Nonideal habitat selection by a North American cavity excavator: pecking up the wrong tree?

Abstract

Nonideal habitat selection occurs when preferred habitat attributes differ from those associated with increased fitness. These mismatches have been widely studied in open cup-nesting birds, but the relationship between habitat-associated preferences and fitness in cavity-nesting birds has received relatively little attention. We studied patterns of preference and fitness during 2006–2007 in an Idaho, USA, population of Red-naped Sapsuckers ( Sphyrapicus nuchalis S.F. Baird, 1858). Using a suite of nonparametric tests, we examined the associations between habitat attributes and both nesting-area preferences and nest productivity (number of fledglings per pair) across four spatial scales. Nest productivity was associated with tree- and cavity-scale attributes, whereas preference was associated with attributes of home ranges. Live trees and southeasterly oriented cavities had higher nest productivity but were not preferred. Microclimates in nests with these attributes may enhance nestling survival, whereas nonpreference for these attributes may be due to energetic constraints in some individuals. Additional studies comparing patterns of nonideal habitat selection between open-cup nesters and cavity nesters should advance our understanding of how life-history characteristics influence selection patterns.