High goose abundance reduces nest predation risk in a simple rodent-free high-Arctic ecosystem

Abstract

Breeding geese are the preferred prey of the Arctic fox Vulpes lagopus in the high-Arctic Svalbard archipelago. According to the apparent competition hypothesis (ACH), less abundant prey species (e.g. ptarmigan, waders and small passerines) will experience higher predation rates when breeding in association with the more common prey (geese), due to spill-over predation by the shared predator. As many of these less abundant species are endemic and/ or red-listed, increased predation can have negative repercussions on their populations. We used a one-year baited artificial nest study to assess relative nest predation risk on Svalbard Rock Ptarmigan Lagopus muta hyperborea, small waders (Purple Sandpiper Calidris maritima, Dunlin Calidris alpina, plovers Charadrius spp., and phalaropes Phalaropus spp.) and Snow bunting Plectrophenax nivalis in two study locations contrasted by nesting density of Arctic breeding geese (Pink-footed Goose Anser brachyrhynchus and Barnacle Goose Branta leucopsis). We predicted higher predation risk for the less abundant species in the study location with higher goose abundance. However, we found that relative nest predation risk was lower in the study location with higher goose abundance, thus being compatible with apparent mutualism and / or prey swamping mechanisms. Our results contrast with those from more structurally complex Arctic ecosystems and suggest that allochtonous subsidies from temperate ecosystems structure the predation pattern in this high-Arctic tundra ecosystem.

Spatio-temporal responses of predators to hyperabundant geese affect risk of predation for sympatric-nesting species

“…However, [52] found effects on artificial nest predation greater than ~10km away suggesting our scale may be adequate. Overall, these studies support our results and further highlight that predator-prey relationships may vary among sites and regions as indicated by the lower predation rate [elevated survival probability) in the presence of nesting geese reported elsewhere [19,20].…”

“…Predator populations may exhibit numerical responses (increases in abundance) to lemming peaks [16,17] and more specifically, aggregative responses [17] to goose colonies, in both cases resulting in higher incidental predation of nearby shorebird nests. Alternatively, predators may switch their search efforts between prey items (functional response; [18], or become satiated during lemming peaks or within goose colonies, alleviating predation pressure on shorebird nests [19,20]. Local or regional changes in the availability of lemmings and/or geese could therefore dramatically affect the risk of predation and reproductive success of tundra-nesting shorebirds.…”

Contrasting consequences of climate change for migratory geese: Predation, density dependence and carryover effects offset benefits of high‐arctic warming

“…a subset of the total Svalbard breeding population) were included ( N sval,ad ), to test for density‐dependent effects (see Layton‐Matthews et al, for details). The Arctic fox is the main predator of eggs and goslings, but also adults (Eide, Stien, Prestrud, Yoccoz, & Fuglei, ; Fuglei, Øritsland, & Prestrud, ; Pedersen et al, ). Consequently, gosling survival can be strongly influenced by fox predation (Loonen et al, ; Morrissette et al, ).…”

Upland rush management advocated by agri‐environment schemes increases predation of artificial wader nests

“…Eggs were placed in the scrape which was lined with a handful of dried vegetation; artificial nests were thus similar in appearance and location to real wader nests including those of snipe and curlew (Cramp & Simmons, 1982; Supporting Information, Figure ). To aid relocation, a blue wooden golf tee was discreetly placed flush to the ground and a 60 cm bamboo cane topped with red tape was placed 10 m away in a random direction (Smith et al ., 2007; Pedersen et al ., 2018); the use of such canes does not alter wader nest predation rates (Zámečník, Kubelka & Šálek, 2018). The mean distance (95% CI) between nests within a field was 80.97 m (75.80–86.14 m), and from each nest to the nearest field boundary was 50.66 m (47.49–53.84 m).…”

“…Nests were checked every 5 days (AE1 day in both cases depending on weather conditions to avoid disturbing real wader nests in these fields during inclement weather). Nests were classified as predated if at least one egg was missing, damaged or outside the nest scrape in the immediate surroundings (Smith et al, 2007;Pedersen et al, 2018). Trampled nests (7.1% of 184 nests; crushed eggs with contents remaining in the shell or on surrounding ground) were excluded from further analyses and trampling rates were similar in treatment (7.1% of 98 nests) and control fields (7.0% of 86 nests).…”