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Bird Disturbance

Birds perceive us and our canine friends as a potential threat; if we get too close, sensing danger, they change their behaviour. Birds that are disturbed from their natural activities lose valuable feeding time and waste precious energy walking, swimming or flying away.

Over 52 million visits are made to the Solent coast each year, mostly by the 1 million people who live within 5.6km (3.5 miles) of the Solent. New housing will increase this number to 60 million visits per year by 2035. As the coast gets busier with people, disturbance could happen more frequently and have a greater impact on the birds.

Precious time to feed, limited space to rest

For many coastal birds, feeding time is limited by the tides. Birds who feed on the mudflats can only reach their favourite foods when the tide is out; in this period they need to take in enough energy to last them through the whole day. For some coastal species, this means eating the equivalent of their own body weight every single day, that’s a lot of digging! Most birds are also restricted to feeding during daylight hours, which during the winter can be a short window. On some days, when these two factors are combined, with a high tide coming in the middle of daylight hours, birds can struggle to find any time to feed at all!  During the Spring, birds need to feed enough to build up fat reserves which will last them through their migration back to the Arctic.

At high tide birds need to rest in a safe quiet location to conserve energy and wait for the next low tide. Suitable resting areas, known as roosts, are hard to find and are becoming increasingly limited due to sea level rise. If birds are disturbed from one roosting spot they may have to fly for miles to find somewhere else to settle – a flight which can drain them of energy and leave them exhausted. Roosting areas come in many forms; from manmade structures like pontoons and groins to natural areas such as islands and the tops of beaches.

The impacts

When a bird perceives a threat, it becomes alert and watches that threat, deciding whether it needs to flee the area. Time spent watching threats during low tide, is time that should be spent feeding, building up energy reserves for the long migration back to their breeding grounds. If the threat does not go away or gets closer, the birds will either walk, swim or fly away. This activity wastes their energy reserves and, again, wastes precious feeding time. If birds are disturbed at high tide, fleeing the area could mean flying for miles to reach another suitable spot – this flight can, for some species, use as much energy as gained in a whole day’s feeding! Flying uses twelve times more energy than resting; so shorebirds need to spend as little time off the ground as possible.

Another impact is that the birds feel stressed, this may not be as noticeable, but can last for a long time after a threat.  The effects of stress are a faster heart rate and a rise in body temperature; these changes cause a bird to use up more energy.  The more time spent stressed, the less energy you have for everything else.

If disturbance happens regularly, birds may avoid areas completely, leading to more competition for food and resting space elsewhere. If all of the birds in the Solent are competing for a smaller amount of food, some birds will be unable to find enough to eat and go hungry.  The number of safe places for birds to feed and rest is becoming increasingly limited.

If the birds are unable to feed and rest undisturbed, they may not survive the winter or make their migratory journey back to their summer breeding grounds. Those that do complete their migrations, must arrive in a healthy condition in order to breed and produce new members of the population. Without new members of a population, numbers of these amazing birds will decline.

We can all make sure that the birds in the Solent have lots of space to rest and feed while they are here by following the coastal code.