Migrants in the Galápagos Area

Abstract

The last comprehensive report on migrant birds in the region was published more than 30 years ago by Swarth (1931) who excluded most of the procellariiform species previously considered by Gifford (1913) and Loomis (1918). Subsequently, a number of records obtained at sea and on the islands were reported by various authors, chiefly Fisher and Wetmore (1931), Swarth (1933), Murphy (1936), Lack and Venables (1940), Fleming (1950), and Harrison (1962). During the 12-year period, 1952 to 1964, visits were made by one or more of the present writers to all the principal islands of the Galkpagos Archipelago (fig. 1), with numerous opportunities to observe and to collect at infrequently visited coasts and inland areas. The purpose of this report is to bring together all records of Galipagos migrants that have accumulated since 1931 and thereby make available a more up-todate summary of species occurrences, distribution, and relative abundance. The term Galapagos area, as used here, includes the islands and intervening waters of the Galipagos Archipelago, plus a circular band of open ocean, approximately 200 miles in width, measured from the perimeter of a circle that passes through Culpepper and Hood islands (fig. 2). Thus this region in the eastern equatorial Pacific encompasses a circular area of 385,000 square miles, and is approximately 700 miles in diameter. The easternmost end of Chatham Island (Punta Pitt) is 502 miles west of Cape San Lorenzo on the Ecuadorian mainland (Slevin, 1955:99). Guadalupe Island (Mexico), Socorro Island in the Revillagigedo Archipelago, and Clipperton atoll are approximately 2700, 1700, and 1300 miles, respectively, northwest of Culpepper Island in the Galkpagos. To the northeast, Cocos Island (Costa Rica) and Malpelo Island (Colombia) are approximately 425 and 630 miles, respectively, from Tower Island in the Galhipagos. The nearest land west of Galkpagos is the island of Fatu Hiva in the Marquesas, about 2800 miles distant. The islands of San Felix and San Ambrosio (Chile) and Sala-y-Gomez and Rapa Nui (Chil6) are about 1600 miles to the SSE and SSW, respectively, of Galkpagos. The perimeter of the Galipagos area comes to within about 140 and 320 miles of Cocos Island and the nearest Ecuadorian mainland, respectively. To be sure, the limits of the Galkpagos area have been chosen somewhat arbitrarily, since they cut across several oceanographic and meteorological provinces (Abbott, MS; Alpert, 1963; Murphy, 1936). Nevertheless, it is because of this unusual setting that so many interesting avian distributional discoveries are occurring and will continue to do so. The need for more thorough observing and collecting in the Galipagos is clearly indicated by the data presented below.