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Fourteen years of nesting data show how spring weather shapes turkey vulture breeding in Saskatchewan

Turkey vulture chick with white down and dark developing wing feathers standing on a tree
Research · Reproduction & development

A 14-year study of turkey vultures (Cathartes aura) breeding near the northern edge of the species’ range has described nesting phenology, clutch size, productivity and nestling sex ratios in Saskatchewan, Canada. The article was published online on 13 January 2026 in Journal of Raptor Research and assigned to the June issue.

Researchers analysed 833 nesting attempts recorded from 2003 to 2016. Pairs breeding farther north within Saskatchewan began laying later than pairs at lower latitudes, showing a geographic gradient in breeding timing even within the study population.

Year-to-year weather was also associated with timing. Mean annual hatching dates were negatively correlated with average April temperatures, so warmer Aprils were associated with earlier hatching. The authors identify annual weather as an important influence on breeding phenology in this northern migratory population.

Two eggs were the most common clutch size. Of the 833 nesting attempts, 78% contained two eggs. Two-egg clutches were initiated earlier in the season than single-egg clutches, while estimated hatching asynchrony of zero to four days fell within the range reported elsewhere for the species.

Productivity was similar to that reported for turkey vultures breeding farther south. Successful nests produced an average of 1.7 fledglings, leading the authors to conclude that the northern Saskatchewan population does not show reproductive characteristics expected of an ecological population sink — a population that cannot sustain itself without immigration.

The researchers also extracted DNA from feathers of 578 nestlings to determine sex. The overall nestling sex ratio did not differ significantly from an equal ratio, either among years or across the population. Male nestlings nevertheless tended to hatch earlier in the season than females.

The researchers could not calculate population growth precisely because nest sites were not monitored systematically early in the breeding cycle. Some early failures may therefore have been missed, which could make the productivity estimate too high.

Sources and image credit

  1. Wiebe, K. L., & Stoffel, M. J. (2026). Reproductive parameters and breeding phenology of turkey vultures at the northern extent of their geographic range. Journal of Raptor Research, 60(2), 1–8.

Image: Warren Garst — juvenile turkey vulture photographed in July 1965; Colorado State University Libraries / Digital Public Library of America / Wikimedia Commons; representative juvenile image, not a nestling from the Saskatchewan study; cropped to 16:9. · CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/ · Source

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