Habitat Change at a Multi-Species Goose Breeding Area on Southampton Island, Nunavut, Canada, 1979–2010

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2020 Habitat change at a multi-species goose breeding area on Southampton Island, Nunavut, Canada, 1979–2010

Kenneth F. Abraham, Christopher M. Sharp, and Peter M. Kotanen

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Habitat change at a multi-species goose breeding area on Southampton Island, Nunavut, Canada, 1979–2010

Kenneth F. Abraham, Christopher M. Sharp, and Peter M. Kotanen

Abstract: Foraging by hyperabundant Arctic-nesting geese has significant impacts on vegetation of Arctic and subarctic coastal lowlands, but long-term data sets documenting these changes are rare. We undertook intensive surveys of plant communities at East Bay and South Bay, Southampton Island, Nunavut, Canada, in July 2010. Lesser Snow Geese, Ross’s Geese, Cackling Geese, and Brant nest and rear young at these sites; the first three have experienced up to 10-fold increases since the 1970s. At East Bay, we found significant declines in graminoids over the 31-year span, as well as significant declines in lichen and willow cover, and significant increases in rock cover. Transect data indicated graminoids were present at only 15%–36% of points at East Bay, whereas at South Bay, graminoids were present at 28%–90% of points. Moss was more prominent in transects at South Bay than at East Bay (40%–85% vs. 19%–42%), but quadrat data indicated much more of the moss cover at South Bay apparently was dead than at East Bay. Puccinellia phryganodes (Trin.) Scribn. & Merr. exceeded 1% in only two transects. Our data demonstrate a striking decline of preferred forage species and increases in non-forage cover, consistent with the hypothesis that changes resulted from persistent long-term foraging by the four species of breeding geese between spring arrival and late summer departure.

For personal use only. Key words: East Bay, foraging, geese, herbivory, Southampton Island, vegetation change.

Résumé : La recherche de nourriture par les oies en surabondance qui nichent dans l’Arctique a des impacts significatifs sur la végétation des basses terres côtières arctiques et subarctiques, mais les ensembles de données à long terme qui documentent ces changements sont rares. Les auteurs ont entreprisdesétudesintensivessurlescommunautés végétales à East Bay et South Bay, sur l’île de Southampton, au Nunavut, au Canada, en juil- let 2010. Les petites oies des neiges, les oies de Ross, les bernaches de Hutchins, et les bernaches cravants nichent et élèvent leurs petits sur ces sites; les trois premières ont vu leur population se multiplier par dix depuis les années 1970. À East Bay, ils ont observé un déclin significatif des graminoïdes sur une période de 31 ans, de même qu’un déclin significatif de la couverture en lichens et en saules et une augmentation significative de la couverture rocheuse. Les données des transects indiquaient que les graminoïdes n’étaient présents

Arctic Science Downloaded from cdnsciencepub.com by 142.112.211.151 on 12/03/20 que sur 15 à 36 % des points à East Bay seulement, alors qu’àSouthBay,lesgraminoïdes étaient présents sur 38 à 90 % des points. La mousse était plus abondante dans les transects àSouthBayqu’àEastBay(40à85%comparativementà19à42%),maislesdonnéesdes quadrats indiquaient qu’une plus grande couverture de mousse de South Bay était

Received 4 December 2018. Accepted 13 December 2019. K.F. Abraham. Ontario Ministry of Natural Resources and Forestry, Trent University, DNA Building, 2140 East Bank Drive, Peterborough, ON K9L 1Z8, Canada. C.M. Sharp.* Trent University, DNA Building, 2140 East Bank Drive, Peterborough, ON K9L 1Z8, Canada. P.M. Kotanen. Department of Ecology & Evolutionary Biology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON L5L 1C6, Canada. Corresponding author: Peter M. Kotanen (e-mail: [email protected]). *Current address: Canadian Wildlife Service, 335 River Road, Ottawa, ON K1A 0H3, Canada. This article is open access. This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0). http://creativecommons.org/licenses/by/4.0/deed.en_GB.

Arctic Science 6: 95–113 (2020) dx.doi.org/10.1139/as-2018-0032 Published at www.nrcresearchpress.com/as on 14 January 2020. 96 Arctic Science Vol. 6, 2020

apparemment morte comparativement à East Bay. Puccinellia phryganodes (Trin.) Scribn. & Merr. dépassait 1 % sur deux transects seulement. Les données des auteurs démontrent un déclin frappant des espèces fourragères préférées et un accroissement de la couverture non fourragère, ce qui est cohérent avec l’hypothèse que les changements résultent de la recherche persistante de nourriture par les quatre espèces d’oies reproductrices entre leur arrivée au printemps et leur départ à la fin de l’été. [Traduit par la Rédaction] Mots-clés : East Bay, recherche de nourriture, oies, herbivorie, île de Southampton, changement de végétation.

Introduction Populations of many Arctic-nesting goose species around the world have increased four- to six-fold since the early 1970s (Madsen et al. 1999; Fox and Madsen 2017; Fox and Leafloor 2018a, 2018b). Increased survival rates and reproductive success linked to use of abundant foods available on agricultural lands are primary drivers of these trends (Abraham et al. 2005a; Fox et al. 2005; Fox and Abraham 2017). These increases have resulted in persistent, long-term, high foraging pressure by Arctic geese on the plant communities in low-lying wetland regions of the subarctic and Arctic in North America used for all stages of their breeding season (spring staging, nesting, brood rearing, and moult), especially where the hyperabundant and highly colonial Lesser Snow Goose (Anser caerulescens (Linnaeus, 1758)) and Ross’sGoose(Anser rossii Cassin, 1861) occur in high densities (Abraham et al. 2012). The cumulative impacts of high foraging pressure by geese on the coastal ecosystems of western and southern Hudson Bay–James Bay, Canada, are well documented (Kerbes et al. 1990; Jefferies and Rockwell 2002; Jefferies et al. 2003, 2006; Abraham et al. 2005a, 2012; Kotanen and Abraham 2013). Changes to these ecosystems, which serve as major staging areas for spring migration of the mid-continent population of Lesser Snow Geese and Ross’sGeeseaswellasbreedingareasforseveralLesserSnowGoosecolonies,include For personal use only. significant loss of saltmarsh communities, especially those dominated by swards of Puccinellia phryganodes (Trin.) Scribn. & Merr. and Carex subspathacea Wormsk., two species of graminoids found in intertidal and supratidal saltmarshes throughout the Arctic, which are major food plants for Arctic geese in spring and summer (Cargill and Jefferies 1984). These swards have been converted to mosaics of patchy vegetation and bare sediments (Srivastava and Jefferies 1995; Jefferies and Rockwell 2002; McLaren and Jefferies 2004; O et al. 2005). Other changes are reduction of cover of the predominant freshwater sedge Carex aquatilis Wahlenb., an important forage species, and creation of large areas of exposed peat (Kerbes et al. 1990; Kotanen and Jefferies 1997), death of willows and birches due to hypersalinity (Iacobelli and Jefferies 1991; Srivastava and Jefferies 1995, 1996), and soil com-

Arctic Science Downloaded from cdnsciencepub.com by 142.112.211.151 on 12/03/20 paction (Jefferies et al. 2003; McLaren and Jefferies 2004). Impacts at certain central and high Arctic locations have also been studied. In Queen Maud Gulf, central Canadian Arctic, Alisauskas et al. (2006) examined vegetation in relation to density and years of occupancy of nesting Lesser Snow Geese and Ross’s Geese and reported lower vegetation cover, richness and diversity in plant communities occupied by nesting geese for more than 20 years. At the same site, Didiuk and Ferguson (2005) described extensive areas of exposed peat within nesting colonies due to grubbing activities of those species, and Conkin and Alisauskas (2017) extended that work and used land cover classification to show that wet meadows, a preferred goose feeding habitat, had been converted to exposed peat between 1988 and 2011. Gauthier et al. (2004) summarized long term monitoring of Greater Snow Geese (Anser caerulescens atlanticus (Kennard, 1927)) and local plant communities at Bylot

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Island, Nunavut, in the eastern Canadian Arctic, where they showed that goose grazing consistently removed about 40% of graminoid standing crop in polygon fens each year, varying with the size of the local goose population. They saw no increasing trend in grazing impact over 13 years but did find changes in plant species composition and production (e.g., reduced Eriophorum L. production) compared to ungrazed fens. At these two high latitude sites, geese primarily use freshwaterhabitatsandarepresentforbreedingonly when they are at the northern terminus of migration. The condition of habitats in the majority of the eastern Arctic range of the Lesser Snow Goose is largely unknown (Abraham et al. 2012; Arctic Goose Joint Venture 2018:butsee Fontaine and Mallory 2011; Flemming et al. 2019). As research at other sites indicates, differences in local history (e.g., colony size, years of occupancy) and local habitat characteristics (e.g., latitude, saltwater vs. freshwater communities) can be very important, inhibiting generalization from other locations; similar impacts should not be assumed without direct evidence. In addition, mostsuchstudiesarebasedonrelativelybrief (1–10 years) experiments or observations; data sets documenting long-term change (e.g., Gauthier et al. 2004; Conkin and Alisauskas 2017)fromhigherlatitudesarerare. Eastern Arctic Lesser Snow Goose breeding areas also are used by Ross’sGoose,Brant (Branta bernicla (Linnaeus, 1758)), Cackling Goose (Branta hutchinsii (Richardson, 1832)), and by many other migratory bird species (Abraham and Ankney 1986; Fontaine and Mallory 2011), which may be vulnerable to goose-inducedhabitatchangedirectlyorindirectly (Flemming et al. 2016). Many shorebird species (e.g., Red Knot (Calidris canutus rufa (A. Wilson, 1813)) and Ruddy Turnstone (Arenaria interpres (Linnaeus, 1758)) have declined (Andres et al. 2012)overthesameperiodthatLesserSnowGoose,Ross’sGoose,and Cackling Goose populations have increased. Although the relationship between altered plant communities resulting from high goose foraging pressure and shorebird population declines is not completely understood, it has been suggested that connections between reduced vegetation cover and vigour (height and density), invertebrate food resources,

For personal use only. and increased predator pressure may be contributing factors (Leafloor et al. 2012; Flemming et al. 2016), and Flemming et al. (2019) demonstrated a negative relationship between degree of goose influence and sedge meadow availability and nest concealment among some species. Our study is a response to the need for more information about the current conditions and characteristics of migratory bird habitats and plant communities in the eastern Canadian Arctic (Arctic Goose Joint Venture 2018). We undertook intensive ground surveys of the plant communities in a multi-species goose breeding area at East Bay and South Bay on Southampton Island, Nunavut, Canada, in the summer of 2010. We chose the East Bay site because unpublished data, reports, and journals from studies in 1979 and 1980 (KFA) were available for comparison of some components of the ecosystem, providing a unique opportunity for us to describe Arctic Science Downloaded from cdnsciencepub.com by 142.112.211.151 on 12/03/20 changes in vegetation of this remote site over a 31-year period. This constitutes one of the longest histories of vegetation change available for an Arctic goose colony. We chose South Bay because a goose colony was established there after the 1979–1980 study and the site should provide a contrast to East Bay, which has been occupied by goose colonies for at least a century. We employed two different vegetation sampling schemes: nest site ground cover data, illustrating how the habitat selected by geese themselves has changed over the decades; and transect/quadrat sampling, providing an unbiased description of current conditions in nesting and foraging areas. We predicted that the abundance of forage plants at East Bay would have declined over the 31-year period as a result of intense foraging by increasing populations of nesting geese, as has been documented at other Arctic sites.

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Materials and methods Study site This study was conducted at East Bay (63°58′N, 81°50′W) within the East Bay Migratory Bird Sanctuary, an area recognized as a key migratory bird terrestrial habitat site (Latour et al. 2008; Fontaine and Mallory 2011)andSouthBay(64°05′N, 82°50′W), Southampton Island, Nunavut, Canada (Fig. 1). The sites were 30 km apart and both are generally wet graminoid tundra interspersed with lichen–dwarf shrub and heath vegetation and some exposed limestone ridges (Parker 1975; Abraham and Ankney 1986; Fontaine and Mallory 2011). The coastal gradient is very low at both East Bay and South Bay. The south shore of East Bay is a series of terraces with ridges interspersed with lakes and ponds covering 50%–70% of the lowland landscape (Abraham and Ankney 1986), which rises gradually to approximately 25 m above sea level at the edge of an exposed limestone plain; to the southwest of East Bay a low elevation (<20 m) pass connects it to Native Bay, and to the northwest, ridges of 70 m separate it from South Bay. The South Bay sampling site is dissected by the Ford River. Three of the four goose species that nest at East Bay and South Bay (Lesser Snow Goose, Cackling Goose, and the Atlantic subspecies of Brant, Branta bernicla hrota (O. F. Muller, 1776) have likely nested on Southampton Island for centuries, but the first published records of their occurrence and nesting status are from Sutton (1932) and Manning (1942). Cooch (1955) and Barry (1962) conducted studies on Southampton Island on Lesser Snow Goose and Atlantic Brant, respectively. The fourth species, Ross’s Goose, is a relative new- comer to Southampton Island; Barry and Eisenhart (1958) reported the first two nests in 1957, and Abraham and Ankney (1986) reported a nest and broods and suggested a small increase by 1980. Ross’sGeesehaverecentlyincreasedconsiderablyonSouthampton Island as the global populationofthespecieshasincreased(Kerbes et al. 2014; Nissley et al. 2016). James Leafloor (Canadian Wildlife Service Prairie Region, personal communication, 2017) indicated that before 1980, Ross’sGeesemadeup<1% of banding captures of

For personal use only. “light geese” (Snow and Ross’sgeesecombined)duringbanding,butbetween2009and 2018 they represented 12.5% of light geese captured. Lesser Snow Goose colonies on the island have been quantitatively tracked since 1972 (Kerbes 1975; Reed et al. 1987; Kerbes et al. 2006, 2014). The East Bay colony grew from an estimated 17 000 breeding adults (1973) to 164 800 (2008). The colony at South Bay (called the Coral Harbour colony in the survey papers) was established sometime after 1980 and numbered 11 900 breeding adults when first enumerated in 1997, growing to 58 000 in 2008, at which point the two colonies at East Bay and South Bay had merged (Kerbes et al. 2014). These estimates include an unquantified number of Ross’sGeese,whichareindistinguishablefromSnowGeesein the aerial photo methods used in these surveys. The eastern extremity of the combined East Bay–South Bay nesting colony lies within our study site along the south shore of East Arctic Science Downloaded from cdnsciencepub.com by 142.112.211.151 on 12/03/20 Bay (Abraham and Ankney 1986; Nissley et al. 2016). There is no regional or Southampton Island estimate of Atlantic Brant or Cackling Geese. Continentally, the Atlantic Brant population has fluctuated over the past four decades, whereas the Cackling Goose population has increased at a rate similar to the two Anser species (Canadian Wildlife Service Waterfowl Committee 2017; Fox and Leafloor 2018b). Other herbivores that occur on southern Southampton Island include caribou (Rangifer tarandus (Linnaeus, 1758)) (Gunn et al. 2011) and collared lemming (Dicrostonyx groenlandicus (Traill, 1823)).

Data collection We conducted field work on goose populations and habitats from 4 July to 14 August 1979 and 6 June to 14 August 1980 at East Bay within a 36 km2 study site (see Abraham and Ankney 1986) and again at East Bay and South Bay from 24 June to 29 July 2010. Nest site ground cover

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Fig. 1. Southampton Island, Nunavut, showing locations of major place names in the text and the two study sites (South Bay and East Bay) in geographic context. Map was generated using ESRI (2013) ArcMap 10.2. Imagery Source: ESRI (2013) Base Map Imagery — Esri, DigitalGlobe, GeoEye, i-cubed, USDA FSA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community, 6 November 2019. For personal use only.

data were collected at East Bay following nest hatch in 1979 and from 8 to 20 July 2010; the transect and quadrat data were collected along the south shore of East Bay (centroid Arctic Science Downloaded from cdnsciencepub.com by 142.112.211.151 on 12/03/20 81.80°W to 81.96°W) from 21 to 26 July 2010 and at South Bay along the Ford River (centroid 64.14°N, 82.813°W) in an area shown to be in the midst of the Coral Harbour goose colony as defined by Kerbes et al. (2014) from 27 to 29 July 2010. Original 2010 transect and quadrat data and 1979 and 2010 nest site data have been deposited in the Polar Data Catalogue (http://www.polardata.ca). Plant names follow Brouillet et al. (2010); bird names follow the checklist of the American Ornithological Society (Chesser et al. 2018).

Ground cover at nest sites In 1979, goose nest locations at East Bay wereplottedinthefieldonMylar-covered enlarged aerial photomaps obtained from the Canadian National Air Photo library; in 2010, nest locations were georeferenced in the field with Garmin (Olathe, Kansas, USA) global positioning system (GPS) units. Ground cover within 1 m radius from the center of

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asampleofBrant,CacklingGoose,andLesser Snow Goose nest bowls was visually estimated in 1979 and 2010. The minimum distance between nests where habitat data were collected was 9 m and there was no overlap between cover assessments. Ground cover categories identified at nests included graminoid (including both true sedges and, less com- monly, grasses), lichen, Dryas integrifolia Vahl, willow (species of dwarf Salix L.), moss (including both live and apparently dead bryophytes), rock, bare ground, and “other”. Cover of all ground cover types within the circle (vegetation and non-vegetation) was assessed visually as belonging in one of these eight categories in both 1979 and 2010 (trace (<1%), 1%–5%, >5%–25%, >25%–50%, >50%–75%, 75%–95%, and >95%). Midpoint values for each bin were used in subsequent spatial and statistical analyzes. The assessments in 1979 were made by KFA, and in 2010 they were made by CMS with guidance from KFA; the method is simple both in number and type of categories and in visual estimation of the bins, and we do not think observer variation substantially affected the estimates. Prior to the 2010 field season, we made an a priori plan to sample nests of the three species in similar proportion to the 1979 sample; however, we were not aware of the sub- stantial changes in abundance of the two Branta species that had occurred (Brant had declined by approximately 80% and Cackling Geese had increased by approximately 8.6-fold) (K.F. Abraham and C.M. Sharp, personal observation, 2010; Nissley et al. 2016). When the Brant decline was detected in the field in 2010, we subjectively decided to assess all Brant nests as the a priori number could not be met and because they were a special focus for future study of the East Bay population. Additionally, the subset of nests sampled in 2010 for habitat characteristics was distributed throughout the entire study area, but until we returned from the field we did not recognize that nests sampled for ground cover in 1979 were from a smaller, centralized area (shaded area in Fig. 2). Thus, when we restricted our 2010 data for the comparison of nest habitat to the area sampled in both years (common area), the resulting 2010 sample size (n = 80) was much lower than the sample size in 1979 (n = 331), and the relative composition of each species differed from our a

For personal use only. priori target and between years (n for 2010 vs. 1979 was 39 vs. 25 for Cackling Geese, 28 vs. 177 for Brant, and 13 vs. 132 for Lesser Snow Geese).

Transect and quadrat sampling Nest site ground cover data represent habitats chosen by the geese themselves rather than unbiased samples of local vegetation. For this reason, in 2010 we also conducted transect and quadrat vegetation sampling in areas used by nesting and brood rearing geese. Transects TRA11, TRB4, TRB5, TRB7, and TRB9 (Fig. 2)wereestablishedperpendicularto the south shore of East Bay (thus oriented north–south) and spanned 8 km east to west of a two-dimensional grid established in 1979 and subsequently used to facilitate goose nest- searching in both years (see Abraham and Ankney 1986). Transects were 1000 m in length

Arctic Science Downloaded from cdnsciencepub.com by 142.112.211.151 on 12/03/20 traversing from the beginning of terrestrial vegetation at the high tide line (metre 0) across intertidal and brackish communities through to mesic freshwater communities. Transect length and orientation allowed us to cover the majority of the goose nest-search area (Abraham and Ankney 1986;K.F.AbrahamandC.M.Sharp,personalobservation,2010) and to capture the effects of goose foraging on habitat features. We established transects TRCH1, TRCH2, and TRCH3 (Fig. 2)infreshwaterhabitatsatSouthBay,butunlikeEast Bay, there was no linear feature such as the shoreline that could be used to orient these transects. Instead, South Bay transects extended in a cardinal direction from a randomly chosen prominent local feature such as a pond or river, into the surrounding vegetation for the same length as the East Bay transects, to facilitate data analysis (but note that TRCH2 was only 500 m in length due to logistical constraints). For each transect at both locations, cover (vegetation type or unvegetated category) in a visually estimated

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Fig. 2. Study areas. (Upper) East Bay, Southampton Island, Nunavut, indicating nest-associated ground cover data collection sites (1979 and 2010) and transect locations (2010). Underlying shading indicates area where goose nests were sampled in both years (see Fig. 4). (Lower) South Bay, indicating transect locations (2010); note the discontinuity resulting from combining the available images. Map was generated using ESRI (2013) ArcMap 10.2. Imagery Source: ESRI (2013) Base Map Imagery — Esri, DigitalGlobe, GeoEye, i-cubed, USDA FSA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community, 6 November 2019. For personal use only. Arctic Science Downloaded from cdnsciencepub.com by 142.112.211.151 on 12/03/20

10–12 cm × 10–12 cm area at each 1 m point along its length was visually assessed. These categories (Supplementary Table S11) are the same as those collected in the sampling of nest sites, with the exceptions that “water” is a category encountered on transects but not within 1 m radius of nests, and that we partitioned “other” to capture rare species or cover

1Supplementary material is available with the article through the journal Web site at http://nrcresearchpress.com/doi/ suppl/10.1139/as-2018-0032.

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types. For points in which several cover categories co-occurred, all were separately noted; points with no vegetation were classified as appropriate into one or more non-vegetation categories. Sampling along the length of our transects provided a rapid, but approximate, description of ground cover. To provide a more precise description of vegetation at each site, a square quadrat (50 cm × 50 cm) divided into 10 cm × 10 cm cells (n = 25) was used to quantify the occurrence of each plant species or cover class every 50 m along each transect; for the 500 m transect, quadrats were placed every 25 m. Quadrats occurring in ponds and streams were discarded as they added no informationaboutvegetationcomposition.Forthe remaining quadrats, the occurrence of all identifiable species and non-vegetation cover classes present in each 10 cm cell was recorded, and the number of cells in which each occurred was tallied to yield the overall frequency of occurrence in that quadrat, rather than percentage cover. Forty-two species/cover classes were recorded in transect and quadrat samples (see Supplementary Table S11).

Data analysis Statistical analysis of changes in ground cover at East Bay Changes in nest site ground cover data between 1979 and 2010 were analysed using a fac- torial multivariate analysis of variance (MANOVA). Percent coverage for each ground cover type was the dependent variable, and year and goose species were included as categorical predictors. Because the interaction term between year and goose species was significant (P < 0.001). The MANOVA was subsequently separated by species to ensure proper interpretation of each main effect. A Tukey test of means was used to evaluate difference in ground cover between species. Analyses were conducted in R (R Core Team 2018). Means (±SEM) are presented unless otherwise mentioned; results were considered significant at a P ≤ 0.05.

Spatial analysis of changes in ground cover at East Bay To produce a georeferenced nest distribution layer for 1979, Mylar field maps and air

For personal use only. photos were digitized and georeferenced in Arc MAP 10.2 using landscape features such as large boulders, limestone ridges, and identifiable features of large ponds that have been stable over the 31-year sampling interval. Locations from hand-held GPS units were used to produce a georeferenced nest distribution layer for 2010. Goose nest density in the common area was 19.9 per km2 in 1979 and 13.6 per km2 in 2010. Spatial accuracy of the two methods was similar (1979 air photo and field map resolution ≤3 m; 2010 GPS resolution ≤5 m). All nest site ground cover analyses and figureshereinwerecreatedusingdatafromthe common sampling area from the two years (approximately 7 km2:shadedareainFig. 2, upper). Point data from both years were interpolated using the ArcMap 10.2 natural neigh- bour interpolation tool creating a raster of ground cover for each of the main ground cover classes (excluding water bodies). We then subtracted raster values for 2010 from the 1979 Arctic Science Downloaded from cdnsciencepub.com by 142.112.211.151 on 12/03/20 raster in ArcMap 10.2 to visualize relative change in ground cover since 1979. Resulting habitat change rosters indicate where ground cover of a specific cover type has increased (green), decreased (red) or stayed the same (yellow); more intense colour indicates greater change.

Transects and quadrats For analyses of transect data, we chose to focus on composite categories that combine cover classes to capture key aspects of this landscape and correspond to the categories used in our nest site descriptions: “Graminoid” — primarily Cyperaceae, but also including Poaceae; “Moss” — including surficial mosses, living moss carpets (especially predominant in wetter sites) and apparently dead moss, especially predominant in drier sites; “Lichen” — especially predominant in drier sites; “Dryas” — also characteristic of drier sites;

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“Willow” — the dominant local woody species of shrub, mainly dwarf species; “Bare” — equating to near-absence of vascular plants, including mud, algae-covered surfaces, and frost boils; “Rock”; and “Water” (including ponds and streams; not estimated for nest sites). Each transect point was assigned a value of “1” if this cover category occurred there, and “0” if it did not; values may sum to >1 if more than one cover type is present. To provide a more detailed record of the vegetation present, we used the quadrat data to calculate the frequency of occurrence (±SEM) of each of 34 field-assigned cover classes represented in these samples (Supplementary Table S11); again, note that classes generally sum to >1, and that in one case overlapping classes were combined for analysis. The only classes occurring in transect data but not in the quadrat samples were six rare cover classes and (by design) the two water classes (ponds and streams).

Results Changes in ground cover at East Bay Ground cover at nest sites was significantly different between 1979 and 2010 (Pillai = 0.279, F7,399 = 22.090, P < 0.001) at East Bay. The most striking change was a significant decrease in graminoid cover almost everywhere in the sampled area (F1,405 = 90.791, P < 0.001; Figs. 3 and 4). The loss of graminoids between 1979 and 2010 was consistent among species (P < 0.001 for Brant and Cackling Geese, P < 0.01 for Lesser Snow Geese). Graminoids are the major forage for geese in the region, but also provide much of the nest structure material for geese and many bird species. This decrease was most pronounced where graminoids had been historically abundant, e.g., closer to the shore and in lower- lying inter-ridge swales, effectively eliminating sedge domination in most areas (Fig. 5). Smaller, but widespread and significant, declines also occurred in cover of the non-forage categories lichens (primarily foliose and fruticose species) and willows (F1,405 = 20.550, P < 0.001 and F1,405 = 13.004, P < 0.001, respectively; Figs. 3 and 4). Fruticose and foliose lichens were uncommon near Brant nests (<1% cover in both years) and there was no differ-

For personal use only. ence between years (P = 0.481). In contrast, significant losses of lichens occurred by 2010 near Snow Goose and Cackling Goose nests (P = 0.007 and 0.008, respectively), where lichen cover in 1979 was 14% and 8%, respectively. Although losses in willow were observed across all three goose species, losses were only significant near the nests of Snow Geese (P = 0.02). Similar to lichens, historically willow was a major ground cover type in the nesting habitat of Snow Geese (12%), but not Brant (3%) and Cackling Geese (4%; Fig. 3), whereas declines in willows were localized (Fig. 4). In contrast, the proportion of cover classified as rock significantly increased over the study period (F1,409 = 24.693, P < 0.001; Fig. 3), particularly in areas formerly dominated by graminoids (Fig. 4). This increase in rock was driven by changes near the nests of Brant (P = 0.02) and Cackling Geese (P < 0.001). Net changes in cover of the non-forage categories

Arctic Science Downloaded from cdnsciencepub.com by 142.112.211.151 on 12/03/20 moss, Dryas L., and bare ground were non-significant overall (P > 0.5; Fig. 3); however, Dryas increased from 0% cover in 1979 to 1.3% cover in 2010 (P = 0.01) in proximity to Brant nests, and the amount of bare ground near the nests of Snow Geese also increased significantly (P < 0.001; Fig. 3)asreflectedinthelocalchangesinthesecovertypes(Fig. 4). Changes in moss and bare ground were widespread but tended to be reciprocal: areas in which moss increased exhibited decreases in bare ground, and vice versa (Fig. 4). At least one of these cover categories often increased in areas of greater graminoid loss (Fig. 4). For instance, mosses increased in many near-shore areas, whereas bare ground increased farther inland (Fig. 4), although the change was not significant. Goose species had a significant effect on the ground cover at nest sites (Pillai = 0.555, F14,399 = 21.942, P < 0.001). As expected, ground cover differences were related to vegetation communities typical of nest sites of each species and differed most between Brant and

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Fig. 3. Mean ± SEM of major ground cover categories at East Bay, Southampton Island, Nunavut, by species; 1979 (White) and 2010 (Black). Overall, changes between years were significant (P < 0.05) for graminoids, lichen, willows, and rock; all goose species effects were also significant. For personal use only. Arctic Science Downloaded from cdnsciencepub.com by 142.112.211.151 on 12/03/20

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Fig. 4. Relative changes in major ground cover types at East Bay, Southampton Island, Nunavut between 1979 and 2010; see Fig. 3 for quantitative estimates. The coloured section corresponds to the area where ground cover surrounding goose nests was sampled in both years. Arrows indicate north. Map was generated using ESRI (2013) ArcMap 10.2. Imagery Source: Natural Resources Canada (2009).GeoBaseOrthoimage2005–2010 — S4_08125_6402_2009_07_18_P10_LCC00. For personal use only.

Snow Geese (Fig. 3). Willow, lichens, and Dryas were proportionately more dominant near Snow Goose nests compared to Brant (P < 0.0001), whereas proportions of graminoids and mosses were significantly higher near Brant nests compared with those of Snow Geese Arctic Science Downloaded from cdnsciencepub.com by 142.112.211.151 on 12/03/20 (P < 0.0001). Rock cover was also proportionately greater near Brant nests (P = 0.002). Ground cover also differed between Snow Goose and Cackling Goose nests (Fig. 3). Willow, lichen, and Dryas were more dominant near Snow Goose nests than near Cackling Goose nests (P < 0.001 for willow and lichen, P = 0.026 for Dryas), as Snow Geese tended to nest on ridges, which are the first to become snow-free in spring. Additionally, ground cover of rocks was greater by Cackling Goose nests (P = 0.001). Although Brant and Cackling Geese had the most similar habitat preferences in 2010, there were still some differences generally attributable to Cackling Geese tending to nest on inland ridges as well as more low-lying habitats such as coastal lagoons. Graminoids were significantly higher by Brant nests (P < 0.0001), whereas lichen and Dryas proportions were significantly higher

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near Cackling Goose nests (P = 0.003 and 0.001, respectively). Bare ground was also significantly more prevalent near Cackling goose nests (P = 0.018).

Transects and quadrats At East Bay, transect data indicated that graminoid forage species were consistently present at only a minority of sampling points (15%–36% depending on transect, Table 1); the main plants observed were species in the genus Carex (mostly C. subspathacea Wormsk. toward the coast and C. aquatilis inland), and the grass Dupontia fisheri R. Br. These values are somewhat misleading, however, in that they represent presence rather than cover; these graminoids generally were present in low abundance, as indicated by nest site ground cover data (Figs. 4 and 5). In many cases, graminoids emerged from an underlying moss-dominated substrate and the distribution of graminoids tended to resemble (i.e., be correlated with) that of mosses, with roughly similar cover values (Table 1). The occurrence of graminoids was higher along the South Bay transects, in one case reaching 90% (Table 1); however, South Bay transects were generally drier than East Bay transects, resulting in a different graminoid species composition. In particular, species of Kobresia Willd. were abundant at South Bay sites, although grazed plants were often difficult to iden- tify to species or to distinguish from other sedges. Many of the South Bay sites were blan- keted with extensive and nearly continuous expanses of mosses (a non-forage category) from which forage species such as Carex and Kobresia sparsely emerged (these are moss carpets sensu Kerbes et al. 1990; Kotanen and Jefferies 1997; Conkin and Alisauskas 2017). Moss cover was much higher at South Bay (40%–85%) than at East Bay (19%–42%), but much of the South Bay moss cover was extremely dry; although it superficially appeared dead it may have simply been dehydrated. Quadrat data (Supplementary Table S11) confirmed that forage species such as Carex and (or) Kobresia were frequent along most transects, occurring in 11%–46% of samples (quadrat cells) at East Bay (where Carex spp. predominated) and 16%–76% of samples at South Bay (where Kobresia was common). Dupontia fisheri also was common in East Bay (26%–55%), but For personal use only. much less abundant in South Bay (3%–15%). Other graminoids were scarce; in particular, P. phryganodes,whichneverexceeded2%alongatEastBayandwasabsentatSouthBay. Moss was common at all sites, but live moss was more prominent at East Bay than at South Bay (52%–71% vs. 20%–50%), whereas dead moss was more prominent at South Bay (49%–95%) than at East Bay (16%–36%). A few other plant species (Salix sp., species of Saxifraga L., and Dryas integrifolia) occasionally reached or exceeded 10% occurrence.

Discussion Comparison of data sets collected 31 years apart at East Bay, Southampton Island, pro- vides compelling evidence of significant vegetation change over this period, which saw

Arctic Science Downloaded from cdnsciencepub.com by 142.112.211.151 on 12/03/20 large increases in goose populations both locally and continentally (Kerbes et al. 2006, 2014; Nissley et al. 2016). Strikingly, the dominant cover of graminoids preferred by geese as forage has declined, making non-forage vegetation (e.g., Dryas integrifolia) and non-veg- etated areas (e.g., exposed rock and bare ground) predominant. Goose species effects differed for different cover types reflecting goose species use across the gradient of habitats available, but all showed the same direction of change supporting the overall pattern of change. These changes are consistent with goose-induced habitat changes observed elsewhere in the Canadian Arctic (Jefferies and Rockwell 2002; Jefferies et al. 2003, 2006; McLaren and Jefferies 2004; Abraham et al. 2005a, 2005b, 2012; Alisauskas et al. 2006; Kotanen and Abraham 2013; Conkin and Alisauskas 2017). Our results provide empirical support for the interpretations of the land cover mapping and classification study of the southern half of Southampton Island produced by Fontaine and Mallory (2011).Their

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Table 1. Transect data, sampled in 2010. East Bay South Bay

Transect

TRB4 TRB5 TRB7 TRB9 TRA11 TRCH1 TRCH2 TRCH3

Category 1000 1000 1000 1000 1000 1000 500 1000 Graminoid 0.36 ± 0.02 0.19 ± 0.01 0.29 ± 0.01 0.15 ± 0.01 0.22 ± 0.01 0.67 ± 0.02 0.90 ± 0.01 0.28 ± 0.01 Lichen 0.06 ± 0.01 0.01 ± 0.00 0.09 ± 0.01 0.00 ± 0.00 0.02 ± 0.01 0.19 ± 0.01 0.07 ± 0.01 0.00 ± 0.00 Willow 0.09 ± 0.01 0.08 ± 0.01 0.13 ± 0.01 0.02 ± 0.01 0.03 ± 0.01 0.14 ± 0.01 0.27 ± 0.02 0.02 ± 0.01 Dryas 0.05 ± 0.01 0.08 ± 0.01 0.11 ± 0.01 0.01 ± 0.00 0.05 ± 0.01 0.31 ± 0.02 0.15 ± 0.02 0.01 ± 0.00 Moss 0.41 ± 0.02 0.25 ± 0.01 0.42 ± 0.02 0.19 ± 0.01 0.26 ± 0.01 0.40 ± 0.02 0.78 ± 0.02 0.85 ± 0.01 Rock 0.09 ± 0.01 0.06 ± 0.01 0.01 ± 0.00 0.06 ± 0.01 0.02 ± 0.00 0.04 ± 0.01 0.06 ± 0.01 0.06 ± 0.01 Bare 0.28 ± 0.01 0.01 ± 0.00 0.01 ± 0.00 0.02 ± 0.00 0.03 ± 0.01 0.02 ± 0.00 0.01 ± 0.01 0.10 ± 0.01 For personal use only. only. use personal For Water 0.30 ± 0.01 0.65 ± 0.02 0.54 ± 0.02 0.72 ± 0.01 0.66 ± 0.02 0.23 ± 0.01 0.00 ± 0.00 0.02 ± 0.00

Note: Mean frequency of occurrence (range 0–1) of cover categories in transects ± SEM; N, number of points sampled. Data are aggregated to correspond to nest site ground cover categories in Fig. 3. To emphasize the most frequent (>10%) cover categories, values ≥0.1 are bolded. Values do not necessarily sum to 1, as several cover categories can co-occur at the same point. See Supplementary Table S11 for information on the types of ground cover contributing to each cover category. ulse yNCRsac Press Research NRC by Published Arctic Science Downloaded from cdnsciencepub.com by 142.112.211.151 on 12/03/20 on 142.112.211.151 by cdnsciencepub.com from Downloaded Science Arctic 107 108 Arctic Science Vol. 6, 2020

Fig. 5. Percent cover of graminoids at East Bay, Southampton Island, Nunavut, in 1979 and 2010 with corresponding representative pictures of the landscape. The coloured section corresponds to the area where goose nests were sampled in both years. Pictures taken at same location, although the direction of view is different. Arrows indicate north. Map was generated using ESRI (2013) ArcMap 10.2. Imagery Source: Natural Resources Canada (2009).GeoBaseOrthoimage2005–2010 — S4_08125_6402_2009_07_18_P10_LCC00. Photographs by KFA.

For personal use only. opinion was that current habitat conditions in much of the lowlands of Southampton Island, including East Bay, showed signs of having been drastically degraded and were the result of “a low-quality successional replacement of the original graminoid meadow community” (p. 36). Our results also support the conclusions of Flemming et al. (2019) who found that availability of sedge meadow habitat and lateral concealment for nesting shorebirds was lower in areas more heavily used by geese (primarily brood-rearing and moulting Lesser Snow Geese) than more lightly used areas on Southampton Island and nearby Coates Island. These authors also reported a decline in sedge cover over an 11-year period in lightly and moderately used sites. They did not collect comparable data for the heavily used area that included the East Bay nesting colony proper.

Arctic Science Downloaded from cdnsciencepub.com by 142.112.211.151 on 12/03/20 Over our 31-year sampling period, Lesser Snow Goose and Ross’s Goose populations on Southampton Island have more than tripled (Kerbes et al. 2014). Although the largest colony (644 000 birds) is at Boas River on the west side of the island, the East Bay colony increased from 42 660 birds in 1979 to 164 800 birds in 2008, and the South Bay (Coral Harbour) colony grew from nothing in 1980 to 58 600 birds (Kerbes et al. 2006, 2014). The post-hatch dispersal of broods of Lesser Snow Geese and Ross’ Geese now spans the entire reach from west of the town of Coral Harbour almost to the mouth of East Bay at Foxe Basin. In the 1970s and before, the brood rearing area was confined to the tundra between Native Bay and East Bay (Kerbes 1975; Abraham and Ankney 1986). At the same time, Ross’s Geese have increased from incidental status (<1% of Anser species total) to regu- lar occurrence (Nissley et al. 2016), but still represent a relatively small fraction of the total number of geese: up to 12.5% of Lesser Snow Geese and Ross’s Geese combined (J. Leafloor,

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personal communication, 2017; Kerbes et al. 2014). These numbers indicate that foraging pressure attributable to Lesser Snow Geese and Ross’s Geese has been continually increasing over the 31-year period in the East Bay–South Bay region, likely driving the reduction of graminoids and shaping the current landscape. This declining food base also may help to explain the relatively stable East Bay colony size in recent years (144 800 birds in 1997 vs. 164 800 birds in 2008: Kerbes et al. 2014) and its lack of expansion of nesting to the east, due to density-dependent processes such as poor gosling pre-fledging survival. We lack long-term, pre-population growth vegetation data for the smaller colony at South Bay; thus, quantitative statements about changes at this location are not possible from our study. We found that the current habitat conditions at South Bay show similar effects of goose grazing pressure, and the region is included in the coastal lowland zone that Fontaine and Mallory (2011) refer to as having undergone changes due to goose foraging. Differences between the current habitat conditions at East Bay and South Bay may be partially explained by the different durations of occupancy of the two colonies by Lesser Snow Geese. Flemming et al. (2019) showed increased negative effects correlated with increased goose presence, whereas Alisauskas et al. (2006) showed that characteristics of vegetation loss were positively correlated with higher goose density and longer time of occupancy. The East Bay transects were immediately adjacent to the coast, whereas the South Bay transects were inland on sites that were slightly elevated and better drained, which may explain some of the differences in vegetation cover. Although Cackling Geese numbers increased at a rate faster than Lesser Snow Geese and perhaps at a similar rate to Ross’sGeesefrom1979to2010,theiroveralllowernumbers relative to Lesser Snow and Ross’s Geese suggest they may have contributed less to the current state of the vegetation conditions and habitat changes that we documented. Atlantic Brant have declined in the altered ecosystem at East Bay and have been progressively replaced by an increase in Cackling Geese (Nissley et al. 2016;K.F.Abrahamand C.M. Sharp, personal observation, 2010). Although there are some habitat selection

For personal use only. differences among these four Arctic goose species during nesting and brood rearing (e.g., Ankney 1984; Abraham and Ankney 1986; Nissley et al. 2016; this study), there is broad overlap in their use of coastal habitats and they all are generalist grazers that rely on the same type and species of graminoid vegetation for their primary forage sources. The shifting relative abundance of these birds may have resulted in corresponding shifts in pressures and impacts on each species’ most preferred food plants; however, no empirical investigation of foods has been completed and partitioning the foraging effects of each species is not possible with our data. Separate studies of each species are required. Still, the loss of large Puccinellia swards along the coast of East Bay and elsewhere on Southampton Island (e.g., Native Bay, K.F. Abraham, personal observation, 2008) has likely contributed to the decline in abundance of nesting Atlantic Brant that prefer the zone

Arctic Science Downloaded from cdnsciencepub.com by 142.112.211.151 on 12/03/20 where that species is present for nesting and brood rearing (Barry 1962; Lewis et al. 2013). Ankney (1984) concluded that the small body size of Brant limited their capacity to store nutrients for use during incubation and required them to feed throughout incubation. He hypothesized that this was the reason they nested in Puccinellia swards, a habitat that has essentially now disappeared locally. Our interpretation of both the declines in forage species at East Bay and the current condition of lowland habitats at both East Bay and South Bay is consistent with the observed increases in rock cover and local changes in cover of moss and bare ground. As geese remove vegetation, they expose underlying sediment susceptible to erosion, exposing both organic and inorganic substrates (Kerbes et al. 1990; Jefferies and Rockwell 2002; Jefferies et al. 2006). Increase in rock cover primarily occurred in areas formerly dominated by graminoids anchored in peat. Removal of sedges and erosion of peat likely

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exposed the gravel and rock components of the glacio-marine lag that forms the underlying substrate of these lowlands (Fontaine and Mallory 2011). Excessive foraging can also remove emergent graminoids from moss-dominated ground cover such as seasonally flooded polygon centres (Kerbes et al. 1990; Kotanen and Jefferies 1997), resulting in moss carpets such as the extensive areas we observed at South Bay. Furthermore, loss of moss cover in poorly drained areas could have resulted in the exposure of underlying silts and contributed to the negative association noted between moss and bare ground cover. Finally, declines in lichen and willow cover, although small, might also reflect goose-related habitat change. Fruticose and foliose lichens occur most abundantly in drier areas associated with better drained ridges, and losses of lichens were greatest on these inland ridges leading to exposed peat and rock. This could reflect increased use of these habitats by increasing numbers of Snow and Cackling Geese (e.g., trampling and nest building), but may also have resulted from grazing by caribou, which increased from low numbers in the 1970s to a peak in 1997 followed by a decline (Gunn et al. 2011). Although geese are sometimes observed peck- ing at willow leaves and may occasionally consume catkins and young leaves, willows are not a preferred food (Iacobelli and Jefferies 1991). A more likely explanation for reductions in willows is a change in soil conditions (drying, compaction, loss of insulation, and (or) increasing salinity) or disturbance of therootzone,asdocumentedatLaPérouseBay (Srivastava and Jefferies 1995, 1996). Our study illustrates both advantages and pitfalls of using historical data. Thirty-year data sets, a clear strength of this study, are rare for Arctic systems, and pre-existing nest site data allowed us to describe vegetation changes that we would otherwise be unable to docu- ment. Without the information on ground cover around nests, we would only have been able to describe the current vegetation, and we could then only speculate on historical trends (see Fontaine and Mallory 2011). In contrast, our nest site data were not collected with general habitat description in mind, and therefore suffer from some limitations. Data collection was dependent on the locations where geese chose to nest, rather than

For personal use only. representing a truly random sample. Unlike our transects, these samples are likely subtly influenced by the habitat preferences of the geese. For instance, avoidance by nesting geese of sensitive low-lying sites and any vegetation community degraded to an extent that geese no longer deemed it suitable might result in our under-sampling of unvegetated areas, making our estimates of change more conservative. Other uncontrolled factors may also have affected the vegetation at our sites. For instance, the goose community itself has changed over time from one dominated by Lesser Snow Geese and Atlantic Brant to one dominated by Lesser Snow Geese, Cackling Geese, and Ross’s Geese. Nissley et al. (2016) confirmed these changes in the East Bay goose community. Hudson Bay, James Bay, and Foxe Basin coastal communities such as these on Southampton Island are also influenced by other herbivores, notably by grazing caribou,

Arctic Science Downloaded from cdnsciencepub.com by 142.112.211.151 on 12/03/20 by post-glacial uplift (Andrews and Peltier 1976; Dredge 1991), and by climate change (ACIA 2005). Isostatic uplift should lead to increases in above-ground biomass and changes in plant species composition (Hik et al. 1992), but not loss of communities such as Puccinellia,whichwouldcolonizenewlyemergedland.Despitetheuncertaintyofthese influences, our data demonstrate a striking decline in the cover of preferred sedge and grass forage species in areas heavily used by multiple species of geese, and increases in some non-forage cover categories, consistent with the hypothesis of changes resulting from persistent long term, cumulative foraging pressure by high local populations of breeding and moulting geese. Recovery of these systems will likely be highly variable. Reduction of biomass to near zero suggests long-term loss, but where below-ground graminoid tissues are intact, above-ground growth can recover with a reduction or removal of foraging pressure

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(Jefferies et al. 2003). Except in the portions of our study areas dominated by exposed peat and extensive dead or desiccated moss cover, graminoids may recover over time, but not while goose numbers remain at current levels. Extensive dead or desiccated moss areas are unlikely to recover in the near- to mid-term, and the pathway to revegetation is unclear as most of the dominant plants in the pre-degraded system are propagated from vegetative growth rather than seeds. The recovery of the damaged fruticose and foliose lichen communities as has occurred here is a long-term process on the order of decades (Henry and Gunn 1991). Our understanding of the long-term impact of the goose-induced changes we have described would benefit from studies of the rates of recovery or revegetation at our study sites or in similar areas of the eastern Canadian Arctic, including establishment and long-term monitoring of exclosures.

Acknowledgements Financial support for the 1979–1980 work was provided by the Canadian Wildlife Service (CWS), University of Western Ontario, a Natural Sciences and Engineering Research Council (NSERC) grant to C.D. Ankney, and the Atlantic Flyway Council. Permits were issued by Indian and Northern Affairs (land use permit N80J296) and CWS (sanctuary permit WS-80-009). We thank the hamlet council in Coral Harbour for its cooperation with our 1979–1980 studies and for recommending Toomasie Nakoolak as a field assistant in those years. We thank Bill Chappell for field assistance. The 2010–2015 work was supported by CWS and the U.S. Fish and Wildlife Service who funded Arctic Goose Joint Venture projects (KFA), by Trent University and the Ontario Ministry of Natural Resources (OMNR) and by an NSERC Discovery Grant (PMK). The OMNR paid publication charges. We thank Mark Reade for field assistance in 2010. We thank Grant Gilchrist and Paul Smith for including our project as a component of their long-term research on waterbirds and tundra ecosystems at East Bay and for providing logistical support at his camp and through Polar Continental Shelf. The research permits in 2010 were CWS sanctuary permit NUN-MBS- For personal use only. 08004, CWS Scientific Permit NUN-SCI-08-04 and Nunavut Water Board Permit 3BC- EAS0811. We are grateful to Jim Leafloor (CWS Prairie Region) for helicopter support and Coral Harbour accommodation in 2010, and Garth Ball for integrating our logistic needs with his goose banding schedule. Kevin Middel (OMNR) helped with imagery and georefer- encing of historical data and provided general GIS support, and Nora Spencer (CWS Ontario Region) helped with statistical analyses. Kathy Dickson reviewed the figures and provided feedback on their presentation.

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Arctic Science Downloaded from cdnsciencepub.com by 142.112.211.151 on 12/03/20 Canada. Can. Field-Nat. 100(2): 180–185. Abraham, K.F., Jefferies, R.L., and Rockwell, R.F. 2005a.Goose-inducedchangesinvegetationandlandcover between 1976 and 1997 in an Arctic coastal marsh. Arct. Antarct. Alp. Res. 37:269–275. doi: 10.1657/1523- 0430(2005)037[0269:GCIVAL]2.0.CO;2. Abraham, K.F., Jefferies, R.L., and Alisauskas, R.T. 2005b. The dynamics of landscape change and snow geese in midcontinent North America. Glob. Change Biol. 11(6): 841–855. doi: 10.1111/j.1365-2486.2005.00943.x. Abraham, K.F., Jefferies, R.L., Alisauskas, R.T., and Rockwell, R.F. 2012. Northern wetland ecosystems and their response to high densities of lesser snow geese and Ross’s geese. In Evaluation of special management measures for midcontinent lesser snow geese and Ross’sgeese.Edited by J.O. Leafloor, T.J. Moser, and B.D.J. Batt. Arctic Goose Joint Venture Special Publication. U.S. Fish and Wildlife Service; Canadian Wildlife Service, Washington, D.C., USA; Ottawa, Ont., Canada. pp. 9–45. ACIA. 2005. Arctic climate impact assessment. Cambridge University Press, New York, N.Y., USA. 1042 pp. Alisauskas, R.T., Charlwood, J.W., and Kellett, D. 2006. Vegetation correlates of the history and density of nesting by Ross’s geese and lesser snow geese at Karrak Lake, Nunavut. Arctic, 59: 201–210. doi: 10.14430/arctic342. Andres, B.A., Smith, P.A., Morrison, R.G., Gratto-Trevor, C.L., Brown, S.C., and Friis, C.A. 2012. Population estimates of North American shorebirds, 2012. Wader Study Group Bull. 119: 178–192.

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Andrews, J.T., and Peltier, W.R. 1976. Collapse of the Hudson Bay ice center and glacio-isostatic rebound. Geology, 4(2): 73–75. doi: 10.1130/0091-7613(1976)4<73:COTHBI>2.0.CO;2. Ankney, C.D. 1984. Nutrient reserve dynamics of breeding and molting Brant. Auk, 101: 361–370. doi: 10.1093/auk/ 101.2.361. Arctic Goose Joint Venture. 2018. Strategic plan. Available from https://www.agjv.ca/wp-content/uploads/2018/05/ AGJV-Strategic-Plan-2018-FINAL.pdf. Barry, T.W. 1962. Effect of late seasons on Atlantic Brant reproduction. J. Wildl. Manage. 26:19–26. doi: 10.2307/ 3798163. Barry, T.W., and Eisenhart, J.N. 1958. Ross’ Geese nesting at Southampton Island, N.W.T., Canada. Auk, 75:89–90. doi: 10.2307/4082065. Brouillet, L., Coursol, F., Meades, S.J., Favreau, M., Anions, M., Bélisle, P., and Desmet, P. 2010. VASCAN, the database of Vascular Plants of Canada. Available from http://data.canadensys.net/vascan/ [accessed 8 February 2012]. Canadian Wildlife Service Waterfowl Committee. 2017. Population status of migratory game birds in Canada: November 2015. CWS Migratory Birds Regulatory Report Number 49. Environment and Climate Change Canada, Ottawa, Ont., Canada. 257 pp. Cargill, S.M., and Jefferies, R.L. 1984. The effects of grazing by lesser snow geese on the vegetation of a sub-arctic salt marsh. J. Appl. Ecol. 21(2): 669–686. doi: 10.2307/2403437. Chesser, R.T., Burns, K.J., Cicero, C., Dunn, J.L., Kratter, A.W., Lovette, I.J., et al. 2018. Check-list of North American Birds (online). American Ornithological Society, Chicago, Illinois, USA. Available from http://checklist.aou.org/ taxa. Conkin, J., and Alisauskas, R.T. 2017. Conversion of tundra to exposed peat habitat by snow geese (Chen caerulescens caerulescens)andRoss’sgeese(C. rossii)inthecentralCanadianArctic.PolarBiol.40(3): 563–576. doi: 10.1007/ s00300-016-1979-x. Cooch, G. 1955. Waterfowl reconnaissance of Southampton Island and southwest Baffin Island, July 18, 1955. Unpublished Report. Canadian Wildlife Service, Ottawa, Ont., Canada. 24 pp. Didiuk, A.B., and Ferguson, R.S. 2005. Land cover mapping of the Queen Maud Gulf Migratory Bird Sanctuary, Nunavut. Canadian Wildlife Service Occasional Paper 111, Ottawa, Ont., Canada. Dredge, L.A. 1991. Raised marine features, radiocarbon dates, and sea level changes, eastern Melville Peninsula, Arctic Canada. Arctic, 44: 63–73. doi: 10.14430/arctic1520. ESRI. 2013. ArcGIS Desktop version 10.2. Redlands, Calif., USA. Flemming, S.A., Calvert, A., Nol, E., and Smith, P.A. 2016. Do hyper abundant Arctic-nesting geese pose a problem for sympatric species? Environ. Rev. 24(4): 393–402. doi: 10.1139/er-2016-0007. Flemming, S.A., Nol, E., Kennedy, L.V., and Smith, P.A. 2019. Hyperabundant herbivores limit habitat availability and influence nest site selection of Arctic-breeding birds. J. Appl. Ecol. 56(4): 976–987. doi: 10.1111/1365-2664.13336. Fontaine, A., and Mallory, M.L. 2011. Detection and classification of land cover classes of Southampton Island, Nunavut, using Landsat ETM+ data. Canadian Wildlife Service Occasional Paper Number 119. Canadian Wildlife

For personal use only. Service, Ottawa, Ont., Canada. 108 pp. Fox, A.D., and Abraham, K.F. 2017. Why geese benefit from the transition from natural vegetation to agriculture. Ambio, 46(Suppl. 2): 188–197. doi: 10.1007/s13280-016-0879-1. Fox, A.D., and Leafloor, J.O. (Editors). 2018a. A global audit of the status and trends of Arctic and northern hemi- sphere goose populations (component 1). Conservation ofArcticFloraandFaunaInternationalSecretariat, Akureyri, Iceland. Fox, A.D., and Leafloor, J.O. (Editors). 2018b. A global audit of the status and trends of Arctic and northern hemi- sphere goose populations (component 2: population accounts). Conservation of Arctic Flora and Fauna International Secretariat, Akureyri, Iceland. Fox, A.D., and Madsen, J. 2017. Threatened species to super-abundance: the unexpected international implications of successful goose conservation. Ambio, 46(Suppl. 2): 179–187. doi: 10.1007/s13280-016-0878-2. Fox, A.D., Madsen, J., Boyd, H., Kuijken, E., Norris, D.W., Tombre, I.M., and Stroud, D.A. 2005. Effects of agricultural change on abundance, fitness components and distribution of two arctic-nesting goose populations. Glob. Change Biol. 11(6): 881–893. doi: 10.1111/j.1365-2486.2005.00941.x.

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Published by NRC Research Press Table S1. Quadrat data, sampled in 2010. Mean frequency of occurrence (range 0-1) of cover classes in quadrats ± SEM in terrestrial sites; N = number of quadrats sampled along each transect; there were 25 cells sampled/quadrat. Sample size varies since quadrats in large ponds or streams were not sampled (see Methods). Values ≥ 0.1 are bolded. Values do not necessarily sum to 1, since several cover classes can co-occur in the same cell. "Category" indicates the aggregate cover category (Table 1) to which each particular cover class contributes. The same cover classes also were recorded during transect sampling, but an additional eight cover classes were recorded only in transects: Carex maritima, Frost Boils, Saxifraga cernua, Saxifraga tricuspidata, Spergularia sp., Vaccinium uliginosum, and (by design) Ponds and Streams. Site East Bay South Bay Cover class Category TRB4 TRB5 TRB7 TRB9 TRA11 TRCH1 TRCH2 TRCH3 N 18 11 8 5 10 16 21 21 Algae / Algal Mat* Bare 0.08±0.06 0.07±0.07 0.02±0.02 0.00±0.00 0.08±0.05 0.00±0.00 0.00±0.00 0.00±0.00 Arctostaphylos - 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.02±0.02 0.00±0.00 0.00±0.00 0.00±0.00 Cardamine - 0.05±0.04 0.01±0.01 0.01±0.01 0.00±0.00 0.06±0.04 0.01±0.01 0.00±0.00 0.01±0.01 Carex and Kobresia Graminoid 0.40±0.11 0.15±0.09 0.11±0.07 0.40±0.24 0.46±0.16 0.59±0.08 0.76±0.09 0.16±0.06 Cassiope - 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.05±0.05 0.00±0.00 0.00±0.00 Chrysosplenium - 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.03±0.03 0.00±0.00 0.00±0.00 0.00±0.00 Dead Moss Moss 0.29±0.08 0.23±0.08 0.36±0.12 0.16±0.16 0.25±0.10 0.55±0.07 0.49±0.07 0.95±0.05 Dryas Dryas 0.08±0.05 0.15±0.09 0.25±0.12 0.16±0.16 0.14±0.10 0.32±0.10 0.08±0.05 0.01±0.01 Dupontia Graminoid 0.36±0.10 0.55±0.15 0.45±0.17 0.26±0.17 0.28±0.13 0.05±0.04 0.15±0.04 0.03±0.02 Eleocharis Graminoid 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.03±0.03 0.00±0.00 0.00±0.00 Equisetum variegatum - 0.00±0.00 0.01±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 Grass Graminoid 0.02±0.02 0.05±0.03 0.05±0.05 0.05±0.03 0.00±0.00 0.02±0.01 0.04±0.02 0.00±0.00 Konigia† - 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 Lichen Lichen 0.07±0.04 0.12±0.09 0.23±0.14 0.00±0.00 0.05±0.05 0.33±0.11 0.05±0.05 0.00±0.00 Live Moss Moss 0.52±0.11 0.71±0.13 0.65±0.17 0.60±0.24 0.61±0.12 0.37±0.09 0.50±0.10 0.20±0.07 Minuartia - 0.00±0.00 0.00±0.00 0.09±0.09 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 Mud Flat Bare 0.24±0.10 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 Other Mud Bare 0.15±0.08 0.08±0.08 0.00±0.00 0.00±0.00 0.00±0.00 0.08±0.06 0.04±0.04 0.11±0.06 Pedicularis - 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.01±0.01 0.02±0.01 0.00±0.00 Polygonum viviparum - 0.00±0.00 0.02±0.02 0.02±0.02 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 Puccinellia phryganodes Graminoid 0.02±0.02 0.01±0.00 0.00±0.00 0.00±0.00 0.01±0.01 0.00±0.00 0.00±0.00 0.00±0.00 Ranunculus cymbalaria - 0.02±0.01 0.01±0.00 0.03±0.01 0.00±0.00 0.02±0.01 0.01±0.01 0.00±0.00 0.00±0.00 Rhododendron - 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.01±0.01 0.00±0.00 0.00±0.00 Sagina - 0.05±0.05 0.00±0.00 0.00±0.00 0.00±0.00 0.01±0.01 0.01±0.01 0.00±0.00 0.02±0.01 Sagina-like unknown - 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.08±0.04 Salix reticulata Willow 0.06±0.05 0.04±0.04 0.06±0.06 0.00±0.00 0.00±0.00 0.04±0.02 0.06±0.05 0.00±0.00 Salix sp. Willow 0.18±0.08 0.10±0.05 0.22±0.10 0.18±0.11 0.19±0.10 0.19±0.06 0.21±0.06 0.01±0.00 Saxifraga aizoides - 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.01±0.01 0.00±0.00 Saxifraga caespitosa - 0.00±0.00 0.00±0.00 0.10±0.10 0.00±0.00 0.10±0.07 0.00±0.00 0.00±0.00 0.00±0.00 Saxifraga hirculus - 0.03±0.02 0.29±0.11 0.05±0.03 0.24±0.10 0.10±0.07 0.00±0.00 0.00±0.00 0.01±0.00 Saxifraga oppositifolia - 0.00±0.00 0.05±0.05 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 0.00±0.00 Stellaria humifusa - 0.01±0.01 0.01±0.01 0.03±0.03 0.02±0.02 0.02±0.01 0.00±0.00 0.00±0.00 0.00±0.00 Stone Rock 0.23±0.07 0.34±0.13 0.18±0.12 0.43±0.23 0.40±0.12 0.19±0.07 0.12±0.06 0.08±0.05 * Combines two overlapping cover classes † Trace