Effects of nest-box environment on fledgling success rate and pathogen load

Nest boxes have been used for many decades as tools for conservation and to study avian population dynamics. Plastic is increasingly used as a material for nest boxes, but no studies have investigated effects of this different material. Two consecutive studies were conducted to investigate effects of nest-box environment on nidicolous parasites, bacteria and fungi, as well as nest success, in blue tits Cyanistes caeruleus and great tits Parus major. The first compared microclimate and parasite and pathogen load in plastic and wooden nest boxes. The second tested the nest protection hypothesis - that birds naturally incorporate aromatic herbs into nests to decrease nest parasites and pathogens - by comparing parasite and pathogen load in plastic nest boxes to which aromatic or non-aromatic plant material was added. No significant difference in nest-box temperature or relative humidity was found between plastic and wooden boxes. Wooden boxes, however, contained 30-fold higher numbers of fleas and a higher total bacterial load on chicks. Fledging success for blue tit broods was significantly higher in wooden boxes. Parasites and bacteria did not decrease by the inclusion of aromatic herbs. The results increase the evidence base for nest-box design in support of plastic, which can provide an appropriate alternative nest-box material to wood, with apparently no difference in microclimate and no increase in the load of measured parasites and pathogens.

Automated summary

This study investigated the effects of plastic and wooden nest boxes on the nest environment, parasite and pathogen load, and nest success in blue tits and great tits. The results showed that there was no significant difference in microclimate and parasite load between plastic and wooden boxes. However, wooden boxes had higher numbers of fleas and a higher bacterial load on chicks, and blue tit broods had higher fledging success in wooden boxes. Adding aromatic herbs did not decrease parasites and bacteria. This study supports the use of plastic as an alternative nest-box material.