The diet of the eastern bluebird consists of a mixture of insects wild fruit, berries, and seeds. The amount of insects and fruit taken by bluebirds changes throughout the seasons.
Insects comprise up to two-thirds of the diet of an adult eastern bluebird during the breeding season. Wild fruits, berries, and seeds comprise the remaining one-third. In the Fall and Winter, bluebirds switch to fruit and berries but still depend on insects.
Nearly 100% of insects taken by eastern bluebirds are on or near the ground. A high proportion of ground-dwelling insects is a result of the bluebird’s foraging strategy, which consists of scanning the ground beneath elevated perches for insects.
Types of insects and other invertebrates
Based on studies of the eastern bluebird’s diet, it is known that the birds mainly consume:
- butterfly and moth larvae
- katydids, and
Other food items that were also taken included:
- Millipedes and centipedes
- sow bugs, and
Types of fruit and berries
Fruits are essential when insects are scarce in the winter months. Some preferred winter food sources include:
- dogwood (Cornus florida)
- hawthorn (Crataegus spp)
- wild grape (Vitis vinifera)
- sumac (Rhus typhina and Rhus labra)
- and hackberry seeds (Celtis laevigata)
- blackberries (Rubus spp.)
- bayberries (Myrica spp.)
- honeysuckle (Lonicera maachi)
- Virginia creeper (Parthenocissus quinquefolia)
- red cedar (Juniperus virginiana)
- pokeberries (Phytolacca mericana)
Bluebird diet by the numbers
Studies that quantified the food taken by eastern bluebirds throughout its range in a calendar year have determined that approximately:
68% of their food comprises invertebrates.
32% of fruit, berries, and seeds.
Considering only insects, their diet is composed of:
- butterfly and moth larvae (32.4%),
- beetles (30.7%),
- grasshoppers, and crickets (25.6%),
- and spiders (11.3%).
Eastern bluebird diet during the breeding season
Bluebirds consume the same food throughout the year, although the proportions of insects and berries fluctuates during the breeding and non-breeding seasons.
The breeding season is when bluebirds have a protein-rich diet that includes a lot of insects. When raising young, all species of birds switch to a protein-rich diet. Baby bluebirds benefit from protein-rich diets as they grow quickly and healthily.
There are reasons for fast growth.
Baby birds are more likely to be preyed upon in a nest than when they are fledglings. By feeding chicks a diet high in proteins, parents can shorten the time chicks are in the nest.
Studies have shown that bluebirds consume up to 68% of insect protein during the breeding season.
Diet during the non-breeding season
During the non-breeding season, eastern bluebirds change their diet when they are not feeding young, and some migrate.
Bluebirds eat fruit and berries primarily in winter when insects are scarce, but they also eat insects and other invertebrates. Dogwood, hawthorn, wild grape, sumac, and hackberry seeds are some of the best winter food sources.
Bluebirds catch insects beneath their perches, primarily within a distance of 16 to 65 ft. Distances of up to 130 ft to spot and catch an insect are rare.
How do Eastern Bluebirds find their food?
Bluebirds hunt for insects by perching on high points such as branches, snags, utility cables, or fenceposts. They visually scan the ground beneath the perch and swoop down to catch an insect on or near the ground.
Most insects and other invertebrates are caught using the “scan-and-swoop-down” method. On occasions, bluebirds catch insects in the air, hover over the ground searching for prey, briefly walk on the ground, or pursue insects in the air.
Bluebirds usually chose perches of 2 to 49 feet above the ground that has sparse understory, short grass, or even bare ground.
Bluebirds have remarkable eyesight. According to field observations, bluebirds scan the ground beneath their perches for insects at distances ranging from 16 to 65 feet, sometimes as far away as 130 feet.
Upon capturing an insect, bluebirds can either eat it on the ground if it is a small one or bring it to a perch if it is a large one.
The bluebird proceeds to knock out and kill the insect on the perch by smacking it against the perch to also soften it before consumption.
Bluebirds’ foraging strategy is similar throughout the year and during breeding and non-breeding seasons.
When it comes to eating fruit and berries, bluebirds generally perch next to the fruit or berry and pluck it. Bluebirds often hover near a berry and pluck it to take it to a perch for further handling before eating it.
- Goldman, P. (1975). Hunting behavior of eastern bluebirds. Auk 92:798-801.
- Gowaty, P. A. and J. H. Plissner (2020). Eastern Bluebird (Sialia sialis), version 1.0. In Birds of the World (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.
- Pinkowski, B. C. (1977c). Foraging behavior of the eastern bluebird. Wilson Bulletin 89:404-414.