Introduction

Editor's Note: this accounts cover both the Red-whiskered and Red-vented bulbul. Future revisons may provide separate coverage for each species. 

Bulbuls are slim, long-tailed passerines with small crests. Red-vented Bulbuls are native from Pakistan to southwest China, Red-whiskered Bulbuls from India and southeast China to northern Malaya. Popular cage birds, both species have been introduced to many regions of the world, including Australia, New Zealand, islands in the Indian and Pacific Oceans, and the United States.

During the 1960s, populations of introduced Red-whiskered Bulbuls became established in southern Florida and southern California, although these populations remain small and limited in distribution. In contrast, populations of Red-vented and Red-whiskered bulbuls released during the same time period on O‘ahu I., in the Hawaiian Archipelago, have undergone explosive growth and range expansion, although the Red-whiskered has shown a less dramatic increase in numbers and range than the Red-vented. Populations of bulbuls in the above-mentioned regions were either deliberately or accidentally released.

Both species are associated with human habitation in their natural and introduced ranges. They frequent agricultural and urban areas, including parks, suburban gardens, and arboreta. However, on O‘ahu I., HI, Red-whiskered Bulbuls range regularly into low-elevation forested areas, and Red-vented Bulbuls occur sparingly in forests up to the highest summits of the Ko‘olau Mtns. Both species are sedentary throughout their distribution and have protracted breeding seasons in most of their introduced and native ranges; thus pairs are able to raise 2–3 broods annually. Bulbuls are highly gregarious during the nonbreeding season and gather in large communal roosts. They are primarily frugivores but also feed on animal and plant material, including leaves, flowers, buds, and nectar. In addition, they feed on a variety of cultivated fruits, vegetables, and flowers and thus are in direct conflict with humans. Bulbuls are potential dispersers of noxious weed seeds and compete with native bird species in their introduced ranges.

Because Red-whiskered Bulbuls pose a potential threat to agricultural crops, the U.S. Department of Agriculture Code of Federal Regulation prohibits their importation into the U.S. and its territories. Red-vented Bulbuls, however, are not specifically prohibited.

Few key studies have been undertaken on the Red-whiskered and Red-vented bulbuls in North America. Carleton (1971) and Carleton and Owre (1975) detail the release, population expansion, feeding ecology, and breeding biology of the Red-whiskered Bulbul in Florida. On O‘ahu I., van Riper et al. (1979) have studied the feeding habits and breeding biology of the Red-whiskered Bulbul; other studies have examined habitat, distribution, and population trends of both species (Williams 1983a, Williams and Giddings 1984, Williams 1987, Ralph 1991). Elsewhere in their native and other introduced ranges, there are detailed accounts of diet (Watling 1977), vocalizations and behavior (Short 1964, Pernetta and Watling 1978), sex ratio (Watling 1977), breeding biology (Dhondt 1977, Watling 1977, 1983, Vijayan 1980), diseases and body parasites (Watling 1977, Bhattacharyya 1988), and molts (Dhondt 1976a, 1976b, 1977, Watling 1977, Balachandran et al. 1995).