James W. Wiley

Reproductive Interactions of the Shiny Cowbird and the Yellow-Shouldered Blackbird

1967) and in the Caribbean (Bond 1973). with deciduous trees located along the mangroves, and on offshore mangrove cays. The climate around The race M.b. minimus, aided by man-made La Parguera is arid tropical, with a mean annual introductions (Post and Wiley 1977)) has been rainfall of 56 cm (12-year average recorded at La expanding its range NW through the CaribCueva Island, 1962-1973). The Ceiba study site

The decline of an adaptation in the absence of a presumed selection pressure

The colonial nesting Village Weaver (Ploceus cucullatus) lays eggs that vary in ground color and pattern, but individual females lay similar eggs each time. Tests on captive African stocks have shown that females reject eggs of other cohorts if such eggs are sufficiently different. The Village Weaver may have evolved rejection behavior and variable eggs in response to cuckoo parasitism in Africa. The Village Weaver was introduced into Hispaniola from Africa as early as the 18th century. Before the arrival of the Shiny Cowbird (Molothrus bonariensis) in the early 1970s, there were no brood parasites on Hispaniola. Furthermore, in an experimental parasitism study, Hispaniolan Village Weavers accepted both dummy eggs and dissimilar Village Weaver eggs. The Village Weaver may have decreased the egg‐rejection behavior in the absence of the selective pressure of brood parasitism. Now Hispaniolan populations of the Village Weaver are parasitized by the Shiny Cowbird, which lays eggs dissimilar to those of the weaver. Brood parasitism by the Shiny Cowbird exerts a detrimental impact on the Village Weaver by reducing nest success and productivity.

Conservation of the yellow-shouldered blackbird Agelaius xanthomus, an endagered West Indian species

Abstract The yellow-shouldered blackbird Agelaius xanthomus, endemic to Puerto Rico and Mona Island, is endangered, mainly because of brood parasitism by the shiny cowbird Molothrus bonariensis, which reached Puerto Rico at least 30 years ago. The yellow-shouldered blackbird populations have since declined, about 770–1200 remaining (470–900 on Mona Island) by 1982–1986 compared to a population of about 2400 in 1975. Nearly all nests of blackbirds in most of its habitats are parasitized by cowbirds. This significantly reduces nesting success, but blackbirds have evolved no defenses against brood parasitism. Removal of cowbirds from the yellow-shouldered blackbird nesting grounds, modeled after similar programmes for the brown-headed cowbird Molothrus ater on Kirtlands warbler Dendroica kirtlandii nesting areas, significantly increased blackbird production. Blackbirds readily accept nest boxes, and breeding populations can be established in otherwise unusable sites and can be concentrated in mangrove habitats, were they are more easily protected by cowbird removal. Furthermore, yellow-shouldered blackbird pairs using cavities, including nest boxes, fledged more young per nest than pairs using open nests.

BREEDING SEASON ECOLOGY AND BEHAVIOR OF RIDGWAY'S HAWK (BUTEO RIDGWAYI)

Ridgways Hawk (Buteo ridgwayi) is endemic to Hispaniola and its satellites, where it occurs in a wide variety of habitats. We studied this hawk in the wet limestone karst forest of the Dominican Republic be- tween January and June 1976. The hawk is sexually dimorphic with females somewhat larger than males. Display flights of territorial pairs began in January and were observed most often between 10:00 and 12:O0. Mean home range for three pairs was 57.8 ha. Nest building was first observed on 25 February. Construction was con- centrated in the morning and males did most of the building. Incubation (two eggs) was underway at one nest on 22 March. Females performed all of the incubation except when males took over after food exchanges. Hatching at one nest occurred on 19 and 20 April. At another nest two chicks fledged during the 12th week after egglaying. Both sexes defended nests against intra- and interspecific intruders. Males captured 91% of prey brought to the nests. Lizards and snakes were the most numerous prey brought to nests while mammals formed the bulk of prey biomass. Birds were also brought to young. Ridgways Hawks used four hunting techniques: (1) Still Hunting, (2) Hang-Searching (slow gliding flight), (3) Foot-Thrusting (thrusting foot into vegetation and cavities to flush prey), and (4) Direct Stoop from soaring. The hawk has three basic vocalizations: (1) Kleeah, used in self-assertive and aggressive contexts; (2) Weeup, given in food exchanges and displays, and (3) the Whistle-Squeal, given during high-intensity interactions. Our observations suggest that B. ridgwayi is closely related to B. line&us. Despite current interest in the biology of raptors, relatively little is known about those in the tropics. The habits of Ridgways Hawk (Buteo ridgwayi), a species endemic to Hispaniola (Haiti and the Dominican Re- public), are almost unknown, probably be- cause few ornithologists have worked on that island.

Status and conservation of parrots and parakeets in the Greater Antilles, Bahama Islands, and Cayman Islands

In the 1490S a minimum of 28 species of psittacines occurred in the West Indies. Today, only 43% (12) of the species survive. All macaws and most parakeet species have been lost. Although the surviving parrot fauna of the Greater Antilles, Cayman Islands, and Bahama Islands has fared somewhat better than that of the Lesser Antilles, every species has undergone extensive reductions of populations and all but two have undergone extensive reductions in range, mostly as a result of habitat loss, but also from persecution as agricultural pests, conflicts with exotic species, harvesting for pets, and natural disasters. The Cayman Brae Parrot Amazona leucocephala hesterna , with its tiny population (lessthan 150 individuals in the wild) and range, and the Puerto Rican Parrot A. vittata , with 22-23 birds in the wild and 56 individuals in captivity, must be considered on the of extinction and in need of (in the tatters case, continuing) aggressive programmes of research and management. Other populations declining in numbers and range include the Yellow-billed Amazona collaria , and Black-billed A. agilis Parrots of Jamaica, Hispaniolan Parakeet Aratinga chloroptera , Hispaniolan Parrot Amazona ventralis , Cuban Parrot A. leucocephala leucocephala and, most seriously, Cuban Parakeet Aratinga euops . The population of the Grand Cayman Parrot ( Amazona leucocephala caymanensis ), although numbering only about 1,000 birds, appears stable and the current conservation programme gives hope for the survival of the race. An active conservation and public education programme has begun for the Bahama Parrot A. l. bahamensis , which still occurs in good numbers on Great Inagua Island, but is threatened on Abaco Island. Recommendations for conservation of parrots and parakeets in the region include (1) instituting term programmes of research to determine distribution, status, and ecology of each species; (2) developing conservation programmes through education and management approaches that are culturally, politically, and economically sensitive to the region; and providing and protecting habitat within suitably sized reserves.

The head-down display in shiny cowbirds and its relation to dominance behavior

Brood parasitic cowbirds (Icterinae) often give the headdown display when they approach other birds (Chapman 1928; Selander and La Rue 1961; Rothstein 1977, 1980). The display sometimes results in individuals of the same or other species preening the giver of the display. The function of the head-down is not fully understood, although some have suggested that it may appease a potential aggressor (Selander and La Rue 1961, Robertson and Norman 1976). However, experimental and naturalistic evidence now favors the opposite explanation, that the head-down display is an aggressive display which enables birds giving it to assess at close range the relative dominance of other individuals (Rothstein 1980). In addition, the donor often usurps the space occupied by the recipient of the display, while the probability that the recipient will attack may be reduced (Rothstein 1977, 1980). That some individuals preen the displaying cowbird may be a result of behavioral mimicry, as the head-down display resembles postures shown by birds engaged in body maintenance (Harrison 1965, Rothstein 1980). The head-down display and associated allopreening have frequently been recorded for captive cowbirds (Selander and La Rue 1961; Selander 1964; Rothstein 1977, 1980), but they are less often seen in nature (Darley 1968). This study reports the occurrence of the display among free-living and captive Shiny Cowbirds (Molothrus bonariensis). We also report the frequency of the display, the species to which cowbirds displayed, the responses of recipients, and the contexts in which the head-down occurred. Our objective is to clarify the function of the head-down display in the Shiny Cowbird and to compare our data with similar information for the Brown-headed Cowbird (M. ater).

Birds of Islas Beata and Alto Velo, Dominican Republic

Isla Beata and Isla Alto Velo are small satellites of the Dominican Republic, lying off its southwestern coast. We visited Isla Beata between 26–30 July 1977 and 20–21 October 1978. We explored Isla Alto Velo on 22 October 1978. In addition we made aerial surveys of the islands in 1977 and 1980. In our surveys we found 34 species, including 16 land birds, not before reported for Isla Beata. The Hispaniolan Parakeet (Aratinga chloroptera) and Hispaniolan Woodpecker (Melanerpes striatus) are reported for the first time from offshore islands. This brings the number of reported species for Isla Beata to 93, with 44 land birds. We found 22 species on Isla Alto Velo, for a total of 27 species, including 12 land birds, for the island.