{"id":772,"date":"2016-05-18T04:52:56","date_gmt":"2016-05-18T04:52:56","guid":{"rendered":"http:\/\/blogs.oregonstate.edu\/gemmlab\/?p=772"},"modified":"2016-05-18T04:55:34","modified_gmt":"2016-05-18T04:55:34","slug":"oregon-gulls-trash-birds","status":"publish","type":"post","link":"https:\/\/blogs.oregonstate.edu\/gemmlab\/2016\/05\/18\/oregon-gulls-trash-birds\/","title":{"rendered":"Are Oregon gulls trash birds?"},"content":{"rendered":"

By Stephanie Loredo, MSc student<\/em><\/p>\n

\u201cViolent\u201d and \u201cgreedy\u201d are words often used to describe gulls in populous areas where food or trash are readily available.\u00a0 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.<\/p>\n

Last year, the Seabird Oceanography Lab<\/a> in conjunction with the GEMM Lab began putting GPS trackers on western gulls (Laurus occidentalis) <\/em>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.<\/p>\n

During the 2015 breeding season, 10 commercially brand \u2018i-gotU\u2019 GPS data loggers were placed on gulls from \u2018Cleft-in-the-Rock\u2019 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.\u00a0 \u00a0We 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.<\/p>\n

\"Figure<\/a>
Figure 1. Tracks from 6 western gulls, each color representing a unique bird, from the Cleft-in-the-Rock colony carrying micro-GPS units.<\/figcaption><\/figure>\n

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 \u201ccoastal\u201d 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.<\/p>\n

\"Figure<\/a>
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.<\/figcaption><\/figure>\n

\u2018Cleft-in-the-Rock\u2019 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).\u00a0 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).\u00a0 Each of these areas has different regulatory rules on what is allowed to take, which you can read about here<\/a>. The implication of these protected areas in place means there is more food for wildlife! \u00a0Moreover, 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\u00a0clean, 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.<\/p>\n