This time of year can be very exciting for birdwatchers, as spring migration gets underway. Birds will leave their winter feeding grounds and head for their summertime breeding territories.
Many of the birds we think of as resident throughout the year are in fact winter/summer migrants. Britain is home to around 3.6 million breeding territories of blue tits, but the wintering population is somewhere near 15 million birds.
They are so widespread across Europe and Scandinavia that we don’t notice these birds are a mobile population. It is believed that if you see four to five blue tits at the same time on your garden feeders then you probably have a local feeding population of more than 20 birds.
Other birds that are considered resident but choose to spend winter here in great numbers include the goldfinch, goldcrest, starling, robin, blackbird and chaffinch. Brambling a close relative of the chaffinch is also a bird that will be on the move at this time. Although a very small number of bramblings breed in this country, Britain is home to up to 2 million bramblings through the winter months. A gregarious bird they will often form large flocks along with their chaffinch cousins.
Smaller members of the finch family such as the siskin and lesser redpoll are also preparing to head off for the summer months, often seen feeding in the tops of alders they need to take on enough food to give them the fuel needed for the great journey ahead
Vast numbers of ducks and geese make Britain their winter home and at this time of year you can expect to see great skeins in the sky heading to their summer nest sites. Travelling at high altitude they head north to Greenland and Iceland.
Whilst these birds are leaving the country we are seeing the arrival of our early summer migrants like wheatear. Though they are not necessarily common along the canal network and choose to breed on the moors and uplands they will often be seen at this time feeding on fields and grasslands as they follow the waterways to their breeding grounds.
The sound of the cuckoo is a sure sign that spring is here and late April is the time you are most likely to hear it, as the male birds set up their territory and begin calling to attract a mate. Renowned for using the nests of other birds, particularly reed warblers and dunnocks, which nest along the canal network you may be lucky enough to not only hear but also see a cuckoo.
Two others to look out for as they come into the country are the pied and spotted flycatchers. Heading toward oak woodlands these birds can be seen following rivers and canals taking flies and midges as they go. The pied flycatcher is a black and white bird about the size of a sparrow and is mainly found across Wales, western and northern counties of England. The spotted flycatcher at first appears quite dull, a brownish grey coloured bird, but sit and watch as they spring from their perch to catch flying insects before returning, usually to the same perch.
Why does this migration happen? What makes these birds fly vast distances only to return a few months later? The answer quite simply is food, those who spend the summer in the far north find their food supply covered by snow and ice during the winter so have to travel south in order to feed.
Those that head south for the winter are generally insect eating birds who head north to breed during the summer months, when food is plentiful and the daylight hours are longer in order for them to search for food to feed their offspring.