Effects of weather variation on waterfowl migration: Lessons from a continental‐scale generalizable avian movement and energetics model

Abstract

We developed a continental energetics‐based model of daily mallard (Anas platyrhynchos) movement during the non‐breeding period (September to May) to predict year‐specific migration and overwinter occurrence. The model approximates movements and stopovers as functions of metabolism and weather, in terms of temperature and frozen precipitation (i.e., snow). The model is a Markov process operating at the population level and is parameterized through a review of literature. We applied the model to 62 years of daily weather data for the non‐breeding period. The average proportion of available habitat decreased as weather severity increased, with mortality decreasing as the proportion of available habitat increased. The most commonly used locations during the course of the non‐breeding period were generally consistent across years, with the most inter‐annual variation present in the overwintering area. Our model revealed that the distribution of mallards on the landscape changed more dramatically when the variation in daily available habitat was greater. The main routes for avian migration in North America were predicted by our simulations: the Atlantic, Mississippi, Central, and Pacific flyways. Our model predicted an average of 77.4% survivorship for the non‐breeding period across all years (range = 76.4%–78.4%), with lowest survivorship during autumn (90.5 ± 1.4%), intermediate survivorship in winter (91.8 ± 0.7%), and greatest survivorship in spring (93.6 ± 1.1%). We provide the parameters necessary for exploration within and among other taxa to leverage the generalizability of this migration model to a broader expanse of bird species, and across a range of climate change and land use/land cover change scenarios.

Marginal value analysis reveals shifting importance of migration habitat for waterfowl under a changing climate

“…Northward migration has begun earlier for many migratory bird species in recent decades (Lehikoinen et al., 2019), although the timing of spring northward movements can seldom be strongly predicted based on thaw and green‐up phenology in a given year (Wang et al., 2019). Furthermore, migration timing and forage types vary among dabbling duck species and our results are most relevant for mallards, the species for which the model was parameterized (Aagaard et al., 2022).…”

“…The bottom panel shows nodes that became positive (pos) and negative (neg) in a warm winter, relative to a cold winter. All estimates are based on single‐node knockouts in an energetics‐based movement and foraging model (Aagaard et al., 2022). To better display the variation among nodes while reducing the influence of extreme values, positive values were log‐transformed.…”

“…Days 0, 100, and 200 correspond to September 01, December 10, and February 20, respectively. All estimates are based on single‐node knockouts in an energetics‐based movement and foraging model (Aagaard et al., 2022). All maps use Albers equal area conical projection centered on the contiguous United States.…”

“…To determine the effects of weather on node marginal value, we repeated this simulation using climate data from each of 2 years. We selected 1956–1957 (hereafter referred to as 1957) as a particularly cold winter (Ludlum, 1957) and 2014–2015 (hereafter 2015) as a particularly warm winter (Aagaard et al., 2022; Appendix ). Precipitation levels also differed among the years.…”

Migrating Anatidae as Sources of Environmental Contamination with Zoonotic Giardia, Cryptosporidium, Cyclospora and Microsporidia

“…In addition, due to gradual climate change and negative human impacts, new areas and resting places are being explored by waterbirds [ 26 ]. Therefore, this review is limited to a group of waterbirds from the family Anatidae, as they can form large flocks during the migratory season [ 27 ] and often graze and defecate in both water and fields in urban or suburban areas [ 6 ]. In many regions where they have unrestricted access to the waters they share with humans, they are protected by environmental laws [ 28 ], are an essential component of the natural aquatic environment, and are necessary for the proper functioning of aquatic ecosystems [ 29 ].…”