Patterns of Hatching Success in Subarctic Birds

Data from a single subarctic locality are used to test Ricklef's general conclusions regarding patters of nesting mortality in arctic birds. They provide additional evidence that hatching success is greater among arctic than among Temperate Zone passerines. However, they do not indicate important differences in hatching success between ground—nesting birds with precocial young and those with altricial young, nor do they confirm that predator—induced nesting losses are density dependent in arctic regions. Predation may be a more important cause of nesting failure than Ricklefs acknowledged. Differences in our findings in part from differences in sampling methods. further analyses of nesting morality should combine data from studies of selected species with those from regional studies.