fast facts

Another consequence of global warming is the changes in timing of seasons, and consequently of food availability for migratory birds.

For shorebirds, such as the Semipalmated Sandpiper, that nest in the Arctic, timing is everything. They must arrive from their wintering grounds early enough to obtain enough energy and calcium to lay eggs, but not earlier than the Arctic spring and the f irst availability of food after the thaw. The hatch of sandpiper chicks from their eggs must be timed to coincide with peak insect emergence so that they can grow fast enough to be ready to move south as soon as the short Arctic summer comes to a close. A rctic breeders must accomplish all this within a few short weeks, and are absolutely dependent on the availability of nesting habitat and on the timing of what scientists call "resource flushes" or "times of peak food availability". Global warming is not only beginning to melt the tundra at the breeding sites, but it is changing the timing of spring.

Evidence is emerging that as global warming has accelerated in the last few decades, spring in the Northern Hemisphere has been getting earlier by a week to ten days. Scientists who study birds say that this is already resulting in changes in bird behavio r. In the UK, many birds are affected, including the Greenfinch, Magpie, Dipper, Wren, Redstart, Crow, Willow Warbler and Whitethroat. In the US, spring migrants are being recorded earlier now than in the past as they reach the Upper Michigan Peninsula. Earlier springs could further disrupt the age-old patterns of many migratory birds. For example, during just three or four weeks in May each year, more than one million shorebirds, including Red Knot, Ruddy Turnstone and Sanderling stop at the Delaware Ba y on the Northeast Coast of the US to refuel before pushing on to their Arctic breeding areas. These birds rely on the highly nutritious eggs of the millions of Horseshoe Crabs that emerge from the Atlantic Ocean at exactly the same time as the birds arr ive. Climate change may cause the shorebirds to arrive earlier, while leaving the timing of the horseshoe crab egg-laying unaffected. This could have a devastating effect on the birds' ability to store fat and complete their migratory cycle, resulting in many birds not reaching the Arctic, and in catastrophic breeding failures and population decline.

The Knot and other shorebirds, including Oystercatcher, Redshank, Bar-tailed Godwit and Ringed Plover, along with ducks such as Shelduck and Pintail may lose much of their fall and winter habitat in Europe to global warming. The Wadden Sea, a shallow tida l basin that runs along the coasts of the Netherlands, Germany and Denmark is highly vulnerable to sea-level rise, as are the Dee, Humber and Thames estuaries and The Wash in the UK. Other famous nature reserves in the UK are also at risk, including Minsm ere and Caerlaverock, famous respectively for their avocets and Barnacle Geese. In Australia, populations of migratory Magpie Geese and the endangered Orange-bellied Parrot also risk flooding of their habitat.