An exceptional island in the St. Lawrence filled with gulls is threatened with extinction

Bank erosion and an invasive plant threaten a unique island that is home to the largest colony of ring-billed gulls in the St. Lawrence and has become a popular scientific research site.

Not always appreciated by the population because it is greedy and pilfering even in McDonald’s parking lots, the ring-billed gull (Larus delawarensis) is an excellent “sentinel” species which, like the canary in the mine, teaches us what effects pollution can cause on the brain. Deslauriers Island, off the coast of Varennes, is a nesting paradise for this bird, which has been studied on site for 35 years. But the number of birds has been in free fall for two decades, which experts cannot explain. The newspaper accompanied a team of researchers on site.

Ring-billed gulls are a North American species that experienced a population explosion in the 2000s.

Photo Mathieu-Robert Sauvé


Ring-billed gull nests generally have three eggs that the male and female incubate during the months of April and May.

Photo Mathieu-Robert Sauvé


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Wildlife management technician Thomas Parent, from UQAM, and biologist Anne Lippold, from McGill, approach Deslauriers Island, off the coast of Varennes.

Photo Mathieu-Robert Sauvé

Sentinel birds

If researchers are interested in the ring-billed gull, it is because it is an excellent “sentinel” species, an indicator of changes in an ecosystem. Not very shy, resistant and of good size, it can be recaptured by putting various devices on its back. During nesting, its instinct tells it to return to the nest.


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Ring-billed gull from Deslauriers Island equipped with a GPS which will allow us to know precisely its movements over the last 10 days.

Photo Mathieu-Robert Sauvé

Biologist Anna Lippold, from McGill University, has been conducting doctoral work on the island for four years. During our visit, she examined a gull captured a few minutes earlier by wildlife management technician Thomas Parent: weight measurement, measurements of the beak and certain feathers, blood sample. She also removed the GPS device attached to her back for 10 days.


Gull

Photo Mathieu-Robert Sauvé

His studies of how birds move in space could be used to better understand the effects of certain pollutants on the brain. Over the past few days, for example, she has released gulls in Drummondville and followed their “return home” trajectory. Some birds return in three hours, others take the entire day. “I’m also looking to understand how air pollutants can affect their sense of direction,” she explains.


Gull

Photo Mathieu-Robert Sauvé

Over the last 15 years, the work carried out in this open-air laboratory has made it possible to better understand the persistence of certain pollutants such as flame retardants, these additives added to furniture to prevent it from burning, whose persistent fumes float in the air. air from the dumps. Breathing their fumes would have more effect than ingesting contaminated food through the digestive system.


Gull

Photo Mathieu-Robert Sauvé


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Biologist Anna Lippold takes a blood sample from each captured gull.

Photo Mathieu-Robert Sauvé

Erosion and common reed

“The boats that sail on the St. Lawrence create immense waves which wash away parts of the island every year,” explains biologist Jonathan Verreault, from UQAM, who has been studying the gull colony since 2009. Each year, this professor and researcher obtains the necessary permits for the interventions of the different teams which follow one another from egg laying to hatching, between April and May. Since the 2010s, there has been concern about the reduction in the surface area of ​​the island, which measures less than one square kilometer. It would have lost a third of its surface area in a single decade. “The island is shrinking rapidly due to erosion, and in addition, the common reed, where the gull does not nest, is taking up more and more space,” explains Jean-François Rail, from the Federal Ministry of the Environment. , which notes demographic fluctuations over the past 35 years.


Gull

Photo Mathieu-Robert Sauvé

What if the island disappeared completely? The survival of the species would not be threatened, but it is feared that the birds will settle almost everywhere in urban areas, including on the roofs of houses, causing inconvenience linked to noise and droppings. And researchers would lose an excellent open-air laboratory.

Table leftovers on the menu

Once confined to the shores of the east coast of Canada and the United States, the ring-billed gull has adapted wonderfully to table scraps in urban areas, thrown into garbage and now into compost. “There are three large dumpsites around the island, which constitute open-air banquets for this omnivorous and opportunistic species,” explains biologist Jonathan Verreault.

The trips back and forth between the nest and certain dumpsites left marks on the garden furniture of suburbanites, which forced the dumpsites to chase away the birds with different means such as scaring off with gunshots and falconry.

Once the largest colony in Canada and possibly the world

Last year, there were only 17,644 nesting pairs remaining on Deslauriers Island. This is three times less than 20 years earlier, when we had recorded 50,810 pairs, therefore more than 100,000 individuals, reports Environment Canada. At its peak, the Deslauriers Island colony represented 5% of all individuals of this species in the world, according to the ornithological site IBA Canada. The colony was then the largest in Canada, and possibly in the world, according to available ornithological data.

The number has fallen over the past 20 years for reasons that experts cannot fully explain. “It’s not necessarily about mortality. Perhaps some birds have chosen other breeding places,” says Professor Verreault. Phragmites, an invasive plant that makes nesting difficult, has also colonized a large part of the island.

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