Each year millions of waterfowl migrate from their breeding grounds in arctic, northern and mid-latitudes to more southern locales to exploit abundant food and wetland resources as freezing wetlands and snowfall progress from north to south in North America. These migrating ducks, geese, and swans consume an abundance of wetland plants and seeds, as well as agricultural waste grain; they distribute seeds and invertebrates in their guts and on their feathers and provide a substantial cultural resource for wildlife watchers and hunters alike. The age old migration of waterfowl has been awaited by many generations of North Americans but, in an age of emerging and evolving science regarding climate change, discussions among scientists, waterfowl hunters and bird watchers about the stability of these traditional migrations are increasingly common. Anecdotal, as well as empirical evidence suggest that waterfowl are now migrating later than traditionally observed and remaining at northern latitudes later into autumn-winter.

Autumn migration is influenced by three main factors that result in yearly differences in the timing of duck movements in North America. Individual species of waterfowl migrate based on cues that helped their species survive for millennia including, 1) changes in day length (photoperiod), 2) habitat suitability, and 3) weather severity. The species of waterfowl we see migrating each autumn, the timing of their arrival to southern latitudes, and their abundance are a combination of these three main factors.

A Weather Severity Index (or WSI) to explain changes in abundance of Mallards and Other Dabbling Ducks at staging areas during autumn migration was developed because an experimental method was needed to estimate the potential influence of a warming climate on autumn-winter distributions of ducks in North America. Thus, we answered the question (Schummer et al. 2010), “What weather thresholds make dabbling ducks migrate?” Using different combinations of temperature and snow depth data available on the Internet and waterfowl counts from Conservation Areas in Missouri, it was determined that the cumulative effects of temperature and snow over several days significantly influenced southward migrations by Mallards.

This web application allows you to view a animated map of waterfowl migration and download a table which has summed the square kilometers of area with WSI values ≥ 7.2 (for mallards). You can select your Area of Interest category (Entire dataset, Flyway, LCC, Joint Venture, or state) and a sub-category (Example: If you select LCC as the category you will select one of the available LCCs as the sub-category). Once these have been selected you must input dates of interest. The dataset starts September 01, 1979 and ends December 31st, 2012.

Upper Midwest and Great Lakes Landscape Conservation Cooperative Long Point Waterfowl Ducks Unlimited Mississippi State

In using this open-access WSI web application to obtain data you agree to cite any work derived thereafter using these data as

Mitchell, M., M. L. Schummer, J. Coluccy, R. Macleod. 2014. An open-access web-based tool for querying weather severity index data used to predict mallard migration in the Central, Mississippi, and Atlantic Flyways, September - March 1979 - 2012. Accessed online: