Thanks to volunteer Phil for his article on changes in blackcap behaviour which explains why you may now see a blackcap during your Big Garden Birdwatch.
The blackcap is a relatively common bird in Britain during the summer when many migrate here from Africa to breed. There are estimated to be 1.2 million territories during the breeding season and several can be found at Pulborough Brooks. However blackcaps are also becomingly more commonly seen in winter too when an estimated 3000 birds are believed to visit from Europe, instead of migrating to Africa, to take advantage of our bird feeders. Last year I was able to report one on my feeders to the Big Garden Birdwatch for the first time, so do look out for them.
For anyone not familiar with these birds they are almost but not quite the archetypal “little brown job” but the plumage is tinged with grey and the male has an attractive black cap, hence the name. The female is mostly identical but can easily be distinguished as she has a red-brown cap.
I wrote the following article about blackcaps and how we might distinguish between winter visitors and summer breeding birds for our regular newsletter to volunteers and staff. This was shortly after Lockdown 1 had started last year and just at the time the breeding blackcaps were returning from Africa.
Blackcaps – social mixing or social distancing?
Spring is the time of year when we welcome the returning blackcaps coming North to the UK from Africa and the Mediterranean and say goodbye to wintering blackcaps from Europe taking advantage of our bird feeders. There have been some interesting posts on Sussex Ornithological Society Recent Sightings between 19th and 25th March discussing whether the different migrant populations might mix and breed.
I took an interest because since Christmas I have regularly seen a female blackcap visiting my garden feeders.
I had not seen this bird for 3 weeks and assumed it had gone back to Europe and yet I have just seen it today as I write on 30th March. But really I have made a false assumption it was the same bird purely because it was a single female, when I have no way of telling one female blackcap from another.
Scientific study from Germany shows that a breeding blackcap population there winters in Britain. The same study shows that a separate blackcap population occupying the same area winters in Spain. These groups arrive back in Germany at different times and do not mix. It has also been observed that the UK wintering population is gradually evolving a slightly thicker bill, presumed to help eat seed from bird feeders.
Here is a blackcap male singing vigorously at Pulborough Brooks in June 2015.
I assume he is a summer migrant, but could he be a winter visitor who decided to stay? Research may eventually give an answer. In the meantime many people have made interesting observations, all to be found in SOS posts between 19th and 25th March.
Some are echoed in an interesting article from Cambridge Natural History Society.
http://www.nathistcam.org.uk/wintering-blackcap-survey-update-july-2017/
Over many years I have learned that birds never read textbooks or research articles. So when I saw a female blackcap at my feeder this morning it was certainly not obeying all the guidelines above. Visiting my feeder allegedly puts it in the wintering population and yet it should have already departed for Europe.
Exceptions gradually becoming a norm drive evolution, and scientists have postulated that blackcaps may be in the process of separating into 2 sub-species. But if blackcaps can change their behaviour over roughly 70 years since wintering birds first appeared in Britain, they could perhaps adapt further and mix with summer migrants - social distancing turning into social mixing? Alternatively, maybe summer migrants are now taking advantage of easy food from feeders before they start the serious business of breeding.
Inconclusive but interesting. I wonder if any of our readers have any observations on this subject?
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