Margarops fuscatus

Abstract: This paper presents results of a field study of avian predation on Anolis lizards on islands in the northeastern Caribbean, addressing the question of what causes annual fluctuation in lizard abundance. The two main potential avian predators, the Pearly- eyed Thrasher (Margarops fuscatus) and the American Kestrel (Falco sparverius), were studied on three adjacent islands in the northern Lesser Antilles: Anguilla, St. Martin, and St. Eustatius. Anoles on Anguilla were found to be quantitatively unaffected by avian predation; thrashers there did not eat vertebrates, and the kestrel density was too low to have a significant impact on the lizard population. In contrast, thrashers in moist habitat on St. Martin ate vertebrates including anoles, and thrasher predation potentially accounted for the anole decline to the dry-season abundance low. Additionally, an unanticipated thrasher niche shift was discovered. Thrasher body size and diet appear to be related to the abundance of a congeneric species, M. fuscus. On Anguilla, where M. fuscus was absent, M. fuscatus was smaller and had a non-vertebrate diet. On St. Eustatius, M. fuscus was abundant while M. fuscatus was larger and preyed on anoles. M. fuscus was rare on St. Martin, where M. fuscatus had an intermediate body size and a diet comparable to that on St. Eustatius.

Abstract: Observations of foraging and diet for eight Passerine bird, two Anolis lizard, and one Ameiva lizard species in dry sclerophyll scrub on St. Eustatius (Neth. Antilles) show that none of the bird species competes as much with either anole as does the other anole, or the Ameiva. Anoles feed on insects, primarily on the ground and in low vegetation; on St. Eustatius no mainly insectivorous bird species feeds primarily in these places. Instead, the main presentday interaction between birds and anoles is predation. The abundant pearly-eyed thrasher (Margarops fuscatus) and the sparrow hawk (Falco sparverius) are the major predators on anoles. This predation has little effect on the niche relations of the anoles, according to a model for the coevolution of competing species.

Abstract: Two new species of syringophilid mites parasitizing birds from the family Mimidae are described: Syringophilopsis mimidus sp. nov. ex Margarops fuscatus (Vieillot) from Central America and Rafapicobia toxostoma sp. nov. ex Toxostoma curvirostre (Swainson) from USA. Additionally, Torotrogla mima Kethley, 1970 is redescribed based on the material ex Mimus triurus (Vieillot) from Argentina and M. patagonicus (Lafresnaye and Orbigny) from South Africa.