Extreme climatic variability during migration invokes physiological and dietary plasticity among spring migrating ducks

Abstract

Environmental stochasticity encountered during migration can have negative consequences for individuals and population demographics through direct reductions in survival or cross-seasonal impacts. We took advantage of substantial interannual variation in spring migration conditions over a 4 year field study to examine physiological and dietary variation among two species of migrant ducks. We collected female Lesser Scaup (Aythya affinis (Eyton, 1838)) and Blue-winged Teal (Spatula discors (Linnaeus, 1766)) during spring migration and measured lipid and protein reserves, an index of recent lipid metabolism based on concentrations of lipid metabolites in plasma, and diets. We documented systematic interannual variation among these metrics in both species, contrasting primarily the warmest, earliest spring and the coldest, latest spring. Lesser Scaup had reduced lipid and protein reserves and consumed less energy-rich prey during the coldest and latest spring but showed no interannual variation in the index of lipid metabolism. Blue-winged Teal similarly had reduced protein reserves in the cold, late spring but maintained constant lipid reserves among years, likely facilitated by increased consumption of energy-rich seeds reflected in diets and lipid metabolism. Our results reveal impacts of environmental stochasticity on migrants and suggest that recruitment may be impacted by variable conditions encountered during migration during extreme weather events.

Prairie wetlands confer consistent migrant refueling conditions across a gradient of agricultural land use intensities

“…We rinsed prey samples in a 500 μm sieve and searched under 10× magnification to identify and enumerate key prey species. We focused on 3 taxa that are important prey for spring-migrating lesser scaup and blue-winged teal, based on diet analyses in the present work (Janke et al, 2019) and previous studies (Anteau and Afton, 2008a;Hitchcock, 2009;Tidwell et al, 2013). The three taxa were Mollusca, Amphipoda, and Chironomidae.…”

Factors Affecting Wetland Use by Spring Migrating Ducks in the Southern Prairie Pothole Region

“…Emergent vegetation in wetlands provides cover against harsh weather and protection against predators when compared to open water areas, and the lack of emergent vegetation may increase predation or disturbance risk on these wetlands (Pöysä 1983 a ). Additionally, vegetation provides food resources for many migrating duck species consuming vegetative material, seeds, or aquatic invertebrates associated with vegetation (Hitchcock 2009, Janke et al 2019 a ), which may be another reason these wetlands had higher use (Hagy et al 2017, Gross et al 2020). These energetic contributions of prairie wetlands may be important considerations in planning efforts for non‐breeding waterfowl that have gone largely unstudied in this ecosystem (Williams et al 2014).…”

“…Ducks arriving on the breeding grounds may be required to spend time foraging thus delaying clutch formation because of decreases in body condition from insufficient stopover habitat, consequently affecting survival and reproductive success (Afton and Ankney 1991). Spring migrating ducks on stopover locations primarily refuel and rest (Guillemain et al 2004) but also engage in other energetically costly activities during migration, including courtship (Weller 1965), molt (Anteau et al 2011), and confronting unpredictable weather (Janke et al 2019 a ). Therefore, stopover sites must satisfy nutrient needs while also providing space for courtship, and minimizing disturbance and other threats (Newton 2008).…”

Wetland hydropattern and vegetation greenness predict avian populations in Palo Verde, Costa Rica

“…Blue‐winged Teals are also predicted to be abundant (100–300 individuals) for the same ranges of the two conditions but are predicted to be most abundant (<500 individuals) when water levels are the most unstable (i.e., in April–May). This may be explained by the greater ability of Teals, especially during migration, to adapt their foraging and diet to the environmental conditions of the wetland they are visiting in terms of plant selection (Swanson and Meyer 1977, Janke and Anteau 2019), as opposed to Whistling‐ducks that will also forage in the surrounding agricultural fields if that plant selection is not suitable for them (Cohen et al. 2019).…”