南亞夜鷹的擬傷行為

Abstract

擬傷是部分鳥類的護幼行為。目前關於繁殖過程與護幼行為的展現有兩種假說：(1)隨著親鳥投資程度而增加(2)於雛鳥較容易受天敵威脅的時期展現。本研究擬針對半早熟型的鳥類南亞夜鷹(Caprimulgus affinis)，分別在河床區(有遮蔽)及建物區(無遮蔽)頂樓，檢視不同年齡的雌夜鷹展現擬傷的時機、頻度以其與掠食者間的距離。自2008到2012年間，於河床區與建物區各記錄69與54個成功繁殖巢(雛鳥達到17日齡)。在河床區，雌鳥於雛鳥第5日齡時開始展現擬傷行為，峰期集中在8-11日(加權平均後得到雌鳥於雛鳥9.0日齡時有較多的擬傷行為展現)。在建物區，雌鳥則於雛鳥4日齡時展現擬傷行為，峰期集中在雛鳥6-9日齡(加權平均後得到雌鳥於雛鳥7.9日齡時有較多的擬傷行為展現)。本研究顯示，不論哪種環境，雌鳥擬傷行為展現的時機與雛鳥容易移動日齡有明顯關聯(河床區：rs=0.921，建物區：rs= 0.932)；在無遮蔽的條件下，雌鳥會提早進行擬傷，且延長擬傷天數；年齡越大的雌鳥，展現擬傷的次數要高於年紀較輕的。結果顯示建物區與河床區雌鳥的擬傷時機有所不同，推測是因為環境遮蔽度造成子代受天敵威脅程度有所差異造成的。Injury Feigning, is a kind of bird behaviors of nest defenses. There is two hypothesis referring optimal timing of nest defense: (1) Brood value hypothesis. (2) Vulnerability hypothesis. In this study, I focus on demonstrating the difference of the injury feigning behaviors which take by semi-precocial Savanna Nightjars (Caprimulgus affinis) during different ages, to test the timing, frequency, and settling distance. The study sites include river banks (with cover) and building rooftops (without cover). During 2008-2012, we recorded 54 nests at building rooftops and 69 at river banks (breeding success age: 17 days old). At building rooftops, female began to display injury feigning behaviors when nestlings were 4 days old. And the frequency of this behaviors reached a peak at 6-9 days old (weighted average:7.9 days old). At river banks, female began to display injury feigning behaviors when nestlings were 5 day old. And the frequency of this behaviors reached a peak at 8-11 days old (weighted average:9.0 days old). In both environments, the timing of injury feigning is highly related to the days of nestlings usually moved(river banks：rs=0.921, building rooftops：rs= 0.932). Besides, females displayed injury feigning behaviors early and longer at the uncover site. The older females displayed more injury feigning than the youngers at the uncover surroundings. The difference of timing and sites which females displayed injury feigning behaviors, may be refered to the environment cover provides different protection on nestlings.