In semi-arid ecosystems, timing and availability of water is a key uncertainty associated with conservation planning for wetland-dependent wildlife. Wetlands compose only 1–3% of these landscapes; however, large populations of migratory waterbirds rely on these wetlands to support energetically
demanding life history events such as breeding and migration. Migration is considered a crucial period for birds associated with individual survival and reproductive success, yet our understanding of migration ecology remains limited. To better inform conservation planning supportive of these demands, we quantified synchrony of wetland flooding and waterbird migration by reconstructing bi-monthly surface water patterns from 1984 to 2015 across 11.4 million ha of the semi-arid Great Basin, USA. Results were then linked to seasonal migration chronologies for seven dabbling ducks species. Seasonal patterns were used in landscape planning simulations to assess efficiency in conservation strategies that aligned temporally sensitive wetland flooding and species migration. Wetland data were combined with land tenure to evaluate periodicity in waterfowl reliance on public and private lands. We found migration chronologies misaligned with wetland flooding. In spring, half (43– 59%) to three-quarters (68–74%) of seasonal wetlands were flooded and available to early- and late migrating species while seasonal drying restricted wetland flooding to 13–20% of sites during fall migration. Simulations showed wetland conservation inconsiderate of temporal availability was only 67–75% efficient in meeting waterfowl habitat goals on private lands that made up ~70% of flooded wetland area in spring. Private–public wetland flooding was equivalent during fall migration. Accounting for spatiotemporal patterns of wetland flooding is imperative to improving efficiencies linked to migratory bird conservation.