Changes in the corticosterone level in tooting male black grouse (Tetrao tetrix) infected with Eimeria spp.

Abstract

The black grouse (Tetrao tetrix) is a forest bird species critically endangered of extinction. Enclosed aviary breeding is among the measures taken to protect the species. Complex factors can affect its reproduction success, including coccidiosis. In this article, corticosterone level (as a reliable biomarker of stress in birds) and prevalence of Eimeria spp. were determined in male black grouse kept in aviary breeding center before, during, and after the reproductive season (called tooting). The correlation between those parameters was also analyzed. The corticosterone level was measured with noninvasive method in fecal samples in an immunoassay. The prevalence of Eimeria spp. was determined by the qualitative (Fülleborn's flotation) and quantitative method (McMaster's method as modified by Raynaud). Results show the occurrence of 3 species of Eimeria spp. in males: Eimeria lyruri, Eimeria nadsoni, and Eimeria nonbrumpti. Infestation with E. lyruri was chronic in nature. A co-invasion of E. lyruri, E. nadsoni, and E. nonbrumpti was observed during (prevalence 60%) and after the tooting (prevalence 40%). The study showed no statistical changes in the oocysts per 1 g of feces (CORTl) and oocysts per 1 g of feces (OPG) in assays I-III and absence of correlation between CORTl and OPG. The results of this experiment do not support the hypothesis that chronic infestation with Eimeria spp. can induce chronic stress in grouse. But may suggest that males of black grouse are susceptible to infestation with other species of Eimeria spp. during mating season. The knowledge of the level of individual stress and parasitic infestation can be used to take protective actions for this bird species, especially to achieve higher survival rate and bird reproduction rate. Tangible effects will include an assessment of the relationship between individual susceptibility and chronic environmental stress caused by coccidia.