Effects of local climatic conditions across years on parasite populations attacking blue tits (Cyanistes caeruleus)

Abstract

Models on climate change have predicted an increase of temperature over the earth’s surface with potential drastic effects on living organisms. We analysed the relationships between climatic variables (temperature, rainfall and wind speed) and the abundance of blood-sucking flying insects (biting midges and blackflies) and nest-dwelling ectoparasites (mites, fleas and blowflies) collected from blue tit control nests during bird breeding seasons for a period of ten years (2008-2017). Average temperature, rainfall and wind speed showed significant differences among years. Temperature and wind speed increased during the period of study while rainfall decrease. Biting midge, blackfly and blowfly abundances increased across years but not flea and mite abundances. Infections by the blood parasites Haemoproteus and Lankesterella but not Leucocytozoon also increased across years. Independently of year variation some parasites were related to climatic variables. For example, biting midge, blowfly, mite and flea abundances were positive and significantly related to average temperature. Changes in climatic conditions across years could therefore affect several parasites of birds but also to birds themselves. Parasites appear to be able to adapt to changes in environmental conditions across years although abrupt changes could severely affect parasite populations