By Pablo “Chespi” Elizondo, Costa Rica Bird Observatories Executive Director
Background: Klamath Bird Observatory and USDA Forest Service Redwood Sciences Laboratory have a long-running international capacity building program that is supported by the Forest Service’s International Programs. Costa Rica Bird Observatories is one of the most notable success stories. Emerging from monitoring effort that began over 20 years ago in Torutgeuro, Costa Rica Bird Observatories is now a fully-fledged and sustainable program. Costa Rica Bird Observatories includes 13 field locations where long-term monitoring efforts are ongoing, a support network for coordinated banding efforts throughout Costa Rica (Red de Anilladores de Aves de Costa Rica), and an international capacity building program of its own, that is working towards developing monitoring efforts throughout central and south America as part of the Western Hemisphere Banding Network (Red de Anilladores de Aves del Hemisferio Occidental).
The White-eyed Vireo (Vireo griseus) is a migratory bird that breeds in the southeastern United States from New Jersey west to northern Missouri and south to Texas and Florida. This species winters in eastern Mexico, northern Central America, Cuba, and the Bahamas.
White-eyed Vireos rarely occur in Costa Rica. Garrigues and Dean (2007) indicated that there were very few records for Costa Rica, “… one record for the Puerto Viejo de Sarapiquí area (Jan 2004); and one report of a bird seen and heard in Monteverde (March 1997).” eBird only shows two other records (one from 2012, and one from 2010) (eBird 2013).
This year at Costa Rica Bird Observatories we captured three individual White-eyed Vireos in Tortuguero, one at our Airport station (Nov-19-2012) and two at the Caribbean Conservation Corp station (Nov-11 and Dec-14 2012). Two of the individuals were unknown age, but suspected to be young birds, and one was confirmed to be a hatch year bird by observed molt limits between newly grown formative (i.e., 1st adult) and retained juvenal (i.e., fledgling) feathers. There have been additional White-eyed Vireo observations in Tortuguero this winter; Daryl Logh, a well know birdwatcher from Casa Marbella, has seen this rare vireo a couple of times this year.
Ornithologists suggest that individual birds that stray beyond their wintering range (i.e., vagrants) such as White-eyed Vireos in Costa Rica, are predominantly young birds. Our capture data collected over the past 20 years in Tortuguero provide plenty of additional evidence that rarities and vagrant birds are usually younger individuals. For example, 6 out of 6 Black-throated Blue Warbler and 8 out of 8 Yellow-breasted Chats, both rarities to the Caribbean slope of Costa Rica and captured at our Totuguero stations, have been young birds.
eBird. 2013. eBird: An online database of bird distribution and abundance [web application]. eBird, Ithaca, New York. Available: http://www.ebird.org. (Accessed: April 4, 2013).
Garrigues, R. and R. Dean (2007). The Birds of Costa Rica. Ithaca, NY, Cornell University Press.
Hopp, Steven L., Alice Kirby, and Carol A. Boone. 2010. White-eyed Vireo (Vireo griseus), Neotropical Birds Online (T. S. Schulenberg, Editor). Ithaca: Cornell Lab of Ornithology; retrieved from Neotropical Birds Online: http://neotropical.birds.cornell.edu/portal/species/overview?p_p_spp=506316