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COSEWIC Assessment and Update Status Report on the Cerulean Warbler in Canada

Limiting Factors and Threats

Factors thought to be limiting Cerulean Warbler populations are well documented in Robbins et al. (1992) and Hamel (2000a).

Breeding Grounds

  1. loss of mature deciduous forest
  2. fragmentation of remaining deciduous forest
  3. changes in forest silviculture practices that result in fewer forests reaching maturity
  4. loss of important tree species due to disease (e.g. oak wilt) and infestation (e.g. gypsy moth)
  5. environmental degradation (e.g. acid rain and stream pollution)
  6. brood-parasitism by Brown-headed Cowbirds.

In Canada, factors 1,2, and 5 are probably the most important.

During Migration

Very little information exists on Cerulean Warbler migration patterns and habitat requirements. Presumably, they need safe stopover locations close to the coast of the Gulf of Mexico and on the Caribbean coast of Central America. Cerulean Warblers fall victim to light pollution during migration. For example, 93 Cerulean Warblers were killed at a Leon County, FL, TV tower between 1956 and 1966 (Stoddard and Norris 1967).

Winter Grounds

  1. loss of humid montane forest
  2. fragmentation of remaining montane forest
  3. use of a narrow elevational range