Hyperabundant herbivores limit habitat availability and influence nest site selection of Arctic‐breeding birds

Abstract

Understanding an organism's habitat selection and behavioural flexibility in the face of environmental change can help managers plan for future conservation of that species. Hyperabundant tundra‐nesting geese are influencing Arctic environments through their foraging activities. Goose‐induced habitat change in Arctic wetlands may influence the availability of habitat for numerous shorebird species that breed sympatrically with geese. We explore whether goose‐induced habitat alteration affects shorebird breeding density and nest site selection. Using habitat data collected at sites with High, Moderate and Low goose influence, and samples collected during two periods separated by 11 years, we document the habitat characteristics influenced by geese. We describe the habitat characteristics preferred by shorebirds and relate their availability to goose influence and shorebird density. Finally, we examine whether shorebird nest site selection has changed over time and whether shorebirds select nest sites differently in habitat influenced by geese. We document spatial and temporal changes in sedge meadow habitat and lateral concealment relating to goose influence. The availability of sedge meadow habitat and the degree of lateral concealment declined with increasing goose influence, and also declined at two sites over the 11 years of the study. Densities of both cover‐ and open‐nesting shorebirds were highest where goose influence was lowest. At sites with Low goose influence, cover‐nesting shorebirds selected nest sites with more sedge meadow and concealment than at sites with Moderate and High goose influence, presumably because these high‐quality sites were more available. Synthesis and applications. Intensive foraging by a colony of hyperabundant geese is limiting the availability of preferred nesting habitat and densities of sympatric‐nesting shorebirds. Where goose‐induced habitat alteration is pronounced shorebird species that select concealed nest sites are nesting in areas with lower concealment and less sedge meadow. Studies examining the degree to which these effects scale up to impact the population sizes of declining shorebirds should be considered a future research priority. Moreover, management strategies for geese should incorporate the habitat needs of sympatric species and reinvigorate efforts for goose population reduction in order to achieve the population targets articulated by management agencies.

Broad‐scale changes in tundra‐nesting bird abundance in response to hyperabundant geese

“…, Flemming et al. ), thereby limiting the availability of habitat used by some shorebirds for nesting. For instance, near a light goose colony in Cape Churchill, Manitoba Sammler et al.…”

“…White‐rumped Sandpiper ( Calidris fuscicollis ), which were influenced up to 13 km from colonies, can be generalist in their nest‐site selection, nesting in habitats ranging from damp sedge‐dominated areas to drier sedge and scrub‐dominated sites (Flemming et al. ). Both Red‐necked Phalarope ( Phalaropus lobatus ; Walpole et al.…”

“…In the vicinity of goose colonies, Cover‐Nesting Shorebirds and passerines may be choosing not to nest or suffering higher nest predation rates resulting in lower overall nest densities (Flemming et al. ).…”

“…Intensive grazing and grubbing in and around light goose colonies can, however, reduce the proportional cover of graminoid (grass and sedge spp.) habitats (Jefferies et al 2006, Flemming et al 2019) and the height of vegetation (O et al 2006(O et al , Flemming et al 2019, thereby limiting the availability of habitat used by some shorebirds for nesting. For instance, near a light goose colony in Cape Churchill, Manitoba Sammler et al (2008) found densities of Cover-Nesting Shorebirds and passerines werẽ 60% lower in goose-altered habitat than in intact sedge meadow habitat.…”

“…Total population estimates that include breeding and non-breeding birds show larger increases, and suggest that the population may now be greater than 15 million individuals . In some areas, these hyperabundant populations of light geese have significantly altered their breeding habitats (Kotanen and Jefferies 1997, Jefferies et al 2006, Flemming et al 2019, and these changes could cascade through other components of Arctic ecosystems.…”