EXPERIMENTAL MANIPULATION OF NEST TEMPERATURE AND RELATIVE HUMIDITY REDUCES ECTOPARASITES AND AFFECTS BODY CONDITION OF BLUE TITS (Cyanistes caeruleus).

Abstract

Studies exploring the effect of microclimatic changes on host-parasite relationships are scarce, however, many models predict changes in the distribution and incidence of diseases associated with climate change. In this study, we increased both temperature and relative humidity in blue tit nest-boxes during the breeding season, trying to discern between the effect of both variables on the abundance of ectoparasites reported in previous studies and, also, on the body condition of the nestlings and adults. Temperature and relative humidity were experimentally increased an average of about 2ºC and 15 units respectively. The abundance of blowfly Protocalliphora azurea pupae was significantly reduced in nests with increased temperature as compared to control nests and nests with increased relative humidity, and was also significantly reduced in nests with increased relative humidity as compared to control nests. The abundance of Dermanyssus spp. mites and Ceratophyllus gallinae flea larvae was significantly reduced in nests with increased relative humidity. However, there was no significant effect of the experiment on flying insect vectors abundance (Blackflies and biting midges.). On the other hand, body condition and mass of nestlings were lower in nests with increased relative humidity and nestlings’ mass was also lower in heated nests. However, the body condition and mass of the adults was not significantly affected by the experiment. In addition, blowfly Protocalliphora azurea pupae and biting midges Culicoides spp. had a significant negative effect on body condition and mass of nestlings and adults. In conclusion, an increase in temperature, on the one hand, and relative humidity, on the other, reduces the abundance of ectoparasites, which suggests that these parasites are sensitive to sudden changes in the microclimate in which they develop. In addition, these fluctuations negatively affect the body condition and mass of blue tit nestlings despite the concurrent decrease of parasites in nests.