A Comparison of Losses in Artificial and Naturally Occurring Capercaillie Nests

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Abstract
During 1980-84 I studied the fates of 831 artificial nests, 96 naturally occurring capercaillie (Tetrao urogallus) nests, and 12 black grouse (T. tetrix) nests at Varaldskogen, Norway. In 4 of the 5 years artificial nests with poor cover had higher loss rates than natural capercaillie nests. In 1981 natural capercaillie nests had a higher loss rate than artificial nests with poor cover. In 1981 the loss rate of natural capercaillie and black grouse nests increased as the season progressed, while the loss rate of artificial nests was constantly low. Capercaillie nests were probably detected by scent by predators most years, while predators oriented mainly by sight probably robbed most artificial nests. Loss of artificial nests was not an index to the loss of capercaillie nests. In artificial nests the losses depended on nest cover; however, natural capercaillie nests in poor cover had higher losses than nests in good cover only during 1 year.