Are Oregon gulls trash birds?

By Stephanie Loredo, MSc student

“Violent” and “greedy” are words often used to describe gulls in populous areas where food or trash are readily available.  Humans are used to seeing gulls in parking lots, parks, and plazas eating left over crumbs. Many people have even experienced menacing gulls ripping food away from their hands. Anecdotes like these have caused people to have negative perceptions of gulls. But could the repulsive attitude towards these birds be changed with evidence that not all gulls are the same? Well, Oregon may be home to an odd bunch.

Last year, the Seabird Oceanography Lab in conjunction with the GEMM Lab began putting GPS trackers on western gulls (Laurus occidentalis) off the Oregon Coast. One of the goals was to determine where gulls scavenge for food while raising chicks: at sea or on land in association with humans. We were particularly interested to see if western gulls in Oregon would behave similarly to western gulls in California, some of which make trips to the nearest landfill during the breeding season to bring not only food but also potentially harmful pathogens back to the colony.

During the 2015 breeding season, 10 commercially brand ‘i-gotU’ GPS data loggers were placed on gulls from ‘Cleft-in-the-Rock’ colony in Yachats, Oregon. The tags provided GPS locations at intervals of two minutes that determined the general habitat use areas (marine vs. terrestrial). After a two-week period, we were able to recapture six birds, remove tags, and download the data.   We found that these western gulls stayed close to the colony and foraged in nearby intertidal and marine zones (Figure 1). Birds showed high site faithfulness by visiting the same foraging spots away from colony. It was interesting to see that inland habitat use did not extend past 1.3 miles from shore and the only waste facility within such boundaries did not attract any birds (Figure 1). Tagged birds never crossed the 101 Highway, but rather occurred at beaches in state parks such as Neptune and Yachats Ocean Road.

Figure 1. Tracks from 6 western gulls, each color representing a unique bird, from the Cleft-in-the-Rock colony carrying micro-GPS units.
Figure 1. Tracks from 6 western gulls, each color representing a unique bird, from the Cleft-in-the-Rock colony carrying micro-GPS units.

While it is hard to determine whether gulls avoided anthropogenic sources of food at the beach, preliminary analysis shows a high percentage of time spent in marine and intertidal habitat zones by half of the individuals (Figure 2). At a first glance, this is not as much as it seemed on the tracking map (Figure 1), but it nonetheless confirms that these gulls seek food in natural areas. Moreover, time spent at the colony is represented as time spent on coastal habitat on the graph, and thus “coastal” foraging values are over represented. To get a more exact estimate of coastal habitat use, future analysis will have to exclude colony locations and distinguish foraging versus resting behaviors.

Figure 2. Bar plot of the percentage of time spent in three distinct habitats for each gull carrying a GPS unit. The three-letter code represents the unique Bird ID.
Figure 2. Bar plot of the percentage of time spent in three distinct habitats for each gull carrying a GPS unit. The three-letter code represents the unique Bird ID.

‘Cleft-in-the-Rock’ is unique and its surroundings may explain why there was high foraging in intertidal and marine zones rather than within city limits. (The Cleft colony can also be tricky to get to, with a close eye on the tide at all times – See video below).  The colony site is close to the Cape Perpetua Scenic Area and surrounded by recently established conservation zones: the Cape Perpetua Marine Reserve Area, Marine Protected Area, and Seabird Protected Area (Figure 1).  Each of these areas has different regulatory rules on what is allowed to take, which you can read about here. The implication of these protected areas in place means there is more food for wildlife!  Moreover, the city of Yachats has a small population of 703 inhabitants (based on 2013 U.S Census Bureau). The small population allows the city to be relatively clean, and the waste facility is not spewing rotten odors into the air like in many big cities such as Santa Cruz (population of 62,864) where our collaborative gull study takes place. Thus, in Yachats, there is more limited odor or visual incentive to attract birds to landfills.

Field crew descends headland slope to reach ‘Cleft-in-the-Rock’ gull island in Yachats, OR (colony can be seen in distance across the water). The team must wear wetsuits and carry equipment in dry bags for protection during water crossing.

In order to determine whether gull habitat use in Yachats is a trend for all western gulls in Oregon, we need to track birds at more sites and for a longer time. That is why during the breeding season of 2016, we will be placing 30 new tags on gulls and include a new colony into the study, ‘Hunters Island’. The new colony is situated near the Pistol River, between Gold Beach and Brookings in southern Oregon, and it is part of the Oregon Islands Wildlife Refuge.

We will have 10 ‘i-gotU’ tags (Figure 3) and 20 CATS tags (Figure 4), the latter are solar powered and can collect data for several weeks, months, and hopefully even years! These tags do not need to be retrieved for data download; rather data can be accessed remotely, providing minimal disturbance to the gulls and colony. With long-term data, we can explore further into the important feeding areas for western gulls, examine rates of foraging in different habitats, and determine how extensive intertidal and marine foraging is throughout the year.

Figure 3. Taping an i-gotU tag for temporary attachment on the tail feathers of a gull.
Figure 3. Taping an i-gotU tag for temporary attachment on the tail feathers of a gull.


Figure 4. Rehearsing the placement and harness attachment of a CATS tag which must be secured on the bird‘s back, looping around the wings and hips.

We are excited to kick start our field season in the next couple of weeks and see how well the new tags work. We know that some questions will be solved and many new questions will arise; and we cannot wait to start this gull-filled adventure!


Osterback, A.M., Frechette, D., Hayes, S., Shaffer, S., & Moore, J. (2015). Long-term shifts in anthropogenic subsidies to gulls and implications for an imperiled fish. Biological Conservation191: 606–613.

Seabirds eat weird things

Chicken wings, toy dinosaurs, Easter eggs, driver’s licenses, ham, broccoli, and toy cars, to name a few things. I’ve even seen a gull try to eat a live, 2 ton elephant seal (and have got the pictures to prove it!).

Recently researchers from the GEMM lab, and the Seabird Oceanography lab (SOL) at Hatfield Marine Science Center, have been collaborating with Dr. Scott Shaffer’s Avian Physiology and Ecology laboratory at San Jose State University to investigate the causes and implications of these strange eating habits.

When they aren’t scavenging off of your plate of French fries, Western gulls (Larus occidentalis) are either foraging for fish and invertebrates out at sea, or visiting the local dump to pick up dinner for the little ones. Unfortunately, during the breeding season dinner at the dump comes with the risk of bringing harmful contaminants and pathogenic microbes back to the colony. In addition to littering colonies with refuse, gulls can serve as potential vectors of disease that may affect other nearby wildlife. Seabird ecologists at OSU and SJSU are using GPS tags in order to better understand how different colonies of Western gulls along the West coast are affected by access to landfills. Over the past month, a handful of gulls at colonies in California and Oregon have been outfitted with these light weight tracking devices. The data gained from these tags will allow researchers to study the foraging ecology and habitat use patterns of these individuals. When the tags are recovered, biological samples such as blood and feathers will be collected to determine how these habitat-use patterns (and potentially, trips to the local landfill) are affecting these birds in terms of microflora and contaminant loads.

Last week I (Erin Pickett) assisted the GEMM and SOL labs in capturing a few of these birds in order to outfit them with tags. The local field site is just south of Yachats on a guano-covered rock that a small colony of Western gulls call home. Like all great fieldwork and adventures, our day began at 4:00 am (and it was raining!). About an hour later we arrived at our field site, where we assessed the ocean conditions and determined that the treacherous crossing from the mainland to the colony was passable (it was low tide). There is some great GoPro footage of a crossing the week before that consisted mostly of a current rushing over rocks and the occasional flash of a wetsuit or a yellow dry bag while two hands reached out for something stable to hold onto. When I heard about this I became even more excited about the opportunity to join in on the fun.

We spent our morning focused on two tasks. The first was to recapture the two birds who we had put tags on the previous week. Since the tags have to be small and light-weight, they can only collect data for as long as their battery lasts. However, this is long enough to log a few foraging trips and get a good idea of where the gulls are concentrating their foraging effort. Our second goal was to put tags on eight more birds. We used a combination of capture techniques, including a very long pole with a small noose on the end of it, to recapture one of our birds from last week, along with seven new birds who we deployed new tags on. By the end of the second morning the weather was nice enough to enjoy changing into a wetsuit and jumping into the water for the crossing back to shore. Now we just need to get the rest of our tags back. Wish us luck!

P.S. It’s not often that you purposely put photos of gulls in photo galleries, so I’ve taken this opportunity to find my best shots. These are a couple more of the field sites where our collaborators are working- on Southeast Farallon Island, and Ano Nuevo Island, California