Basin Notes - December 2007

Seasonal Climate Change

Weather! The vagaries of the British weather is a constant source of conversation. The balmy days of October have contrasted sharply with the indifferent days of summer in Montrose but the sudden dip in temperatures of the past week comes as a welcome return to the weather we expect for this time of year. But while we can stay comfortable by switching on the central heating, the birds of the Basin must look to other strategies to survive.

Without the warming waters from the Gulf Stream, Britain would be gripped by icy winters, so it is no surprise that birds migrate here from the Arctic and northern Europe to escape the privations of the snow and ice. However, just coming to a warmer place is not enough; to keep warm a bird must eat - a lot! This is where the all-year-round food supply in the Basin comes to the fore.

Wading birds can come to Montrose, safe in the knowledge that the larder is always stocked, even if a little effort is involved in prizing the the foodstuffs from the mud. Of course the inrushing tide closes the larder door twice each day and then the diners must explore the sheltered margins of the Basin to find a safe roost and wait for the tide to retreat.

The flocks of waders can be seen standing on one leg and all facing into the wind. These are energy saving strategies as heat can be lost through the skin of an unfeathered leg and they need to keep their sleek feather duvet unruffled to retain the maximum amount of body warmth.

The balance between energy produced from the food taken in, against the energy expended in flying or just standing around in very cold temperatures is critical, so the more food the bird can find, the better chance it has to survive. Even when the tide is out at night, the birds must try to feed and many waders can do so, because the tip of the beak is very sensitive and can "feel" prey deep down in the mud. So as long as they can find the prime feeding areas, darkness is no bar to them finding food.

The impressive arrays of closely packed birds at high tide is testament to the attractiveness of the Basin, but it also attracts the attention of the hungry peregrine falcon, whose speedy attacks raises the knot, dunlin and redshank into swirling clouds of birds. While all these amazingly acrobatic manoeuvres can foil the attempts of the attacker to catch one of the flock, it takes its toll on the energy reserves of all the birds, and in hard times may spell the end for those weaker members of the flock.

However, it is the old and incautious or inexperienced young birds that will be the food for the falcon and the majority of the flock live to fly another day.

In the long term it seems likely that the invertebrate food in the basin will be more resistant to climate change than the open seas, and the tides will continue to refresh the mud with the microscopic particles that sustains the food chain. This will keep the mud larder stocked and we will see our winter visitors for many years to come.