The Costa Rican rainy season marks the time of year when a large majority of Neotropical migratory birds arrive to the Osa.  Some birds arrive as early as August such as the Yellow Warbler (Setophaga petechia), and the Black-and-white Warbler (Mniotilta varia) while others such as the Ovenbird (Seiurus aurocapilla) and the Summer Tanager (Piranga rubra) typically arrive a bit later from mid to late September. Other species simply pass through the Osa such as the Swainson’s Thrush (Catharus ustulatus), the Scarlet Tanager (Piranga olivacea) and the Swainson’s Hawk (Buteo swainsoni) on their way to their wintering grounds in Panama and South America.  These are just a few examples amongst dozens of migratory birds that over-winter on the Osa.

Several species that are found on the Osa during the northern winter are suffering population declines and considered to be of conservation concern such as the Golden-winged Warbler (Vermivora chrysoptera), Prothonotary Warbler (Protonotaria citrea), the Yellow-billed Cuckoo (Coccyzus americanus) and the Olive-sided Flycatcher (Contopus cooperi) for example.  These birds are on our own watchlist of species here on the peninsula and are closely monitored through our avian monitoring program.  Any information gained through sightings, longterm scientific monitoring or through our citizen science activities such as the Audubon Christmas Bird Count (CBC) is disseminated to the international avian science community through the Audubon CBC database and ebird, as well as the local community of the Osa Peninsula.

Please visit our research page for more information on past and upcoming monitoring projects, International Migratory Bird Day Festival the first Saturday in March, and other activities.  To report sightings or have any migratory bird questions please contact us.

Featured Image Photo Credit: Black-and-white Warbler (Mniotilta varia) by Don Filipiak at

Photo Credit: Painted Bunting by Daniel Hernandez.