Monday, 7 March 2011

Blackcaps that winter in the UK.

The Blackcap (Sylvia atricapilla) is a migratory warbler that breeds across most of northern Europe and winters in southern Europe and North Africa.
In the 1960’s it was noted that some blackcaps were spending the winter in the UK. The Blackcaps wintering in the UK were found to be part of a central European population that bred in Germany and Austria and instead of migrating south, migrated North West.
The reason for this is twofold. Some blackcaps happened to carry genes that caused them to migrate northwest and with the onset of garden feeding in the UK allowed them to survive the winter.
This appears to have an added advantage as it has been determined that the Blackcaps wintering in the UK arrive at their breeding grounds on average 10 days earlier (shorter route) than their counterparts that winter further south and tend to mate with others that follow the same route.
Subsequently researchers have found subtle differences in the now two populations. The birds that winter in the UK have slightly shorter, broader wings and smaller beaks.
These two distinct populations are known as Ecotypes and represent the initial step of differentiation among populations of the same species, the researchers explained. If ecotypes continue down that path, they can ultimately become separate species.

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