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Lesser Black-Backed Gulls Increasing on Sanibel and Captiva
Every winter, Sanibel and Captiva Islands are home to a larger variety and number of gull species than in the summer.
We see herring gulls (Larus smithsonianus), Franklin’s gulls (Leucophaeus pipixcan), Bonaparte’s gulls (Chroicocephalus philadelphia), laughing gulls (Leucophaeus atricilla), ring-billed gulls (Larus delawarensis), and lesser black-backed gulls (Larus fuscus) — this article’s highlight species. Lesser black-backed gulls can be found across much of the globe, but it hasn’t always been that way.
America’s recent uptick in lesser black-backed gulls is evident here on Sanibel and Captiva. The gulls are primarily seen November to March on the islands, and according to the last five years of SCCF’s monthly survey data, lesser black-backed gull counts have been steadily on the rise (see graph).
“Historically, lesser black-backed gulls have nested in Siberia, Scandinavia, and parts of the United Kingdom and Europe. While they’re still primarily present in these areas, their range has been slowly expanding over the past century,” said SCCF Shorebird Technician Aaron White. “Lesser black-backed gulls have been considered vagrants in North America for quite some time, but their numbers seem to be steadily increasing.”
Cross-Continental Expansion
The first record of a lesser black-backed gull in North America was in 1850 in Greenland, but the first record in North America outside of Greenland wasn’t until 1934 in New Jersey. Records began to slowly accumulate after that point until the 1970s, when reports of lesser black-backed gulls began to rise rapidly.
“By the 1980s, lesser black-backed gulls had been observed across all the Great Lakes and the entirety of the Atlantic and Gulf coast of the U.S.,” White said. “Today, these birds have been observed in every U.S. state and Canadian province!”
In the 1920s, lesser black-backed gulls established breeding grounds in Iceland, which by 2004 had reached 40,000 breeding pairs. In the 1990s, lesser black-backed gulls (likely from Iceland) were confirmed breeding in Greenland, where there is now an established breeding population, including an estimated 2,060 breeding pairs in 2016.
Boertmann (2008) suggests that the increasingly large source population in Iceland — in combination with the migratory tendencies of the species — were the primary causes of range expansion into Greenland.
“Climate change is also a known factor contributing to avian range expansion, since it can affect the timing and availability of food and suitable breeding habitat,” White said.
Boertmann predicts that lesser black-backed gulls will further expand their breeding range in Greenland and into eastern Canada over the next few decades in response to climate change.
Research published in 2021 by Zawadzki et al. also considers the expansion of lesser black-backed gulls and suggests Iceland’s population likely contributed to vagrancy in the U.S. before 2005. The study also notes the recent upsurge in reports of lesser black-backed gulls in the states over the past two decades is likely attributed to the growth of Greenland’s breeding population.
The researchers drew these conclusions based on reports of banded individuals (or lack thereof). There’s been a substantial color banding effort in parts of Iceland, Netherlands, and the British Isles, yet only two banded lesser black-backed gulls have been re-sighted in North America — one in 1997, and one in 2002.
“There have been no other band sightings in North America since then, despite thousands of observations of these gulls year after year,” White said.
Since there haven’t been any recent band sightings in North America, and there hasn’t been a banding project in western Iceland or Greenland, the researchers propose that most lesser black-backed gulls seen in North America come from western Iceland and Greenland.
“It’s fascinating to see this species undergoing substantial range expansion,” White said. “SCCF will continue to monitor gulls and other shorebirds and seabirds on the islands and educate residents and visitors about how to respect these birds on the beach, including not feeding or flushing them.”
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