Abundance and Distribution of Mangrove Landbirds in Florida

Abstract

Abstract Florida's mangroves provide habitat for an eclectic mix of bird species, including five taxa rarely found elsewhere in North America. Little is known of the natural history of any of these birds, which poses an obstacle to effective conservation. To help fill some of the basic gaps in our understanding of this avifauna, we conducted extensive surveys in Florida's mangroves during 2008–2011, with the goals of quantifying distribution and estimating breeding-season abundance of mangrove landbirds. We detected 80 species in the mangroves during the breeding season; most were species in Passeriformes (n = 29), but other important taxa included Ciconiiformes (n = 13) and Charadriiformes (n = 12). We focused our analysis on the 18 landbird species (including members of Falconiformes, Columbiformes, Cuculiformes, Piciformes, and Passeriformes) that had >90 detections and that were detected at >5% of the survey points. The landbird avifauna of Florida's mangroves is lower in both species richness and total number of individuals than other vegetation types of southern Florida. The breeding assemblage of mangrove landbirds was dominated numerically by four species that accounted for 58% of all detections of landbirds (this same group accounted for 52% of detections of all species encountered): red-bellied woodpecker Melanerpes carolinus, northern cardinal Cardinalis cardinalis, Florida prairie warbler Setophaga discolor paludicola, and white-eyed vireo Vireo griseus. Only Florida prairie warbler is restricted to mangroves; the other three species are common throughout much of eastern North America. Each of these species was also widely distributed in the mangroves. Of the other species unique to the mangroves of Florida, black-whiskered vireo Vireo altiloquus was widespread but was less abundant than Florida prairie warbler. White-crowned pigeon Patagioenas leucocephala, gray kingbird Tyrannus dominicensis, and Cuban yellow warbler Setophaga petechia gundlachi were detected only in the Florida Keys and on the islands of Florida Bay, but were found in high densities where present. Mangrove cuckoo Coccyzus minor was found throughout the mangroves but occurred at very low density and at only a small percentage of survey points. Overall, mangrove landbirds reflect the biogeographic condition common throughout southern Florida, in which largely temperate faunas coexist with largely tropical floras. The predominance of temperate species in Florida's mangroves has produced an avifauna apparently more species-rich than that found in the mangroves of West Indian islands, which include additional tropical species but no species of temperate origin.