Site Fidelity: Definition, Measurement And Implications For Population Structure Using Mark-Recapture, Genetic, And Comparative Data In The Hooded, Red-Breasted, And Common Merganser

Abstract

For species that return each year to the same breeding or nonbreeding area, subsequent biological assumptions have included population genetic structure, demographic independence, and possible irreversible extirpation of a site-faithful group due to low immigration. Little is known about patterns of site fidelity, population structure, and migratory patterns of the three species of mergansers that breed and winter in North America: the Hooded Merganser (Lophodytes cucullatus), the Red-breasted Merganser (Mergus serrator ) and Common Merganser (M. merganser). The primary objective of this study was not only to infer general levels of site fidelity with different data types (mark-recapture and genetic), but also to examine the inherent assumptions of site fidelity studies and biases of various methods, such as genetic and mark-recapture. A secondary objective was to provide additional information on the natural history of merganser species in North America. Genetic characteristics of the three merganser species represented a range of subdivision from panmixia to differentiated, likely resulting from species-specific nesting ecologies, life history traits, and responses to historical climate change. These patterns were not always consistent with expectations from other data sets, such as mark-recapture estimates of nest site fidelity. The main conclusions of this study are: (1) the definition and implications of site fidelity must be carefully considered, (2) the assessment of site fidelity is best undertaken with multiple and independent markers, and (3) merganser species in North America offer a wide range of dispersal and migratory patterns, demonstrating the importance of adequately assessing site fidelity and its influence on population structure during both breeding and nonbreeding periods.