Flocking behaviour does not favour high chewing lice load in shorebirds.

As shorebirds show a high variability in the flocking behaviour among species from solitary ones to species forming flocks of hundreds of individuals, they offer a good opportunity to test if the proximity of individuals in highly gregarious species increases the risk of horizontal ectoparasite transmission in comparison with solitary species. We investigate whether there exists a higher ectoparasite load in gregarious shorebirds compared to solitary ones at Salinas del Cabo de Gata, Almeria, Spain. Seven species of shorebirds (Scolopacidae and Charadriidae) were captured with mist-nets during the night. Ectoparasites were estimated by means of visual examination of seven body regions and differentiated in five levels of infestation. Flock size was divided into three categories: solitary species, species forming flocks up to 99 individuals and species forming flocks of more than one hundred. Based on the application of a phylogenetic comparative method, our results show that the abundance of chewing lice is not related with flocking behaviour.