Body condition and parasite load predict territory ownership in the Galápagos Hawk

We tested for associations between body condition, territory ownership, and permanent parasite load of Galápagos Hawks (Buteo galapagoensis) on Isla Marchena, Galápagos. Two louse species were collected from most of the 26 hawks sampled: the amblyceran Colpocephalum turbinatum and the ischnoceran Degeeriella regalis. Nonterritorial hawks were in significantly poorer body condition than territorial hawks. Body condition was negatively correlated with the abundance of C. turbinatum. Nonterritorial hawks had significantly higher mean abundances, mean intensities, and median intensities of both louse species than territorial hawks. The amblyceran's mean abundance and intensity were significantly higher than the ischnoceran's. Abundances of the two lice were positively related when the population size of C. turbinatum was <100 individuals, and negatively related when >100 individuals. Parasite load and body condition both predicted territory ownership well.