Author’s update: While sightings of Mountain Bluebird from different locations in Chicago strongly suggested multiple individuals and a possible invasion, photo analysis has revealed that there was simply one Mountain Bluebird on the move, which was documented by birders in five different locations on the west and north sides of Chicago over multiple days. Credit to the Chicago birding community for such thorough coverage of the area. The original and unedited text of the article is below, but some of the information is outdated.

Before yesterday, April 20, there had never been a Cook County, Illinois, record for Mountain Bluebird, Sialia currucoides. But today, April 21, there are three.

Chicago may be experiencing a Mountain Bluebird invasion. A bird found in Humboldt Park on April 20, represented a first county record, and was seen by several dozen birders before eventually flying west out of the park. Another Mountain Bluebird sighting happened today, April 21, in the morning at Winnimac Park, with yet another sighting occurring this afternoon in Loyola Park. These parks are all some distance from each other, but it’s unclear whether these sightings are of the same bird or not.

Historical records of Mountain Bluebird in Illinois mostly have occurred in different counties. The earliest record is from May 10, 1969, in Peoria County, central Illinois. There is another spring record of April 9–11, 1982, in Sangamon/Christian County, also central Illinois. Other fall and winter historical records from central Illinois are December 13, 1987, Mason County, and November 4, 1998, Sangamon County. In northern Illinois, there are two historical records: La Salle County, November 1995, and Stephenson County, January 1983. About ten more recent records are visible on eBird.

Mountain Bluebird is an early spring migrant which winters as far south as central Mexico, often migrating in flocks. Their breeding range extends as far north as Alaska and eastern Manitoba.

Birders patrolling their Lake Michigan patches for spring migrants should be on the lookout!

Frank Izaguirre is an Editor of Birding magazine. He lives in Pittsburgh, PA, with his wife, Adrienne, and daughter, Maya.