Where have all the birds gone in summer?
29 October 2009
I can no longer hear any bird song. What's happened to the dawn chorus?
Because birds sing to establish and defend a territory and to attract a mate, they sing mainly during spring and early summer.
Some birds only raise one brood and even those that raise several broods in a year have little need to continue singing much after June. When chicks from the first broods of many birds have left the nest, the adults no longer need to defend their territory so vocally.
People notice this rather sudden end to the dawn chorus and often think that something has happened to the birds. There's no need to worry though - it's just a normal change in their behaviour.
It's late summer, and all the birds have disappeared!
The apparent disappearance of birds in August is another natural change and a part of the annual cycle of birds. There are two reasons for this.
Firstly, once birds have completed their breeding for the year, they start to moult into fresh new feathers. Completing a moult of all feathers takes several weeks. During this period birds look rather scruffy, and while they are moulting their wing feathers, they are less able to escape predators.
During this time, they conceal themselves as much as possible to avoid predators and territory disputes. It's easy to get the impression that they've disappeared.
Secondly, in late summer a bounty of natural food becomes available as grain, berries and fruit ripen. Many birds abandon their nesting areas and move to where the most food is. This is probably the time of the year when birds are least interested in the offerings on our bird tables.
In areas where farmland is nearby, house sparrows, starlings and many finches move out to fields to feast on the abundance of grain before it is harvested, and on the spilt grain after the harvest. Depending on the location, this can cause a sudden disappearance of these birds from residential areas and gardens.
Even in cities, sparrows and finches are attracted to any piece of rough ground that provides a good crop of weed seeds. Tits tend to abandon their territories soon after their young fledge, and spend most of their time in the late summer (first in family groups, later in larger flocks) high up in tree canopies, where they are easily missed. Even blackbirds and song thrushes tend to move to where there is an abundance of fruit or berries.
Birds often only return to our gardens when autumn frosts appear.