CES ringers finally get a lie-in

Greg Conway writes:

As the breeding season draws to a close, so the hundreds of dedicated ringers who run the 120 Constant Effort Sites (CES) scattered across Britain and Ireland can start to relax and recuperate after a summer of early morning starts. As they use the same mist nets in the same places each year to catch the birds, the information they collect tells us about changes in numbers of adults and juveniles over time, so abundance, breeding success and survival can all be measured, making this one of the most valuable ringing projects.

Target species include many of our long-distance migrants (e.g. Reed Warbler, Sedge Warbler, Garden Warbler, Whitethroat, Willow Warbler) plus resident scrub species such as Wren, Dunnock, Blackbird and Robin.

The CES scheme started in 1983, so ringers have just completed the 29th season and will soon be focussing their attention on getting all their data to BTO HQ ready for analysis. The results of the most recent CES analysis can be found on the species pages here and the preliminary results from 2011 will be available later in the autumn. These will provide the first indications of abundance and breeding success of birds nesting this summer, helping to assess the potential impact of yet another harsh winter.

Early indications suggest that a number of migrant species have returned in greater than usual numbers. However, despite an early start to the breeding for many species, prolonged periods of cool and wet weather, particularly in the north and west of Britain and Ireland, were associated reduced breeding productivity levels.

A big thank you to everyone whole has help with CES this year and those ringers who have already submitted their data.

Thanks to Dorian Moss for the above picture of Lucy Yates and Kate Risely for the top picture of Nick Moran.

Nightjars and Lightbugs

Nightjars are now returning to the Forestry Commission's Thetford Forest and are pairing up ready to start nesting. Thetford Forest Ringing Group members were out on Thursday night in order to catch these birds to understand more about their movements on migration and particularly in their wintering quarters, as surprising little is currently known about this species. A first catch of four birds was a marvellous start to this new BTO/Biotrack project, supported by Shoreham & District Ornithological Society.

Unlike the Cuckoo, previously reported, the Nightjar is too small to have a Satellite transmitter fitted. Geolocator tags are an excellent alternative but we have to catch the birds again next year to download the information on their movements. These tags, known as Lightbugs, collect data on day length and time, which is used to calculate the bird’s global position to within 100km, each day. These daily locations will help reveal migration routes and wintering locations within Africa.


Just when you thought a near perfect night couldn't get any better, one of the females was discovered to be already ringed, RP01170. She was originally caught on migration, 171km away at Icklesham, Sussex on 15 September 1999 and we had not seen her since she was caught in the forest in 2008.

RP01170 has now broken the previous British and Irish longevity record, which stood at 11 years and 10 days, by 257 days. Amazingly, Brian Cresswell who helped fit the Lightbug to RP01170, originally caught the previous oldest Nightjar, in Dorset, back in 1992! So, quite a privilege to have handled the two oldest Nightjars in Britain and Ireland.

Thanks to Brian Cresswell and Forestry Commission for their valuable help and to Kate Risely for the photo (Lee Barber on left and Brian Cresswell on right).

CES with a difference

As you would expect, here at the BTO we take part in our own ringing Constant Effort Site (CES). This is a nationally standardised ringing project where we put the same nets in the same place at the same time of year. This means that the numbers of birds caught are comparable between years and fluctuations in the numbers of adults and young can be monitored.

This morning was session number 4 for the Nunnery Ringing Group and the weather was set to give us some good ringing and we were hoping for a large catch. It turned out that the weather was fabulous but as usual we didn't get great numbers of birds, but we did get some unusual species.

As you might have seen from Springwatch last year, we have Cuckoo on the reserve laying their eggs into Reed Warbler nests, but we have never caught one. This is not surprising, as in 2009 for example only 34 Cuckoo were ringed (13 of which were ringed as chicks) over the whole country. This morning though we caught a female that hatched last year (aged on plumage charateristics)!


Out of the 31 birds we caught this was the highlight but we also caught some great birds including Reed Warbler, Blackcap, Garden Warbler, Jay and also some recently fledged Dunnock. It is also nice to know that all these birds were caught on a CES session and the results are even more valuable than normal ringing. For more information on CES check out http://www.bto.org/ringing/ringinfo/ces/index.htm

Thanks to all of the ringers that have helped with our CES sessions over the years, Paul Stancliffe for the photo and to Kate Risely for kindly 'volunteering' to ring the Cuckoo.