Effects of a novel ectoparasite on condition and mouth coloration of nestling barn swallows

Abstract

Parasites have profound and widespread implications for the ecology and evolution of hosts, and human activity has increased the frequency of interactions between hosts and parasites that have not co-evolved. For example, by building habitat attractive for nesting, humans might have facilitated range expansion by cliff swallows (Petrochelidon pyrrhonata) and barn swallows (Hirundo rustica) in North America, concurrently allowing a haematophagous ectoparasite of cliff swallows, the swallow bug (Oeciacus vicarious), to infest the nests of barn swallows. We found that in barn swallow nests infested with swallow bugs, nestlings weighed less and had lower haematocrit, and the within-brood variation in body mass and tarsus length was higher. Information about these negative effects might be available to parents via mouth coloration, a condition-dependent component of the begging signal. We found that nestlings from infested broods had lower-intensity carotenoid-based and ultraviolet mouth colours, although most elements of colour were unrelated to parasites. Host switching by the swallow bug offers excellent opportunities to understand the direct and indirect effects of a novel parasite and might also afford insights into how parasites cope with selective pressures exerted by closely related hosts with key ecological differences.

Experimental ectoparasite removal has a sex‐specific effect on nestling telomere length

“…Imperfect repair of DNA damage induced by oxidative stress could then shorten telomeres. In addition, parasites can stunt body growth (Hoi et al, 2018; as seen in birds: Pryor & Casto, 2017; Romano et al, 2021; but see Dugas & Border, 2022a) in multiple ways. Parasites may limit resource allocation (Lochmiller & Deerenberg, 2000) toward body growth via consumption of blood or by increasing metabolic rates during infection (Cutrera et al, 2022; Lind et al, 2020; Ots et al, 2001; but see Smith et al, 2017).…”

“…Ectoparasitism in particular may also cost time and energy via increased grooming (Mooring et al, 1996; Simon et al, 2005), although this removal of parasites could aid host nutrition (Johnson et al, 2010). Interestingly, parasitism is also linked to low quality ornaments in young birds, which may influence resource allocation among siblings from parents (Dugas & Border, 2022a, 2022b; Romano et al, 2021). Such stunted growth could theoretically decrease oxidative stress and slow telomere loss (Alonzo‐Alvarez et al, 2007; Monaghan & Ozanne, 2018; but see Vedder et al, 2017); however, slowed growth accompanied by other parasite‐induced oxidative stress may still lead to telomere loss.…”