Eastern Bluebird

Sialia sialis

Rangewide Distribution: Southeastern Canada, eastern United States to Central America
Abundance: Common but declining in some areas
Breeding Habitat: Open areas adjacent to woods & forests
Nest: Cup of grass, weeds, twigs & pine needles in tree cavity or nest box
Eggs: 4-5 pale blue, occasionally white & unmarked
Incubation: 12-14 days
Fledging: 15-20 days
image of Eastern Bluebird

Eastern Bluebirds breed primarily in rural areas. They favor rolling grasslands with scattered trees and shrubs that provide tree cavities or other sheltered sites in which they raise their young. Although their numbers cycle in response to the harshness of winter and nesting conditions, the Missouri state bird had a robust population throughout the Atlas Project. The fact that citizens build and place bluebird nest boxes in rural areas is likely responsible in part for the size of the Eastern Bluebird population.

Code Frequency

Where they occur, Eastern Bluebirds are likely the easiest of birds to find, identify and confirm to breed. Even novice birders recognize their field marks and their "cheer-cheery-up" song. Once sighted, adult bluebirds usually quickly reveal the location of their nest sites. The inspection of nest boxes often results in immediate confirmation of breeding. Considering these parameters, Eastern Bluebirds likely did not occur in the white areas on the map.

Distribution

Eastern Bluebirds were distributed statewide except for the Mississippi Lowlands. Scarcity in the Mississippi Lowlands was unexpected but may have been due to pesticides, a scarcity of grasslands and associated insect prey, or a shortage of natural nest sites. The Eastern Bluebird was absent in some blocks in the heavily-forested regions of Shannon and Reynolds counties and scarce in large metropolitan areas, especially St. Louis. These patterns reflect the bluebird's preference for open grasslands. The apparent scarcity of bluebirds in the extreme northwestern corner of the state was unexpected.
Average number of Eastern Bluebirds/100 stopsAverage Number of Birds / 100 stops

Abundance

Eastern Bluebirds were most abundant in the Osage Plains followed by the Ozark and Ozark Border natural divisions, presumably because of the adjunct nature of grasslands and woodlands in those natural divisions. They were less numerous in the Glaciated Plains and essentially absent from the Mississippi Lowlands.

Phenology

Eastern Bluebirds winter as far north as mid-Missouri (Sinnott 1981) insuring an early arrival on the breeding ground. The earliest observation of a nest with young, near Eunice in Texas County, indicates nest initiation in mid-March. Eastern Bluebirds commonly nest two or three times in a season (Harrison 1975). Nest initiation for the first brood occurs in late March, the second in mid- to late May and the third in July (Sinnott 1981). Accordingly, the latest observation of nest building probably documented a third nesting.

Notes

Eastern Bluebirds are extremely rare hosts to Brown-headed Cowbirds (Harrison 1975). The Atlas Project reported no brood parasitism.

Breeding Phenology
Evidence (# of Records) MAR APR MAY JUN JUL AUG SEP
NB (23) 4/05 7/31
NE (48) 4/09 7/09
NY (113) 4/07 8/12
FY (144) 4/12 8/25

Breeding Evidence

Reported in 1,118 (92.6%) of 1,207 blocks

image of pie chart
Blocks % of Blocks
  Confirmed 923 82.6%
Probable 123 11.0%
  Possible 72 6.4%
image of Missouri map

Home|Lists of Illustrations and Tables|Preface|Acknowledgments|Introduction|The Natural Divisions of Missouri|Guide to Species Accounts|Index of Bird Accounts|Appendix A.|Appendix B.|Appendix C.|Appendix D.|Appendix E.|Literature Cited

Document ID: --
Content revision: --