築巢對東方毛腳燕(Delichon dasypus)繁殖行為的影響

Abstract

動物的生活史演化與個體差異有關，個體所採用的投資策略則依據可獲取的資源不同而改變，產生生活史特徵的差異。巢對鳥類繁殖是重要的資源，由於築巢需要消耗能量與時間，使用舊巢繁殖可能是鳥類偏好的繁殖策略。但舊巢是會被消耗的資源，因此部分個體勢必需要築巢。然而，我們對使用舊巢或築新巢的成本與利益理解有限。本研究檢測亞熱帶山區東方毛腳燕(Delichon dasypus)的築巢行為對其繁殖表現的影響。我們利用破壞舊巢來誘使部分個體築新巢，亦容許部分個體使用舊巢。同時，我們也考慮伴隨築巢行為產生的影響—繁殖時間、巢內溫度變化、以及親代照顧。我們發現毛腳燕偏好使用舊巢，而築新巢的個體相較於使用舊巢的個體會延後下蛋時間，並且生較少蛋，顯示築巢確實造成額外的能量與時間成本。築新巢以及使用舊巢的個體之間繁殖成功率並無異，可能是因為築新巢的個體有較高的親代照顧，且新巢不像舊巢一樣容易受到巢內溫度變化而影響育雛所需時長。整體而言，這些結果顯示儘管築新巢會產生額外成本，毛腳燕仍可以透過調整繁殖投資—例如親代照顧的強度—來緩解築巢在繁殖初期所帶來的負面影響。本研究凸顯出不同築巢選擇(使用舊巢、築新巢等)之間具有複雜的成本利益關係，這有助於維持築巢行為的多樣性。

Life-history is linked to individual variation of which investment strategies owing to different available resources, hence varied the life-history traits. Nests are important resources for avian breeding. As nesting building takes time and energy, reusing nests is likely preferred reproductive strategy among bird species. However, given that old nests are depletable resources, some individuals are bound to build new nests. The costs and benefit of reusing versus rebuilding nests are not well understood. In this study, we tested the influences of nesting behavior on breeding performance of Asian house martins (Delichon dasypus) in a subtropical montane region. We experimentally induced some martins to rebuild nests by breaking old nests while allowing others to reuse nests. Meanwhile, we considered the cascade effects of building new nests—egg-laying date, nest temperature variability, and parental care. The martins showed a preference of reusing over rebuilding nests. The martins that rebuilt nests had a delayed egg-laying date and a lower number of eggs compared to those that reused nests. This indicated that additional time and energy costs involved in nest building. Nevertheless, both martins that reused and rebuilt nests have similar breeding success. This was likely achieved by our findings that martins that rebuilt nests had increased parental care. Moreover, nestling and breeding periods are less sensitive to nest temperature variability to martins that rebuilt nests. Taken together, our findings suggest that Asian house martins were able to alleviate the negative consequences in early stage of the breeding due to additional energy and time costs from building nests through their flexible breeding investments. This study highlights the intricate cost-and-benefit relationships among different nesting decisions, which underlies the maintenance of nesting behavior diversity.