to determine the degree of investment. To clarify the relatedness between breeders and helpers, and to deduce the possible benefits to the helpers, the blood samples were analyzed. The results suggested that the food resource was not an important factor for their reproductive success. Between the nests with and without helpers, there were no significant differences in clutch size (4.94 0.24 vs 4.75 0.22), nestling period (27.06 0.83 vs 28.58 0.90 days), fledging success (0.87 0.05 vs 0.86 0.06), predation rate of nestlings (0.13 0.05 vs 0.14 0.06),weight (39.67 0.54 vs 39.46 0.64 g), tarsus length (14.33 0.22 vs 15.08 1.13 mm), tail length (88.97 0.66 vs 89.46 0.78 mm), and provision rate of breeders and helpers combined together; the provision rate of un-helped breeders was significantly higher than helped breeders (p=0.0144). The prediction of the optimal breeder investment model suggested that the provision rates of the breeders were decreased in the nests with helpers. It was suggested that the effects of helpers is compensatory, and the energy saved by breeders might enhance their survival rate or the opportunity of future reproduction. There were 9 male and 3 female helpers, and only one helper was the son of the male breeder. Besides, the relatedness ( ) between males within the same group were not significantly different from random expectation of relatedness between all males ( ) (p=0.474). It implied that the breeders and helpers were not relatives. The result of the generalized linear mixed model suggested that the presence of helper, time-period of a day, offspring age, and weather were the important factors to the provision rate of the breeders. The presence of the helpers probably reduced the workload of breeders. The lowest provision rate of the breeders occurred during 0600-0800 and the highest occurred during 0800-1000. The breeders fed more food after the tube-falling period of nestlings than before tube-falling. The breeders fed least on rainy days and highest on mostly clear days.