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Providing evidence to improve practice

Individual study: Removing blowfly Protocalliphora spp. larvae from eastern bluebird Sialis sialis and tree swallow Tachycineta bicolor nests has limited impacts on nestling weights and does not alter survival rates

Published source details

Roby D.D., Brink K.L. & Wittmann K. (1992) Effects of Bird Blowfly Parasitism on Eastern Bluebird and Tree Swallow Nestlings. The Wilson Bulletin, 104, 630-643


This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.

Remove ectoparasites from nests to increase survival or reproductive success Bird Conservation

A replicated, controlled experiment during 1987-8 in New York State, USA (Roby et al. 1992) found that survival rates and fledging age of both eastern bluebird Sialis sialis and tree swallow Tachycineta bicolor chicks did not differ significantly between nests where blowflies Protocalliphora spp.were experimentally removed, control nests or nests with blowfly larvae added (bluebirds: 78% survival for removal nests, n = 25 vs. 87% for controls, n = 26; fledging age of 18 days for both treatments; tree swallows: 97% for removal nests, n = 29 vs. 90% for addition nests, n = 30 and 94% for controls, n = 32; fledging ages of 19.4, 19.7 and 19.8 days for removal, addition and control nests respectively). Bluebird nestlings were significantly heavier at 14 days old in removal nests, but the authors note that this was a small change (averages of 28.2 g in removal and 27.0 g in control nests).