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.

No comments:

Post a Comment