Cohabitation with farm animals rather than breeding effort increases the infection with feather‐associated bacteria in the barn swallow Hirundo rustica

Abstract

Feather-associated bacteria are widespread inhabitants of avian plumage. However, the determinants of the between-individual variation in plumage bacterial loads are less well understood. Infection intensities can be determined by ecological factors, such as breeding habitat, and can be actively regulated by hosts via preening. Preening, yet, is a resource intensive activity, and thus might be traded-off against reproductive investment in breeding birds. Here, we studied barn swallows Hirundo rustica to assess the bacterial cost of reproduction in relation to nesting site micro-habitats. Barn swallows prefer to breed in the company of large-sized farm animals, although the presence of mammalian livestock in barns assures a warm and humid micro-climate that favours bacterial proliferation. Thus, we experimentally manipulated brood sizes of birds breeding in barns with, or without, farm animals and measured total cultivable bacteria (TCB) and feather-degrading bacteria (FDB) from the plumage. We found that the abundance of feather-associated bacteria (i.e. both TCB and FDB) in females, but not males, breeding in barns with livestock were significantly higher than in conspecifics breeding in empty barns. Plumage bacterial loads, however, were not affected by brood size manipulations in either sex. In addition, we report a negative relationship between both TCB and FDB and hatching date in females, and several sex and seasonal differences in plumage bacterial abundances. Our study is the first to show that breeding micro-habitat (i.e. livestock co-tenancy) has consequences for the abundance of feather-associated bacteria.

Selection on multiple sexual signals in two Central and Eastern European populations of the barn swallow

“…Barn swallows in the Czech population breed in small colonies of up to 40 pairs, where the competition for nest sites can be low due to the large number of empty nests built over years and because the microhabitat of breeding sites from the same barns are similar, which render the nests similarly attractive. In the Romanian population, however, barn swallows usually breed solitarily in separate stall buildings, and birds preferentially occupy nests within barns populated with farm animals (Fülöp et al, ), possibly because of more favorable microhabitat conditions. The difference in colonial behavior between the two populations may explain the more intense selection on tail length for early laying in first‐time breeding males from the Romanian population, where the number of favorable breeding sites is probably more limited, because experienced birds arrive first and occupy most of the preferred nest sites (PLP, pers.…”

“…Nests from the Czech population were located at two isolated farms (Šaloun, Lomnice nad Lužnicí and Hamr, Lužnice; Petrželková et al, ) where barn swallows breed in colonies of up to 40 pairs. Birds from Romania were located in stall buildings where they breed mostly solitarily or in small colonies of up to ten pairs (Fülöp, Vágási, & Pap, ). The number of nests we monitored in both populations varied between 50 and 120 each year.…”

The landscape of fear in cattle farms? How the presence of barn swallow influences the activity of pest flies

“…Having co-evolved with humans since the onset of agriculture and settlements, breeding barn swallows are strongly related to open habitats and farmlands, where they feed over hayfields, crops or pastures (Turner, 2010). The warm and humid environment of cattle sheds can favour feather-associated bacteria in swallows (Fülöp et al, 2017), but the presence of stabled animals and the availability of pastures nearby the shed create an environment particularly suitable to the species (Ambrosini et al, 2002(Ambrosini et al, , 2011Sicurella et al, 2014).…”