Contemporary knowledge of migrant waterfowl chronologies is important for effective population management, especially in the context of shifting phenology and climate change. We used a dataset of year-round, every other week, comprehensive bird counts during 2002–2013 on a 461 ha island of shallow water impoundments in central Chesapeake Bay to define the migration period for 21 species of surface and diving waterfowl. Migrant periods for species going north ranged from 7 January through 31 May, with nearly all species reaching a mean date during 19 February through 23 March. South migrant periods ranged from 1 August through 12 February, with most experiencing a mean date during 23 October through 8 January. The migration period average for both surface and diving species was 7 d longer going north than south, whereas both the north and south surface species migration period averages were 15 d longer than the diving species. We found significant differences (P < 0.001) among the migration periods of many individual species. When comparing the 2002–2013 migration period mean date with pre-1958 peak migration periods, we found 14 species are now arriving north earlier, south later, or both, which could be attributed to various factors, including warming temperatures on northerly breeding grounds. Results from this study provide definitive migrant waterfowl chronologies for species commonly traversing the mid-Atlantic area and are the first available for that region in more than half a century. Received 25 March 2016. Accepted 14 July 2017.

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