Empirical Measurement of Parasite Transmission Between Groups in a Colonial Bird

Abstract

Abstract. While epidemiological models have suggested that the spread of parasites and infectious diseases often depends critically on the extent of movement by infected individuals between populations, there is little empirical information for any organism on the frequency of between-group parasite transmission or how it varies spatially. The transmission of parasites between discrete social groups or populations may also help determine a host's total parasite or pathogen exposure. We measured the introduction of parasitic bugs (Oeciacus vicarius) into colonies of Cliff Swallows (Petrochelidon pyrrhonota) by transient birds from outside each group. The transmission of bugs increased strongly as the size of a nesting colony increased. More total transients visited the larger colonies, and the direction of change in transient numbers and the numbers of bugs introduced at a site from week to week tended to vary together. Transients at large colonies were more likely to have previously or subsequently visited other large, infested colonies. The greater likelihood of parasites being introduced into larger colonies by transient birds contributes to an increase in parasite load with increased colony size in Cliff Swallows.

Seasonal Variation and Age-Related Correlates of Buggy Creek Virus (Togaviridae) Infection in Nestling House Sparrows

“…Mean (6SE) clutch size for sparrows at latitudes similar to that of our study area is 4.6-4.8 (60.8) eggs, and nestlings fledge at 14-17 days of age (Anderson, 2006). Cliff Swallows are highly colonial, migratory passerines that breed across much of western North America (Brown and Brown, 1995). They build gourd-shaped mud nests on the sides of cliff faces, inside road culverts, and under bridges.…”

“…Buggy Creek virus is ecologically distinct from other alphaviruses in that its vector is the swallow bug, rather than a mosquito (Rush et al, 1980(Rush et al, , 1981. Prevalence of BCRV in swallow bugs averages ,25% of bug pools over the whole study area and across different years (Brown et al, 2001Moore et al, 2007).…”

“…Nests can be closely spaced (often contiguous), and colonies may contain up to 6,000 active swallow nests. The mud nests persist from year to year and are frequently reused by Cliff Swallows for multiple seasons (Brown and Brown, 1996). Swallows arrive in our study area in early to mid-May and typically raise a single brood, with most nestlings fledging by mid-July.…”

“…Numbers in Cliff Swallow colonies can be up to 2,600 bugs per swallow nest (Brown and Brown, 1996) and 2,400 per House Sparrow nest (V. O'Brien, unpubl. data).…”

“…The study area also includes portions of Lincoln, Garden, Duel, and Morrill counties (Brown and Brown, 1996). Each year we monitor approximately 170 Cliff Swallow colony sites that are occupied to varying degrees by Cliff Swallows and/or House Sparrows.…”