- Minnesota Breeding Bird Distribution
- Breeding Habitat
- Population Abundance
- Literature Cited
A regular breeding species and migrant; since 1998 there have been occasional reports of individual birds observed during the winter months from the Twin Cities south to the Iowa border. The Franklin’s Gull was a rare species during the Minnesota Breeding Bird Atlas (MNBBA).
The Franklin’s Gull is strictly a species of the interior Great Plains, stretching across the Canadian Prairie Provinces of Alberta, Saskatchewan, and western Manitoba south into Montana, Oregon, Idaho, Utah, Wyoming, the Dakotas, and western Minnesota (Figure 1). Breeding densities are high wherever this highly colonial species nests.
Assigned a Continental Concern Score of 14/20 by Partners in Flight; ranked as a Species of Moderate Concern by the North American Waterbird Conservation Plan and identified as a Common Species in Steep Decline by the North American Bird Conservation Initiative. Officially listed as a Minnesota Special Concern Species and designated a Species in Greatest Conservation Need by the Minnesota Department of Natural Resources. The Franklin’s Gull was identified as a Target Conservation Species by Audubon Minnesota.
A long-distance migrant that primarily winters along the Pacific Coast of South America.
Feeds primarily on insects, both aquatic and terrestrial, and small fish. Often feeds in agricultural lands adjacent to nesting colonies.
A semi-floating mat of emergent vegetation often perched atop a mat of vegetation from the previous breeding season; old muskrat houses are also used.
The Franklin’s Gull was formerly found throughout the state’s western grasslands from the Iowa border north to Canada. Roberts (1932) considered it an abundant summer resident, nesting “throughout western Minnesota in great colonies.” Its fidelity to a given nest site was quite low. “Unlike most birds that breed in colonies, they usually change nesting-sites from year to year; in successive years these may be miles apart, though still within the limits of the same big lake or slough. Occasionally, however, the birds arrive in force at the old locality and then, after a brief stay, all disappear to locate for that season at an entirely new lake.” Roberts surmised that changes in water levels or food availability might be responsible. Despite his comments on their wide distribution, the only documented nesting account was from Heron Lake in Jackson County, where at least 50,000 nests were reported in 1916 (Roberts 1932) and 100,000 nests in 1937 (Green and Janssen 1975).
When Green and Janssen (1975) provided their updated account of the gull’s status decades later, they reported that nesting had been documented at only two locations since the 1960s: 1) Lake Osakis in Todd County; and 2) the Agassiz National Wildlife Refuge (NWR) in Marshall County. A few years later, Janssen (1987) also mentioned that breeding had been reported from Clay, Kandiyohi, Traverse (1942), and Wilkin Counties. Since 1970, however, nesting had only been documented in three counties: Marshall (Agassiz NWR where the total number of birds ranged from 0 in 1980 to 65,000 in 1982, and Thief Lake Wildlife Management Area (WMA) where 5,000-10,000 pairs were reported in 1980); Jackson (2,000-3,000 nests at Heron Lake in 1986); and Todd (5 nests at Lake Osakis in 1981). By 1998 no new nesting sites had been documented (Hertzel and Janssen 1998). One of many challenges with the Franklin’s Gull is that observers variously report the size of the colonies as broad estimates of the total number of adults, the number of pairs, and/or the number of nests, making it difficult to assess the true status of the breeding population.
Overall, since the early twentieth century and up to the initiation of the MNBBA, reports suggest that nesting was confirmed or attempted at 16 different sites stretching from Jackson County in the south, north to Marshall and Lake of the Woods Counties, and east to Kandiyohi County (Pfannmuller 2014). Documentation for the Clay County nesting record mentioned by Janssen (1987) could not be found. The vast majority of sites are used for just one to three years before they are abandoned; two of the 16 sites were sewage lagoons.
Despite the range of sites identified, only three large wetland complexes have been used repeatedly in the past hundred years: Agassiz NWR and Thief Lake WMA in Marshall County and Heron Lake in Jackson County. Rarely are all three sites used in a given year. Despite the large size of most nesting colonies, field reports documenting the location, size, and ultimate success of these colonies have been sporadic, making it difficult to assess the gulls’ movements within a given season or even over a few years.
Although Heron Lake supported the largest known colony in the early 1900s, activity at the site has dramatically decreased since then. Breeding records were largely absent from 1949 to 1983 (Vorland 1984). Intensive cultivation in the lake’s small watershed means that spring and summer rains have an immediate impact on water levels, often drowning nests, eggs, and young. Conservation efforts in the watershed have improved, but the site is still used only intermittently. Since 1984 documented nesting attempts were limited to four years: (1) 2,000 nests in 1984 (Vorland 1984); (2) 100 nests in 1985 (Wilson and Shedd 1986); (3) approximately 2,000 to 5,000 nests in 1986 (Shedd and Wilson 1987; Janssen 1987); and (4) approximately 500 young observed in 1992 (Chaffee 1992). Annual surveys from 1993 through 1995 failed to document any nesting attempts, although a few hundred to a few thousand adults have been observed on the lake in any given year. A more recent visit to the site in 2013 also failed to document nesting (Gelvin-Innvaer pers. comm.).
Documentation of the gulls’ presence at the second major site, Agassiz NWR, dates back to when the refuge was first established in 1937. Wetlands in the area were drained in 1911, but, following creation of the refuge, wetland restoration work soon attracted the birds. The first documented nesting occurred shortly thereafter in 1939 (Vorland 1984). Intermittent accounts over the years show population numbers ranging from zero nesting pairs to at least 125,000 in 1968, a year when nearly all the nests failed due to fluctuating water levels (U.S. Fish and Wildlife Service 1968). Between 2002 and 2005, the population varied from a low of 15,046 nests to a high of 71,924 nests (U.S. Fish and Wildlife Service 2005a). Then, for three consecutive years, the gulls began the nesting season at Agassiz but soon abandoned, moving instead to nearby Thief Lake WMA, located just 20 km north of the refuge. High predation was thought to be the primary culprit prompting the move; in other years moves have been a response to drought conditions. Generally, the gulls display such a strong tenacity to Agassiz, they relocate to Thief Lake only when the former site is deemed unsuitable (Vorland 1984).
The history of the birds’ use of Thief Lake WMA is poorly documented. Janssen (1987) reported 5,000 to 10,000 nesting pairs in 1980 and Burger and Gochfeld (2009) reported 2,000 pairs in 1994, and none in 2005-2007, even though the Agassiz colony was reported to have relocated to Thief Lake those very same years.
Although the number of nest sites is limited, each summer birds are reported from locations distant from any potential nesting sites. During the summer of 2014, for example, there were reports throughout the western, west-central, and southwest regions of the state and as far east as Goodhue and Steele Counties (Kessen et al. 2015). These may be post-nesting birds that are known to range widely following the breeding season, birds whose nests failed that year, or first-year birds. Although there is no definitive data on the age of first breeding, biologists believe it may be initiated at two years of age (Burger and Gochfeld 2009).
During the MNBBA, participants reported 42 Franklin’s Gull records from only 0.8% (37/4,735) of the surveyed atlas blocks and from 0.9% (20/2,337) of the priority blocks. Breeding was documented in only 1 block on the Agassiz NWR (Figures 2 and 3; Table 1). A small group of 60 adults and immatures were observed at Salt Lake in early July 2013, but the birds were likely dispersers from a nearby colony in South Dakota. Adults were observed in several other western and west-central counties, including 1 record in Dakota County (Figure 2).
The gull’s dependence on the Agassiz NWR is not unlike that seen elsewhere in its breeding range, where the establishment of large, managed wetland complexes has provided critical nesting habitat. The species’ expansion into many western states during the twentieth century is attributed, in part, to the creation of new refuges beginning in the 1930s. Burger and Gochfeld (2009) hypothesized that numbers may have increased in the 1920s only to decline in the drought years of the 1930s, when many nest sites disappeared. Some of the historic colony sites have never been reoccupied.
*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.