Our Liviiii; Rfsoiircfs — Nnn-iuUivc Spccit's 



437 



Thomas, R.A.. P.J. Thomas. J.O. Coulson. and T. Coulson. Wilson. L.D.. anJ L. Porras. 19S.1. The etological impact of For further inrormation: 



iWI). Aiuilis sagrei .sagrei (brown anole). Herpetological 

 Review 21:22. 

 Tyler, M. 1989. Australian frogs. Viking O Neill Publishers. 

 Ringwood, Victoria. 220 pp. 



man on the south Florida hcrpeiofauna. University of 

 Kansas Museum of Natural History Special Publ. 9. 89 

 pp. 

 Zug, G.R., and P.B. Zug. 1979. The niarme load. Unfa mar- 

 imis: a natural history resume of native populations. 

 Smithsonian Contributions to Zoology 284. 58 pp. 



Michael James McCoid 



Caesar Kleberg Wildlife Research 



Institute 



Campus Box 218 



Texas A & M University 



Kingsville 



Kincsville, TX 78363 



TWO of the three most common nesting 

 species in North America today are birds 

 whose ancestors were brought here from 

 Europe. Some non-native birds are more con- 

 spicuous than others, so comparisons are only 

 relative, but according to the two largest conti- 

 nental surveys, non-native species (excluding 

 house finches) constitute, on average, about 6% 

 of the bird population during the summer 

 months (Breeding Bird Survey [BBS]) and 

 about 8% in winter (Christmas Bird Count), 

 Percentages vary considerably by habitat and 

 geographic location. 



Many exotic bird species were introduced to 

 the United States by European colonists who 

 missed the familiar birds of their homeland and 

 tried to establish populations of familiar Old 

 World species. Farmers also saw opportunities 

 for pest control by birds such as starlings and 

 house sparrows, but they did not anticipate the 

 degree to which these exotic species would out- 

 compete native birds for nesting sites. Most 

 introductions, however, were by sporting or 

 hunting organizations and state game depart- 

 ments that wished to provide more hunting 

 opportunities. 



Competition between exotic and native 

 species has been particularly severe on islands. 

 In the Hawaiian Islands, introduced songbird 

 species far exceed native ones. Visitors to 

 Honolulu, for example, see only exotic song- 

 birds unless they hike mountain trails in search 

 of the few remaining endemic species. 

 Mac Arthur and Wilson ( 1 967 ) predicted that for 

 every new species colonized or introduced on 

 an island, an average of one species will 

 become extinct. Even Puerto Rico has breeding 

 populations of about 20 kinds of exotic song- 

 birds, far outnumbering the endeinics. 



The best-known introductions in North 

 America are those that were highly successful: 

 the house sparrow (Passer domesticiis), 

 European starling (Stunuis vulgaris), rock dove 

 or common pigeon (Columba livia), ring- 

 necked pheasant (Phasianus colcliicus), mute 

 swan (Cygnus olor), gray or Hungarian par- 

 tridge (Perdi.x perdi.x). and the chukar (Alectoris 

 chukar). They readily adapted to their new envi- 

 ronments, and most have prospered here for 

 more than 100 years. 



Data Sources 



Before the mid-20th century, information on 

 the distribution and population trends of exotic 

 birds came primarily from scattered accounts in 

 the literature, from state bird books, and from 

 the Audubon Christmas Bird Count (CBC), 

 Since 1966 in the eastern states and Canada, 

 and 1968 in the West, the BBS (Robbins et al, 

 1986) has provided information on geographic 

 distribution, relative abundance, and population 

 trends for all but the rarest species. A condensed 

 summary of BBS trends of exotic species 

 (Table) based on as many as 2,500 fifty-stop 

 roadside transects per year is presented for the 

 three major regions of the continent. 



History and Status 



Cattle Egret (Bubulcus ibis) 



The only records of intentional release of 

 this African species in the United States are 

 from Hawaii, where the bird was deliberately 

 introduced on five major islands in July and 

 August 1959 to control flies around homes and 

 cattle (Breeze 1959). These birds were obtained 

 in Florida, where they arrived in the early 

 1940"s from South America by way of the West 

 Indies. The species had been known from 

 British Guiana since the 1870's (American 

 Ornithologists" Union 1983), but no firm docu- 

 mentation of its arrival there from Africa is 

 known. The species' spread across the continen- 

 tal United States is well documented by the 

 BBS (Table) and the CBC. The cattle egret is 

 highly migratory, and many of the American 

 birds winter in Latin America. Cattle egrets 

 feed primarily in pastures with cattle. 

 Concerns that cattle diseases might be carried 

 across international boundaries have so far 

 lacked documentation, but populations are 

 being monitored and movements of banded 

 birds are being tracked. 



Waterfowl 



Many species of exotic waterfowl have 

 found their way into the wild through inten- 

 tional introductions and by escaping from cap- 

 tivity. The large, heavy-bodied muscovy duck 

 (Cairina moschata) from Mexico, in both nat- 

 ural and white plumage, is a common sight in 



Non-native 

 Birds 



by 



Chandler S. Robbins 



National Biological Service 



