Along with the pigeon, the gull might be the most detested of all birds. They can be loud, aggressive and particularly annoying when you’re trying to eat some fries near a coastline. But Perry Poon, Ocean Wise’s prop master, does not think of them as a common pest. He is curious about where they might be nesting around the Lower Mainland and likes to speculate about which big-box store roofs the birds might have colonized recently. When four dead gulls arrived at his office at the Vancouver Aquarium, he felt sorry for them.
Perry converts donated animal remains into props for the Mobile Education AquaVan and the Vancouver Aquarium’s on-site Wetlab. His closet-sized office at the aquarium is piled high with shark jaws and octopus beaks, pickled frogs and deep-sea fishes, and now four dead gulls. But before he could preserve the gulls as teaching tools, he would take peek inside their guts — for research’s sake.
Birds are some of the most mobile animals in the world, making massive migrations that frequently land them in the crossfire of human activities. The four gulls in Perry’s possession were no different. Struck down by cars and planes across the Lower Mainland, the Vancouver International Airport and the Wildlife Rescue Association of BC donated them to Perry in the hope of finding out more about their deaths.
The Vancouver International Airport employs a falconry team to drive birds away from plane turbines, however, one staff falconer wondered whether a dietary approach might help save bird lives. If Perry could pin down the insects in the gull guts, the airport might have a new tool to lure birds away from runways and out of harm’s way. Exhibits writer Catherine Po also attended Perry’s dissection, curious about whether the seabirds were eating microplastics (small plastic measuring less than five millimetres in diameter).
There are over 40 gull species in the world, ranging from the massive Great Black-backed Gull on the North Atlantic to the small prairie-nesting Franklin’s Gull in the Midwest. The Glaucous-winged gull (Larus glaucescens) Perry was operating on is a typical west-coast gull that lives year-round along the Pacific Coast from Alaska to Washington.
Compared to the Ring-billed and Mew gulls, Glaucous-winged Gulls are truly gigantic. They breed freely with other closely related gulls that live at the southern and northern reaches of their territory. Gulls are the most difficult birds to identify; they all look somewhat similar with a white body and grey back. But these hybrid gulls present an extra-special challenge to birders keen to test their taxonomic knowledge in the wild.
As the most commonly sighted bird in the world, gulls seem like they’re doing just fine. However the Glaucous-winged Gull is facing unique challenges wrought by climate change. As the oceans warm, plankton are dropping lower in the water column and the smaller fish, that gulls would normally pluck from the surface, swim deeper as well. In warmer years, researchers have noticed a higher propensity for cannibalism among Glaucous-winged Gulls who take to feasting on unhatched eggs.
Inside the gulls’ stomachs, Perry found a few ground-up mussel shells and not much else. The crop —where many birds store undigested food in a pouch branching off from the throat — was similarly barren. Perhaps the gulls regurgitated their stomach contents on impact, Perry speculated.
This isn’t the end for these gulls. In the coming weeks, Perry will preserve the gulls for posterity’s sake. After soaking them in liquid, any plastic fibres in the gulls’ stomach will float to the top. He’ll also take a closer look at the stomach contents under a microscope and, if any useful dietary information turns up, Perry will pass it along to the falconry team at the Vancouver International Airport. This sharing of information between two Vancouver institutions just might save a few gull lives.
Laura Trethewey is Ocean Wise’s Senior Writer and Editor.