Dissertational Improvement: Ecological Pressures Selecting for Dietary Plasticity During Migration in Two Neotropical Migratory Passerine Genera

9411650莫尔斯 许多新热带迁徙鸣禽种群的减少在过去十年中引发了对这些物种在温带繁殖地和热带越冬区的生物学的大量研究。尽管在这一过渡时期，移民有着极端的精力需求和非常不同的行为，但对过渡移民时期的关注要少得多。在迁徙过程中，许多鸣禽的繁殖季节行为多样化，以选择不同的栖息地，使用更多的觅食行为，并在更多样化的饮食类型比在一年中的其他时间。 这种行为可塑性进化背后的生态因素以及这些不同行为的生态和保护意义仍然是推测性的。 这项拟议中的研究将从秋季迁徙鸣禽行为多样化的一个方面调查这些问题--饮食从吃昆虫转变为吃水果。 对罗得岛布洛克岛的初步研究表明，在迁徙中途停留地资源丰富的不可预测性和在要求苛刻的迁徙期间扩大饮食的能量摄入增加导致了鸣禽的行为可塑性。将继续监测中途停留地点昆虫和水果的丰富程度，以监测1994年和1995年秋季这两种资源的不同程度的可预测性，从而进一步推动这项研究。此外，还将给移徙者喂食含有不同程度水果的实验性饮食，以确定他们在扩大饮食后能在多大程度上增肥，从而检验移徙期间为最大限度地摄入能量而进行的选择导致摄入食物种类多样化的假设。最后，实验将允许评估（通过双标记水技术）的数量的能量节省的候鸟在不同的饮食喂养。 这些技术允许估计鸟类的能量消耗，这可以在鸟类具有单一型和多样性饮食的情况下进行艾德。这些研究将提供深入了解行为可塑性的进化压力以及有关迁徙鸣禽生物学的重要信息。 这反过来又将使更好的保护决策，以这些下降的人口。 ***

9411650 Morse The decline of many populations of Neotropical migratory songbirds has triggered much research over the last decade into the biology of these species on their temperate breeding grounds and their tropical wintering areas. The interim migration period has received much less attention, despite the extreme energetic demands and the very divergent behavior of migrants during this transient period. During migration, many songbirds diversify their breeding-season behaviors to select different habitats, use more foraging behaviors, and feed on more varied diet types than at other times of the year. The ecological factors behind the evolution of such behavioral plasticity and the ecological and conservation implications these divergent behaviors remain speculative. The proposed research will investigate these questions in one aspect of behavioral diversification in autumn migrating songbirds - the shift in diet from eating insects to one of eating fruit. Preliminary research on Block Island, Rhode Island suggests that unpredictability in resource abundance at migratory stopover sites and increased energy intake on expanded diets during the demanding migration period have led to behavioral plasticity in songbirds. This research will be furthered with continued monitoring of insect and fruit abundance at stopover sites to monitor different degrees of predictability of the two resources during Autumn, 1994 and 1995. Furthermore, migrants will be fed experimental diets with varying degrees of fruit to determine the extent they can fatten on expanded diets, thus testing the hypothesis that diversification of ingested food types has resulted from selection to maximize energy intake during migration. Finally, experiments will allow evaluation (through doubly-labeled water techniques) of the amount of energy saved by migrant birds in feeding on diverse diets. These techniques allow estimation of the energy expenditure of birds which can be follow ed under situations where birds have monotypic and diverse diets available to them. These studies will provide insight into the evolutionary pressures for behavioral plasticity as well as important information about the biology of migrating songbirds. This in turn will allow better conservation decisions to be made regarding these declining populations. ***