Science & technology

Urban gulls: researching ‘public enemy #1’

Dr Tom Dickins discusses the differences in gull populations across the UK and his current project on the urban gull population in the City of Bath

Professor Tom DickinsA collaboration between Middlesex University and the University of the West of England is hoping to find new ways to help urban gulls live in harmony with humans. In this post, Professor of Behavioural Science Dr Tom Dickins talks gull science.

An open bag of chips at the seaside has always been fair game for a passing gull. I remember this from holidays in Devon and Cornwall over 30 years ago. It was considered part of the experience – we were getting closer to nature, but in recent years, we humans appear to have become less tolerant of gulls. Last summer in particular, the press reported a small number of negative incidents in lurid detail. For example, The Mirror (23 July 2015) published an article entitled ‘Seagull menace: Truth about Britain’s new Public Enemy No1 following spate of attacks. This story listed raids on picnics, aggressive defence of chicks and also attacks on pets. It then presented a sequence of photographs of a lesser black-backed gull (Larus fuscus) eating a starling (Sturnus vulgaris), above the caption ‘Bird murder’. Clearly The Mirror had taken a negative view of these events, in spite of pointing out the protected status of gulls and claims from conservation groups that these birds were behaving normally – this is really a problem of two populations trying to live alongside one another.

During my lifetime the number of urban gulls has increased, while coastal populations are generally in decline. Overall, gulls are under threat and are of conservation concern. The Guardian (6 June 2010) carried a conservation-oriented story earlier in this growing controversy, pointing out the RSPB’s claims that any negative intervention, such as culling urban breeding gulls would challenge their status even further. At various points the UK government has promised to look into this, and under the last administration allocated £250,000 of DEFRA funding for research into managing urban gull populations. This money was promptly cut after the last election and there are currently no plans to support research.

A Great Black-backed Gull predating a Kittiwake nest (Photo: Tom Dickins, 2015)
A great black-backed gull predating a kittiwake nest (Photo: Tom Dickins, 2015)

What needs researching? 

The basic argument is that coastal populations are under resource stress, quite possibly induced by climate change. For example, gulls are surface feeders, diving to about one metre below the surface of the sea to catch fish. These fish are in this one-metre zone as it is the right temperature for them, but with rising sea temperatures this layer is increasing beyond the depth that gulls can reach. There is also evidence that changes in the North Atlantic Oscillation are shifting fish stocks and impacting upon breeding success in other ways. Stressed populations will disperse if they can, and find other resource, and gulls are not only good at fishing but also scavenging. Most gull species are excellent generalists as the predation of a starling indicates. From my own observations of large gulls they not only eat fish, but also neighbours’ chicks and other birds. Indeed, great black-backed gulls (Larus marinus) regularly predate kittiwake (Rissa tridactyla) colonies and other marine birds as a staple part of their diet during the breeding season. This is nature – red in tooth and claw. Gulls need to convert whatever calories they can find into chicks.

The gulls I watch in the wild are not randomly distributed about the coast. They are expert foragers and make sound decisions about where to position their breeding sites and where to hunt. Great black-backed gull pairs breed in isolation or small clusters and appear to nest very close to kittiwake colonies at my field site. This enables a regular mid-morning and mid-afternoon visit to take eggs and later chicks from particular zones in the site. The great black-backed gulls also take other cliff nesting and coastal birds in flight, either at take off or landing, to supplement their diet. There is some evidence that these predated populations choose to be close to a great black-backed gull nest as this apex predator actually deters other gull species and thereby reduces predation costs.

Ground nesting gulls, such as great black-backed gulls, but also herring gulls (Larus argentatus) and lesser black-backed gulls, are not only threatened by neighbours looking at their chicks as a resource, but also by ground predators such as foxes and rats. Needless to say, gulls will defend their interests in all of these situations and we have been researching this in wild populations recently.

So, gulls need to have access to food resource but also to defensible nest sites. Urban planners have not thought about these issues when designing towns and cities, but they have organised urban spaces into areas with higher proportions of food outlets, outdoor seating, green spaces and tall buildings. Buildings, especially with flat roofs, are like islands isolated from the ebb and flow of people below and also from many ground predators. Moreover, building managers usually take great pains to control rodents so even rats are few and far between at this height, and heat will leak from these buildings providing a fairly stable thermal environment for breeding.

Studying urban gulls in the City of Bath

In collaboration with Dr Chris Pawson (University of the West of England) and Bath and North East Somerset Council, we are embarking on a project in the city of Bath to map the behaviours of the large urban gull population that is resident there. The project will involve directed field work – accessing roofs, mapping breeding sites, and counting eggs and chicks, and observing behaviour – but it will also involve the citizens of Bath reporting on incidents involving gulls through a dedicated website.

Through all of this data we hope to gain a sense of the gulls’ decisions: Where are they most likely to breed and nest? Where do they find it easiest to forage? How does this change across the year, across the day? In doing this we hope to see Bath as a gull does – a true bird’s eye view. And then we can use this information to suggest benign interventions to benefit the gulls and humans that live in the city.

It is likely that some of the advice we produce will be common sense; for example, the nature of food waste disposal in retail areas of the city may need better protection and different organisation. The behaviour of citizens around gulls may also need some direction. But we may also be able to think of how to design gull neighbourhoods, which remove these birds from direct contact with people while allowing them to thrive. We may also be able to change the nature of the interaction from one of antagonism to one of celebration, as some have done in the North East.

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