Effects of Weather on Hazel Grouse Reproduction: An Allometric Perspective

We analyzed the effects of weather during prelaying, incubation, and early chick periods on the reproductive success of Hazel Grouse Bonasa bonasia in southwestern Finland (14 years) and southern Poland (6 years). Reproductive success was most clearly correlated with weather during the prelaying period in both areas, with days of precipitation correlating negatively and temperature positively. We suggest that the availability of nutritionally rich food and the ability of the females to obtain it during the prelaying period, when the females are rapidly gaining mass and forming eggs, determine in large part the reproductive success of Hazel Grouse. A literature review suggested that this is generally true for small grouse species. The larger species, which have greater endogenous reserves and invest relatively less in their clutches, are less affected by prelaying weather conditions. Chicks of larger species have higher growth rates and energy requirements, however, which is probably the reason why the reproductive success of the larger species is more affected by weather during the early chick period.