舊巢洞使用與否對栗喉蜂虎繁殖成功的影響

Abstract

本論文第一章回顧舊巢使用對於繁殖個體帶來的好處和壞處，以及環境因子如何影響鳥類選擇使用舊巢繁殖；一般而言使用舊巢能降低築巢所需投資的時間跟能量，但是使用舊巢也可能有寄生蟲以及巢洞不穩固的風險。第二章為栗喉蜂虎(Merops philipinnus)使用新、舊巢個體分別進行生殖對其生殖成功之探討。栗喉蜂虎每年4月到金門進行繁殖，在土坡挖掘洞穴營巢。過去的研究中發現在沙質坡面築巢的栗喉蜂虎不太會使用舊巢洞繁殖，而在土質較硬的營巢地則有觀察到使用舊巢洞繁殖的行為。本研究於2008年4-8月栗喉蜂虎繁殖季時，針對栗喉蜂虎使用新、舊巢洞的生殖行為進行觀察。本研究將營巢地分為有舊巢使用(昔果山OA、復國墩OB)與沒有舊巢使用(田埔NA、青年農莊NB,NC)兩種類型，於繁殖季前期照像記錄各營巢地坡面上舊巢洞的位置，進入繁殖季後，每兩天使用針孔式攝影機記錄洞內生殖狀況，繁殖結束後則測量坡面上巢洞位置以及高度。結果顯示：1.使用舊巢洞的栗喉蜂虎繁殖成功率顯著高於使用新巢洞者(P=0.0005)、且顯著較早開始下蛋(p=0.0048)及離巢(p<0.0001)，推測因使用舊巢洞降低挖巢洞所需的時間和能量，導致了使用舊巢洞繁殖者較早開始繁殖且有較好的繁殖成功率。2.有舊巢使用的營巢地繁殖成功率顯著高於無舊巢使用的營巢地(p=0.0015)，且顯著較早離巢(p=0.0001)，並且有舊巢使用的營巢地土壤壓力較高(p=0.0335)；推測有舊巢使用的營巢地具有較好的環境品質，且因為土壤壓力高所以營巢地不易崩毀，因而土壤壓力高可能是栗喉蜂虎選擇使用舊巢的原因之一。3.有使用的舊巢離地位置較高(p=0.0387)且巢洞較深(p=0.0148)；栗喉蜂虎天敵主要從坡面下方捕食，推測栗喉蜂虎會傾向使用巢位較高的舊巢洞。

The first chapter of this thesis is about factors which may influence birds to choose old nest as well as the benefit and cost of using old nests. Environment factors were also discussed. The second chapter is about the nest reuse behavior of Blue-tailed Bee-eater (Merops philipinnus). Breeding via old nest might save the energy and time of building a new nest, but reusing old nests could be unstable and in danger of an ectoparasitic infection. Blue-tailed Bee-eaters breed by migrating to Kinmen Island in April every year, where they roost by digging holes on soil banks. From previous studies it was found that bee-eaters generally do not breed in the old nest on sandy banks, and only a minority of birds breed in old nests, which are mostly located in Ci-Kuo-Shan and Fou-Kuo-Dun. I monitored the nest by observing the behavior of Bee-eaters during April-August in 2008. In this study I divided the colonies into two groups, which were: 1) those within nest-reuse behavior group (Ci-Kuo-Shan and Fou-Kuo-Dun) and 2) those without nest-reuse behavior group (Youth farm and Tien-pu). Before the arrival of breeding season, I recorded the locations of old nests on the banks, and when the breeding season ended , I recorded the breeding situations inside the nests every two days. After the young fledged, I then measured the location of their nests. According to the data obtained, I found the followings: 1. birds breed via old nests had higher reproductive success compared to birds that excavated new nests. I also found that “old nest breeder” bred earlier; therefore, I suggest that the nest-reusing behavior in Blue-tailed Bee-eater is time and energy saving since those birds that use old nests do not need to excavate new ones. This resulted in an earlier breeding and increased reproductive success. 2. Birds bred earlier in the sites with nest reuse than those without, and the average reproductive success was higher in the former group, too. In addition, I also found that the soil pressure of breeding sites with old nests was higher. The average reproductive success of a site could be an index of its quality. For this reason I suggest that these sites are higher in quality thereby promoting higher reproductive success. Furthermore, if the soil pressure on banks are high, nests wouldn’t collapse easily. According to reasons above, I suggest that bee-eaters prefer to use old nests which are located on a good site with higher soil pressure. 3. The old nests that were used in 2008 were located higher than those that were unused, indicating that bee-eaters prefer using old nests that were located higher up the ground in order to avoid predators.