PAIRING STATUS OF MALE WILLOW PTARMIGAN - IS POLYGYNY COSTLY TO MALES

Polygyny appears to be beneficial for males, yet comprises less than 2 0% of all pair bonds formed by male willow ptarmigan, Lagopus lagopus. This study tested whether polygyny was costly to males. Polygynous ma les defended larger territories than monogamous and unpaired males and were more likely to be adults than males of other pairing status. Pai ring status changed throughout the life of some males. Naturally polyg ynous males were in better body condition in the early part of the bre eding season than other male types, and unpaired territorial males had the lowest condition. Naturally polygynous males had a tendency to lo se the least amount of body mass over the season. Naturally polygynous and monogamous males had larger combs than males of other pairing sta tus. Polygynous males had higher reproductive success, similar surviva l and similar future reproductive success compared with monogamous and unpaired territorial males. Even in years of high clutch predation, a nd accounting for higher levels of extra-pair paternity in the clutche s of polygynous males, naturally polygynous males were more successful than other male types. A group of experimentally polygynous males (i. e. they became polygynous because of a male removal experiment) had si milar reproductive success to naturally polygynous males, but lower ov erwinter survival than other male types. These results suggest that na turally polygynous males were older and 'better' than other males and this allowed them to defend larger territories and attract more than o ne female. Males that became polygynous only as a result of our experi ment, however, appeared to suffer costs from this increased breeding e ffort. (C) 1997 The Association for the Study of Animal Behaviour.