Cerulean Warbler now Endangered

Posted by: Mark Andrew Conboy

Cerulean Warbler
The Cerulean Warbler is now a federally endangered species. QUBS is one place in Ontario where this species is actually still rather common. Photo: Philina English. Click on image to see a larger version.

The Cerulean Warbler (Dendroica cerulea) is emblematic of QUBS and the southern Frontenac Arch. It has been the subject of research at the biological station since the 1990’s and indeed much of the basic natural history knowledge biologists have about this canopy-dwelling bird is the result of field work done right here at QUBS. In addition, hundreds of birders flock to Opincion Road and the area around Frontenac Provincial Park every spring to tick this species off their checklists. Cerulean Warblers are therefore a big deal to those of us who live, work and play in this part of the Arch. It’s therefore worth noting that Cerulean Warblers are now classified as endangered in Canada.

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) is the governmental body that assesses the conservation status of species in Canada and recommends them for protection under federal species at risk legislation. In November COSEWIC reassessed the status of Cerulean Warbler and upgraded it from a species of special concern to an endangered species. The previous designation (special concern) was conferred in 1993 and reassessed as such in 2003. A species of special concern is one that has not yet become so severely imperiled as to be considered threatened (yet another official level of classification) or endangered but could become so if certain risk factors are not mitigated. Classification as endangered is far more serious and means a species is “facing imminent extirpation or extinction” in Canada (see COSEWIC). There are a number of factors that make extirpation a realistic possibility for Cerulean Warblers. Logging, forest degradation and fragmentation in the wintering habitat (the South American Andes), the apparent rarity of suitable breeding habit in Canada, and continued rapid population decline throughout much of its range since the 1960’s are all cause for grave concern.

COSEWIC reports that there are an estimated 1000 Cerulean Warblers breeding in Canada annually. Intensive field work in May and June this year estimated about 100 breeding pairs (200 individuals) at QUBS. If those estimations are correct then lands owned by the biological station are home to 20% of Canada’s Cerulean Warbler population. The importance of our mature forest tracts which, Cerulean Warblers use for breeding cannot be overstated.

Cerulean Warblers are now classified as endangered on a national scale but still only as special concern provincially; even though nearly the entire Canadian population of Cerulean Warblers breeds in Ontario. However, reassessments of species at risk are ongoing at the provincial level so their classification may or (may not) come into line with the federal list. For an explanation of how the federal and provincial species at risk lists differ click | here |.

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One thought on “Cerulean Warbler now Endangered”

  1. The recently released “Management Plan for the Cerulean Warbler (Dendroica cerulea) in Canada” states that there may actually be only about 500 pairs (or possibly less) of Cerulean Warblers breeding in Canada, not up to 1000 as previously reported by COSEWIC in 2003 and on this blog.

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