Nest boxes increase reproductive output for Tree Swallows in a forest grassland matrix in central British Columbia

PLoS One. 2018 Oct 10;13(10):e0204226. doi: 10.1371/journal.pone.0204226. eCollection 2018.

Abstract

Secondary cavity-nesting birds depend on tree cavities for nesting and roosting, but many studies of these birds are conducted using nest boxes. Implementation of effective conservation strategies for cavity-nesting species such as nest-site supplementation requires careful comparisons of fecundity and other vital rates for birds using both natural and artificial nest site types. We compared breeding phenology, clutch and brood sizes, and fledging success of Tree Swallows (Tachycineta bicolor) nesting in tree cavities and nest boxes during 2001-2003 in British Columbia, Canada. Swallows using nest boxes initiated egg-laying and hatched young at approximately the same time as those in tree cavities (2 June, 23 June, respectively). Female Tree Swallows in boxes laid larger clutches (5.9 ± 0.9 eggs, N = 76) than those in tree cavities (4.2 ± 1.6 eggs, N = 67). The mean number of nestlings hatched was greater in nest boxes (5.2 ± 1.1 nestlings, N = 67) than in tree cavities (2.6 ± 2.0 nestlings, N = 58). Pairs in boxes were over twice as successful in producing fledglings (93.4%; 57 of 61 pairs fledged > 1 young) than those in tree cavities (35.8%; 19 of 53 pairs). Of those successful nests, pairs nesting in boxes fledged 5.1 ± 1.1 young (N = 57), whereas those in tree cavities fledged 3.5 ± 1.2 young (N = 18). Because cavities in nest boxes averaged 60% larger in volume and 1.8 cm wider internally than tree cavities, we suggest that increased reproductive output was correlated with boxes enabling a larger clutch size. In previous research, we found that Tree Swallows were a poor competitor with other cavity-nesting passerines for tree cavities. The addition of nest boxes may serve as an effective way to supplement local reproduction for secondary cavity-nesting bird populations by reducing competition for limited nest sites. This is especially true in regions where the availability of natural nesting sites is highly variable, and where species compete with many other cavity-nesting passerines using a similar ecological niche and nesting cavities.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • British Columbia
  • Ecosystem
  • Female
  • Grassland
  • Nesting Behavior / physiology*
  • Reproduction / physiology*
  • Swallows / physiology*

Associated data

  • Dryad/10.5061/dryad.g85t15k

Grants and funding

This research was funded by The Natural Sciences and Engineering Research Council of Canada (NSERC Special Strategic Grant to KM), Environment and Climate Change Canada, Sustainable Forest Management Network, and Forest Renewal BC. ARN was supported by a post-doctoral fellowship from NSERC CREATE, post-graduate scholarships from NSERC, a Four Year Doctoral Fellowship and a Pacific Century Graduate Scholarship from the University of British Columbia, and research grants from the Forest Investment Account Forest Science Program (Graduate Student Pilot Project and Mountain Pine Beetle Initiative Graduate Research Fund), the Southern Interior Bluebird Trail Society, and a Junco Technologies Award from the Society of Canadian Ornithologists and Bird Studies Canada. KEHA was supported by NSERC (Industrial Post-graduate Scholarship sponsored by Lignum Ltd, and Doctoral Post-graduate Scholarship), Science Council of British Columbia, Van Dusen Graduate Fellowship in Forestry, North American Bluebird Society, Brink/McLean Grassland Conservation Fund, Canfor Corporation Fellowship in Forest Ecosystem Management, Bert Hoffmeister Scholarship in Forest Wildlife, and a University of British Columbia Graduate Fellowship. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.