In “On the Move,” our regular column about migration, we present pairs of distribution maps from eBird that you can use to compare where interesting birds are at different times of year. We featured Violet-green Swallow, pictured above, and Greater White-fronted Goose in our February 2015 issue.
Compiled from 2004-2014, the eBird maps above compare the distribution of Violet-green Swallow in February and July. In February, the species is on the move, migrating north from wintering areas in southern California, the desert southwest, Mexico, and northern Central America. Violet-green tends to migrate along major water bodies and should be looked for with other swallow species over lakes and rivers. The first mild temperatures in February often lead to a pulse of birds arriving in the Pacific Northwest. In July, the species is found across the western lower 48 states, western Canada, and central Alaska, where it occurs only patchily north of Fairbanks. On the July map, many of the purple squares in Mexico represent uncommon nesting records. The bird is rarely reported outside its normal western range, although it can turn up across the eastern states and provinces at any time of year.
Greater White-fronted Goose
Greater White-fronted Goose breeds across arctic and sub-arctic regions of Alaska and northern Canada and winters primarily along the Pacific coast, in the southern Great Plains, and in parts of Mexico. Key wintering concentrations are in California’s Central Valley, Texas, Louisiana, and northern Mexico. These eBird maps cover the last 10 years and show how the bird’s distribution changes from February to July. In February, many geese have begun migrating and are found in the Pacific states, throughout much of the Midwest, and in small numbers in the Northeast, where they often join with flocks of Canada Geese. By July, the species has mostly vacated its winter range and occurs in northern and central Alaska and across the arctic regions of northern Canada. Purple squares along the Pacific coast and in the central and southern United States represent non-breeding geese that didn’t fly north for summer.
eBird is the real-time online checklist operated by the Cornell Lab of Ornithology and Audubon. “On the Move” is written by eBird’s Garrett MacDonald, Chris Wood, Marshall Iliff, and Brian Sullivan. Submit your bird sightings at ebird.org.
A version of this article appeared in “Birding Briefs” in the February 2015 issue of BirdWatching. Subscribe.Originally Published