Climate-related range shifts in Arctic-breeding shorebirds

Abstract

Aim: To test whether the occupancy of shorebirds has changed in the eastern Canadian Arctic, and whether these changes could indicate that shorebird distributions are shifting in response to long-term climate change.

Location: Foxe Basin and Rasmussen Lowlands, Nunavut, Canada.

Methods: We used a unique set of observations, made 25 years apart, using general linear models to test if there was a relationship between changes in shorebird species' occupancy and their species temperature Index, a simple version of a species climate envelope.

Results: Changes in occupancy and density varied widely across species, with some increasing and some decreasing. This is despite that overall population trends are known to be negative for all of these species based on surveys during migration. The changes in occupancy that we observed were positively related to the species temperature index, such that the warmer-breeding species appear to be moving into these regions, while colder-breeding species appear to be shifting out of the regions, likely northward.

Main conclusions: Our results suggest that we should be concerned about declining breeding habitat availability for bird species whose current breeding ranges are centered on higher and colder latitudes.

Keywords: Re‐distribution; climate tracking; global change; poleward shifts; range dynamics; wader.

FIGURE 1

White‐rumped Sandpiper, 1 of the 12 species of shorebirds observed in this study. Shorebirds are the most abundant and diverse group of birds in many tundra habitats.

FIGURE 2

Expected changes in plot occupancy as species distributions shift north in response to warming temperatures. Species are assumed to have higher occupancy in the center of their range and lower occupancy at the edges of their range (Gaston, ; indicated in this figure by opacity of the orange and blue species ranges). Plots are surveyed within the study area outlined by the black box. The STI (mean June temperature of the range) for species 1 is 5°C; in this case, making it a colder‐breeding species. At time 1, the mean temperature of the study area is also 5°C, therefore, the occupancy of species 1 is high. At time 2, the mean temperature of the study area has increased to 10°C. Species 1 has shifted its distribution northward. The study area is now on the southern edge of its range, and the occupancy of species 1 has declined. The STI of species 2, a warmer‐breeding species, is 10°C. At time 1, the study area is at the northern edge of its range, therefore, the occupancy of species 2 at time 1 is low. At time 2, the study area is now in the center of its range and the occupancy of species 2 has increased.

FIGURE 3

Map of Eastern Arctic study areas showing plots where breeding shorebirds were surveyed in 1994–1997 and then 22 to 25 years later in 2019.

FIGURE 4

Species richness (right) and density of breeding shorebirds per km² (left) observed in the two time periods of our study, for both regions combined.

FIGURE 5

Change in individual species occupancy in plots surveyed in 1994–1997 and 2019 (n = 64) in both study regions combined.

FIGURE 6

Linear model of the relationship between the percent change in occupancy of shorebird species from 1994–1997 to 2019 and their species temperature index. Intercept = −95.49, slope = 55.72, p = .01, and adjusted R² = 0.51. The species temperature index is the mean June temperature from 1970 to 2000 across the species range. See Table 2 for a legend of four‐letter bird species codes.