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W. B. Robertson

Publications and source records attributed to W. B. Robertson.

3 recordsLinked to original sources

Bald eagle nest site characteristics in South Florida

Florida had nearly 20% of the coterminous United States population of nesting bald eagles ( Haliaeetus leucocephalus ) in 1990 (U.S. Fish and Wildl. Serv. 1991), yet the nesting ecology of bald eagles in subtropical environments has not been investigated. We examined nest site selection (n = 156 sites) by bald eagles in Florida Bay, Florida, from 1959 to 1990. Black ( Avicennia germinans ) and red mangroves ( Rhizophora mangle ) were used as nest trees almost exclusively (96.9%), and more than half were snags. Eagles also built nests on the ground (n = 3) and raised young on the ground after nests collapsed (n = 5). Eagles preferred (P < 0.05) higher keys (grass, hardwood-buttonwood [ Conocarpus erecta ]) over low-lying keys (mangrove, marsh) for nesting. Management strategies should include the preservation of live and dead mangroves and large, undisturbed keys as potential nesting sites for bald eagles in the subtropical portion of the eagle's range.

Florida

Organochlorine residues in eggs of the endangered American crocodile (Crocodylus acutus)

Most of the 27 species and subspecies of surviving crocodilians have declining populations and 22 of them are considered to be severely endangered (IUCN 1971). The United States population of the American Crocodile is no exception; it probably numbers between I00 and 300 individuals (OGDEN 1976). Nests of the species have been regularly surveyed by the staff of Everglades National Park. Our sample consists of eggs that remained in nests after the hatching of broods and of one clutch laid in captivity by an unmated female. Analysis of these samples for organochlorine contaminants has permitted a detailed examination of their contaminant loads and has allowed comparisons with a small sample analyzed in 1972 (OGDEN et al. 1973).

Florida