24 July 2017

From the land of ice and Blackcaps

For Hugh Insley, ringing at this time of year means trying to catch Siskins in his garden in Drummond, Inverness for his Retrapping Adults for Survival (RAS) project and so far this year he has caught 3,000. Inevitably, he also catches a few other birds which are not part of his RAS project.

On 11 July, he extracted a Blackcap from the net that was already wearing a ring. This wasn't one of the c. 50,000 that are ringed in Britain or Ireland every year though, but the first record of a Blackcap that was ringed in Iceland! Now the BTO has to add a new row to the long list of countries that Blackcaps have come from or have gone to with a connection to our ringing scheme.

Female Blackcap wearing an Icelandic ring. Photo by Hugh Insley.

As we have posted previously, Blackcaps have a very interesting and complex migration, possibly associated with climate change and supplementary feeding, which is currently being studied. Many of our British & Irish breeding birds are known to winter in the south, around Spain and Portugal, whilst those that now winter here are known to come from continental Europe - using a novel northwest migration rather than the typical southwest route to reach Iberia. 

The individual that Hugh caught was ringed on 3 November 2016 as a full grown adult female in the garden of the vicarage at Siglufjordur, N. Iceland (see the blue pin below). It was caught again twice more at the same location (on 20 January and 30 March 2017) before heading south to Inverness.



Blackcaps are a vagrant species in Iceland and only 222 have been ringed there; only five of these have been caught again in the country. Additionally, eight Blackcaps that were ringed abroad (five from Belgium and one each from Denmark, The Netherlands and France) have been caught in Iceland. 
 
So, was this a 'British bird' making a novel northwest instead of southwesterly (mirror-image migration) before returning to breed, or was it part of a wider northward movement now undertaken by central European Blackcaps into northern Europe?  

07 July 2017

Who gives a hoot

Occurring throughout England, Scotland and Wales the Tawny Owl is well known, especially during the winter when their territorial calls can be heard during the night.

The Tawny Owl is amber listed, i.e. a species of medium conservation concern due to recent population declines. Surveying this species can be difficult, but studying them is easier due to their readiness to use nestboxes. Ringing the adults and their chicks, as well as following the progression of the nesting attempt (nest record), provides very useful information to help interpret population changes.
 

Adult Tawny Owl. Photo by Rachael Barber


Adult Tawny Owl with a more grey plumage. Photo by Lee Barber

The number of Tawny Owls ringed each year varies considerably; in the last five years the number ringed has ranged from 920 to 2,748 birds. The number ringed also varies by county, with ringers in Northumberland topping the list with an average of 183 birds per year. This is followed by Lincolnshire (107), North Yorkshire (100), Nottinghamshire (92), Norfolk (81) and Cumbria (81). Around 80% of the birds ringed each year are chicks. Ringing chicks enables researchers to follow an individual throughout its lifetime, providing vital information on where birds move to and exactly how long they live.

Tawny Owl chicks. Photo by Lee Barber

For most of the recoveries the BTO receive, the cause of death is unknown, but for some the cause of death is clear. Being hit by a vehicle is the most reported cause of death for Tawny Owls, followed by train casualty and drowning in artificial water containers like horse or cattle troughs. This doesn’t mean that 66% of all Tawny Owls die from vehicle strikes, however. Birds killed by vehicles are inevitably more visible than a bird that dies of natural causes in the middle of a wood. Also, as most of the birds that are reported are from areas with high concentrations of people, these are more likely to be reported when found.


By recapturing ringed birds, licenced bird ringers are in the privileged position to be able to gather information on the presence and condition of Tawny Owls that are alive and well. Last year one of our ringers re-caught a Tawny Owl that was originally ringed as long ago as 2003. This bird was ringed as a chick and re-caught in the same place (Kielder Forest, Northumberland), so the exact age of this bird is known (13 years). A bird ringed in 2004 at Rowlands Gill in Tyne and Wear which was also caught during 2016, that was an adult (at least 1 year old) so she could have been much older. It would have been doing very well to break the longevity record of 21 years 10 months.

Unlike some other owl species, Tawny Owls doesn’t generally travel very far or cross large bodies of water, so their distribution is restricted to mainland Britain.  Due to this behaviour we have had no foreign recoveries in the history of the BTO Ringing Scheme.

Tawny Owl chick about to be ringed. Photo by Lee Barber

I have received one recovery while working at the BTO, of a ring found in Iceland (without a bird) which was originally put on a Tawny Owl chick. This was an amazing record so (as with all our recoveries) some investigation followed. Unfortunately, this wasn’t quite as amazing as we’d hoped as we had a previous record that this bird had already died. The ‘used’ ring was put on a binocular strap for safe keeping after reporting. Some years later the finder was on holiday in Iceland when the strap broke and the ring was lost, only to be found later by someone else who reported it to the BTO via www.ring.ac.

The vast majority of data from ringing and the resulting finding of dead birds can provide an amazing amount of information, so if you do find a ringed bird please report it via www.ring.ac.  As a thank you, you will receive the information on where and when the bird was ringed.