Habitat conservation strategies of the North American Waterfowl Management Plan (NAWMP) are guided by current understanding of factors that limit growth of waterfowl populations. The 1998 implementation plan of the Upper Mississippi River and Great Lakes Region Joint Venture (UMR and GLRJV) assumed that availability of foraging resources during autumn in wetlands actively managed for waterfowl was the primary limiting factor for duck populations during the nonbreeding season. We used multistage sampling during autumn and spring 2001–2004 to estimate energetic carrying capacity (ECC) of actively and passively managed wetlands in Ohio, USA, and examine this assumption. Energetic carrying capacity during autumn was similar between actively and passively managed wetlands each year. Averaged across years, energetic carrying capacity was 3,446 and 2,047 duck energy‐days (DED)/ha for actively and passively managed wetlands, respectively. These estimates exceeded the UMR and GLRJV assumption that 1,236 DED/ha were provided by managed wetland habitats. Energetic carrying capacity declined each year by >80% between autumn and spring migration. Consequently, ECC of actively and passively managed wetlands was low during spring ( = 66–242 DED/ha). These results suggested that duck foraging resources in actively and passively managed wetland habitats are abundant during autumn, but overwinter declines may create food‐limiting environments during spring.

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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.

Despite greater harvest rates of males, mallard (Anas platyrhynchos) populations exhibit male‐biased sex ratios, presumably because females experience greater mortality during breeding seasons than do males. Nest success and adult female survival during the breeding season greatly impact mallard population growth; however, no study has evaluated breeding‐season survival of males and females simultaneously using radiotelemetry. We captured, radiomarked, and monitored 90 male and 272 female mallards during 2 breeding seasons in the Prairie‐Parkland region of Canada (Manitoba 1998, Saskatchewan 1999). Model‐averaged estimates of female breeding season (i.e., 15 Apr–14 Jul) survival probabilities were 0.84 (SE = 0.031) in 1998 and 0.71 (SE = 0.040) in 1999. Estimated survival probabilities of paired males were 0.99 (SE = 0.016) in 1998 and 0.98 (SE = 0.025) in 1999; survival estimates for unpaired males were 0.92 (SE = 0.052) in 1998 and 0.85 (SE = 0.083) in 1999. Female mortality was greatest during periods of intensive nesting, whereas limited male mortalities precluded identification of attributes linked to mortality. Our results suggest that breeding‐season survival of males has little impact on mallard population growth, and that management efforts to increase female survival rates offer greater potential to enhance mallard production.