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

Abstract

Environmental changes can propagate through food webs in complex ways via trophic cascades. In the North American Arctic, hyperabundant populations of geese are causing significant habitat change and the resulting trophic cascades are known to impact plant and invertebrate communities. However, the potential impacts on other tundra‐nesting birds are not fully understood. Here, we evaluate the impacts of light geese (Snow Geese, Chen caerulescens, and Ross’ Goose, Chen rossii) populations on other tundra‐nesting birds, using count data collected during bird surveys conducted at varying distances from light goose colonies across the Canadian Arctic. From a dataset of 920 12–16 ha plots distributed across the Canadian Arctic, we identified 527 that were within 200 km of the mapped extent of known light goose colonies. After accounting for regional variation, we demonstrate that densities of most Cover‐Nesting Shorebirds and passerines are depressed in the vicinity of light goose colonies. We suggest that these trends are the results of the combined effects of goose‐induced changes in habitat and predator–prey interactions. These direct and indirect effects of light geese could be contributing to the declines experienced by some tundra‐nesting bird populations in parts of their range. Ongoing climate‐related changes to habitat, predators, and arthropods could interact with this effect of geese to further alter the suitability of tundra habitats for Arctic‐breeding birds, in additive or even unanticipated ways.

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

“…When faced with locally elevated predator abundances, birds may choose to nest and suffer elevated predation [15], abandon, or forego nesting [56]. Goose-augmented predator communities have already been implicated in the locally depressed densities of shorebirds around goose colonies [52,57,58]). Goose-induced habitat alteration is also well-documented [50,57,59] and may decrease the availability of vegetative concealment that influences nest survival for some species [14,15,60], potentially compounding the effects of geese.…”

Subpopulation contributions to a breeding metapopulation of migratory arctic herbivores: survival, fecundity and asymmetric dispersal

“…Climatedriven alterations in the synchrony of dynamics among subpopulations can pose threats to persistence (Kahilainen et al 2018), while dangers from sudden habitat loss can be mitigated by dispersal (Sardanyés et al 2019). Against a background of ongoing climatic change and landscape alteration (Abraham et al 2005(Abraham et al , 2020, and with high breeding densities compromising integrity of preferred habitats (Ankney 1996, Abraham et al 2012, Flemming et al 2019a, this snow goose metapopulation has experienced marked fluctuations over the last five decades (Fig. 6).…”

“…Their rapid increase in abundance since the 1970s was driven by a nutritional subsidy from agriculture that increased survival outside of the breeding season (Francis et al 1992, Abraham et al 2005). Exponential growth led to high densities of snow geese and consequently intensified herbivory over larger areas in the subarctic and Arctic that altered coastal and inland vegetation and freshwater aquatic communities (Abraham et al 2012, Conkin and Alisauskas 2017, Mariash et al 2018), with potential impacts to sympatric species (Flemming et al 2016, 2019a, b). Concern that the increasing Midcontinent population of snow geese could have negative consequences for Arctic terrestrial ecosystems motivated proposals for population control on a large scale (Ankney 1996, Batt 1997).…”

Habitat alteration and fecal deposition by geese alter tundra invertebrate communities: Implications for diets of sympatric birds

“…However, the potential benefits of enhanced prey availability may also be offset by a reduced availability of preferred shorebird nesting habitat [13] and elevated risk of nest predation [12] within and near goose colonies. Combined, these complex interactions may be contributing, in part, to the spatial [68] and population-level declines documented in northern-breeding shorebirds [1,3,4,69].…”