Chewing Lice From the Wings of Migrating Shorebirds: Diversity, Host Specificity, and Associations With Host Body Condition

Ectoparasites may negatively affect their hosts throughout life, especially during breeding and other energetically demanding periods. In birds, feather‐feeding ectoparasites may reduce host condition and performance during seasonal migrations. This study aimed to investigate the diversity of wing‐collected chewing lice (Phthiraptera) and their associations with two groups of avian hosts, Charadriidae and Scolopacidae. We examined 1403 individuals from 20 migratory shorebird species to estimate louse prevalence and abundance, and a subsample of lice was identified using microscopic examination and DNA barcoding. In total, 26 lice species were identified across all hosts. Measures of louse prevalence and abundance varied widely among host species (9%–94% infested individuals and 0.2–26.4 lice per individual). Infestation differed significantly between age classes (higher in first‐year than in adult birds) and between habitats used by birds during migration (higher at an artificial reservoir than in a natural river valley). Notably, louse abundance was negatively associated with condition (fat load and size‐corrected body mass) in a time‐constrained long‐distance migrant, the wood sandpiper Tringa glareola , whereas no such pattern was found in a short‐distance migrant with fewer time constraints during migration, the common snipe Gallinago gallinago . Our findings suggest that chewing lice may negatively influence avian hosts during critical stages of the annual cycle, such as migration, but these effects may be modulated by host behavior, particularly migration strategy.