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Originally Posted by Cozza1969  Hi, Just read your article with great interest, ... We normally get them visiting our garden in the summer, and I'm aware that they are probably German Blackcaps. However, this year, for the first time, I heard one singing from the woods in early March, long before I would expect the summer visitors to arrive. It was singing with full gusto too, not just the scratchy sub-song. So if this is a continental species, I'm wondering why they would sing in such a manner if they're not in their breeding grounds? |
Birds, like people, are generally assigned nationality according to the country they breed/are born in.
The Blackcaps that arrive in the UK to breed here ie. summer Blackcaps, are the British population that winter in Southern Spain/Africa. It's the ones that arrive in late autumn and winter here that are from the German populations. (Although it's possible a few British Blackcaps may winter over too given the fairly recent propensity for other warblers such as Chiffchaff and occasional Whitethroats to winter here).
The Blackcap singing it's heart out in early March in a wooded area could well have been an early British arrival since it was in habitat - they generally arrive during the last week of March beginning of April though. The wintering German Blackcaps are on the whole more visible in gardens/non-breeding habitats and relying more heavily on artificial food sources.
As far as German singers go, why they sing in their wintering grounds is one of the questions I posed above. It's not something that scientific surveys has yet established AFAIK. However, it has been established that there is micro-evolution taking place between the German Blackcaps that winter in the UK and the German Blackcaps that winter in Spain etc. Singing in winter could be related to this. I'm not sure whether there's been any moult studies either, but again, it's possible moult timing is different between the evolving German populations as migration journeys/departure times are different, so again, that could effect the timing of singing between the evolving group of German Blackcaps wintering in the UK and German Blackcaps wintering in Spain. (Generally, all Blackcaps have a complete Summer moult and depending on ssp/locality, a partial or completely suppressed winter moult)
In other words, German Blackcaps wintering in the UK could have an earlier breeding potential than their Spanish wintering counterparts so it's a case of the early bird getting the worm (the best nest sites/fittest females) and pre-mig singing could be part of pre-nuptial selection with females also wintering here - thus making the evolving group a competitive force with their Spanish winter counterparts once they all arrive back on their breeding grounds strengthening the micro-evolutionary directive of this group.
Interestingly, in possible response to this, again something I mentioned above, Spanish wintering Blackcaps were also noted to be singing en masse in February!), so perhaps again, it's a competitive evolutionary thing going on between the Germans. (or seeing as they're German, early singing is a case of tying the proverbial towel round the deckchair to secure their place in the gene pool
)
I think the next interesting stage would be to do sonagrams of the different populations to see if they are developing vocal as well as genetic distinctions. At that point, there would be an interesting taxonomical development if it's established there is selective breeding going on now between the diverging European populations based on vocal recognition.
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