In our February 2014 issue, we’re introducing a new format for “On the Move,” our migration column written by eBird project leaders Chris Wood, Brian Sullivan, and Marshall Iliff. It presents species distribution maps from eBird for specific time periods so you can compare where birds are at different times of year. In their February column, Chris, Brian, and Marshall show us maps for White-winged Scoter and Common Merganser.
White-winged Scoter migrates each year between September and early December, moving from breeding areas in Canada and Alaska to wintering spots along the Atlantic and Pacific coasts, the Great Lakes, and large bays. The eBird maps above were compiled between 2009 and 2013. They show how the species’ distribution changes between July and January. In July, scoters can be found along Hudson Bay and as far north as Alaska’s Arctic coast. Purple squares along the Atlantic and Pacific coasts of the lower 48 states and southern Canada represent sub-adult scoters that remained south for the summer and adults that likely returned from breeding areas early. In January, scoters are uncommon inland but may show up on any large lake or reservoir in the lower 48 states, if only for a few days.
Compiled over the last five years, the eBird maps above show the fall movement of Common Merganser, which is often the last duck to fly south in fall and the first to return north in spring. The map at left shows where mergansers were reported in October. Throughout the winter months, the ducks move to wherever they can find open water. By January (right), mergansers can be found on fast-moving rivers or on open lakes and bays from Alaska to northern Florida. The birds prefer freshwater. Reservoirs on the Great Plains from Nebraska to Oklahoma often host thousands of individuals. In mid-February, birds wintering in the southern states begin heading north, and by April most mergansers are on the move.