- Minnesota Breeding Bird Distribution
- Breeding Habitat
- Population Abundance
- Literature Cited
A regular breeding resident and migrant. The Purple Martin was an uncommon species during the Minnesota Breeding Bird Atlas (MNBBA).
Broadly distributed across the eastern United States and the southern regions of central and eastern Canada. Smaller populations are found along the coast of the Pacific Northwest, from southwestern British Columbia through California, and in the southwestern states of Utah, Colorado, New Mexico, and Arizona. Highest breeding densities are found in the southeastern region of the United States (Figure 1).
Assigned a Continental Concern Score of 10/20 by Partners in Flight; officially listed as a Special Concern species in Minnesota and designated a Species in Greatest Conservation Need by the Minnesota Department of Natural Resources.
Long-distance migrant that spends the winter in South America.
An aerial insectivore.
A secondary cavity nester. Eastern populations nest almost entirely in man-made nest cavities, while western populations can still be found nesting in natural cavities.
Roberts (1932) considered the Purple Martin to be a common summer resident throughout the state, noting that even in the prairies it was found in “considerable numbers in the towns and about farmhouses.” Although today we associate the species strictly with artificial nesting structures, in Roberts’s day Purple Martins were still found nesting in natural tree cavities, in cavities excavated by woodpeckers, on cliff ledges, and in rock crevices, especially in the less settled regions of the state.
Roberts’s 1932 status account of the species included his own photograph of martins nesting among large boulders on two tiny islands in Lake Mille Lacs, Spirit Island and Hennepin Island. The birds’ unique use of these boulder-strewn islands was first reported in 1886 by Washburn, an early student of the state’s ornithology. Nearly thirty years later, in 1915, Roberts and his colleague William Kilgore visited the site, describing how the martins were nesting “in the midst of the Common Tern colonies, with which birds they were at constant war, as the Terns no doubt ate the eggs and young of the Martins when they could reach them.” Despite these challenges, the martins continued to persist. A visitor in 1930 estimated 300 pairs were nesting on Spirit Island, and 50 pairs on Hennepin Island (Roberts 1932). Together the two islands, now a national wildlife refuge, supported a natural nesting colony of Purple Martins for at least 44 years, from 1886 to 1930.
Elsewhere in the state, Roberts had compiled breeding evidence (both confirmed and inferred nesting records) from 13 counties and from Itasca State Park and Cass Lake. The counties were primarily restricted to the Eastern Broadleaf Forest, the Tallgrass Aspen Parklands, and the western and southern regions of the Laurentian Mixed Forest Provinces. Their status in the far north-central and northeastern regions was not clear from Roberts’s account.
When Green and Janssen (1975) published their updated description of the species’ status several decades later, they reported that martins were a breeding resident throughout the state but were most common along the Mississippi River and about the towns and cities of central and western Minnesota. Janssen (1987) delineated a total of 36 counties, distributed across all regions of the state, where martins had been confirmed nesting since 1970. Included were 2 northern counties, Itasca and Lake. Hertzel and Janssen (1998) later added 7 more counties to the list, including several in north-central Minnesota.
Survey work by the Minnesota Biological Survey (MBS) reported a total of 101 breeding season locations of Purple Martins, restricted primarily to central and southern Minnesota. However, the MBS’s focus on natural communities precluded an in-depth survey of the small residential communities and recreational areas where the species is most common (Minnesota Department of Natural Resources 2016).
During the MNBBA, observers reported 878 Purple Martin records in 11.2% (537/4,781) of the surveyed atlas blocks and in 11.3% (265/2,337) of the priority blocks. Breeding evidence was documented in 350 blocks (Figures 2 and 3; Table 1). The birds were observed in 75 of Minnesota’s 87 counties and were confirmed breeding in 68 counties (one block straddled both Big Stone and Lac Qui Parle Counties). Thirty-two of the confirmed nesting counties were additions to the list published by Hertzel and Janssen (1998). Overall, Purple Martins were most abundant in central Minnesota, from the Twin Cities north to Leech Lake, and west to Otter Tail and Kandiyohi Counties. Certainly the focused effort of many energetic atlas observers in this region contributed to the high number of records. But the region is also populated with many lakeshore residents who actively encourage local Purple Martin colonies by erecting and maintaining martin homes on their property. The birds were virtually absent, however, from the extensively forested regions farther north in the state.
None of the confirmed breeding records documented during the MNBBA mentioned use of a natural nesting cavity. Like nesting populations throughout eastern North America, Minnesota’s Purple Martin population may now depend entirely on artificial nesting cavities constructed and maintained by local residents.
In the past 100 years, the Purple Martin has remained a species widely dispersed across all but the densely forested counties of northern Minnesota. Elsewhere the species’ breeding range has receded southward during the 20th century, particularly in northwestern Canada (Brown and Tarof 2013). Farther east, a similar retraction has been documented in Ontario, where the northern periphery of the species’ breeding range moved 56 km south during the 20 years between their first and second atlases (Cadman et al. 2007). Factors responsible for the range contraction are unclear. Cadman and his colleagues (2007) speculated that several successive years with late frosts and cold spring rains could result in a significant loss of birds, with a subsequent impact on local populations for years. On the other hand, increasingly warm spring temperatures may result in the birds arriving before sufficient food resources are available. Farther south, in the Great Plains, the installation of martin houses has facilitated a small westward expansion of the species’ core breeding range (Brown and Tarof 2013).
*Note that the definition of confirmed nesting of a species is different for Breeding Bird Atlas projects, including the definition used by the Minnesota Breeding Bird Atlas, compared with a more restrictive definition used by the Minnesota Ornithologists’ Union. For details see the Data Methods Section.