Plastic Pollution in Gull Colonies – Meg’s Dissertation Journey… so far

So, you know when you’re about to start third year and you realise this is the year when you do your dissertation and it’s the biggest assignment of your whole university degree? Yeah, so that moment hits you a lot faster than you would ever think.  For me, I had 100s of ideas with only a few being remotely realistic.  I am a very practical person and therefore I wanted to do something in the field that was both rewarding and significant.

Why I chose my topic

I knew I wanted to conduct a project on plastic pollution as I feel it is currently the biggest threat to the health of the planet, our wildlife and us.  It is a major issue which the human population are entirely responsible for and therefore it is down to us to minimise the plastic cover we are smothering the earth in.  Having bags for life and recycling our rubbish is just not enough anymore, after all, plastic can only be recycled a limited amount of times until it is unusable and will either sit in landfill or be blown into the sea and remain there for 100s of years.  Just to get a feel for the widespread impact of plastic, here are a few facts:

• Every year we produce an amount of plastic that is equivalent to the weight of the human population.
• 8 million tonnes of plastics end up in our oceans annually
• Plastic endangers approximately 700 different marine species, with many animals dying from entanglement or starvation
• Microplastics are in the majority of tap water worldwide
• Studies have found microplastics are accumulating in the human body

As you can see from these facts, it is a global issue of great concern and already affecting hundreds if not thousands of species, including humans.  I believe that research into this topic will make people more aware of the problem and more conscious of their plastic consumer habits.

Planning My Project

After discussions with my dissertation supervisor, Matt Wood, I decided that for my dissertation I would analyse the plastic content of gull pellets.  A pellet consists of any materials that the bird has eaten but can’t digest and are then regurgitated as a clump (sounds a bit gross I know, but it’s a much less smelly way of finding out what a bird has ingested than sifting through its faeces). Numerous groups of species produce pellets, such as corvids, raptors and seabirds.  In seabirds, these can be made of bones, feathers, fur, shells and unfortunately, more commonly, now contain non-natural materials such as plastic.  I decided that this project would give a snapshot of the plastic pollution problem and represent the distribution of plastic pollution within seabird colonies.

Location and Species

Fortunately, Matt does a lot of research on some wildlife-rich islands off the coast of Pembrokeshire that are known to have large colonies of seabirds.  The wardens and fieldworkers from the islands had already collected pellets from colonies of lesser black-backed gulls (LBBGs) from the island of Skomer, so I had no problem choosing which island or species.  I felt it would be interesting to study plastic pollution within a species known to inhabit Skomer, as it is an off-shore island with either none or very few people living there and has a strict ‘no-litter’ rule when tourists visit the island. Any plastics found within the pellets would highlight that off-shore islands and their species are being affected by plastic pollution. The plastics found could either be brought there by birds from marine or urban litter, or be blown onto the island from towns, bins and landfill sites.

I felt LBBGs would be an interesting species to study regarding plastic pollution, as they forage over a wide range and are an amber listed species of conservation concern by the RSPB. There are also other amber and red-listed species on Skomer, whose conservation concern could increase due to plastic pollution, and it is therefore necessary to analyse the quantity of plastic within the diet of these species.

Methods and Madness

First, I re-labelled and re-packaged each pellet as the envelopes they were in were looking a bit funky after being in the freezer for a few months, so the pellets were baked to kill any bacteria or fungal spores. Before baking, I spent a good hour or more wrapping each pellet in tin foil and labelling the tin foil with the date, colony and species.  They went in the oven and once baked, I was looking forward to dissecting them and discovering what the birds had eaten.  But here came my first hurdle, when I unwrapped the pellets I found that the heat from the oven had evaporated most of the ink…all my labels had pretty much come off! My dissertation was doomed! I was in the panic zone!
That was when Will Carpenter (science technician and absolute legend) came to the rescue!  He helped to carefully unwrap each pellet and we then realised that there was a very faint amount of writing on each piece of foil, which was enough to identify each pellet.  I had also done something useful (it doesn’t happen often) when I’d first looked at the pellets, which was write down the quantity of pellets within each original envelope, their colony label, appearance and anything unusual about their contents that could be seen pre-dissection.
I then realised that out of the 54 pellets I had, only 27 of them were actually from LBBGs, a much smaller sample size but also a more manageable one.  Dissecting the pellets was very interesting and I was surprised to find materials such as beetle remains and small bird legs, as not knowing much about gull pellets I thought they would be mostly fish bones.  I found three pellets containing macro plastics which may seem a small amount, but considering they were collected on only a few different days in one season of one year and from only a few colonies I think it is an important result that should awaken people to the magnitude of plastic pollution.

Dissertation Poster

At this stage the dissertation poster presentation was looming, and to be honest I wasn’t really worried about it until the day.  A poster was a relief from essay-style assignments especially as it needed to be brief. After the lecture on ‘what makes a good dissertation poster’ I went to the IT suite and just made a quick draft poster, putting together everything I had remembered from the lecture.  I am not normally this quick off the mark with assignments but to be honest I was just putting off doing other uni work.  Presentation day came, and I thought we would be presenting to lecturers from 11 onwards but just after 10 Matt Wood and Adam Hart came up to me and my poster and said ‘shall we do it now and get it over with?’ So wanting to get it over with asap I agreed and it was over before I knew it. When all presentations were done, Matt congratulated us all and said they had chosen the top three best posters from each course.  I had completely forgotten it was a competition as well as an assignment! Animal biology top three winners were announced, ‘Jess Sweeney…Meg Stone…’ sorry what? I was so surprised, there was honestly so many well-designed and eye-catching posters, I wish I’d looked round at more of them myself.  The top three winners from all natural and social science courses go into the final.  The final was a week later and although I didn’t get picked as one of the best 3 posters, I did come fourth which I still feel is an achievement to be very proud of. I found the poster presentations a really good experience and because I am so passionate about minimising plastic pollution I honestly loved telling all the guests and lecturers about my dissertation.

Next Steps

The next stage of my dissertation is to dissect another group of pellets that are from in-land gull colonies in Bristol, Bath and Gloucester.  I will then compare the macro plastic content of these pellets with the Skomer pellets.  I am expecting the in-land pellets to contain a lot more macro plastic than the Skomer pellets due to high human populations in urban areas compared to that of Skomer.  To investigate if the difference in macro-plastics from the different colonies is significant I will perform some sort of statistical test(s) which I am not looking forward to but guess I’ll have to do it because it is my actual dissertation.  When I’ve got all my results, I would like them to be published to spread awareness of plastic pollution and for my dissertation to have an impact and not just be ‘another dissertation’.

If Time Allowed

If I have time I would like to analyse the quantity of microplastics in the pellets, to find out their prevalence compared to macro plastics and to that of other gull pellet studies.

If I could have unlimited time for my dissertation or to further my study I would like to analyse other seabird pellets from Skomer, to find out if the plastic content varies between species. It would also be interesting to investigate what effects plastic pollution has on the gulls as I expect it is having a detrimental affect on the colony’s population density, reproductive success and decreasing the skeletal growth and fitness level of individual gulls.

Tips and Tricks

• Start thinking of ideas as soon as possible and talk them through with your supervisor, they are there to help
• Read journal articles in any free time from assignments, as the more journals you read the better your writing is likely to be
• Let the technicians know what equipment you need asap as someone else might need the same equipment and it is given out on a first come first served basis (this only really applies if you are doing your dissertation within uni)
• Look at previous dissertations as you may find one that you want to take a step further
• Don’t compare your dissertation to others, dissertations are meant to be unique and the more you look or think about someone else’s the more chance yours will be similar to theirs


Such a good read! Congratulations on your fantastic dissertation project Meg, I hope you get excellent results from the other gull colonies.

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