Seagull Nests on UBC Rooftops
learning about our non-human neighbours and how we accommodate them
Seagulls lay their eggs in nests that are the epitome of minimalism. A flat surface, some rocks, perhaps a modest depression, and some plant matter. That is all they need. This makes city buildings with flat roofs ideal for urban seagulls.
Personally and professionally I have an abiding interest in our non-human neighbours. What are our relations with them, what sorts of conflicts -or sharing relations- do we engage in? Gulls seem readily adaptable to humans. Any trip to Granville Island Public Market is likely to include some interaction with a gull. For many years there was a gull that would visit my northerly facing office window. The gull would sit there and tap on the window to attract my attention. I suspect some colleague somewhere in the building was sharing food.
Indigenous communities all along these coasts (essentially everywhere gulls nest) have harvested gull eggs. Family and friends on the north coast look forward to June when seagull egg picking season starts. A very rich, pinky white cake has become a seasonal favourite of many up coast residents.
Gulls on campus
In my search for info about gulls on campus I contacted folks at UBC Facilities Group and UBC Campus and Community Planning.
John Metras, Associate VP Facilities shared the following via email (April 5, 2023):
We don’t have a formal inspection program to check for nests on building rooftops. We do record reports from our Trades and Project Services staff when they notice nesting activity where they are working. Here is a list of buildings for which we have received reports over the last number of years:
2022 – AMS Nest roof, Seagull Nest; 2022 – Henry Angus roof, Seagull Nest; 2021 – War Mem Gym roof, Seagull Nest; 2018/19 – Chan Centre roof; 2017 – Sing Tao & CK Choi roof
This is the extent of information that we have available.
Campus Planning acknowledged the information request, expressed support for further study, but were’t able to provide any specific information before the start of the long weekend.
As I waited for replies to my queries to filter back I thought there must be a colleague somewhere on campus who studies seagulls. As luck would have it there is. Ed Kroc, Assistant Professor in Measurement, Evaluation and Research Methodology, Faculty of Education. Ed has been engaged in applied urban ecology projects for several years. He has authored several papers on the topic of urban seagulls in the Salish Sea area. He in fact has conducted informal seagull nest surveys on campus.
Ed Kroc and his passion with seagulls.
Ed and I met on Friday, April 7, 2023 at the picnic table next to the UNA Children’s Garden to talk seagulls - glaucous winged gulls in particular. One of Ed’s abiding research interests, one might say his passions, is the study of seagulls.
“So what on earth,” I said, “if you don't mind, got you interested in gulls? Has this been a lifelong passion? Is this something that just emerged? Are you a birder?”
“I have always been interested in biology and ecology,” Ed said. “Ever since I was a kid. I had great teachers from math and physics, and I started going in that direction. I never really gave seabirds or gulls much thought until I moved to Vancouver. I'm originally from the States, from Chicago.”
“I came here to do a master's and PhD. That was in 2007. I lived downtown pretty much all the time. I was in grad school and everything. I just started to notice these gulls. It's kind of hard to not notice them, especially in the summer. Living downtown, there's so many and, in particular, [there was a] pair that nested across the street from me, they were incredible homebodies.”
This pair nested in the same spot for five or six years until the building was demolished.
“They would stay at their nest site almost year round, just hanging out. I started watching them and watching them, and I did this for a couple of years, and by this time I was in my PhD here, and it was maybe like two or three years into my PhD. I realized, like, I've got a lot of these questions. Why are they doing this? It occurred to me, well, I'm scientifically trained. I know people. I can do this stuff. Why don't I just do it myself? So, I started doing it myself. … it kind of just started from curiosity in front of me and realizing I'm a trained scientist, generally speaking, I can do something about it.”
Ed’s observation of the homebody gulls, ‘Boris and Doris,’ became the basis of one of his first seagull papers.1
I asked Ed to explain some of the work he did with the seagulls that lived across from him. He noted that gulls are quite stubborn and not easily chased away from their nests. Watching a long term nesting pair across from his downtown home captured his interest.
“This one particular pair,” said Ed. “I watched for years because they were right across the street from where I lived, so I could watch them literally every day. They have nested on the same rooftop for, I don't know, I've been watching them for five, six years or something. But then the city tore the building down. And they started tearing it down right at the beginning of the breeding season.”
“Which would have been a violation of the regulations,” I suggested.
“It would. However, the way it's defined,” Ed said, “and I have many opinions on how we should update some of these laws, but how it's defined is the nest is only protected if there are eggs in it. This is their home and they had literally built a nest.”
The building demolition began in early May before the eggs were laid.
“It wasn't a tall building, it was about four or five stories. It took about a week to dismantle the building. Workers were coming in and gutting it, stripping all the insides and taking everything off. Every single day the nest would be destroyed because [the workers] would move things. After work, literally, because I could see from across the street, as soon as the workers got off, the gulls would come back and build a nest as close as possible to where they were before and go about their business. And then the same thing would happen the next day. And this happened for about a week until the building was actually demolished. So they are notoriously stubborn with their nesting sites, which is kind of amazing.”
Seagull nesting preferences.
I asked Ed about the preferred building heights for urban seagulls and what kind of roof is most preferred by gulls.
“The building height thing is one that's occupied me. There's another paper with Louise [Blight] that I've been working on trying to finish. It dives really deeply into that question. What features of the built urban environment seem to either correlate with attractive or repulsive nest presence? Building height is a particularly interesting one because it seems like there's kind of a quadratic relationship there.”
“In general gulls seem to like higher structures until they get too high and then they start to dislike them. This is just speculation, but it kind of makes sense, at least in the context of the landscape of Vancouver (because each city is built differently). It's very hard actually to move between different cities with these things, but lower to the ground, more disturbance, more humans, more traffic, more noise. So that kind of makes sense. You want to be a little bit off the ground, but then if you get too high, and especially you think of some buildings downtown, like the really, really high buildings, you get really exposed to eagles in particular.”
“Just like crows gulls have mobbing behaviour. They'll mob with the crows against eagles. But eagles are fast, they're quick, and they're big. So the more isolated you are -I haven't tested this formally- the more susceptible you are to predation from an eagle. That's the hypothesis. There does seem to be some relationship there that's interesting.”
“It seems to me,” I said, “that as we talk about biodiversity as a university and as a ‘green’ campus we should be thinking about how we create the buildings, not to repulse animals, but actually to support them, to bring interactions in.”
“This is something,” Ed said, “a lot of us who work in urban ecology spend a lot of time talking about. How can we well, two questions, I guess. … Number one, when should we be promoting an urban habitat? And two, how do you most effectively do that? Gulls, I think, are an interesting one. Because of the rooftop nesting. They tend to do well. If cities got a bit smart about it, they could minimize a lot of conflict that arises.”
“The gulls nest on the rooftop here, right next to somebody's bedroom window in the next building. Obviously, that's going to create conflict. But if cities got a little bit more conscious about, okay, well, what types of features are likely to attract the gull to nest here? If you're going to have buildings like that, you could ensure that this spot is not going to be attractive to gulls.”
“Is there any kind of particular substrate or roof surfacing that is more amenable to gulls nesting than something that repulses them?” I asked.
“There is a bit of variation from city to city, as you might imagine. But certainly at least in Vancouver, where we've done the most work on this, those very common around campus here, too, just the little pebbly rocks. That really closely mirrors their natural wilderness colonies. They have rocky little islets, so flat, not too much of a gradient. Once you get above about 15 degrees of an angle, they won't nest there. If you want to discourage nesting, that's a really easy thing to do.” Just put a tilt of 17 or 18 degrees and that's probably going to dissuade them.”
“Relatively flat pebbly, like that can vary in size of pebbles - they don't really seem to care that much. There does seem to be an attraction to smaller little rooftops. So especially on tops of things like stairwell landings. That's a really popular one, they have their own little rooftop, of course. It's a nice little space. It actually mirrors kind of the exact same size of a territory you would see in a large wilderness gull colony. It's a very natural fit for them. There's attraction to that. Even on large rooftops you'll have multiple nesters. But those in particular, those little isolated stairwell landings around top of air conditioning or HVAC type system, those are very attractive.”
I asked Ed if green roofs were attractive to gulls.
“Gulls seem uninterested in the green roofs, Ed said. “They will raid the green roofs for material to build nests. But they want the rocks, they don't want grass. And I guess that probably makes some intuitive sense because yeah, when you look in their wilderness colonies on these rocky islets, you see the nests happen along the beach on the rocky outcroppings, but before you actually get to the developed vegetation.”
Salish Sea gull population falls by 50%
One of Ed’s papers2 suggested there is a higher rate of reproductive success for the urban rooftop nesters than their rural compatriots. At the same time his paper said there was a 50% decline in the Salish Sea seagull population.
“That’s quite phenomenal,” I said.
“Absolutely,” Ed said. This comes out of a lot of work that dates back to the graduate work of one of my frequent collaborators, Louise Blight, who's on the island at University of Victoria. She did a lot of that work during her PhD here and afterwards. She and I collaborate all the time. She analyzed not just recorded data, but stable isotope analyses of museum samples. Not just counts, but also in terms of the relative fecundity. One big thing that we seem to see pretty consistently in the Salish Sea is not only decline in the numbers but decline in the reproductive output in terms of how many eggs are typically laid. That's a very big thing for seabirds. Unlike the passerines here, like robins or something like that, gulls nest once per year and they have small clutches. Traditionally the typical lay for most gull species is three eggs in the Salish Sea. It's much closer to two now. And Louise has been able to track this through the stable isotope analysis dating back to at least the 80s, where you really start to see these declines.”
“There was some experimental work done on this back in the 1950s and 1960s on glaucous winged gulls in the Salish Sea and in California on the western gull. Trying to understand what are the motivators, the biological motivators, for laying a certain number of eggs or laying a certain number of times.”
“It doesn't seem like the populations [outside the Salish Sea] are in the same level of decline. They certainly don't behave the same way outside the Salish Sea.”
“I've done some survey work in Prince Rupert, Juneau and up to Anchorage, and found very different dynamics there. But there's so much less human influence. I mean that broadly construed. I mean, even though you might, okay, have humans going into certain colonies and harvesting eggs, that's just a completely different realm than having gigantic tanker ships going right by traditional colonies and completely disturbing that ecosystem, not to mention the decline. A lot of Louise's work was really trying to nail down and establish what the most plausible explanation for these massive declines in the Salish Sea are: (1) possible pollutants, contaminants that biologically affect the ability of a female gull to produce the necessary ingredients to produce eggs, and; (2) is the decline of forage fish population here. Those are so important, not just for feeding newborn gulls, but because females need to stock up before they start laying eggs.”
Seagull futures
Seagull populations are generally higher than they were at the start of the 20th century, but have been in moderate decline since at least the 1990s across their range. The late 1800s and early 1900s was witness to a frenzy of egg and seabird hunting. The effects of settler colonialism had disrupted the longstanding ecological relations between Indigenous communities and seagulls. Settler hunters harvested as if in a gold rush and without regard to well established Indigenous knowledge and practices. Conservation regulations in the early 20th century allowed seagull populations to grow.
In some regions a community controlled First Nations egg harvest continues. There is some research into traditional practices of gull egg harvesting - most focussed on Alaska. Indigenous harvesters have a detailed knowledge of gull ecology and nesting practices that guide their harvesting approach. The dominant approach to picking eggs is to take only from nests with one or two eggs and leave nests with three or more alone. This is the same advice community harvesters from north coast BC give as well. Community-based harvests continue to follow protocols that highlight respect of gulls ahead of individual gain or accumulation.
One outcome of the research and writing of this story is a plan to do a baseline census of nesting gull on UBC’s campus this spring and summer. The census will involving weekly observations starting mid-May through late August.
I leave you with a ‘traditional’ recipe for seagull egg cake.
Kroc, E. 2018. “An example of year-round nest fidelity among urban resident glaucous winged Gulls (Larus glaucescens) in Vancouver, B.C., Canada.” British Columbia Birds 18:28–31.
Kroc, E. 2018. “Reproductive ecology of urban-nesting glaucous winged gulls (Larus glaucescens) in Vancouver, B.C., Canada.” Marine Ornithology 46: 155–164.