Brood size manipulation modifies the intensity of infection by Haematozoa in female Blue Tits Parus caeruleus

We have studied the effects of a brood size manipulation on the infection by blood parasites in a Blue Tit Parus caeruleus population in central Spain. Overall, 98% of the birds were infected by at least one parasite species. Haemoproteus majoris was the most prevalent parasite (92%), followed by Trypanosoma spp. (48%), Leucocytozoon majoris (44%), and Hepatozoon parus (15%). An experimental brood size manipulation was carried out by means of adding two chicks. Nestlings from enlarged group were lighter than reduced and control groups. Also females from enlarged group had less weight than those from reduced and control groups. Results shown a higher intensity of infection by Trypanosoma and Leucocytozoon in females, but not in males, from enlarged group. Experimental brood size reduction had not detectable effects on infection status in either sex. There were no associations between parasite infection and parental body measurements. The experiment modified the intensity of infection only in some haemoparasite species, suggesting that different haemoparasite species seem to have a different response to the same manipulation of bird reproduction

Fargallo J.A. & Merino S, ARDEA 87 (2): 261-268