Variable reproductive effort for two ptarmigan species in response to spring weather in a northern alpine ecosystem

• Published in: Journal of Avian Biology
• Main Authors: Wilson, Scott, Martin, Kathy
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2010
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Yukon; Lagopus muta; rock ptarmigan
• Online Access: http://dx.doi.org/10.1111/j.1600-048x.2009.04945.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1600-048X.2009.04945.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1600-048X.2009.04945.x

Predicting how animal populations respond to climate change requires knowledge of how species traits influence the response of individuals to variation in anuual weather. Over a four‐year study with two warm and two cold years, we examined how sympatric rock ptarmigan Lagopus muta and white‐tailed ptarmigan L. leucura in the southern Yukon Territory respond to spring weather in terms of breeding phenology and the allocation of reproductive effort. The onset of breeding was approximately synchronous; for each one‐degree rise in spring temperature, mean breeding dates of rock and white‐tailed ptarmigan advanced by about 2.7 and 4 days respectively. Although onset of breeding was similar, the two species differed in their reproductive effort. As breeding was delayed, average first clutch sizes of rock ptarmigan declined from 9.4 to 5.8 eggs over the breeding period, while those of white‐tailed ptarmigan only declined from an average of 7.8 to 6.8. Rock ptarmigan were also less likely to re‐nest if their first clutch was lost to predators and as a consequence they had shorter breeding seasons. White‐tailed ptarmigan produced about 25% more offspring annually than rock ptarmigan and contributed more young through re‐nesting. While white‐tailed ptarmigan had higher annual reproductive output, adult rock ptarmigan had a 20–25% higher annual survival rate, which may indicate a reproduction–survival trade‐off for the two species. These results show that even within the same location, closely related species can differ in how they allocate effort as environmental conditions fluctuate.