The Cold Spell Brings Redwings
January 15th saw the beginning of a short, severe cold spell which brought flocks of Redwings from the countryside to towns, where conditions are less exposed and there is a plentiful supply of berries to feast on.
Views of Redwings in Hastings
We had a flock of more than twenty birds regularly feeding on the berries of an old holly tree at the bottom of our garden in St Leonards (near Hastings). They would spend a lot time rummaging in the thick of the tree, while individuals would occasionally emerge to sun themselves for a while at the top. On the odd occasion when they were startled we saw the full extent of the flock.
Identification
Redwings are members of the Thrush family, and similar to the Song Thrush in appearance, except the Redwing has a strong pale stripe over the eye, and has a flash of deep russet brown under the wing.
Breeding and Migration
They breed in Iceland, Scandinavia, and Russia and migrate south in large numbers during the winter. Some will travel as far south as the Mediterranean.
The majority of Redwings that overwinter in the UK come from Russia. Their influx can be quite spectacular, as those that are destined to remain here mix with those that will be flying across the channel to winter in France, Spain and Portugal.
In record years, tens of thousands of Redwing, and the closely related Fieldfare, are counted in a single day funnelling along their main migration routes (flyways).
The massive flocks show up on weather radar assembling in the southern tip of Norway waiting for the right weather conditions to cross the North Sea. When they judge conditions are good, they cross en masse, some flying directly south, to reach the Dutch coast, and others south west to reach the north east of Britain. From here they head inland and then turn directly south, down through central and west England, to cross the channel.
The majority of these birds winter in Europe, but around 70,000 are estimated to remain in the UK for the duration of the winter. Their preference is for open rural areas, feeding on worms and berries, but when conditions get tough they move into urban areas to feed.
Richard Smith gives a wonderful description of the spectacle that was observed in October 2022, in the north east of England, during a record year. His analysis of the migration flyways is fascinating: http://www.deeestuary.co.uk/news1222.htm#first
How decisions are made on which flyways to use, and where to overwinter is still not well understood. We tend to assume that migratory behaviour is hardwired in the individual bird’s DNA, but there seem to be many determining factors. Clearly weather conditions are an important factor, but research on the migration of thrushes from Scandinavia indicates that a certain amount of individual preference on the day is part of the equation1.
Life Expectancy
One thing for certain though, is that individual experience is probably the least important variable. The Redwing has an average life expectancy of only two years which is very little time to build a history of migratory experience to influence the decision making of individual birds.
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Notes
Footnote: 1.
“To cross or not to cross – thrushes at the German North Sea coast adapt flight and routing to wind conditions in autumn” Vera Brust, Bianca Michalik, Ommo Hüppop; Movement Ecology volume 7, Article number: 32 (2019)