The traveling insects: Ectoparasite records on Hawaiian wedge-tailed shearwaters, Ardenna pacifica, with a focus on Phthiraptera.

Abstract

Ectoparasites were collected from 35 live Ardenna pacifica Gmelin chicks (wedge-tailed shearwaters) in October and November 2022 using a fumigant and plastic bag collection method. Additionally, 206 naturally-deceased post-fledging grounded birds were sampled opportunistically over eight years (2015-2023), with fledglings collected during the fledging season (November - December) and adults collected during the breeding season (May - October). Eight species of Phthiraptera were documented in samples from these birds. While four species (Halipeurus mirabilis Thompson, Trabeculus hexakon Waterson, Austromenopon paululum (Kellogg & Chapman), and Naubates harrisoni Bedford) were present on chicks that had fledged and subsequently "fallen out", only H. mirabilis was present on chicks that had not yet fledged. Saemundssonia puellula Timmermann, and Longimenopon puffinus Thompson, were only collected from adult fallout birds in the spring. Of the recorded ectoparasites, four species (H. mirabilis, T. hexakon, A. paululum, and N. harrisoni) constituted a species assemblage that did not significantly vary from year to year. Lice abundance and diversity varied across bird age classes (pre-fledging chicks, fledged chicks, adults), but a significant increase in lice abundance during 2015 coincided with a major El Niño event, suggesting that the ectoparasite loads may be affected by external conditions such as air temperature. There was also a significant increase in lice prevalence between pre-fledging and fledged chicks, which likely coincided with the lice hatching. These results underscore the consistency of lice assemblages on A. pacifica, while highlighting the influence of endogenous (e.g., bird life history) and exogenous (e.g., weather) ecological factors.