© John Harding
Blackbirds are absent from many gardens in winter – but why?
“Where have all my birds gone?”
This is perhaps the most frequently asked question of the BTO Garden Ecology Team at this time of year.
“Has something terrible happened? Is there anything that can be done?”
In fact, reduced activity during late summer and early autumn is completely normal, and the disappearing act is particularly noticeable in blackbirds.
Change of scene
Being such familiar garden guests, it feels as though blackbirds are always around – singing, scolding and eating their way through the days.
The BTO Garden BirdWatch survey shows that almost all gardens are visited by this thrush throughout most of the year. Now, however, around two in 10 householders lose their blackbirds.
So, where have they gone?
Average percentage of gardens visited by blackbirds – data from BTO Garden BirdWatch 2009–11. Photograph © John Harding
Over recent months, blackbirds have been moulting into new plumage. As they replace their feathers they are vulnerable to predation, and so individuals tend to be reclusive and, subsequently, are less easily spotted.
Now, however, replete with their smart new attire, blackbirds have headed off into the wider countryside to profit from nature’s late-summer bounty. Berries, in particular, are high up on the menu.
Some years yield excellent berry crops; others do not. The early signs from this year suggest that berry crops are patchy.
Gardens provide different foraging options for birds than those found in the countryside, including the berries of countless native and non-native cultivars.
However, some of these non-natives, such as certain varieties of berberis and cotoneaster, may have different fruiting seasons to native plants, and could even be preferred by blackbirds.
Is this good news? Plants use berries as tasty treats to attract birds. In return, the seeds contained within the berries are dispersed elsewhere after passing through the birds’ digestive tracts.
If the berries of non-native plants are favoured over those of native ones, it is possible that birds will spread the seeds of these exotic plant species far and wide.
On the move
Blackbirds are among the ‘secret migrants’ that move into gardens during autumn.
People tend to assume that blackbirds are here with us all year round but, while this is true for some individuals, huge numbers of continental breeding blackbirds – from as far afield as Russia – migrate to our shores to spend the winter.
Within the UK there can also be big movements. Data collected by BTO bird ringers show that some blackbirds move south and west within the UK each autumn in pursuit of milder conditions.
Amazingly, one blackbird was observed commuting from a garden in Thetford (Norfolk), where it spent the summer, to another in Newton Abbot (Devon), where it spent the winter, for three years in a row.
When freezing conditions descend, blackbirds and other thrushes struggle to probe their beaks into the ground for invertebrates. At such times, providing food for them can provide a lifeline.
Windfall fruit is taken readily by blackbirds, so don’t be too tidy-minded around the garden over the coming weeks.
Raisins, soaked first in water (please note that raisins are toxic to dogs), and mealworms can also be a big hit with blackbirds.
The British Trust of Ornithology (BTO) works in partnership with over 40,000 volunteer birdwatchers to chart the fortunes of UK birds.
Among the surveys that we coordinate is our popular Garden BirdWatch, the largest year-round survey of garden birds in the world.
For more information about Garden BirdWatch or to speak to the Garden Ecology Team please email firstname.lastname@example.org