The Cerulean Warbler (CERW) is a Neotropical Migrant that has lost 70% of its population since 1966 and has maintained its decreasing trend. In Costa Rica the threats to CERW involve the loss and fragmentation of habitat due to deforestation and the change in land use for livestock and agricultural activities such as intensive banana and pineapple plantations.

In fall 2005 we discovered the first evidence of unusual numbers of Cerulean Warblers at Las Brisas Nature Reserve on the eastern flanks of Turrialba Volcano, counting 13 individuals in one flock! From that moment on we set out to discover more details about this species in the region: does this occur every year? How much time were these birds spending at the reserve? Does this phenomenon occur anywhere else in Costa Rica?

Through collaborations with organizations including SELVA (selva.org.co) and Birds Canada’s MOTUS Wildlife Tracking System (motus.org) we implemented surveys, banding, and radiotelemetry. The data we have collected so far strongly supports the importance of this region of Costa Rica as a unique fall migration stopover site for Cerulean Warblers and many other Neotropical migrants en route to South America.