LAUSR

Ectoparasites are ubiquitous symbionts of most vertebrates, and some species can have severe fitness consequences for their host (Lehmann 1993). Host species in turn have evolved a broad array of immunological, morphological, and behavioral traits to combat ectoparasites (Owen et al. 2010, Clayton et al. 2010). Birds, in particular, display numerous traits for controlling ectoparasites, including the production and application of waxy oil secretions from the uropygial gland onto their feathers, specialized pectinate claws for grooming the head and neck (present in some families), an overhanging upper maxilla (present in many species), as well as behavioral traits such as sunning, dust-bathing, anting, and a suite of feather-preening behaviors among others (see Clayton et al. 2010 for review of ectoparasite defenses in birds). Birds devote a significant proportion of their daily time budget to maintenance behaviors (9.2% on average across taxa), much of which involves preening (Cotgreave and Clayton 1994). The time investment and the evolution of specialized traits underscore the importance of controlling ectoparasite numbers. Despite their pervasiveness, there is substantial variation in ectoparasite prevalence and burdens within and among host species. Environmental conditions such as aridity/humidity can impact ectoparasite infections, as can habitat type and a bird’s ecological niche (Moyer et al. 2002). Birds also differ in feather structure, presence of pectinate claws, and the effectiveness of their bill in removing ectoparasites, as well as in the amount of time they spend performing self-maintenance (Clayton et al. 2010). Some anti-ectoparasite traits are shared across most or all taxa (scratching the head and neck with claw), whereas others are more limited (crushing ants and rubbing formic acid on the feathers) (Clayton et al. 2010). Here I describe a unique preening behavior that putatively employs multiple tactics to help rid the birds of ectoparasites. On two occasions (July 14th, 2015 and July 4th, 2017), I observed a green heron (Butorides virescens) at the same retention pond in Champaign, Illinois, USA, exhibiting what appears to be a unique form of preening behavior. In both instances, the bird was initially performing routine preening behavior, including drawing body and flight feathers through its bill, and scratching its head with the pectinate claw. After these classic maintenance behaviors, the bird lifted one wing up, spread all the feathers out while holding the wing horizontally, and cocked its head underneath to look up at the feathers while they were backlit (Fig. 1). In both instances the bird performed this behavior in bright, midday light. While the bird held its wing out, it could be seen visually inspecting the feathers from below, and occasionally picking at them. It did not do any of the classical preening behaviors such as drawing feathers through its bill or