New York Natural Heritage Program
Cerulean Warbler
Setophaga cerulea (Wilson, 1810)

Conservation Overview [-]
Cerulean Warblers face numerous threats on their breeding and wintering grounds including conversion of forest for coffee and cocoa production, forest fragmentation, incompatible forest management practices, and high predation rates (Buehler et al. 2013). Conservation in New York, where Cerulean Warblers breed, focuses on maintaining heavily forested landscapes. Populations in New York largely occur on protected lands where conversion of mature forest is limited. However, forest management on private lands and maintaining heavily forested landscapes surrounding known breeding populations are still of concern (McGowan and Corwin 2008). Wood et al. (2013) developed guidelines for forest management practices that promote habitat for this species within heavily forested landscapes that are available to public land managers and private landowners.

Threats [-]
Threats to the persistence of Cerulean Warblers exist in their winter and breeding habitat, as well as during migration (Buehler et al. 2013). Habitat loss is a primary concern. On wintering grounds in the tropics, the clearing of land for coffee and particularly cocoa production are significant threats. In the core of the breeding range in the central Appalachians, threats include mountaintop removal coal mining and hydraulic fracturing. During migration, Cerulean Warblers suffer high mortality from collisions with human structures (Klem 2008). In New York, the largest populations occur on protected lands; however, habitat loss, including incompatible forest management practices and conversion and fragmentation of mature forest, may still pose a threat on private lands (McGowan and Corwin 2008). High nest predation rates are limiting population growth in the Midwest, and even in the Northeast and Appalachian Mountains where nest success is higher, recruitment may not be adequate to compensate for mortality (Buehler et al. 2008). Known nest predators include chipmunks, snakes, and birds; particularly blue jays (Cyanocitta cristata) (Boves and Buehler 2012; Buehler et al. 2013).

Conservation Strategies and Management Practices [-]
Maintaining large blocks of unfragmented mature forest is the primary management considerations for this species, particularly in riparian areas and on uplands and ridgetops with oak-hickory or mixed mesophytic forest. Maintaining heavily forested landscapes surrounding known breeding populations is also a concern (Buehler et al. 2008).
Forest management strategies were recently developed to maintain and enhance habitat for this species in the Appalachian Mountain Bird Conservation Region, which includes much of south central and south western New York (Wood et al. 2013). The recommended management practices are largely based on the results of the Cooperative Cerulean Warbler Forest Management Project, a robust study replicated at seven locations across four Appalachian states within the core of the Cerulean Warbler breeding range. The results of this project suggest that in mature forest with high Cerulean Warbler densities (>5 territories /25 acres) and high nest success, not harvesting is the best option to retain successful breeding populations. The study also found that in actively managed oak forests that exist within a highly forested (>70% with a 6-mile radius) landscape, retaining residual basal areas of ~40-90ft2/acre after harvest creates a forest structure that is generally favorable for Cerulean Warblers. In managed stands, retaining large diameter trees and dominance of white and chestnut oak is important; other important tree species include hickories and sugar maples. Harvest practices have not been tested in landscapes with lower forest cover and recommendations for these areas may differ (Wood et al. 2013).

Development and Mitigation Considerations [-]
Maintaining mature forest habitats and landscapes with a high composition of forest is recommended. See conservation and management strategies for specific compatible forest management practices.

Research Needs [-]
Further research is needed to examine the long-term response of Cerulean Warbler populations to varied harvest regimes as well as to study post-fledgling survival in diverse habitats and under different management practices (Buehler et al. 2013). Also, work is needed on the wintering grounds to determine winter survivorship, relative abundance by habitat, and to identify conservation focal areas and threats facing them (Buehler et al. 2013). In New York, a site-specific monitoring program targeting the largest populations statewide is needed (Rosenberg et al. 2000).

Regional Conservation Needs [-]
Conservation of the largest forest blocks and encouragement of forest regeneration in the lake plain region of New York is a primary concern (NYSDEC 2005). This region supports two of the largest populations of Cerulean Warblers in the state (Rosenberg et al. 2000). Continued fragmentation by human development will likely affect the landscape-level composition of forest which could impact populations, even those on protected lands (NYSDEC 2005).