Early breeders choose differently - Refining measures of habitat quality for the yellow-bellied sapsucker (Sphyrapicus varius), a keystone species in the mixedwood boreal forest

PLoS One. 2018 Sep 12;13(9):e0203683. doi: 10.1371/journal.pone.0203683. eCollection 2018.

Abstract

Despite the prevalent use of nest-site selection studies to define habitat quality for birds, many studies relying on use-availability analysis have found poor correlations between selected vegetation and reproductive success. Using 3 years of data from northeastern British Columbia (2007-2009), we determined timing of breeding from hatching dates and contrasted the nest-site selection of earlier (n = 22) with later-nesting pairs (n = 36) of yellow-bellied sapsuckers (Sphyrapicus varius), because early breeders were expected to be more reproductively successful. We then compared these choices with those identified from use-availability analysis, and determined whether reproductive performance (fledgling production) was related to selected vegetation. None of the vegetation characteristics selected for nest sites from available vegetation predicted reproductive performance. Earlier-nesting pairs fledged more young on average than later breeders (4.41, SE = 0.18 versus 3.92, SE = 0.16), and chose less decayed aspen trees for nesting, that were surrounded on average by 3 times the number of food trees (paper birch, Betula papyrifera). Potential preference for birch trees was masked in the use-availability analysis, because the selection rate was dominated by the choices of the larger number of later-nesting pairs. Similarly, the majority (69%) of nest cavity entrances faced south, but earlier breeding pairs excavated northward-oriented cavities more frequently than did later breeding pairs, which strongly predicted their higher fledgling production. To our knowledge, our study is the first to compare the choices of early versus later breeders to test the efficacy of use-availability studies in defining habitat quality. We found that use-availability analysis was inadequate for determining vegetation characteristics related to reproductive performance. In contrast, measuring the distinct preferences of earlier breeders resulted in an improved ability to measure habitat quality and explain the spatial distribution of yellow-bellied sapsuckers, a keystone species of the mixedwood boreal forest.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Birds / growth & development
  • Birds / physiology*
  • Ecosystem*
  • Models, Biological
  • Nesting Behavior / physiology*
  • Taiga

Grants and funding

Funding for this research was provided by the FIA Forest Science Program of British Columbia to K. Squires and by CanFor Ltd to F. Bunnell. K. Squires was supported by a Canada Graduate Scholarship from the Natural Sciences and Engineering Research Council and a Mitacs Accelerate scholarship with the West Moberly First Nation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.