Modelling the impact of environmental change on wading birds

Every autumn 70,000 birds descend on the mudflats and salt marshes of the Severn     Estuary to spend the winter refuelling before heading on to their spring breeding grounds.

The estuary is one of the largest in Europe and one of the most important wildlife habitats in the world.

While the squawking, fighting and feeding behaviour of the wildfowl and waders may appear random to onlookers, a small team at BU can predict exactly what the birds are up to.

Led by Professor Richard Stillman, they have created a computer program called MORPH that models the              behaviour of birds and fish in response to a host of environmental changes.

There is a lot of environmental change – from climate change to habitat loss – that puts pressure on plants and animals. Conservationists want to know what the effect will be on these creatures and how concerned they should be, says Professor Stillman.

Much of the team’s work focuses on wading birds. “They occur in the winter in very large numbers around coastal sites and they have international protection. But these sites are important for people too – we use these coastal     areas for recreation or shell fishing or port development,” Stillman says.

Overwintering birds are the easiest to model. They are not concerned with breeding or nest making, just survival, so their food supply is a key factor influencing their behaviour and population size.

To create the model, researchers divide a river or estuary into sections and collect information about the food, tidal and river behaviour from each. The characteristics of the birds are then added, including how quickly they feed, whether they are aggressive in close proximity and how much they need to eat.

“The model birds react in the same way as real birds. They are programmed to behave in ways that maximise their chances of survival. That means they avoid risky behaviour and always go for the best quality of food,” Professor Stillman explains.

Once the computer model has been constructed, it is run to see how well it compares to the real world. If it works, and the model birds feed in the same places on the same things and at the same times as their real-life counterparts, the programmers can start manipulating the simulated environment. This allows them to measure the potential impact of environmental changes on the birds.

MORPH has been used to assess the impact of the Severn Barrage – a current proposal to dam the estuary to       generate renewable energy.

It showed that the internationally important colonies of wading birds such as redshank and curlew would have       significantly less time to feed on the mudflats if the project went ahead.

In another project, BU researchers looked at how plans to build 80,000 coastal homes in the Solent would affect birds. Increased visitor numbers to the coast were shown to cut the bird’s survival rates.

Fish behaviour can also be studied. One model looks at the impact of brown trout in an English chalk stream after changes to river management and predator population size.

Other models look at the impact of changes in UK rivers on dace, pike and roach.

Professor Stillman believes the technique could be extended to farmland birds as well as ponies and deer in the New Forest.