The Cerulean Warbler is a species of special conservation concern and considered “Near Threatened” by the International Union for Conservation of Nature (IUCN) because its population has decreased by more than 70% between 1970 and 2014 (http://pif.birdconservancy.org/ACAD/Database.aspx). This steep population decline is attributed mainly to the loss, degradation, and
and fragmentation of their habitat on both their breeding and wintering grounds, as well as stopover sites used during migration.
In Canada, agriculture as well as the logging industry have affected the habitat quality of the Cerulean Warbler and the greatest long-term challenge seems to be the lack of knowledge and studies about this warbler’s basic ecology and this is an obstacle for conservation efforts.
In the sites in the United States with the highest numbers of Cerulean Warblers, open-pit mining for coal extraction represents one of the most significant threats to habitat loss, especially in the Appalachian region. To adapt it to our local context, mining, as an activity that generates a high environmental and health cost, is similar to pineapple production in Costa Rica. By 2001, almost 1000 km² were designated for mining in West Virginia (Wells, 2007), a state whose territory is like that of Costa Rica; this is equivalent to approximately half of Costa Rica's Greater Metropolitan Area. In addition to mining, deforestation, and changes in land use in habitats of importance to warblers also add to the list of threats.
To these anthropogenic reasons we must also add natural causes that increase their vulnerability such as nest parasitism by the Brown-headed Cowbird (Molothrus ater) which affects their survival, and migration which exposes them to predation, mortality and stress (COSEWIC, 2003, p. 11).
On their wintering sites in the tropics the threats to CERWs also involve the loss and fragmentation of habitat due to deforestation and the change in land use for livestock and agricultural activities such as intensive coffee and coca plantations.
COSEWIC (2003). COSEWIC assessment and update status report on the Cerulean Warbler Dendroica cerulea in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa.
Wells, J. V. (2007). Cerulean Warbler (Dendroica cerulea). En Birder’s Conservation Handbook (329-332). Princeton University Press.