Do Eastern Bluebirds Migrate for the Winter?

do eastern bluebirds migrate for the winter

The Eastern Bluebird (Sialia sialis) performs movement and goes through regional abundance changes throughout the year. Not many North American birds show such unique moves.

Do Eastern Bluebirds migrate for the winter?  Some do, and some don’t.  Some populations migrate from the southern and middle states to northern states and Canada to breed; they return to winter in the South. However, other bluebirds are residents and stay on or near their territories throughout the year.

Bluebirds’ foraging strategy to find food is consistent throughout the year, but the proportion of invertebrates and fruit varies during migration and the breeding and non-breeding seasons.

Bluebirds generally roost in cavities. But no one seems to know where Bluebirds roost during migration. The same goes for migratory Bluebirds arriving in southern states where resident bluebirds and other cavity-nesting/roosting birds have already taken over available cavities.

Migration of the Eastern Bluebird

In most of its range in the U.S., the Eastern Bluebird is a year-round resident (see map below). Within its range though, there are populations that perform south-north-south annual migrations.

There is no external difference between birds that migrate every year and those that stay in place throughout the year.

During the summer season, the migratory bluebirds fly north from the middle and southern states to the northern states and Canada, expanding the overall species’ range. During the wintertime, birds retreat to the central and southern states to mingle, again, with resident bluebirds.

Birds of the far northern regions, such as the Canadian provinces and parts of some U.S. northern states, are long-distance migrants. These birds leave the region during the winter.

Banding studies have demonstrated general patterns regarding the movements of the Eastern Bluebird.

Birds banded in the region that encompasses western Manitoba’s Canadian province to central Ohio fly south to spend the winter in Texas, Louisiana, Mississippi, Alabama, and Mexico.

Birds banded in the region encompassing New Hampshire to southeast Michigan fly south to spend the winter in the southeastern states of Florida, Georgia, North, and South Carolina.

As noted before, these birds fly over and then join resident bluebirds that remain in their territories year-round.

Situational Migrants are typically resident bluebirds that stay in or in the vicinity of their breeding territories year-round. It is only during inclement weather events such as blizzards and snowstorms, making it difficult to find food in their territories, that these birds are forced to migrate south for better foraging conditions.

Situational migrations are temporary. Once the weather conditions improve, birds will return, sometimes within days, to their year-round territories. Birds in the northern states are more likely to be affected by inclement weather conditions.

bluebird range-map

Range Map showing the occurrence of the Eastern Bluebird through an annual cycle.

  • In most of its range (purple area), the Eastern Bluebird is a resident species.
  • Migratory bluebirds occupy the northern portion of the range map (orange area) only during the period of approximately May 17 – August 31, which corresponds to the breeding season. It is important to note that the Eastern Bluebird breeds through its entire range.
  • Part of the Southwest (teal area) is occupied only during the non-breeding season, presumably by birds that breed in the northern U.S. and Canada.
    Source: eBird-Eastern Bluebird.


This animation shows the movements and abundance of the Eastern Bluebird throughout an annual cycle.

Play de animation multiple times and note how the abundance of bluebirds changes in the area where birds are resident. Bluebirds are more abundant (concentrated) within the “resident birds range’ during the non-breeding season of  December 7 – May 1. Source: eBird-Eastern Bluebird.

What Distances do Bluebirds Cover During Migration?

Migration distances have a good deal of variation. Long-distance migrants from Canada’s northernmost regions cover distances of over 1,400 miles to the southern states and Mexico.

The distance covered by situational migrants varies with the intensity of the weather event.

Severe and long-lasting weather events push Bluebirds further south than mild and short-lasting weather events. Situational migrants likely move only a few hundred miles.

What is the range of the Eastern Bluebird?

The Eastern Bluebird is a widespread bird in eastern North America. The northern edge of its range includes part of the Canadian provinces of south-central Saskatchewan, southern Manitoba, and central Ontario (See range map).

The Eastern Bluebird also occurs in most Quebec, locally in New Brunswick, on the Prince Edward Islands, and in central and southwest Nova Scotia.

The Western boundary of the Eastern Bluebirds’ range includes a small region of eastern Montana, about the eastern half of Wyoming, Colorado, and New Mexico.

Bluebirds also occur in Mexico and west-central Belize, Southwest Guatemala, east El Salvador, northeast Honduras, and northern Nicaragua in Central America.

The Eastern Bluebird is also residents on the Island of Bermuda, located some 621 miles east of Florida.

eastern bluebird habitat
Eastern Bluebird habitat typically includes forest edges, open spaces, plenty of perches, and a mixture of generally short ground cover.

What is the Eastern bluebird habitat?

Eastern Bluebirds prefer open and semi-open habitats with no or little understory and with sparse ground cover.

Habitat types that meet these characteristics include lowland pine savanna, orchards, clear-cuts, burned tracts of pine forests, young pine stands, swampy habitats, pastures, golf courses, and low-density urban areas.

But the Eastern Bluebird not always used these types of habitats.

Before the European settlement of America and before the land had any significant human influence, the Eastern Bluebird likely used naturally occurring open and semi-open woodlands and swamps.

Habitat for the Bluebird perhaps included fire-maintained savannas, open stands of mature pinewoods, xeric forest, and openings caused by natural landslides.

The Eastern Bluebird still uses structurally similar habitats with no or little understory and with sparse ground cover.

Bluebirds appear to tolerate and sometimes even thrive in disturbed habitats. The addition of nesting boxes and suitable perches to disturbed habitats consistently increases the number of territorial bluebirds.

What do Bluebirds eat throughout the year?

Studies of Eastern Bluebirds’ diet throughout their range have determined that approximately 68% of their food comprises invertebrates, while 32% of berries.

If we consider only invertebrates, its diet is composed of butterfly and moth larvae (32.4%), beetles (30.7%), grasshoppers, and crickets (25.6%), and spiders (11.3%). During the breeding season, they consume even more than 68% of invertebrates.

Chicks in the nest need a diet high in protein content to grow fast and leave the nest as soon as possible.

During migration and the non-breeding season, Bluebirds increase the consumption of fruit.

Valuable fruit items in the diet of Bluebirds include mistletoes and sumac berries.

how bluebirds find food

Bluebirds catch invertebrates mostly within 16 to 65 ft. Distances of up to 130 ft to spot and catch an invertebrate are rare.

How do Eastern Bluebirds find their food?

Bluebirds use a sit-and-wait strategy to locate ground-dwelling invertebrates.

They perch on top of a pole, branch, or any other elevated structure to scan the surroundings. Once the prey is spotted, the bird launches a sally to the ground to capture the prey.

The perches Bluebirds use are usually 2 to 49 feet above sparse understory, short grass, or even bare ground.

Bluebirds have remarkable eyesight. Birds scanning the surroundings detect insects at distances of 16 –65 feet. Sometimes as far away as 131 feet.

Once captured, the prey may be consumed on the spot (on the ground) or brought to a perch if it is a large prey item that needs to be banged against a pole to knock it out before consumption.

Only on rare occasions, Bluebirds will catch insects in the air, hover over the ground to spot a prey item or engage in active pursuit of an invertebrate while walking on the ground.

To consume berries and other fruit, Bluebirds perch next to the fruit and eat it. Some birds briefly hover and pluck a berry and then perch on a branch to eat it.

How many subspecies of Eastern Bluebird are there?

The Eastern Bluebird ranges throughout the eastern United States, parts of Mexico, parts of Central America, and Bermuda’s Island.

Only populations of the birds occurring in temperate regions in North America are known to engage in annual migrations.

There is little variation in bluebirds’  coloration and measurements in North America, Mexico, and Central America.

Ornithologists, based on the color variation of museum specimens, have determined that there are seven sub-species of Bluebirds including:

  • Sialia sialis sialis: These birds breed in eastern North America, from southern Canada to northeastern Mexico (southern Tamaulipas). These birds winter from the eastern United States to northern Mexico, rarely to Cuba.
  • Sialia sialis bermudensis: This subspecies is found on the Island of Bermuda.
  • Sialia sialis fulva: This subspecies occurs in southwest U. S. (SE Arizona) South through montane Central Mexico.
  • Sialia sialis nidificans: Found in the Caribbean slope of East-Central Mexico.
  • Sialia sialis guatemalae: Foud in Souteast Mexico (Chiapas) and Guatemala.
  • Sialia sialis meridionalis: Occurs in El Salvador, Honduras and Northern Nicaragua.
  • Sialia sialis caribaea: This subspecies is found in East Honduras and Northeast Nicaragua.

bluebirds roosting
Little is know about the roosting habits of the Eastern Bluebird during migration. It is likely that they do not use cavities but roost in tree branches. Photo: Tom Murray/Flickr/CC by 2.0


Where do Bluebirds spend the night (roost) during migration?

It is not well known where Eastern Bluebirds spend the night or roost during migration. Because they are not familiar with the locations of cavities along the route south, they likely roost in trees outside cavities.

Bluebirds that stay in the same territory year-round roost in natural cavities, cavities made by woodpeckers, or nesting boxes offered by humans. These birds are familiar with the locations of these cavities.

Field observations indicate that Bluebirds often roost communally. Several individuals may use a single cavity for the night.

Little is known about where bluebirds roost when they arrive in the wintering grounds where there are already resident Bluebirds, and most cavities have been taken.

Perhaps, bluebirds roost in trees while they establish or re-acquaint with their wintering territories. Some may roost in trees until they find a cavity. Others may join other bluebirds jor the night in existing cavities.

Migratory bluebirds interact and compete for cavities with other Bluebirds and other birds. Nuthatches, Great Crested Flycatchers, swallows, European starlings, and House Sparrows are among the most common birds that also use roosting and nesting cavities.

Conclusions:

The Eastern Bluebirds that migrate long distances every winter are those that breed in the northernmost region of the species’ range.

Birds of northern states are partial migrants, which migrate temporarily south only in response to inclement weather.

Eastern Bluebirds have a stereotyped foraging behavior. Birds sit-and-wait in perches scanning for insects in the ground.

The Bluebirds’ diet changes throughout the year. It includes a greater proportion of invertebrates during the breeding season and more berries during the non-breeding season.

References:

  • Gill, Frank (1995). Ornithology. New York: W.H. Freeman.
  • Gowaty PA, Plissner GH. (1998). Eastern Bluebird (Sialia sialis), no. 381. In: A. Poole (ed.). The Birds of North America Online. Cornell Lab of Ornithology, Ithaca, New York.
  • Eastern Bluebird, Life History. All About Birds. The Cornell Lab of Ornithology.

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