23 January 2009

Foreign Colour ringed Cormorant reaches UK

Back in October 2008 the BTO received a report of a colour ringed cormorant from Russell Hayes at Boultham Mere, Lincoln, but the bird proved difficult to identify as the colour ring combination didn’t seem to match any colour ringing schemes. We finally discovered that the reason for this was that the bird had lost a colour ring. However, we have been able to establish that it corresponded with a project in Lithuania, making this the first Lithuanian-ringed Cormorant to be found in Britain & Ireland!

Since the bird did not have its full set of colour rings it cannot be identified as an individual, but we can deduce that it is one of 54 individuals ringed in 2008. These 54 birds comprise 23 pulli, 29 first-year birds and 2 adults caught near the Juodkrante Cormorant colony in Klaipedos apskritis (55°31'16"N, 21°06'41"E), which means that this bird has travelled a distance of more that 1,400km!

Surprise in the net!

Last Sunday a group of BTO staff, including two trainees Alice Risely (volunteer) and Paul Stancliffe, went ringing for a few hours at a local site only a couple of miles from HQ. Here we regularly catch Blue, Great and Coal Tits, and this weekend was no exception.

On the penultimate net round, however, we were surprised to see a Woodcock take off from the ground and fly straight into our first net, only to then watch it bounce out again and head off in the opposite direction….into the second net! By this point we had reached the bird and were able to extract it quickly, thus preventing its second great escape!

Although the morning’s total was only 28 birds, this was enough for Alice and Paul, and with the added bonus of a Treecreeper (as well as the Woodcock), all in all it was a very good session.

12 January 2009

Cannon netting gulls on rubbish tips!

Last weekend myself and three others from Norfolk joined Paul Roper and the North Thames Gull Group for a day out cannon netting gulls on a rubbish tip, nice!

With a cold morning the birds were clearly hungry so soon after the net was set and a recent delivery of household waste in place we took a catch of mainly Black-headed Gulls which did include a Polish ringed Med Gull.

This bird was already ringed, bearing a Polish metal ring and a red colour ring. This is only the 24th Polish Mediterranean Gull found in the UK and only the second in Essex (the first was seen at Southend in 2006).

After extractions a small team reset the net and took another catch of 179 composed mainly of Herring Gull. A total catch of 587 was good experience in catching gulls in this situation and training ringers to age larger gulls.

06 January 2009

BTO Barn Owl found in Spain

We have just received details from the Spanish Ringing Scheme of a BTO-ringed Barn Owl found dead in northeast Spain. This is an amazing movement, as we have very few records of British-bred Barn Owls going anywhere interesting!

This bird was originally ringed as a nestling in Essex in July 2008. It was then found on 8 November at Pals, in the Girona region of Spain. We're not sure how it died, but it didn't have a head!

We have had a few movements of Barn Owls to Britain from abroad (shown in blue on the map), but fewer reports of birds ringed here and subsequently found abroad (shown in green on the map). Note the rather unusual report from Afghanistan of a bird ringed near an RAF base in Oxfordshire..... Presumably it didn't make it all the way there under its own steam!

View Larger Map

This is a fully functioning Google map, so you can zoom in and out and click on the markers to view the details for each movement.

05 January 2009

What is demography?

In a nutshell, where the Census Team at the BTO identifies trends in bird populations, so the Demography Team provides some of the tools to explain these changes.

Changes in birth rates (productivity), death rates (mortality and survival), immigration and emigration are what drives these changes in populations, so it is these that we are interested in. Even at the small scale, what we see can be fascinating. Just since the Christmas break, one small net in my Norfolk garden has caught 99 Blue Tits and Great Tits.

Now this isn't an exceptional catch, but what was interesting was that three quarters of these birds were adults. So where are all the young birds?

The past two summers have been incredibly poor for tits, with the wet weather causing havoc with adults trying to feed hungry chicks. Both species have had their lowest ever productivity, producing half as many chicks compared to the 'norm'.

So will this run of poor breeding seasons affect the population as a whole? Demography may well have the answer, so watch this space.