Risky business in Georgia's wild birds: contact rates between wild birds and backyard chickens is influenced by supplemental feed

Abstract

Backyard chickens are increasingly popular, and their husbandry varies widely. How backyard chickens are housed may influence the accessibility of chicken feed and water to wild birds, and thus, the contact rates between both groups. Increased contacts have implications for pathogen transmission; for instance, Newcastle disease virus or avian influenza virus may be transmitted to and from backyard chickens from contaminated water or feed. Given this potentially increased pathogen risk to wild birds and backyard chickens, we examined which wild bird species are likely to encounter backyard chickens and their resources. We performed a supplemental feeding experiment followed by observations at three sites associated with backyard chickens in North Georgia, USA. At each site, we identified the species of wild birds that: (a) shared habitat with the chickens, (b) had a higher frequency of detection relative to other species and (c) encountered the coops. We identified 14 wild bird species that entered the coops to consume supplemental feed and were considered high-risk for pathogen transmission. Our results provide evidence that contact between wild birds and backyard chickens is frequent and more common than previously believed, which has crucial epidemiological implications for wildlife managers and backyard chicken owners.

Keywords: Avian influenza virus; Newcastle disease virus; backyard chickens; contact rate; wild birds.

Fig. 1.

One hour-long point counts were performed from February through May 2018 at each of the three points highlighted in the upper left county map. Farm S is represented by the top point (Jackson county), Farm C is represented by the middle point (Athens-Clarke county) and Farm L is represented by the bottom point (Oconee county). The inset image (lower right) demonstrates the location of each county (in red), in North Georgia. Each farm is indicated by a point on the inset image.

Fig. 2.

Schematic of how observations were performed at each farm. Each D_x corresponds to a distance class. D₁ demarks the inside of the coop (the square on right of the coop) and wire mesh enclosure (the rectangle to the left of the coop), D₂ correlates to the perimeter of the coop, D₃ is 10–25 m from the coop perimeter, D₄ is 25–50 m and D₅ is >50 m from the coop. The black arrow denotes the observer point of view. During observations, each bird was placed into one of the five distance classes based on distance observed from the coop: (1) within the coop (distance class one, D1), (2) from the edge of the coop to <10 m (distance class two, D2), (3) between 10 and 25 m from the coop (distance class three, D3), (4) between 25 and 50 m from the coop (distance class four, D4) and (5) >50 m from the coop (including flyovers) (distance class five, D5).

Fig. 3.

Seasonal breakdown of the frequency of detection for high-risk species. On the y-axis, FOD stands for the frequency of detection, and on the x-axis are the four-letter alpha codes for each species. The blue denotes the per cent frequency of detection in the winter, and the pink denotes the per cent frequency of detection in the spring. For each species, the alpha codes are as follows: BLJA, Blue Jay; CACH, Carolina Chickadee; CARW, Carolina Wren; CHSP, Chipping Sparrow; EAPH, Eastern Phoebe; EATO, Eastern Towhee; HOFI, House Finch; MODO, Mourning Dove; MYWA, Myrtle Warbler; NOCA, Northern Cardinal; SOSP, Song Sparrow; TUTI, Tufted Titmouse; WBNU, White-breasted Nuthatch; WTSP, White-throated Sparrow.