BTO: Listen out for arrival of redwings

Redwing. Picture: BTO/John Harding ANL-141024-105852001
Redwing. Picture: BTO/John Harding ANL-141024-105852001
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As the clocks change so the night sky resonates with the soft calls of newly arrived redwings. With the exception of occasional breeding records, these small thrushes are winter visitors to Britain, arriving from two distinct breeding populations: one in Iceland and the other extending from Russia west to the Norwegian coast.

While the Icelandic arrivals winter in Ireland, western Scotland and south to Spain and Portugal, it is the arrivals from the east that winter across most of England, including Suffolk.

Our visiting redwings can be rather nomadic in their habits, wintering in widely different areas in different years. This means that a bird wintering in Suffolk in one winter could be in northern Italy the next. Information on the patterns of movements has come from the hundreds of volunteer bird ringers whose efforts have tracked the movements of individual birds over time. Ringing also provides information on the timing of the arrivals each autumn and departures each spring, something that is now being supplemented through BirdTrack (www.birdtrack.net) and the records collected by birdwatchers logging what they have seen when out birdwatching.

One of the main reasons behind the movements made appears to be the redwing’s susceptibility to cold weather. They are particular susceptible to snow or hard frost, which prevents access to the invertebrates on which they feed. Fruits and berries are also taken during the autumn and winter, and redwings will turn to those available on garden plants and shrubs if conditions within the wider countryside are proving challenging. Windfall apples may also be well used, with visiting redwing feeding alongside blackbird, song thrush and fieldfare.

It is the more familiar song thrush that the redwing most resembles but the latter can be identified by its darker tones, strong white stripe above the eye and the deep chestnut red extending from below the wing and on to the bird’s flank. Be aware though that the underwing of a song thrush is washed with warm brown colouration.

Newly arrived redwings will be seen in farmland, typically feeding on the ground where they search for insects and other soil-dwelling invertebrates, only moving into gardens in any numbers later in the winter. Feeding flocks can vary in size from just a few birds to many hundreds, with the birds also roosting communally in thick scrubby cover or that provided by mature conifers.

The nocturnal calls of overflying redwings underline the numbers entering the country at this time of the year. The calls are used by the birds to stay in contact with other individuals as they migrate. Migrating at night is thought to deliver a number of advantages to a small bird like a redwing. Levels of predation are lower at night and cooler temperatures reduce the risk of overheating during what is a long journey.