Breeding Biology of the Svalbard Rock Ptarmigan Lagopus mutus hyperboreus

The breeding biology of Svalbard Rock Ptarmigan was studied by recording moult, body weight, egg laying dates, clutch size, hatching success, brood behaviour and chick growth in 1981 and 1982. Adult hens were heavier and moulted and laid eggs earlier than first year hens. Hens in good condition laid eggs earlier and produced larger clutches with higher hatching success than hens in poor condition. The body weight of hens decreased about 130 g during incubation. Hens with chicks lost weight during the first weeks after hatching, whereas hens without chicks gained weight. The physical condition of hens prior to breeding seemed to be the most important factor in determining chick production.