Fall stop-over ecology of neotropical migrants: Are inner or outer coastal habitats energy sources for migrants
Research within the mid-Atlantic region have shown that the majority of neotropical migrants utilizing the outer coastal plain as a migration route are young of the year, and that many are not replenishing fat reserves during times of stop-over. Research has also shown that foraging rates are higher in deciduous habitats than in pine habitats. The general composition of the forests of the mid-Atlantic coastal plain shift from pine dominated on the outer coastal plain to hardwood dominated along the fall line of the inner coastal plain. Studies were initiated to determine if these hardwood dominated habitats are better stop-over habitats than the pine dominated forests of the coastal fringe, and to determine differences in age ratios, condition, foraging rates, and energy gains of selected species of neotropical migrants using these habitats. Study sites were established within the outer and inner coastal plain to assess the availability of prey items, perform foraging observations, and capture birds for evaluation of age and condition. Habitats on the inner coastal plain seem to be superior to the pine habitats of the outer coastal plain. While sites on the outer coastal plain produced more arthropods over all, sites on the inner coastal plain had greater numbers of arthropods associated with foliage, where migrants were observed foraging most often. Greater percentages of after hatch year birds were captured on the inner coastal plain, and although new birds captured on the outer coastal plain initially carried more fat and had higher masses, recapture data show that during stop-over birds tended to gain mass on the inner coastal plain and lose ,mass on the outer coastal plain. Black-throated blue Warblers on the inner coastal plain were the only birds analyzed that were ingesting sufficient numbers of prey items to meet their daily metabolic needs and produce fat. The results suggest that the hardwood dominated forest of the inner coastal plain contain superior stop-over habitats for neotropical migrants than the pine dominated forests of the outer coastal plain.