Population status

Black-billed Cuckoo
(Coccyzus erythropthalmus)

The Breeding Bird Survey (BBS) is the most reliable survey for monitoring the Black-billed Cuckoo in Canada, providing good coverage of the breeding population. However, local Black-billed Cuckoo populations are known to fluctuate markedly with insect outbreaks, and the wide fluctuations in the annual estimates make it difficult to determine an overall trend for Canada. BBS results suggest an increasing population, but the wide variation among years (see Canada graph in table below) makes it clear that the species' population status depends as much on annual fluctuations as any clear long-term trend. The graph shows a generally negative trend between 1970 and the early 1990s, followed by a period of relative stability until the unusually high counts in recent years. The national trend appears to be overly influenced by the large, but very imprecise, positive trend in the Boreal Softwood Shield Bird Conservation Region (BCR), which again is itself influenced by the unusually high count in 2016. Trend estimates derived using an alternative statistical method suggest a long-term negative trend (-2.1% / year; Smith, A.C., ECCC, pers. comm). This slope-based estimate places emphasis on the overall slope and not the estimates' end-points and is therefore less influenced by the recent spike in population. Relying mainly on the slope-based estimate, the species' population status in Canada is perhaps best assessed as having experienced a moderate decrease relative to 1970. However, the magnitude of that decrease is not yet larger than the variation among years. At the regional level, results suggest varying levels of decline in all BCRs, except the Boreal Softwood Shield BCR. Results for all BCRs are shown below, regardless of reliability. The large fluctuation in recent years suggest that the Black-billed Cuckoo is currently at an acceptable level relative to its national population goal, though it has been below these levels for the past 25 years (see Canada graph below).

Population goal and acceptable levels of variation

Breeding Bird Survey (BBS) - Canadian analysis

Additional information on: Breeding Bird Survey (BBS) - Canadian analysis

References

• Hughes, J.M. 2001. Black-billed Cuckoo (Coccyzus erythropthalmus), The Birds of North America Online (A. Poole, Ed.). Cornell Lab of Ornithology, Ithaca, New York. Hughes, J.M. 2001. Black-billed Cuckoo (Coccyzus erythropthalmus), The Birds of North America Online (A. Poole, Ed.). Cornell Lab of Ornithology, Ithaca, New York. (Link)
• Jauvin, D. and M. Bombardier. 1996. Black-billed Cuckoo. pp. 578-581 In: The Breeding Birds of Québec: Atlas of the Breeding Birds of Southern Québec. Gauthier, J. and Y. Aubry (eds). Association québecoise des groupes d'ornithologues, Province of Québec Society for the Protection of Birds, Canadian Wildlife Service, Environment Canada, Québec Region. Montréal, QC. Jauvin, D. and M. Bombardier. 1996. Black-billed Cuckoo. pp. 578-581 In: The Breeding Birds of Québec: Atlas of the Breeding Birds of Southern Québec. Gauthier, J. and Y. Aubry (eds). Association québecoise des groupes d'ornithologues, Province of Québec Society for the Protection of Birds, Canadian Wildlife Service, Environment Canada, Québec Region. Montréal, QC. (Link)