The European Starling (Sturnus vulgaris) is a stocky, medium-sized bird, easily recognized in winter by its dark, speckled plumage and long, pointed bill. This bird is not native to North America; it was successfully introduced in 1890 in New York City’s Central Park by a group aiming to establish all bird species mentioned in the works of Shakespeare. The starling proved exceptionally adaptable, rapidly spreading across the continent and establishing itself as a widespread, non-native species. The success of the starling is due in large part to its ability to thrive in human-altered landscapes, which raises the question of whether this hardy bird needs to migrate.
Migration: The North American Distinction
The question of whether starlings fly south for the winter has a nuanced answer, as their movement is best described as a partial, regional migration. Unlike many native North American birds that undertake long-distance journeys to the tropics, starling movement is highly variable depending on where they live. Generally, populations breeding in the northernmost parts of their range, such as Canada and the upper Great Lakes region, are migratory and head south for the winter.
Birds in the central and southern United States, however, are largely considered permanent residents, remaining in the same general area year-round. Southern states receive an influx of wintering starlings, augmenting the already resident population. Even within a single northern population, some individuals may choose to stay put, illustrating that the decision to migrate depends on individual and local conditions.
The Mechanics of Starling Movement
Starling migration is typically a short-distance shift, rarely involving the thousands of miles covered by species like warblers or thrushes. Birds moving south usually travel only a few hundred miles, following a general south or southwesterly direction. These routes are often dictated by geographic features, with starlings utilizing river valleys and coastal plains as corridors for their movements.
The severity of the winter weather acts as the primary trigger for these movements, often described as irruptive shifts rather than fixed migrations. A sharp drop in temperature or heavy snowfall that covers feeding grounds will push northern birds further south to find accessible food sources. These shifts often conclude in warmer urban and agricultural areas, where reliable resources allow the birds to survive the cold months.
Why Some Starlings Stay Put
The starling’s success as a resident species, particularly in developed areas, is rooted in its remarkable adaptability to an environment shaped by human activity. Urban environments offer a warmer microclimate due to the “urban heat island” effect, mitigating the worst of the winter cold. This warmer environment allows the birds to conserve energy that would otherwise be spent on thermoregulation.
Food availability promotes residency, as starlings are highly opportunistic omnivores. They can sustain themselves through the winter by foraging on agricultural leftovers, livestock feed at concentrated animal feeding operations, and refuse in human waste. Their flexible nesting habits allow them to utilize natural tree cavities and a variety of sites within human structures, such as eaves, vents, and utility poles, providing year-round shelter close to their food supply.
The Spectacle of Winter Roosting
Once starlings have settled into their winter locations, they engage in communal roosting, one of the most visible behaviors in the avian world. As dusk approaches, starlings gather in enormous flocks, sometimes numbering in the tens of thousands, before settling into a shared night roost in dense thickets or on city structures. These large, dense congregations provide both warmth and protection from nocturnal predators.
Before dropping into their chosen roost, the flocks engage in a massive, coordinated aerial display known as a murmuration. Hundreds or thousands of birds twist, turn, and shape-shift in the sky with astonishing synchronicity. This collective movement is hypothesized to deter aerial predators like peregrine falcons. The sheer number of birds moving as a single, fluid mass makes it difficult for predators to single out an individual. This pre-roosting ritual also allows the birds to share information about the most profitable foraging sites they found during the day.