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.

From across the pond

Britain and Ireland are part of the East Atlantic Flyway, so we regularly get a few high Arctic breeding birds from Greenland or Canada in our country like Greenland Wheatear, Barnacle Goose, Pink-footed Goose or Purple Sandpiper.

The majority of recoveries are of Brent Geese (66%), but 19 species have been recorded either coming from, or going to, North America, Canada or Greenland (the latter is covered by the Denmark Ringing Scheme).

Brent Geese have been excluded from the pie chart to better illustrate the other species involved.

These are not all recent recoveries however. The oldest report is from 18 July 1948 (juvenile Arctic Tern ringed in the Bay of Fundy and found by Lairg, Highlands three months later). Due to a colour ringing project on Ellesmere Island, Nunavut, we have received quite a few Turnstone reports (37% of the total). Several species stand out, including Great Shearwater (one caught by a trawler and the other caught on a boat), Peregrine (downed by a falconer's Peregrine) and a Caspian Tern (found dead).

Below are a few examples of more recent recoveries :

Ringed Plover - you may remember that Ringed Plovers from Canada have been featured recently on the Demog Blog, so we have several reports of them.

Ringed Plover. Photo taken by Lee Collins

Green-winged Teal - one turned up on the Hayle estuary, Cornwall on 9 November 2016 and it didn't take long to notice it was ringed! It took the Cornish ringers and birders quite a while to get enough photos of the bird to get the ring number, but finally on 19 January 2017 they had enough to trace it. Amazingly this bird was ringed as an adult in Quebec in August 2015!

Green-winged Teal. Photo taken by Anne Carrington-Cotton

Knot - in February we received a report of a dead Knot at Old Hunstanton, Norfolk. The likely ringer would have been the Wash Wader Ringing Group but the ring was clearly from the American Ringing Scheme. American rings are also used in Canada, which is probably where this bird was ringed. If this is the case, then this would be the 10th Canadian ringed Knot to be found in Britain or Ireland. Several BTO staff travel to Delaware every year for their holiday to ring 'Red Knot' as part of the Delaware Shorebird Project, so there was quite a 'flap of excitement' until it became clear that it was not one of theirs. We, and the finder, are awaiting the ringing details from the scheme.

Recoveries from the States are still very few and far between so each one is unusual in itself. The information from the tagged Ringed Plovers will be very interesting to follow in the coming years.

For more information on the movements of birds look at our Online Ringing and Nest Recording Report on our website.

Want to see a Whimbrel? Den mark it with a colour ring

It's always a pleasure to hear the Whimbrel's distinctive call when flying over and it's very special when one is caught (see online reports). Relatively few are ringed in Britain & Ireland and with the addition of colour rings the reporting rate has increased substantially. The pie chart below shows how few dead birds are found in relation to the number of reports received of colour rings.


The Mid Wales Ringing Group started a colour ringing project in 2010 to try to answer some basic questions regarding Welsh birds in particular, like movements, staging areas, survival and site faithfulness. Some of these birds have been reported (dead and alive) in quite a few areas including Scotland, France and North Africa.

A Whimbrel wearing a Mid Wales colour-ring combination was recently reported in Denmark. The BTO online reports show this to be only the fourth BTO-ringed Whimbrel to be reported in Denmark. Yellow D74 was ringed on 30 April 2016 at 2:50 am and 72 days later it had travelled a minimum distance of 1,059 km to Storevorde, Denmark.

If you were hoping to see a BTO-ringed Whimbrel outside Britain & Ireland, there is a much greater chance of seeing one in Guinea (195 reports), Guinea Bissau (224 reports) and Iceland (366 reports).



Colour-ringed Whimbrel photo taken by Jens Veilgaard Vendelbo

Whimbrel photo taken by Jens Veilgaard Vendelbo

So if you ever see a Whimbrel, or any other wild bird for that matter, report it at www.ring.ac. The information will be very useful and could hint towards a new movement or behaviour.

For more information on this and other Mid Wales goings on, click here.

Avast! There be BTO buried treasure

From Viking hoards to Roman coins, metal detecting can be a very rewarding hobby. Many hours can be spent on the beach or in a field trying to uncover a hidden link to the past or some real life treasure. Why is the BTO interested in this, I hear you ask. Well we are increasingly getting reports of BTO treasure... bird rings!

Metal detector and spade. Taken by Martyn Franklin

The majority of these rings usually belong to birds that have been dead for 10 or 20 years, but our most recent metal detector report from Martyn Franklin was a touch older than that. He was searching near Shipton-on-Cherwell, Oxfordshire when he came across 323412 in nearby farmland.

The mis-shapen ring of Martyn Franklin's find, that has been under the plough quite a few times.

After some searching, the ringing details of an adult Stock Dove were found in the deepest, darkest areas of our archive. Many thousands of ringing records are stored here, covering hundreds of species. This Stock Dove had been ringed 13 km away on 12 March 1943 and is the first Stock Dove to be reported by 'metal detector'. This joined other single reports of 14 species including Brent Goose, Bullfinch, Sandwich Tern, Goldeneye, Wren and Tree Sparrow.

The archive of many thousands of ringing details for birds that are long gone.

The BTO database shows that rings from 67 different species, ranging from Yellow Wagtail to Osprey, have been found over the years by metal detectors. The majority of reports cover urban and farmland birds, but coastal species like Shags and gulls also feature.

One very interesting use of metal detectors has been to find rings in the nests of birds of prey (licences may be needed). Lots of these have been in Peregrine nests or below roost sites and mainly cover thrush sized birds like Starling, Redwing, Dipper and even a Jay. Interesting nest studies in Norway have revealed rings in Eagle Owl nests and to date have found 19 BTO rings including from Oystercatcher, Teal, Common Gull, Tufted Duck, Blackbird and Guillemot.

If you have a metal detector why not get out there and find some bird rings. You never know, you might find one of the first rings ever used, from 1909! Don't forget to report it at www.ring.ac.

What happened to the recoveries?

After looking at how many recoveries we get from predators in the last posting, I thought it would be nice to look at the recoveries we get as a whole.

I have used all the recoveries that we have received from August up until now. We use two codes to say what happened to the birds. The finding condition tells us, for example, if the bird was found dead or alive. The finding circumstances give the cause for what happened to the bird, if known.

The pie chart below is of the condition of the bird reported. As you can see the vast majority of reported birds are dead but a reasonably large slice goes to ringers catching birds after that have already been ringed (this generally only includes birds travelling more than 5km from the site of ringing).



The second pie chart is of the finding circumstances. We have a multitude of codes for the circumstances but I have just highlighted those that we have had more than 10 reports.

The 'bird found' slice is when the finder just finds the bird's body but doesn't know what happened to it. Obviously the pie chart results are very specific to this time of year and the proportions change very quickly. For example this is the start of the shooting season and we get a sudden increase in the number of birds shot compared with earlier in the year.


It should be pointed out that these portions are of reported individuals, for example you would hope that 100% of all shot birds would be reported but not all birds are reported that end up in a cat's belly.

Ringing in numbers

Things are getting very exciting here in the Demography team as most, if not all, of the ringing data are computerised for 2010. We can now start analysing the information and try to understand why we ringed over a million birds last year!

As we had a great breeding season last year, you would think that the number of juvenile birds and those ringed as chicks would provide a large chunk of the ringing totals. Looking at the Pie Chart below shows this is the case.


So 66% of birds ringed in 2010 hatched in the year. The 3% of unaged birds would largely be down to birds that do a complete post juvenile moult, a couple of months or so after hatching, so they will have adult plumage and can not be aged as an adult or juvenile reliably.

To compare with 2009 the Pie Chart below shows the percentage of birds ringed for that year. As you can see there is not a massive difference but 2009 was also another record year for the number of birds ringed.


The bar chart below shows the number of chicks ringed for the past 6 years. Fingers crossed for another good year and success in nest recording.


Thanks to Richard Vaughan for the photo in the bar chart and apologies for the overload of graphs in one blog post.