House sparrows offset the physiological trade-off between immune response and feather growth by adjusting foraging behavior

Growing feathers and mounting immune responses are both energetically costly for birds. According to the life history trade-off hypothesis, it has been posited that the costs of feather growth lead to temporal isolation between molt and other expensive activities, reproduction for example. In contrast to life cycle events, the need to mount an immune response can occur at any time, including during feather growth. Thus, we hypothesized that mounting an immune response during feather growth may divert energy and resources from feather growth and impair feather renewal. To test this hypothesis, we clipped or plucked the same feathers of male house sparrows, Passer domesticus biblicus. In the clipped group (n = 16), the feathers were absent with no regrowth; in the plucked group (n = 14), feathers were absent and regrowth was initiated. We also had an intact control group of 15 sparrows. We then initiated an inflammatory immune response by subcutaneous injection over the left breast muscle...对于鸟类而言，羽毛生长与免疫应答激活均会消耗大量能量。根据生活史权衡假说，已有研究提出：羽毛生长的能量成本会导致换羽与其他高能耗活动（例如繁殖）之间出现时间上的分离。但与生命周期内的其他事件不同，免疫应答的触发时机并无固定规律，甚至可能出现在羽毛生长期间。据此，我们提出假说：在羽毛生长期间触发免疫应答，可能会从羽毛生长过程中转移能量与资源，进而损害羽毛更新。为验证该假说，我们对雄性家麻雀（Passer domesticus biblicus）的同一部位羽毛分别进行修剪或拔除处理。修剪组（n = 16）的羽毛被移除且无再生现象；拔除组（n = 14）的羽毛被移除后启动了再生过程。此外我们设置了15只未做处理的麻雀作为空白对照组。随后我们通过在左侧胸肌皮下注射的方式，触发了炎症性免疫应答……