Timing of breeding and offspring number covary with plumage colour among Gyrfalcons Falco rusticolus

• Main Authors: Jeff A. Johnson, Kurt K. Burnham
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Arctic; colour polymorphism; indi; Greenland; Falco rusticolus
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.472.3371; http://www.higharctic.org/wp-content/uploads/2011/12/Johnson-Burnham-2013.pdf

Plumage colour variation exists among Gyrfalcons throughout their Arctic and sub-Arctic circumpolar distribution, ranging from white through silver and grey to almost black. Although different colour variants coexist within many populations, a few geographical regions, such as northern Greenland, possess a single variant, suggesting that local environments may influence plumage colour variation. In central-west Greenland (66.5–67.5°N), where multiple colour variants exist, white male Gyrfalcons fathered sig-nificantly earlier clutches than grey males. No significant association was observed between female colour and lay date. However, significantly more offspring were pro-duced by both male and female white Gyrfalcons than by grey variants when controlling for lay date, and silver Gyrfalcons produced an intermediate number of offspring for both sexes. This pattern was further supported by breeding plumage colour pairings. Grey females paired with grey males nested significantly later in the season and produced fewer offspring than those paired with white males, whereas no difference in lay date or offspring number was found between white males paired with white or with grey females. The difference in the number of offspring produced at each nest-site was also