The role of scratching in the control of ectoparasites on birds

Abstract

Grooming by birds is thought to serve essential anti-parasite functions. While preening has been well studied, little is known about the function of scratching in birds. We conducted a series of experiments to determine the effectiveness of scratching for controlling feather lice (Columbicola columbae) on Rock Pigeons (Columba livia). First, we used a hobbling technique to impair scratching. After 6 mo, hobbled birds had significantly more lice than controls that could scratch. In addition, lice on hobbled birds were concentrated on the birds’ heads and necks (i.e. the regions that birds scratch). Secondly, we tested the role the claw plays in scratching by declawing nestlings. Once mature, declawed pigeons had significantly more lice than control birds with claws. Moreover, lice on declawed birds were concentrated on the head and neck. Next, we tested whether the flange found on the middle claw of many bird species enhances scratching. We experimentally manipulated the flange; however, the number and location of lice on birds without flanges was not significantly different than that on control birds with intact flanges. Finally, we tested whether scratching removes parasites directly or indirectly by “flushing” them onto body regions where they can be preened. When we impaired scratching (with hobbles) and preening (with “bits”) we found that scratching no longer reduced the number of lice on birds. Our results indicated that scratching and preening work synergistically; scratching reduces parasite load by flushing lice onto regions of the body where they can be eliminated by preening.

The exceptional attachment ability of the ectoparasitic bee louse Braula coeca (Diptera, Braulidae) on the honeybee

“…Thorax and abdomen of B. coeca are always elevated above the substrate surface which is very untypical for ectoparasites. Normally, the thorax is dorso‐ventrally flattened and the entire body is kept very close to the surface to reduce drag and to avoid physical removal by the host (Clayton et al, 2010; Goodman et al, 2020), as it is the case for example in the feather lice Columbicola columbae (Linnaeus, 1758) and Campanulotes compar (Burmeister, 1838) (both Insecta: Phthiraptera).…”

Chewing lice of passerine birds in reed beds in Slovakia, with a special focus onPanurus biarmicus

“…One of these factors could be a simple inability to devote sufficient time to comfort behaviour including preening during the period of courtship and breeding season (Price et al, 2003). In general, whenever a bird cannot adequately care for its feathers, not only during reproduction but also, for example, due to illness, beak or leg deformity, the number of lice can increase significantly (Goodman et al, 2020; Loye & Zuk, 1991).…”

Coevolutionary analysis of the Philopteroides Mey, 2004 (Phthiraptera: Ischnocera) parasitizing bulbuls (Passeriformes: Pycnonotidae)

“…Presumably, similar selection pressures operate on lice living on the host's head regardless of host identity, resulting in similar gross morphology in distantly related louse groups. For instance, the main host defense against head lice is foot scratching (Clayton and Cotgreave, 1994), which flushes lice from the head to the body feathers (Goodman et al, 2020). Convergence in morphology among different head louse groups is likely at least in part to withstand foot scratching.…”