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About the Authors:
Charlotte L. Roy
* E-mail: [email protected]
Affiliation: Wetland Wildlife Populations and Research Group, Minnesota Department of Natural Resources, Bemidji, Minnesota, United States of America
John Fieberg
Affiliation: Department of Fisheries, Wildlife and Conservation Biology, University of Minnesota, St. Paul, Minnesota, United States of America
Christopher Scharenbroich
Affiliation: Minnesota Department of Natural Resources, Bemidji, Minnesota, United States of America
Christine M. Herwig
Affiliation: Minnesota Department of Natural Resources, Bemidji, Minnesota, United States of America
Introduction
Managing wildlife to achieve population abundance goals requires sufficient resources for all stages of the annual cycle. The post-fledging period is an important link between the brood-rearing period and recruitment into the breeding population, but remains one of the least studied periods [1]–[3]. Recognition of this information gap has resulted in a proliferation of studies of post-fledging ecology in the last decade, but studies of post-fledging waterfowl remain relatively sparse [4]–[11].
Importantly, habitat requirements may differ for each life-history stage (e.g., post-fledging, breeding, and post-breeding birds) [4], [12]. Differences in habitat use and requirements of juveniles and adults could be due to dissimilarities in diet [13]–[15], avoidance of conflict with conspecific adults [4], [16], the need of young birds to become familiar with the landscape compared to prior knowledge of adults, and differences in the timing of migration [17] and molting chronology [17]–[18]. Differences in habitat use are evident between breeding black ducks (Anas rubripes), which use forested wetland and scrub-shrub habitats, and post-fledging black ducks, which use palustrine emergent and riverine habitats [4]. Like many other species of waterfowl [19], female ring-necked ducks (Aythya collaris) usually leave broods to molt and may undergo a molt migration [17]–[18]. Similarly, adult male ring-necked ducks depart for wintering areas before adult females and juveniles [17]. Differences in the needs of young and adults may even result in trade-offs between offspring survival and future fecundity of adult females [10], [20].
We expected habitat use and movements of newly flighted birds to be dynamic during the fall because they are exploring the landscape for the first time. Few studies have examined movements of post-fledging birds in the context of exploration and preparation for migration [1], [3], [12], [21]–[22], but see [7] and [9], in part because the high mobility and mortality of...