Weight-related renesting in capercaillie Tetrao urogallus

In a population study during 1979-1988 at Varaldskogen in southeastern Norw ay, 234 capercaillie Tetrao urogallus nests and broods were classified as f irst nests or renests. Of the females that had their first nest depredated, 9-87% (mean 36%) renested. Over a 6-year period, autumn brood production i ncreased from 30 to 38% due to renesting. Renesting is physically demanding for the females; the eggs in renests are fewer and smaller, and the female s take more and longer recesses than when incubating first nests. All the f emales incubated their first nests till the eggs hatched or the nest was de predated. Two of the renesting females took more and longer recesses until they gave up their nests. The ability to renest seems to be weight-related, as yearling females, which weigh less than adult females, did not renest, and the weight of adult females on leks was highest in the two years when m ost renesting occurred. The female will renest if the nest is depredated du ring the first three days of incubation. Each of the following 19 days, all years combined, a mean of 26% of females who lost their nests renested. Ca percaillie renesting was related to the vole cycle; it was highest in the y ear before the small rodents peaked and decreased through the vole crash an d the year after.