Burrowing Owl

Summer and migration vagrant, last observed breeding in Minnesota in 2007; summer visitant from 1880 to 1980 and was observed breeding in many of those years. The Burrowing Owl was very rare during the Minnesota Breeding Bird Atlas (MNBBA).

The Burrowing Owl in North America has two subspecies: the Western Burrowing Owl (A. c. hypugaea) and the Florida Burrowing Owl (A. c. floridana). The disjunct population of the Florida Burrowing Owl formerly was found primarily in the prairies in the central Florida peninsula; however, its range expanded as land development created more open country. Currently its nesting is concentrated north and west of Lake Okeechobee, with other breeding sites along the southeastern Atlantic Coast. The range of the Western Burrowing Owl covers the Great Plains from southern Alberta and Saskatchewan south to the Texas Panhandle, then westward to the Great Basin and the interior valleys of California, Washington, and Oregon. Within these range boundaries, the Burrowing Owl is found at scattered nesting localities in landscapes of expansive open country. In recent decades, the population of the Western Burrowing Owl has declined and the eastern margin of its range has contracted westward. It no longer breeds regularly in Manitoba, Minnesota, and Iowa; in the Dakotas, it is now rarely found east of the Missouri River (Klute et al. 2003). The largest population in the Western Hemisphere occurs in South America, where its breeding range is extensive and where it occurs year-round in suitable open habitat south to Tierra del Fuego. There are disjunct breeding populations on some Caribbean Islands as well. In North America the highest breeding densities are found in southeastern Colorado (Figure 1).

Officially listed as an Endangered Species in Minnesota and designated a Species in Greatest Conservation Need by the Minnesota Department of Natural Resources; assigned a Continental Concern Score of 12/20 by Partners in Flight.

The Burrowing Owl is a year-round resident in the southern part of its range, but owls that nest in Canada and the northern United States migrate to the southwestern states or Mexico. The Florida population is considered nonmigratory. Although it is considered a permanent resident in Florida, vagrants along the coast in the Carolinas have been shown to be owls dispersing from the Florida population (Davis 1977).

Feeds primarily on insects but also takes small mammals, birds, reptiles, and amphibians.

The species’ underground nesting and roosting habits are unique. The western population is mostly dependent on burrows of prairie dogs or (in Minnesota) Richardson’s ground squirrels, although burrows excavated by other animals can be used; the eastern Caribbean and Florida populations dig their own burrows.

The Minnesota population of the Burrowing Owl is on the eastern periphery of the species’ breeding range. The status of rare birds like the Burrowing Owl in Minnesota in the nineteenth century is poorly known because of the paucity of natural history observers in that time. Even now, the species is encountered infrequently, and its abundance and site occupancy fluctuate. Although Roberts (1932) called this little owl “a comparatively recent immigrant from the west,” he might have been influenced by the fact that he had not encountered it on his big prairie trip in June 1879 to Grant and Traverse Counties (Roberts and Benner 1880). But, in July 1881, he did find two pairs with young in southwestern Swift County. Roberts also cites several other nineteenth century records: Jackson County, sometime in the 1880s; Lac qui Parle County, 1893; Heron Lake, Jackson County, 1896; Lake Benton, Lincoln County, 1897; Warren, Marshall County, 1897 (nesting) (Roberts 1932). In the early twentieth century, a few more observations were published in the new periodical The Flicker; and by 1924, Roberts found that “it was nesting commonly throughout Grant, Traverse, Pipestone, Lincoln and Lac qui Parle counties” (Roberts 1932). At the end of the twentieth century, Grant (1965) and Martell et al. (2001) had compiled a list of breeding records in 27 counties. These records were exclusively in the Prairie Parkland Province, ranging along the state’s western border, from Marshall County south to Rock County, east to the prairie enclaves in Mahnomen County, and south to Stearns, Sibley, and Martin Counties.

Throughout the twentieth century and into the twenty-first, observational records from the Minnesota Ornithologists’ Union (MOU) that lacked breeding evidence occurred almost entirely within the Prairie Parkland Province. The birds could have been either migrants or birds establishing a territory. The only exceptions were obvious migrants reported in various locations: the Duluth harbor on May 26, 1956, May 15, 1979, and May 31, 1997; in Rochester, Olmsted County in 1965; and at the Rochester Airport from May 9 to June 24, 2006. The many specimens, mostly from the nineteenth century, in the Bell Museum of Natural History (BMNH) are also all from the Prairie Parkland Province. Another specimen, collected May 19, 1939, in a “wooded region of Ottertail [sic] County” was put on display in the biology museum of the St. Cloud State Teachers College (Sauer 1940). The last specimen collected, on May 13, 2003, was found dead near a burrow in Moyer Township, Swift County, where it had been observed beginning on May 5, 2003 (BMNH #44835).

Although there have been judgments made about whether the population of the Burrowing Owl has declined from the 1920s to the 1980s, it is difficult to tell from the observational record how abundant this rare owl was during these decades. Its population seemed to fluctuate and its site occupancy seemed random, probably based on suitable habitat or landscapes. Some anecdotal descriptions provide clues. In a letter in the Bell Museum files from Alfred Peterson of Pipestone County to Roberts on August 12, 1924, Mr. Peterson comments: “burrowing owls in a dozen known places – probably more numerus [sic] than usual.” In his field study in 1963 and 1964 of the nesting behavior of the Burrowing Owl, R.A. Grant found only four breeding pairs after travelling about 10,000 miles searching in western Minnesota. He also commented that “all who knew this species agreed that it was no longer as common as formerly” (Grant 1965). From the actual number of documented breeding records in the Roberts and MOU files in each decade, the number of breeding pairs ranged from five to six in the 1920s, 1930s, and 1940s, to seven to eight in the 1950s, 1960s, and 1980s, and three in the 1970s. These numbers are difficult to interpret based on the variability of observer effort and concentrated surveys. The slightly higher numbers in the 1960s and the 1980s may have been due to special surveys in the 1960s (Grant 1965) and public outreach efforts in the 1980s. During the 1980s, Martell (1990) documented “13 successful nestings at eight sites in Minnesota, mostly in Rock and Pipestone counties [that] fledged from two to eight young each.”

In the 1980s, in response to the proposed state listing of the species, field surveys conducted by the Minnesota Department of Natural Resources concluded, “The last viable population was present in the early 1960s in the west-central part of the state at a time when uncultivated land was retained in the ‘soil bank’ program” (Coffin and Pfannmuller 1988). That conclusion is probably valid for a sustained population; any observations or breeding evidence since the 1980s has been at isolated sites scattered throughout the western prairie. In the 1990s there was only one documented breeding location near Blue Mounds State Park in Rock County, where a pair of owls successfully nested in 1989, 1990, and 1991 (MOU Seasonal Report Archive); the site would later become Touch the Sky Prairie, a component parcel of the Northern Tallgrass Prairie National Wildlife Refuge that spans both Minnesota and northern Iowa. The MOU seasonal reports during the 1990s also recorded incidental observations in southwestern counties (Lincoln, Martin, Murray, Nobles, Pipestone, Rock, and Traverse) during spring and summer months that could be either migrants or birds on territories.

During the twenty-first century, including the MNBBA survey years, the number of reported records increased. It is not clear whether these records represent the usual random pattern of the Burrowing Owl’s occurrence on the eastern fringe of its range or if they indicate a different trend. Most field observers no longer record more than the presence of this casual species on a single date, making it difficult to determine its breeding status at any given site. Records reported for the years 2000–2015 occur in three categories: incidental (5), unsuccessful breeding (5), and successful breeding (2). Some of these records were during the MNBBA survey years but were only submitted to the MOU database.

The incidental records and unsuccessful breeding records are detailed in Table 1. The five incidental records of single birds could be either migrants or vagrants. Two incidental records reported during the MNBBA atlas years did not include locational data precise enough to ascribe them to an atlas block; since they were observed in May they were likely migrant birds. Together these observations document an increase in reports from the 1990s, when there was only one successful breeding location and no documented unsuccessful breeding attempts.

Finally, two observations of successful nesting were documented during the 2000s. One report was of a family of two adults and two juveniles from August 8 to 18, 2007, near Edgerton in Pipestone County (Svingen 2008; Budde et al. 2008). The most noteworthy breeding records for these years was on land managed by the Nature Conservancy north of Glacial Ridge National Wildlife Refuge (NWR), near the Tilden/Kertsonville township line in Polk County. At least two adults were observed and photographed at a burrow there by many observers from April 17 to May 6, 2006 (Svingen 2006a, 2006b; Budde et al. 2006). Then, in 2007 a successful nesting was confirmed. Two adults and two juveniles were observed from June 1 to July 28, 2007, near Glacial Ridge NWR (Svingen 2008; Kessen and Svingen 2008). Unfortunately, directions given by the observers who originally found the owls, or by many subsequent observers, are not explicit enough to determine if these nesting pairs were at the same burrow in 2006 and 2007, if there was more than a single pair each year, or which township they were in.  The 2007 nesting records were the first documented nesting reports of the Burrowing Owl in Minnesota since 1991.

In 2010, during the MNBBA, a record from the Nature Conservancy site in Tilden Township was submitted to the atlas indicating “pair observed at burrow throughout breeding season,” but no young were ever seen (Figure 2, Table 2). Because the breeding site for the Burrowing Owl(s) on the Nature Conservancy land was not monitored and reported to the atlas database consistently (or elsewhere) during the 2009–2013 survey, it is not possible to determine a more definitive breeding attempt for this Minnesota endangered species other than the information given above for 2006 and 2007. Two incidental records for the atlas years are listed in Table 1: near Bluestem Prairie SNA, Clay County, 2010; and at the Joe River State Wildlife Management Area, Kittson County, 2011. As noted, these are single May records, so the birds could have been migrants, vagrants, or birds prospecting a potential nesting site. These records are not included in the MNBBA database.

*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.

In the American West, the Burrowing Owl occupies short-grass open country in the Great Plains and the Great Basin, such as prairies, deserts, steppes, grazed farmland, and airports. Historically in Minnesota the species was found “amidst the high, rolling prairies of our western counties [where] these birds find suitable homes among colonies of Richardson’s ground squirrels or ‘flickertails.’ The ground squirrels, in turn, are usually found in pastures where the grass has been grazed short by cattle . . . Because of their preference for short grass, it is probable that both the burrowing owl and the Richardson’s ground squirrel were associated with the coming and going of the bison in Minnesota.” (Schladweiler 1985). The Florida subspecies is more eclectic in its choice of open land and may nest on “wet and dry prairie, cemeteries, airports, ball parks, golf courses, open field, and cleared vacant lots” (Brevard County Natural Resources Management Office).

The Partners in Flight Population Estimates Database provides estimates for the Burrowing Owl for several geographical areas. These estimates are based on the size of the range and route data from the federal Breeding Bird Survey (BBS) (Partners in Flight Science Committee 2013). The United States population estimate is 700,000 adults and the Canada estimate is 400. The global population, which includes Central and South America, is estimated at 2 million adults. However, in 2017 Partners in Flight updated the global estimate to 3.5 million birds.

Long-term monitoring data collected by the BBS indicate a declining population that decreased an average of approximately 1% per year from 1966 to 2015 (Sauer et al. 2017). Because most regions across the survey area lack sufficient routes with a large enough sample, the results lack statistical precision. Nonetheless, no region, province, or state has populations that demonstrate a significant increase in numbers since 1966. This is particularly notable in the Prairie Pothole Region, where BBS data suggest the species has experienced the largest decline. Indeed, immediately west of Minnesota, Murphy and his colleagues (2001) noted that in North Dakota the Burrowing Owl has “disappeared from the eastern third of the state and is uncommon to rare in the best habitats north and east of the Missouri River.” The primary cause of the declining populations is considered to be habitat loss as large landscapes are converted from grass to intensive row-crop agriculture. Urban development and reductions in burrowing animal populations, mostly prairie dogs, has also contributed to declines in some regions.

The U.S. Fish and Wildlife Service considers the Burrowing Owl to be a national Bird of Conservation Concern and a Bird of Conservation Concern in its western regions (Regions 1, 2, and 6). Its global heritage status rank is G4 (apparently secure globally, although quite rare in parts of its range), and the species is listed as of Least Concern on the IUCN Red List. Its status is Endangered in Canada and Threatened in Mexico. Partners in Flight (2017) assigned it a moderate Continental Concern Score of 12/20. Its declining population and threats to its breeding habitat were of particular concern. In the United States, the Burrowing Owl’s designation varies: Endangered (Minnesota), Threatened (Colorado) and Special Concern (seven western states and in Florida) (Klute et al. 2003). After the species was designated in Minnesota in 1984 as Endangered, an effort was made to establish a reintroduction program, which was ultimately unsuccessful (Martell et al. 2001).

Preservation of grasslands and other open native vegetation is a critical management requirement for this species. Loss of habitat is not the only threat to the species future. The National Audubon Society classified the species as “climate endangered” based on its analysis that the species could lose 77% of its current summer breeding range by the year 2080 (National Audubon Society 2017; Langham et al. 2015). In the near term, the U.S. Fish and Wildlife Service recommends research on land use trends and population demographics, as well as better population monitoring because the “[c]urrent large-scale monitoring efforts are generally inadequate” (Klute et al. 2003). Greater understanding of these factors could significantly improve our understanding of this unique member of the prairie avifauna.