Effects of forest management on haematological parameters, blood parasites, and reproductive success of the Siberian tit (Poecile cinctus) in northern Finland

This study aims to investigate whether forest management has an effect on reproduction, haematological parameters and blood parasites of breeding Siberian tits Poecile cinctus. Birds breeding in heavily managed forests had significantly higher heterophil and lower lymphocyte concentrations and a higher heterophil/lymphocyte (H/L) ratio than those breeding in moderately managed forests. Although this suggests the increased level of physiological stress in Siberian tits breeding in heavily managed forests, reproductive parameters of the birds did not differ between the two habitats. Nestlings in moderately managed forests had higher total leukocyte and lymphocyte counts than nestlings in heavily managed habitat. The total count of parasites and Leucocytozoon majoris was significantly higher near streams, while the count of Plasmodium circumflexum was higher both near streams and lakes. Although blood parasites were detected in the blood of 80% adult birds, this study did not reveal any parasite-related effects on haematological parameters.