Blackcap female in the snow © David Chapman
The blackcap is regarded by many as a summer visitor to Britain, and though it is more numerous here during summer it is actually less visible. Winter is the best time for seeing blackcaps in our gardens for one simple reason, in winter they come to take food from our bird feeders.
Prior to the 1960s, wintering blackcaps in the UK were virtually unheard of. British-born blackcaps migrate to Spain or Africa for the winter; the birds we see here in the winter months come from Germany. Most German blackcaps migrate in a south westerly direction to Spain for the winter but at some point during the middle of the last century a few started to spend the winter in Britain, where they found a bountiful supply of food because of our habit of providing bird food in gardens.
When they returned to Germany to establish breeding territories they had a shorter migration so had an advantage over those returning from Spain. Because they had less distance to fly they also tended to arrive earlier and pair up with other birds that had the same migration. Over the last half century these birds have become distinct with slightly different genes and even some structural differences. For example British-German blackcaps have slightly shorter, more rounded wings which are better for manoeuvrability but not as good for flying long distances.
Scientists have found that the direction in which the birds migrate is determined by their genes. So a pair of British-migrating blackcaps will give rise to young which migrate to Britain and similarly for a pair of Spanish birds. But when a British migrant was crossed with a Spanish one the youngsters migrated in a direction between the two!
It is possible that in years to come the blackcaps which breed in Germany will split into two distinct species but for now we can all enjoy watching these pretty birds in our gardens, providing we put out some food.
For a bird which is quite shy during the breeding season the blackcap is remarkably adaptable and bold at the bird table. I have watched them feeding on apples, raisins, peanuts and bird seed in our garden and the blackcap is dominant over all but the most aggressive resident birds. They enjoy berries so I often see blackcaps in a small holly tree outside our window and also in the pyracantha, which unfortunately hasn't produced as many berries as normal this year.