DEFORESTATION AND ITS EFFECTS ON FOREST-NESTING BIRDS IN THE FLORIDA-KEYS

Uplands in the tipper Florida Keys are covered by a tropical, seasonal deciduous forest containing many plant species found nowhere else in the continental United States. Before European settlement there were 4816 ha of seasonal deciduous forest in the keys. By 1991 the extent of this seasonal deciduous forest had decreased by 41%, the number of fragments increased by an order of magnitude, and the acreage in large fragments decreased by 84%, To examine the effects of fragment size on the presence of breeding birds, we censused bird populations of singing males that occurred in 27 forests that ranged in size from 0.2 ha to more than 100 ha. We also examined the occurrence of forest-breeding species at road-stop census points relative to nine measures of habitat around these points Northern Cardinals (Cardinalis cardinalis) and Black-whiskered Vireos (Vireo altiloquus) were found singing in virtually all fragments. The distribution of Red-bellied Woodpeckers (Melanerpes carolinus) occurred independently of the size of forest fragments belt was positively correlated with other measures of forest area. Great Crested Flycatchers (Myiarchus crinitus) occurred independently of fragment size and showed no correlations with other measures of habitat White-eyed Vireos (V. griseus) were not present in fragments smaller than 2.3 ha. Northern Flickers (Colaptes auratus) were not present in fragments smaller than 3.5 ha, but their numbers showed the highest positive correlations with the percentage of area in lawns and were negatively correlated with measures of total forest area. Yellow-billed (Coccyzus americanus) and Mangrove (C, minor) Cuckoos were absent from fragments smaller than 7.5 ha and 12.8 ha respectively The effective habitat loss for the four ''area-sensitive'' species exceeds the actual loss of deciduous forest. To maintain viable populations of species native to the seasonal deciduous forests of the Florida Keys will require protection of additional acreage of upland habitat from deforestation. A network of reserves that maintains dispersal possibilities among the remaining larger forest fragments is crucial.