Collaborative Research: Population Limitation of Neotropical Migratory Birds and the Seasonal-Interaction Hypothesis

Smithsonian Institution, Washington DC

Investigators

Abstract

0089565 Marra Understanding the biology of small migratory animals is hampered by the difficulties involved in tracking individuals and integrating ecological impacts year-round. The work proposed here addresses seasonal linkages in two migratory bird species. This study will test the hypothesis that reproductive success depends on habitat quality occupied in the prior tropical winter period in contrast to the conventional alternative that breeding conditions alone matter. Winter habitat signatures will be identified in breeding birds using stable carbon isotopes sampled in blood tissue. Reproductive success will be measured and assessed according to winter habitat occupancy patterns and to indices of breeding territory quality and individual condition. Food manipulations in winter will assess the mechanisms linking habitat quality in winter to breeding events. The abundance and diversity of migratory birds comprise a spectacular natural phenomenon. Such species control insect pests, modify plant communities via seed dispersal and pollination, and stabilize ecosystems upon which humans depend. This research will contribute fundamental new insights into how the abundance of migratory birds is limited and regulated year-round, thereby helping structure seasonally linked population models more accurately. Population models are crucial to understand these animals' responses to human impacts on global habitat quantity, quality, and climate change.