Data from: Plasticity in nesting adaptations of a tidal marsh endemic bird

If individuals can perceive and manage risks, they may alter their behaviors based on prior experience. This expectation may apply to nest site selection of breeding birds, for which adaptive behavioral responses may enhance fitness. Birds that nest in tidal marshes have adapted to the challenges posed primarily by periodic, monthly tidal flooding and secondarily, by predation. We investigated adaptive responses in nesting behavior of the saltmarsh sparrow (Ammodramus caudacutus), an obligate tidal-marsh-breeding bird, using 536 nests monitored across five years. Using linear mixed effects models, we tested whether nest characteristics differed among nests that were successful, depredated, or flooded, and we investigated if females made changes in nest structure and placement according to outcome of their previous nesting attempt. Nest characteristics differed among females with different nest fates. Fledged and depredated nests were built higher in the vegetation and in higher elevation areas of the marsh than those that flooded. Successful nests had more canopy cover and were comprised of a lower proportion of high marsh vegetation (Spartina patens) than those that were flooded or depredated. Females with nests that failed due to flooding constructed subsequent nests higher in the vegetation and at higher elevation than those that were successful in their prior attempt, consistent with a response to previous experience. 85% of females renested within the average core home range distance (77 m), indicating a high degree of nest placement fidelity. Females for which nests were depredated in their prior nesting attempt renested at a greater distance than females for which the previous nesting attempts were successful. Our findings suggest saltmarsh sparrows exhibit plasticity in nesting behavior, which may be important for balancing selective pressures in a dynamic environment. This plasticity, however, is insufficient to enable them to adapt to the increased flooding predicted with sea-level rise.

若个体能够感知并管控风险，则可基于过往经验调整自身行为。这一推论可延伸至繁殖鸟类的巢址选择场景，适应性行为响应或可提升其繁殖适合度。在潮汐沼泽中筑巢的鸟类，已适应了主要源自周期性月度潮汐洪水、其次来自捕食活动的生存挑战。本研究以专性潮汐沼泽繁殖鸟类——盐沼麻雀（saltmarsh sparrow, Ammodramus caudacutus）为研究对象，依托5年间监测的536个鸟巢，探究其筑巢行为的适应性响应。本研究采用线性混合效应模型，检验成功繁殖、被捕食以及被洪水淹没的鸟巢在巢特征上是否存在差异，并探究雌鸟是否会根据过往筑巢尝试的结果，调整鸟巢的结构与选址。不同繁殖结局的雌鸟，其鸟巢特征存在显著差异。成功育幼出飞以及被捕食的鸟巢，相较于被洪水淹没的鸟巢，其搭建位置的植被高度更高，且所处沼泽的海拔也更高。成功繁殖的鸟巢，其上方冠层覆盖度更高，且相较于被洪水淹没或被捕食的鸟巢，筑巢材料中高沼泽带植被（Spartina patens）的占比更低。过往筑巢因洪水失败的雌鸟，后续搭建的鸟巢在植被中的高度以及所处沼泽的海拔，均高于此前繁殖成功的雌鸟，这一结果与其基于过往经验做出的行为响应相符。85%的雌鸟会在其核心家域的平均距离（77米）范围内重新筑巢，这表明其巢址选址具有高度的忠实性。过往筑巢被捕食的雌鸟，其重新筑巢的选址距离相较于此前繁殖成功的雌鸟更远。本研究结果表明，盐沼麻雀的筑巢行为具有可塑性，这或对其在动态环境中平衡各类选择压力具有重要意义。然而，这种可塑性并不足以使其适应海平面上升所预期的洪水强度与频率的增加。