Action: Reduce nest ectoparasites by providing beneficial nesting material
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A randomised, replicated and controlled experiment in Canada found lower numbers of some, but not all, parasites in nests provided with beneficial nesting material, but that there was no effect on fledging rates or chick condition.
Some birds incorporate sprigs of volatile-rich plants into their nests, possibly as a method of reducing parasite burdens. Adding similar material may therefore represent a low-cost method of reducing the impact of parasites on nestlings.
Supporting evidence from individual studies
A randomised, replicated and controlled experiment in 2000 at four sites in New Brunswick and Nova Scotia, Canada (Shutler & Campbell 2007) found that the number of purple martin fleas Ceratophyllus idius was significantly lower in tree swallow Tachycineta bicolor nests with fresh yarrow Achillea millefolium foliage added every two days whilst clutches were being laid, compared to control nests with no added foliage (419 fleas/nest for 23 experiomental nests vs. 773 fleas/nest for 44 controls). There were no corresponding differences in the number of blowfly Protocalliphora spp. pupae (3.3 and 2.5 pupae/nest for experimental and control nests respectively), nestling mass (23.5 g in experimental nests vs. 23.8 g in controls), nestling leukocyte profiles, or proportion of young fledging (5.3 fledglings/nest for experimental nests vs. 5.1 fledglings/nest for controls). The authors speculate that adult tree swallows may increase provisioning rate to compensate for flea parasitism.