LATE-SUMMER PRESENCE OF THE PATAGONIAN TYRANT, COLORHAMPHUS PARVIROSTRIS (DARWIN) ON NAVARINO ISLAND, CAPE HORN COUNTY, CHILE

STEVEN M. MCGEHEE; RICARDO ROZZI; CHRISTOPHER B. ANDERSON; SILVINA IPPI; RODRIGO VÁSQUEZ; SUE WOODLAND

ANALES DEL INSTITUTO DE LA PATAGONIA

Universidad de Magallanes

Lugar: Punta Arenas; Año: 2004 vol. 32 p. 25 - 33

0718-6932

The southernmost representative of the Tyrannidae, a diversified family with approximately 420 species endemic to the Americas, belongs to a monotypic genus Colorhampus with only one species: C. parvirostris. Little is know about the Patagonian tyrant, which is consuidered rare throughout its breeding range and vulnerable to forest disturbances and habitat fragmentation. Even its distribution and life history are poorly known. During the breeding season it migrates to higher latitudes (more than 40ºS) in southern Chile and Argentina, but small numbers remain within central-southern latitudes year-round (30-40ºS). In the high latitudes of Tierra del Fuego it is said to be an accidental visitor, but records of C. parvirostris are extremely rare. As part of the long-term misnetting and bird census program at the Omora Ethnobotanical Park on Navarino Island, Cape Horn County, Chile (55ºS) a total of 1,542 birds beloging to 17 species have been captured with mistnets on Navarino Island. Only 12 were C. parvirostris (less than 1%). Therefore, this species is indeed rare. However, from 2000 to 2003 all the few Patagonian tyrants have been captured from late March and April. Its presence on Navarino Island could have become more frequent due to an extension of its latitudinal range associated with global climate change. However, additional observations made on successive years during late summer and fall suggest an alternative, and perhaps complementary, explanation - a short southward migration performed by some individuals prior to their northward migration. This would be the first time that this phenomena is reported to the Southern Hemisphere. Taken together these two hypotheses could re-enforce on other, whereby the souther limit of post-reproductive southerly migrations could be extending due to global warming.