CLUTCH DEFENSE BY MALE AND FEMALE WILLOW PTARMIGAN LAGOPUS-LAGOPUS

We analyzed variation in anti-predator behaviors by Willow Ptarmigan d uring the incubation period, in relation to several characteristics of the nest and parents. Defense behaviors were ranked in terms of the r isk taken by parents, i.e. their proximity and conspicuousness to the predator. Defense levels by females increased with stage among first n ests, were higher overall for first than for second nests (renests), i ncreased with the age class of the pair, and correlated positively wit h the female's condition before incubation. Female clutch defense did nor vary with clutch size or any measure of realized nesting success. Male defense levels and the distance males were initially found from t he nest did not correlate with any features of the nest or parents, an d male and female defense levels were not correlated. We suggest that defense by females is related to the value of the present brood, weigh ed against the female's body condition. Together with previous experim ents, our results suggest that males do not fine-tune their level of d efense to the potential contribution of offspring to the parents' repr oductive success.