Spring arrivals and the return home – the remarkable facts of bird migration
By Bob Jarman
The spring migration has started! Already the first birds have arrived on the south coast and will be gradually filtering north.
The story of bird migration has some astonishing facts.
In the last week of February, a small duck, the garganey is usually the first to arrive followed by wheatears and sand martins. Hobson’s Park is a good place to see early wheatears, usually single birds but occasionally groups appear such as an unusual party of 10 near Impington in March 2021.
In flight they have a distinct white rump which accounts for their name, which means “white bum”! Wheatears that appear in late April and early May are probably on their way to Greenland.
The earliest county record for swallows is also from Impington on March 7.
But the spring migration is also about departures. The blackbirds and robins in our gardens may not be the same birds that breed here during our springs and summers.
Ringing recoveries of 140 blackbirds in Cumbria show that many come from Scandinavia and winter locally there or pass through to Ireland. In 2019, a blackbird ringed in Denmark was recovered in Cambridge, and in the county wintering blackbirds have come from Norway, Finland, the Netherlands and Yorkshire.
Where do our local birds go in winter? Well most, it seems, may move to southern counties or northern France in winter. Last year’s exceptionally hot, dry summer that hard-baked garden soils forced many garden blackbirds into a temporary local summer migration to find new places to breed with softer soils where they could grub for worms to feed their young. Hopefully, they will be back.
Other local residents have returned. The peregrine falcons that breed in the city centre are already back. Evidence from remains of their prey and sightings suggest they may spend their winter around the Ouse Washes between Earith and Welney feeding on wildfowl and waders.
Most of the wintering gulls feeding along the River Cam and on our parks and commons will soon return home. It is surprising how far some travel.
Jon Heath, the Cambridgeshire bird recorder, has seen ‘colour-ringed’ black-headed gulls this winter that were ringed or have been re-sighted from The Netherlands, Norway, Denmark, Poland, Belarus, Spain and Germany. He also found a rare Caspian gull, which was ringed as a chick in a rooftop nest in Berlin last year.
The rings do no harm to the birds and their individual numbers can be read in the field, helping us learn of their migration patterns. Many of these gulls are attracted to our landfill rubbish tips, which provide them with an important source of winter food. “A silver lining to our wastefulness,” as Jon says.
The most astonishing migration record was recently reported in the birdwatchers‘ monthly journal, British Birds. Bar-tailed godwits are common wintering coastal waders on muddy estuaries such as The Wash using their long bills to probe for food. They breed around the globe in the Arctic tundra.
A young five-month-old bird wearing a satellite tag has been recorded flying continuously for 13,560km (8,426 miles!) over the Pacific from Alaska to Tasmania without stopping for 11 days. It is a world record for the longest non-stop migration flight. Unbelievable! Any day soon it will make the return journey.
In our local parks and gardens the wintering thrushes, redwings and fieldfares will be feeding-up for their return to breeding sites in Scandinavia and eastern Europe. They are always shy, flighty birds here, but I have seen them in Sweden and Poland where they hop around gardens and parks like our blackbirds and song thrushes.
Just before they leave, redwings congregate, sometimes in small groups, sometimes in flocks of two to 300 and sing a quiet pre-migration sub-song together. This chorus is a joy to hear and is rarely commented on. Make a sudden movement and this union of song stops instantly and the birds take flight.
