Citizen science reveals waterfowl responses to extreme winter weather

Abstract

Global climate change is increasing the frequency and severity of extreme climatic events (ECEs) which may be especially detrimental during late-winter when many species are surviving on scarce resources. However, monitoring animal populations relative to ECEs is logistically challenging. Crowd-sourced datasets may provide opportunity to monitor species' responses to short-term chance phenomena such as ECEs. We used 14 years of eBird-a global citizen science initiative-to examine distribution changes for seven wintering waterfowl species across North America in response to recent extreme winter polar vortex disruptions. To validate inferences from eBird, we compared eBird distribution changes against locational data from 362 GPS-tagged Mallards (Anas platyrhynchos) in the Mississippi Flyway. Distributional shifts between eBird and GPS-tagged Mallards were similar following an ECE in February 2021. In general, the ECE affected continental waterfowl population distributions; however, responses were variable across species and flyways. Waterfowl distributions tended to stay near wintering latitudes or moved north at lesser distances compared with non-ECE years, suggesting preparedness for spring migration was a stronger "pull" than extreme weather was a "push" pressure. Surprisingly, larger-bodied waterfowl with grubbing foraging strategies (i.e., geese) delayed their northward range shift during ECE years, whereas smaller-bodied ducks were less affected. Lastly, wetland obligate species shifted southward during ECE years. Collectively, these results suggest specialized foraging strategies likely related to resource limitations, but not body size, necessitate movement from extreme late-winter weather in waterfowl. Our results demonstrate eBird's potential to monitor population-level effects of weather events, especially severe ECEs. eBird and other crowd-sourced datasets can be valuable to identify species which are adaptable or vulnerable to ECEs and thus, begin to inform conservation policy and management to combat negative effects of global climate change.

Keywords: GPS telemetry; citizen science; climate change; distributions; eBird; extreme climatic event; polar vortex; waterfowl; weather severity.

FIGURE 1

Temperature anomalies (°C) on February 15, 2021 across the conterminous United States. Data used to produce the map are daily locational temperatures from the unrestricted mesoscale analysis (URMA) by National Weather Service of the National Oceanic and Atmospheric Administration. Map credit is owed to the National Weather Service Weather Prediction Center 2021.

FIGURE 2

Changes in distributional centers between “early” (January1 to February6; red) and “late” (February7–28; blue) periods during 2020 (column 1; a,c) and 2021 (column 2; b,d) for Mallards using GPS telemetry (row 1; a,b) and eBird data (row 2; c,d). We bounded eBird analysis between 32.5° N and 37.5° N latitudes in the Mississippi Flyway for this comparison. eBird predicted distributional shifts within 6 km of GPS‐marked Mallards in 2020 and within 38 km in 2021 (right panel bar graph).

FIGURE 3

North–south median distribution shifts (km) and 95% credible intervals (CRI) for continental waterfowl populations in response to the February 2021 ECE (a) and severe February temperatures in 2021, 2019, and 2015 (c) compared with non‐ECE years. Estimated marginal median distribution shifts (km) and 95% CRI among waterfowl foraging strategies in response to the February 2021 ECE (b; blue) and severe February temperatures (d; blue) compared with non‐ECE years (red). Foraging strategies included generalists (i.e., Mallard, Northern Pintail, and Teal), grubbing/browsing foragers (i.e., Lesser Snow Goose, and White‐fronted Goose), and wetland obligate species (Northern Shoveler and Gadwall).