The regional, national, and international importance of Louisiana's coastal avifauna

Abstract

Coastal Louisiana - and its Mississippi River Delta, in particular - provides large and diverse habitats for many types of birds in North America and beyond. The Mississippi River and its distributaries have shaped Louisiana's unique coast, which includes extensive marsh and marsh islands, sandy barrier headlands and sandy islands, and isolated patches of maritime forest on natural levees, cheniers, and canal spoil banks. Louisiana thus supports large populations of many obligate marsh bird species as well as marine bird species that require islands for breeding sites. Here, we have collated available data and attempt to estimate the breeding population sizes of 17 bird species in coastal Louisiana. We then summarize the importance of the Louisiana coast for these bird species in the contexts of regional, national, and global bird populations. These preliminary estimates indicate that Louisiana's coast supports a high percentage of regional, national, and, in some cases, global populations of several coastal bird species. For example, we estimate that 73% of the United States population of Sandwich Tern (Thalasseus sandvicensis) breeds in Louisiana, and comparable estimates range from 24 to 55% for Mottled Duck (Anas fulvigula), Clapper Rail (Rallus crepitans), Tricolored Heron (Egretta tricolor), Wilson's Plover (Charadrius wilsonia), Royal Tern (Thalasseus maximus), Black Skimmer (Rynchops Niger), and Seaside Sparrow (Ammodramus maritimus). Because most of these other bird species are distributed across state, regional, and national jurisdictions, management of birds and bird habitats in Louisiana has wide-reaching implications for the conservation of these shared natural resources. In this light, this paper is intended to be a resource for managers of avian resources in North America and beyond.