Because bottomland forests of the lower Mississippi Alluvial Valley (MAV) are valuable as breeding, wintering, and en-route habitat during migration, we investigated the impact of changing land uses in the MAV on avian abundance and diversity at the local and continental scales. Checklist inventories from 5 studies conducted in the MAV during 1985-1992 confirmed that bird species that occur in the MAV represent a substantial proportion of the entire avifauna of eastern North America (ENA). Of 236 landbird species reported for ENA, 200 (85%) occur in the MAV; we recorded 149 landbird species (63%). The frequency distribution of population trends as determined from Breeding Bird Surveys (BBS) varied significantly among species according to migratory status, geographic area, and habitat. Neotropical migrant landbird (NTMB) and temperate species were much more likely to show population declines than increases in the MAV. Woodland species exhibited fewer declines than expected in the MAV and ENA. However, analysis of population trends may be biased because populations of some species significantly declined prior to the establishment of the BBS.
