The White-tailed Kite (Elanus leucurus) is distributed from the southern United States (California, Oregon, Arizona, Florida, and South Carolina: Dunk 1995, in A. Poole and F. Gill [Eds.], The birds of North America, No. 178. The Academy of Natural Sciences, Philadelphia, PA and the American Ornithologists' Union, Washington, D.C. U.S.A.) to southern Argentina and Chile (Couve and Vidal 2003, Birds of Patagonia, Tierra del Fuego and Antarctic Peninsula, Fantastico Sur Birding Ltds., Punta Arenas, Chile) inhabiting shrubland, grassland, savannah, marshes, and agricultural areas. In Argentina, the species ranges to central Chubut (43–44°S; Daciuk 1977, Physis 36:201–213; Narosky and Barbarskas 2000, Aves de la Patagonia, Vasquez Mazzini [Eds.], Buenos Aires, Argentina). In Chile, the southern limit of the White-tailed Kite was believed to be Llanquihue Province (41°S; Araya et al. 1998, Guía de campo de las aves de Chile, Editorial Universitaria, Santiago, Chile). However, recently it was recorded on the Isla Grande of Chiloé at latitude 42°24′S (McGehee et al. 1999, Bol. Chil. Ornit. 6:23–24). Here, we describe observations of White-tailed Kites made between 1997–2003 in the Aysén region (44–48°S), representing the most austral records to date.
On 15 October 1997, during a waterbird census along the highway between Puerto Aysén (45°24′S, 72°42′W) and Puerto Chacabuco (45°29′S, 72°50′W), Chile, one of us (J. Mella) observed the first reported White-tailed Kite for the Aysén region. The adult bird was observed hovering for 2 min ca. 50 m aboveground. The area is characterized by an extensive flat marshy terrain dominated by pastureland. The main human activity on the site consists of free-range livestock ranching. On 12 December 2003 at 1900 H local time, we observed an adult White-tailed Kite hovering for 1 min ca. 5 m aboveground near Cruce Ibañez (46°12′S, 72°00′W), 4 km northeast from Cerro Castillo village. The area is an undulating transitional terrain between the Patagonian shrub-steppe and deciduous southern beech (Nothofagus sp.) forest, with small, dispersed ranches and agricultural lands. On 15 December 2003 at 1500 H local time, we recorded a White-tailed Kite 7 km southwest from Mallín Grande village (46°43′S, 72°28′W). It was kiting 4–5 m aboveground and flew about 30 m. During this movement, the kite mobbed a pair of Crested Caracaras (Caracara cheriway) until they abandoned the area. Because we were relatively far from the kite (ca. 80 m), we could not determine if it was an adult or juvenile. This area is characterized by flat terrain covered by pasture, rangelands, and mixed-deciduous shrubs.
The geographic expansion of the White-tailed Kite has been documented in both extremes of its distribution range (Pruett-Jones et al. 1980, Am. Birds 34:682–688; Rodriguez-Estrella et al. 1995, J. Raptor Res. 29:30–31; McGehee et al. 1999). Similarly, Black-shouldered Kites (Elanus caeruleus) have also expanded their distribution in Europe (Carbajo-Molinero and Ferrero-Cantisán 1985, in I. Newton and R. Chancellor, [Eds.], Conservation studies on raptors, ICBP Tech. Publ. 5, U.K.). These expansions have mainly been attributed to changes in land-use practices such as forest fragmentation, conversion of lands to pasture, increased irrigation for agriculture, and road building (Carbajo-Molinero and Ferrero-Cantisán 1985; Johnsgard 1990, Hawks, eagles, and falcons of North America, Smithsonian Inst. Press, Washington, D.C. U.S.A.; Eisenmann 1971, Am. Birds 25:529–536; McGehee et al. 1999). In Aysén, the widespread clearing of forests with fire in the 1930s and 1940s led to the creation of extensive pasturelands (Grosse 1974, Visión de Aysén, author's edition), which could have caused an increase in the open-land raptor populations because of the increased availability of suitable hunting habitats and prey (Jaksic and Jiménez 1986, Birds of Prey Bull. 3:95–104). However, the White-tailed Kite was not previously documented in Aysén; it is possible that the absence of previous kite records in southern areas of Patagonia are due to inadequate field surveys. Our observations represent an extension of White-tailed Kite latitudinal distribution ca. 300 km south. Only subsequent monitoring will confirm if the White-tailed Kite is a resident or an accidental species in Aysén.
Observations were made during a study of waterbirds of Aysén and the monitoring of Hantavirus Reservoirs, financed by the Gobierno Regional of Aysén and the Servicio Agrícola y Ganadero (SAG) in Aysén. We thank J. Cerda and H. Saldivia who provided support and advice. Obtaining field data was made possible by collaboration of the SAG's technician personnel. We also thank D. Haughney who helped us with the English translation. A. Trejo and three anonymous referees made helpful comments on the manuscript.