The Red-headed Woodpecker (\(Melanerpes\) \(erythrocephalus\)) is an iconically colored bird of North America whose movements defy the traditional definition of migration. Unlike species that follow established routes, this woodpecker is best described as a partial and irregular mover. This unique pattern means some populations remain year-round residents while others undertake movements determined not by a calendar but by the local success of the fall harvest.
The Nature of Their Movement
The Red-headed Woodpecker is classified as a facultative migrant, meaning its decision to leave its breeding grounds is optional and depends on environmental factors. This contrasts sharply with obligate migrants, such as warblers, which must travel to the same wintering grounds annually. This partial nature means individuals within the same population may exhibit different behaviors, with some birds staying put while others move.
The movement is often described as irruptive, characterized by unpredictable timing and destination. A population may be present in a location one winter and completely absent the next, making its presence highly erratic. When they do move, it is typically a short-distance shift, often traveling during the day in loose, small groups.
What Drives Their Irregular Movement
The primary factor dictating the Red-headed Woodpecker’s movement is the annual availability of mast crops, such as acorns and beechnuts. These birds engage in extensive food caching, a behavior that allows them to remain in northern latitudes through the winter. A successful mast crop provides a reliable, high-calorie food source, eliminating the need to move south.
They gather and stockpile large quantities of nuts, wedging them into crevices, natural tree cavities, or under the bark of trees and utility poles. They are also known to store insects, such as grasshoppers, in these caches. The density and accessibility of these stored provisions determine their winter distribution. If the local mast crop fails, the birds are forced to move, or “irrupt,” in search of areas that experienced a better harvest.
Tracking Their Seasonal Presence
The breeding range of the Red-headed Woodpecker extends across the eastern United States, stretching north into southern Canada and west to the Rocky Mountains. When the birds decide to move, the shift is typically modest, generally involving a movement slightly to the south or west. This movement often keeps them within the central and southeastern U.S. states, where they can find reliable winter foraging habitat, especially in mature oak-hickory forests.
The best time to observe whether a local population has chosen to migrate is during the fall, specifically from late August through early November. This is the period when the birds are actively assessing their winter food stores and making the decision to depart or stay. If a location has a robust crop of nuts, many woodpeckers will remain at or near their breeding sites, defending their small winter feeding territories. Conversely, a lack of local food will prompt movement that can result in large concentrations of the species in a newly abundant area.