Brood defence in a precocial species: variations in the distraction displays of red grouse, Lagopus lagopus scoticus.

Abstract

Large temporal and spatial variations in both the frequency (percentage of birds) and intensity of distraction displays performed by red grouse were examined in relation to four hypotheses. First, that the display is performed in response to the risk of brood predation was supported by an increase in the frequency of high-risk distraction display with predator pressure, brood size and poor cover (for males but not females) although females disturbed when brooding were not more likely to display than females not brooding. Second, that the frequency of display depends on the predation risk on the parents was supported by a lower level of display by females whose mate was absent and a significant correlation between the levels of display of members of a pair. Third, that the condition of the parent bird influences the frequency of display was refuted since distraction displays in females with reduced parasite burdens and hence improved body condition did not display more than parasitized females. Fourth, that the frequency of display is related to the costs of replacing a brood was not supported since there was no association between frequency of display and either clutch size or brood age. The adaptive value of the large variation in the frequency of brood defence is discussed in relation to predator naivety.