02 February 2017

Where do our wintering Blackcaps come from and why?

Over the next three winters, a new study focusing on Blackcaps wintering in Britain and Ireland will help reveal how novel migratory changes arise and spread.  The study will look at genetic and morphological differences between breeding populations and migration strategies, as well as investigate aspects of wintering behaviour, movements and survival of individuals wintering in Britain.

Up until 50 years ago, wintering by Blackcaps in Britain & Ireland was quite unusual, but numbers have since increased considerably, with many thousands now counted each winter by BTO Garden BirdWatch. Gardens are favoured sites where a combination of ‘natural’ berries and fruit along with specially provided fat, seeds, cake and pastry is the main attraction, often fiercely defended by some individuals. 

Male Blackcap. Photo by Greg Conway.

Typically, the majority of Blackcaps breeding in northern Europe migrate to the Mediterranean region for the winter. However, this is changing – some of these birds may now be migrating in a north-westerly direction to the British Isles instead! These changes appear to be facilitated by milder winters and the abundance of food provided by people, according to research carried out using Garden BirdWatch data.

A number of studies have suggested that our wintering birds come from central Europe (southern Germany/Austria), but the small number of ringing recoveries available (see map below) indicates that many may originate much closer to home, or even be resident!  Unfortunately, few recoveries confirm movements between the breeding and winter season.

Origins of ringed Blackcaps wintering in Britain and Ireland and their locations from the breeding season (red), autumn (blue) and spring (grey) (Migration Atlas – Wernham et al 2002).

To improve our knowledge of migration and breeding origin, a number of wintering Blackcaps have been fitted with Geolocators (accurate to around 70km).  These will reveal where they spend the summer, but only once re-caught back at their wintering sites.

Female Blackcap fitted with a geolocator. Photo by Greg Conway.

Colour ringing allows individuals to be identified with unique combinations and this will be used to learn more about winter behaviour, movements and use of wintering sites in Britain, which is surprisingly little understood.  Some appear to remain in the same garden all winter, but others do not!

Male Blackcap with unique colour rings. Photo by Greg Conway.

We would be very grateful for your help with the following:
Blackcap sightings - If you have wintering Blackcap in your garden please let us know and report your counts using BirdTrack or consider joining Garden BirdWatch.

Colour ring sightings - Please report all observations to: blackcap@bto.org

Ringers – Help with catching and colour ringing more Blackcaps over the coming winters would be much appreciated.  If you don’t have sites with Blackcap we can provide details of local sites where ringing is required.

To find out more about getting involved please contact: blackcap@bto.org

Greg Conway (BTO) & Benjamin Van Doren (Oxford University)
This study is collaboration between Oxford University, BTO, Exeter University and the Max Planck Institute for Evolutionary Biology, Germany.

5 comments:

  1. It will be very interesting to see how things have changed since my Bird Study paper from 1981 http://www.tandfonline.com/doi/abs/10.1080/00063658109476693

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  2. Perhaps this is one of the most important reasons for the drastic fall of the wintering population in the south of Spain.
    The data collected in the last 2 years are very discouraging.

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  3. I have had at least one male Blackcap coming to my Garden feeders for the last 5 winters it arrives around Christmas time and leaves around the time they start singing in March. I have seen 1 other male and 2 females, but are only around for 1 day. Non have had rings.

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  4. So if I'm reporting them in my GBW returns, I don't need to put them on Birdtrack, yes?
    This is the first year I've had them regularly in my garden in winter. There is also one at my golf course five miles away, just doing tiny bursts of song while surrounded by singing robins!

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  5. Excellent that you are recording for GBW so no need to also record in birdTrack. But please do record all your non-garden records in BirdTrack. The song is quite early but no too unexpected with the milder weather.

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