Status of the everglade kite in Florida--1968-1978

Abstract

The population status of the Everglade Kite (Rostrhamus sociabils plumbeus) was studied in Florida from 1968 through 1978. Sixty-four nestlings (40% of known fledged young) were leg-banded with unique color combinations, and of these, 17.2% were seen 1 or more years after they were banded. Kites were capable of breeding at 3 years of age or possibly younger. The population was nomadic; its sex ratio unknown. From 1968 through 1976 breeding success was determined for 175 nests, of which 48% were successful: 161 young were fledged, x = 20.1 per year, or 1.9 per successful nest (N = 84). The percentage of successful nests ranged from 17.1 (N = 35) in 1974 to 84.6 (N = 13) in 1968 (x= 54.1 per year). From 1968 through 1976 there was a significant increase (r = 0.685, P < 0.05) in the number of nests ohserved (excluding 1971, and reproduction was not studied in 1977 and 1978). The mortality rate for young in the nest was 41%. Some individuals live for at least 8+ years. The mean number of kites for 10 annual censuses was 120.2 with a range of 65 (1972) to 267 (1978). The severe drought of 1971 resulted in a significant decrease in the population for that year and 1972, with no nesting attempts being observed in the dry year. From 1974 through 1978 the population increased significantly (r = 0.92, P < 0.025), apparently the result of favorable water conditions and increased food supply. The loss of suitable habitat is the major problem facing the species in Florida. A high water level is essential, as this affects food supply and its availability, as well as nesting success.