Which Birds Migrate?
Some birds never move far from where they were born whereas others migrate and can travel huge distances in the process. Indeed, it is surprising just how many of the birds that you see in Britain will have migrated here to escape cold weather further north. Over 4,000 different species in the world are regular migrants.
Most species in Northern Canada and Scandinavia migrate south to escape the cold colder winter temperatures. Roughly half the species in the UK migrate south as their natural sources of food become too scarce.
The migrant birds of Britain can be divided into several different groups.
Irruptions, Altitudinal Migrants and Moult Migrants
An irruption is the mass arrival of birds which do not usually visit the UK. This can occur when certain northern species’ populations grow too large and there isn’t enough food for them in their native country. They are then forced to fly to the UK in search of food. From time to time you may see waxwings arrive from Scandinavia but this only happens approximately once every ten 10 years.
Altitudinal migrants are birds which descend to lower terrain during the winter rather than migrating south. Skylarks, meadow pipits and snow buntings are all altitudinal migrants.
Moult migrants are birds which are unable to fly during the moulting process. This leaves them vulnerable and so they migrate to areas where there are fewer predators in order to moult. For instance, shelducks fly to the island of Heligoland in the North Sea.
Summer, Winter, Passage and Partial Migrant Birds
Many birds are summer visitors to our shores which arrive in spring from the
south. Swallows, martins, flycatchers, nightingales and cuckoos all breed here and stay for the summer before flying south for the winter. Many seabirds including gannets and puffins, spend the summer months around the shores of Britain and then the winter at sea.
Other birds migrate to Britain for the winter in search of a milder climate and sources of food. Fieldfares, redwings and bramblings visit us during the winter before flying north to breed in the spring.
Passage migrants are birds that stop off here during their long journey north or south. These include green sandpipers and black terns. They stopover to rest and refuel before continuing their journeys.
Partial migrants are species which migrate from some places, but not in others. For instance, British starlings tend to stay here for the winter. But starlings that breed in eastern Europe migrate in winter. Chaffinches, robins, lapwings and coots are also partial migrants. Partial migrants react to the weather, and so their behaviour varies from region to region.
The Wonder of Migration
Migration is a fascinating and ever changing phenomenon. By watching the visitors to your garden and observing the birds in the countryside and around our shores, you can see just how many birds are on the move every year. The bird populations of Britain are constantly fluctuating with the seasons.