Ring-billed Gull

A regular breeding resident and migrant; regular in winter. Late migrants have been observed every winter since 1977, and the first reports of overwintering birds were during the winter of 1992. The Ring-billed Gull was an uncommon bird during the Minnesota Breeding Bird Atlas (MNBBA).

Widely distributed across southern Canada, from British Columbia to the Maritime Provinces, and across the northern United States, from the mid–Pacific coast through the Great Lakes; small populations also occur in New England. Breeding densities are quite localized, reaching some of their highest densities in southeastern Manitoba and along the lower Great Lakes and St. Lawrence River (Figure 1).

Assigned a Continental Concern Score of 6/20 by Partners in Flight and considered a species not currently at risk by the North American Waterbird Conservation Plan.

A short- to medium-distance migrant that winters along the coasts, in the southern United States, and in northern Mexico.

An opportunistic omnivore that employs a diversity of foraging strategies to secure insects, earthworms, fish, rodents, and refuse.

A ground nest in low areas with sparse vegetation; usually nests in colonies numbering from just a few pairs to thousands.

Widely dispersed throughout the state today, the Ring-billed Gull was known 100 years ago primarily as a common spring and fall migrant in Minnesota (Roberts 1932). Nonbreeding adults and immature birds were occasionally observed during the summer months, but there were no known breeding records. Despite the lack of breeding evidence in Minnesota, in the 1800s the species was known to be a breeding resident from British Columbia, east through the Great Lakes, and farther east to the northern Atlantic coast. Nesting was documented in southern Wisconsin in 1860 and on islands in Lake Michigan in 1879–1881 (Matteson 2006). West of Minnesota, Bent (1922) observed a colony on Stump Lake in North Dakota in 1901, and to the north, a colony on Manitoba’s Lake Winnipegosis in 1913. These colonies may have been the source of the nonbreeding adults and immatures observed in Minnesota in the late 1800s and early 1900s.

Notwithstanding these accounts, during the late 1800s and early 1900s, Ring-billed Gulls were quite uncommon across their breeding range. They had declined precipitously in response to widespread persecution, including the collection of eggs for food and the slaughter of adults for the millinery trade. Not only had populations plummeted, the species’ breeding range had become limited to undisturbed sites in the northern Great Plains of the United States and the Prairie Provinces of central Canada (Pollet et al. 2012). Following this carnage, passage of the Migratory Bird Treaty Act in 1918 would be one of many factors that would launch an unprecedented growth in population numbers (Pollet et al. 2012).

The account of the gull’s breeding history in Minnesota begins with an unconfirmed account of a pair of Ring-billed Gulls nesting on an island in Lake Superior, in Cook County, in June 1905. Although the observer was a competent ornithologist, he made his observations from a steamer en route to Isle Royale. Roberts (1932) included the account in his 1932 treatise but noted that the unconventional nesting site described by Dr. Dart, a ledge 20 to 30 feet above the water, left the observation “open to doubt.” Another 31 years would pass before the first confirmed nesting report was documented by Thompson (1936), who found 2 adults and 2 downy young on the rocky shoreline of Lake Superior, just west of the Cascade River in Cook County.

A second nesting effort was not documented until 1957, when a single nest was found nestled within a colony of approximately 100 Common Tern pairs in the Duluth Harbor (Cohen 1958). Within a few years multiple reports began to accumulate from a few key sites across the state. In 1960, a single egg was found on Tern Island in southern Leech Lake (Dickerman and Fefebvre 1961), and in 1963 at least 100 nesting pairs were found on Hennepin Island on Lake Mille Lacs (Hiemenz 1964). Then, in 1981, two large colonies were found on the U.S. side of Lake of the Woods: 2,255 pairs at Techout Island, and 640 pairs at Fourblock Island (Hirsch 1981).

As the Ring-billed Gull continued its recovery and population expansion, nesting pairs were eventually found at scattered locations throughout the state. Outside of the lone records in Cook County, however, the four sites where the birds were initially discovered (Duluth-Superior Harbor, Lake Mille Lacs, Leech Lake, and Lake of the Woods) would grow to support the majority of the statewide breeding population.

Of the four, the largest population occurs in the Duluth-Superior Harbor. In 30 years, the number of breeding pairs grew from 1 pair in 1960 to 8,224 in 1990 (Penning 1993). During this time the birds occupied and moved among a number of different sites in the harbor, including Barker’s Island, Minnesota Power’s Hibbard Power Plant, and the Duluth Port Terminal. As these sites each became unsuitable, due largely to disturbance and vegetative growth, the majority of the population eventually settled on Interstate Island (Harris and Matteson 1975; Davis and Niemi 1980; Penning 1993; Penning and Cuthbert 1993). Here, during the fourth decadal census of colonial waterbirds nesting in the North American Great Lakes, conducted from 2007 through 2009, a total of 10,578 nests were counted. The island was the fifth largest colony across the entire Great Lakes (Morris et al. 2011).

Farther west, on Leech Lake, the small colony that began on, appropriately enough, Gull Island, grew from just 1 nest in 1960 to 1,069 nests in 1991. As this site reached carrying capacity, the birds moved to nearby Little Pelican Island, where the number of nesting pairs reached 5,000 in 2015 (Hamilton and Cuthbert 2016). Meanwhile on Lake Mille Lacs, the number of Ring-billed Gulls grew from the initial estimate of 100 nesting pairs in 1963 to approximately 500 pairs in 2015 (Hamilton and Cuthbert 2016).

Smaller colonies have become established and have grown at other sites as well, including on Marsh Lake, which straddles Lac qui Parle and Big Stone Counties in west-central Minnesota, and in Crow Wing, Pennington, and Stearns Counties (Minnesota Ornithologists’ Union 2016). Over time, the birds have moved beyond using natural and dredge-spoil islands to nesting on gravel rooftops, beginning with a report in 1998 of gulls nesting on the rooftops of two buildings in Hennepin County (Rudelt 1998). By 1998, Hertzel and Janssen had confirmed nesting in 7 counties: Big Stone, Cass, Faribault, Hennepin, Lake of the Woods, Mille Lacs, and St. Louis. Nonbreeding birds were also observed at sites throughout the state.

During the MNBBA, observers reported 902 Ring-billed Gull records in 14.0% (663/4,741) of the surveyed atlas blocks and in 11.8% (276/2,337) of the priority blocks. Breeding was confirmed in just 18 (0.4%) blocks (Figures 2 and 3; Table 1). The birds were observed in 67 of Minnesota’s 87 counties and were confirmed breeding in 12 counties (1 block in Lac qui Parle Lake straddled Lac qui Parle and Chippewa counties). In addition to the well-known colonies in the Duluth-Superior Harbor, Lake Mille Lacs, Leech Lake, and Lake of the Woods, birds were documented nesting at several sites on Marsh Lake in Big Stone and Lac qui Parle Counties, on Lac qui Parle Lake in Lac qui Parle and Chippewa Counties, on Pelican Lake in Crow Wing County, and at a few other smaller sites. To the 7 counties identified by Hertzel and Janssen (1998) where nesting had been confirmed since 1970, the atlas added breeding records in Carlton, Chippewa, Crow Wing, Douglas, Grant, Hubbard, and Lac qui Parle Counties.

Analysis of the Ring-billed Gull atlas observations presented some challenges. Because most birds do not breed until they are 3 to 4 years of age, it is not uncommon for nonbreeding adults and immature birds to wander far from breeding colonies during the summer months. As a result, with the exception of 1 carefully documented “possible” observation in Duluth, all “possible” and “probable” records were changed to “observed” records. In addition, because the species usually nests in relatively large colonies, all “confirmed” records away from the known major colonies were closely examined before making a final determination about the correct evidence code.

The Ring-billed Gull has firmly established itself as a regular breeding resident in Minnesota in the past 100 years, experiencing the most significant growth since 1960. At the same time, the species has recovered from the decimation and persecution it experienced in the 1800s and early 1900s and has reoccupied most of its former North American breeding range. Accounts of rapid growth similar to that documented in Minnesota can be found throughout the Great Lakes region. Expansions beyond its former breeding range have been most significant in the western United States and Canada and in the Maritime Province of Newfoundland (Pollet et al. 2012).

*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.

Although Ring-billed Gulls may be observed foraging in a wide variety of open habitats, including agricultural lands, lake and river shorelines, urban and suburban areas, landfills, and parking lots, their nesting requirements are quite narrow. Breeding colonies are usually located on low-lying, level areas with sparse vegetation (Figure 4). Most sites are islands, either natural or man-made, the latter including dredge-spoil islands and rooftops. Peninsulas on large lakes also may be used. Protection from mammalian predators, however, is paramount.

The nests themselves are usually placed close to the water and may be adjacent to low herbaceous or woody vegetation (<1 meter tall) that provides some protection from aerial predators. The nesting substrate is variable and includes sandbars, small pebbles, exposed rock, driftwood, and even concrete (Wires et al. 2010; Pollet et al. 2012).

The North American population of Ring-billed Gulls is estimated at 1.7 million breeding birds (Kushlan et al. 2002). The estimate for the Great Lakes Region, which includes the Laurentian Mixed Forest Province of Minnesota, is 167,300 breeding pairs (334,600 individuals), or approximately 20% of the North American population (Wires et al. 2010).

In Minnesota there is no statewide survey that provides a one-time estimate of the statewide Ring-billed Gull population. Nevertheless, two recent studies can provide a reasonable approximation. During the 2015 breeding season, a statewide survey of American White Pelican and Double-crested Cormorant colonies in Minnesota was conducted by the University of Minnesota and Minnesota Department of Natural Resources (Hamilton and Cuthbert 2016). Because Ring-billed Gulls often nest in association with these species, the survey also counted nesting Ring-billed Gulls. Excluding the Duluth Harbor, which was not surveyed, a total of 15,429 Ring-billed Gull nests were tallied. Although gulls were not surveyed in the Duluth Harbor in 2015, they were surveyed in 2016 by other researchers, who documented 12,979 nesting pairs (Bracey, Ponshok, and Strand, pers. comm.). Since the 2005 breeding season, all Ring-billed Gull nesting activity in the harbor has been restricted to Interstate Island. The results from the two surveys total 28,408 Ring-billed Gull nesting pairs residing in Minnesota during the 2015–2016 breeding seasons. Nearly 46% of the population is restricted to just one site: Interstate Island in the Duluth-Superior Harbor.

Although the federal Breeding Bird Survey (BBS) is not well suited to monitoring colonial waterbirds, it is the only long-term monitoring data available across the Ring-billed Gull’s breeding range. Since 1966, across southern Canada and the northern United States the species has demonstrated a nonsignificant average annual increase of 1.61% per year, increasing to 4.49% from 2005 to 2015 (Figure 5). The data for Minnesota show a great deal of variability with lower overall reliability. Nevertheless, since 1967, the species demonstrates a statistically significant increase of 3.82% per year; since 2005 the trend has reversed, and the species has declined an average of 1.35% per year (Sauer et al 2017).

More detailed population data have been collected since 1976 as part of a larger, binational effort to census colonial waterbirds nesting throughout the Great Lakes once each decade. The Ring-billed Gull is now the most abundant colonial waterbird nesting on the Great Lakes. Ring-billed Gull nests have increased 92% since the first census was conducted, growing from a total of 305,790 nests during the first survey (1976–1980) to 585,984 in the fourth and most recent survey, conducted from 2007–2009 (Morris et al. 2011). The increase was smaller in Canada (39%), where numbers have steadily decreased since the second census, compared to an increase of 197% in the United States (Figure 6). Throughout the Great Lakes, the number of colonies also has increased, from 151 during the first census to 222 in the fourth census.

Several factors are responsible for the gull’s population increase not only in the Great Lakes but throughout North America. As noted earlier, protection from persecution, following enactment of the Migratory Bird Treaty Act in 1918, initially helped spur the species’ recovery. In the Great Lakes, the introduction of new food sources (rainbow smelt in 1922, alewife in the 1930s) and cycles of low water levels that exposed more nesting areas certainly helped contribute to the increases observed, as did the availability of dredge-spoil islands as new nesting sites (Morris et al. 2011; Cutright et al. 2007). Some of the increase in the Duluth-Superior harbor is attributed to cycles of high water levels on the Great Lakes that swamped lower-lying colonies in the eastern Great Lakes and prompted the birds to explore sites farther west. In the western United States, the expansion of agriculture and the construction of reservoirs likely contributed to the species’ success in this region. Finally, the gull’s omnivorous diet and adaptability to human-modified landscapes, including feeding at landfills and nesting on rooftops, have certainly aided its recovery.

All these factors have likely contributed to the species’ increase in Minnesota, as well as immigration from other expanding colonies elsewhere in the Great Lakes (Davis and Niemi 1980). Indeed, numbers have increased so rapidly in some areas that the gulls have become both a pest and a threat to the recovery of other colonial nesting species. Efforts to control local populations are actively practiced at a number of nesting colonies (Pollet et al. 2012; Morris et al. 2011).

With a rapidly expanding population that is widespread across North America, the Ring-billed Gull is not considered a conservation priority at the state or federal level. It was assigned a relatively low Continental Concern Score of 6/20 (Partners in Flight 2017) and considered not to be a species at risk by the North American Waterbird Conservation Plan (Kushlan et al. 2002).

Despite this low score, like most colonial waterbirds, Minnesota’s Ring-billed Gulls are concentrated at just a handful of sites, making the species quite vulnerable to disturbance and habitat degradation. The birds will often abandon a nesting colony if it is continually disturbed by people, including researchers, during incubation. In Minnesota, suitable nest sites are at a premium, especially for a species that requires open, protected, beach-type habitats within or adjacent to large bodies of water.

The species’ exponential population growth has had serious consequences for one of Minnesota’s rarest colonial waterbirds, the Common Tern. The two species often seek the same nesting habitat. Yet, because Ring-billed Gulls arrive earlier in the spring, they can usurp quality habitat before the terns arrive (Davis and Niemi 1980; Penning 1993; Penning and Cuthbert 1993). Nesting Ring-billed Gulls present serious threats to all four major Common Tern nesting sites in the state: Interstate Island in the Duluth-Superior Harbor, Hennepin Island in Lake Mille Lacs, Little Pelican Island in Leech Lake, and Pine and Curry Island in Lake of the Woods. The gulls were also considered one of the potential predators responsible for mortality of Piping Plover eggs and chicks on Pine and Curry Island in the early 1980s when plovers were still nesting on the island. Although researchers never witnessed acts of predation on this federally threatened species, Ring-billed Gulls were frequently observed in or near the plover’s nesting areas (Wiens and Cuthbert 1984).

A variety of management techniques have been employed to discourage gulls from nesting in Minnesota’s Common Tern colonies and to insure that sufficient habitat is still available for the terns. The handbag of tools includes activities that require federal permits, such as destroying nests and oiling eggs. Researchers have also built overhead grids of monofilament line over tern colonies that discourage gulls from alighting within the colony but still allow enough room for the smaller terns to enter (Figure 7) (Haws 2002; McDowell 2011; Maxson et al. 1996; Mortensen and Ringle 2007; Penning and Cuthbert 1993; Penning 1993). To date these efforts have at least stabilized Common Tern populations. Ring-billed Gulls are also often controlled at sites where their numbers pose threats to airline safety, human health, and agricultural production (Pollet et al. 2012).

Yet, as adaptable and abundant as the bird is, another serious threat looms on the horizon. Recent modeling efforts by the National Audubon Society predict that warming temperatures could eliminate 70% of the gull’s current breeding range by the year 2080 (Langham et al. 2015; National Audubon Society 2016).  In lieu of the analysis, the Ring-billed Gull was classified as “climate endangered.” Clearly, with focused control efforts underway, coupled with the potential impacts of climate change, the long-term future of the Ring-billed Gull requires careful monitoring.