A comparison of the Characteristics and Fate of Barrow's Goldeneye and Bufflehead Nests in Nest Boxes and Natural Cavities

摘要

Abstract. Barrow's Goldeneye (Bucephala islandica) and Bufflehead (B. albeola) arecavity-nesting waterfowl that have received considerable attention in studies using nestboxes, but little is known about their nesting ecology in natural cavities. We found largerclutch size, lower nesting success, and different major predators for Barrow's Goldeneyesnesting in boxes versus those nesting in natural cavities, but few differences for Bufflehead.These differencesa re attributedt o the location and physical differencesb etween Barrow'sGoldeneyen est boxes and naturalc avities that affect theirc onspicuousnesst o predatorsa ndconspecific nest-parasitizingfe males. Goldeneyeb oxes were concentratedin highly visiblelocations such as trees at water or forest edge. Natural cavity nests, on the other hand, wereoften abandoned Pileated Woodpecker (Dryocopus pileatus) cavities, which were more dispersedthroughout the forest interior and concealed under dense canopy cover. Buffleheadnatural cavity nests were typically closer to edges, which may account for their similaritywith boxes. We conclude that in some respects, studies of Barrow's Goldeneye that use nestboxes may not be representativeo f birds nesting in naturalc avities, whereast hose of Buffleheadare more likely to be so.