20 November 2015

Choppy times for Manxies

Manx Shearwaters and their migration provide one of the most fascinating bird stories of the British Isles. They breed in inaccessible places and historically have been difficult to observe, let alone study, outside their breeding period. For this reason, the Manx Shearwater has been a mysterious species for ornithologists for many years. Luckily, technology, the Ringing Scheme and the fact that it is a long lived species have combined to provide us with a lot of information on the life history of the Manx Shearwater, including its distribution and behaviour in summer and winter.

The 300,000 breeding pairs of Manx Shearwaters in Britain & Ireland are distributed among about 50 colonies, the largest ones being Skomer in Wales and Rum in Scotland. Several thousand 'Manxies' are ringed by BTO ringers every year; the table below show the last five years from the Online Ringing and Nest Recording Report.

Most 'regular' recoveries of Manx Shearwaters are generated at their breeding sites, when they return to breed at the same colonies year after year. Since the BTO Ringing Scheme started, over 100 years ago, we have received about 1,000 reports of BTO-ringed birds from foreign countries, all except one on the Atlantic coast, most of them in Brazil, Uruguay and Argentina. 

Nowadays, the more exciting and revealings facts about the pelagic life of this species come not from ringing but from satellite and datalogger tracking. When the birds return to breed in their burrows on islands in Britain & Ireland, they can be fitted with special devices that are safe for the birds and give more detailed information about their movements and behaviour.

Researchers studying this species have been able to reveal where most 'Manxies' spend their winters and what routes they take to and from the breeding colonies. One such research project is led by T Guilford - some result from which, below, show the estimated routes and stopovers of 12 birds fitted with geolocators. 

Different colours indicate different birds, the 'lines' are joined dots and do not represent actual trajectories of the birds. 
Migration and stopover in a small pelagic seabird, the Manx shearwater Puffinus puffinus: insights from machine learning
T GuilfordJ MeadeJ WillisR.A PhillipsD BoyleS RobertsM CollettRFreemanC.M Perrins
Most of the South American reports occur between November and January, and the number of dead birds reported along the coasts of the Atlantic varies from year to year. So far this Autumn we have received 10 reports, a few more than we would expect. Many of the finders who kindly let us know about these Manx Shearwaters mentioned the stormy weather they have experienced on the other side of the Atlantic. These intense stormy periods may be linked to a strong 'El Niño' event in the Pacific, bringing unusual weather to many parts of the world including North and South America. 'El Niño' literally translates as 'the child', because this weather anomaly typically manifests around Christmas time when the birth of baby Jesus (the child) is celebrated. The graph below puts the 2015 'El Niño' event in context compared to previous strong 'El Niño' events.

The graph above shows how this year's event ranks in terms of severity compared to other strong 'El Niño' events. More information can be found at: http://www.srh.noaa.gov/tbw/?n=tampabayelninopage

It is also interesting to see how many birds have been reported washed up on the shores of the east Atlantic in the last two decades. 

In North America, Deaborah Kotzebue, who lives Texas, USA, found a Manx Shearwater in Gulf Shores, Alabama, washed up after a stormy period. She sent us some photographs to illustrate what the place is like

The other nine reports of Manx Shearwaters were of birds washed up on beaches in Brazil, South America. One of them was found on Campeche beach, Santa Catarina, by surfer Paulo Vieira. I asked Paulo if the weather had been particularly stormy and he replied "Yes, it has been very stormy  down here in Santa Catarina State, and southen Brazil in general. We are suffering the effects of 'El Niño', which produces a lot of rain during the Spring (above normal range). Since mid-September until early-November it has been raining a lot down here".

At the end of the wintering period we will give an update on Manx Shearwaters on the other side of the pond.

The Manx Shearwater was chosen as the bird of the month in September 2015. See the distribution map in the Atlas Mapstore.

16 November 2015

Out of Africa... and into Norfolk, for a 13 gram bird

Oliver Fox writes:

Monitoring of wintering passerines is one of the main objectives of the Kartong Bird Observatory (KBO), a project run by volunteer ringers in the south of The Gambia, West Africa. Situated on the Atlantic coast close to the Senegalese border, the Kartong wetlands were formed relatively recently as a result of wet-season flooding of disused sand mines and form part of the Allahein to Kartong coast IBA.

Palearctic passerines being processed at Kartong Bird Observatory taken by Colin cross

The wetland reedbeds and surrounding scrub provides an excellent wintering site for many Palearctic passerines, and mist-net surveys have highlighted the importance of the site for Western Olivaceous Warblers, Common Whitethroats, Subalpine Warblers and Common Nightingales in particular. In dry years the area provides refuge for Sahel-dependent species, such as Western Orphean Warblers and Woodchat Shrikes, when conditions further north become unfavourable. Located on a promontory extending into the Atlantic, the site is also well placed to observe passage migration of Blackcaps and Garden Warblers moving south in October and November and Willow Warblers moving north in early Spring.

Wintering Reed Warblers are regularly encountered at Kartong, both in the Typhus reedbeds and the dry coastal and Acacia scrub that surrounds the wetlands. A proportion of those ringed at Kartong seem to be faithful to the wintering site, with five birds recaptured the winter after ringing and one bird returning to Kartong in two successive winters.

Reed Warbler about to be released at Kartong taken by Oliver Fox

News from the BTO has been received that a Reed Warbler ringed on 18/01/14 at Kartong was recaught at Hilgay Wetland Creation, Norfolk on 11/08/2015 BTO's Graham Austin, only 29 km from BTO HQ. There were several BTO staff members on the expedition in 2014, so it seems fitting that the bird was caught in Norfolk a few months later.

This is the sixth Reed Warbler ringed at KBO to be recaptured back in Europe during the summer months, with three having been previously recaptured in Spain, one on Guernsey and one in Surrey. Similarly, the ringing teams at Kartong have recaptured two Spanish and one British & Irish-ringed bird in the last few years, showing the migration pattern of Reed Warblers from Western Europe to the coast of West Africa.

Details of this latest recovery can be found on the Recoveries and Controls page of the KBO website.