22 May 2012

22 May: Weather forecast suggests departure friday ...

On 20 May all 10 birds we follow by satellite telemetry were still in Denmark. But the weather forecast increasingly suggests that departure soon will take place. According to previous experiences most birds will depart with the first south-souteasterlies after 23 May. The transmitters upload data every five days, and the next uplink is on friday 25 May, where the wind is predicted to come from south. So perhaps there will be some exiting news for the blog on friday ...

18 May 2012

17 May: Will Ludvig fly to Greenland?

Data from the next four birds caught at 7 May on Valsted Enge have now been sent from the radiotransmitters via the satellites to Argos in France, and are available to us. They do not reveal a behavior that is notably different from the other birds presented below. Instead of showing four more maps that is virtually identical with geese mainly staging on the small islets in the inlet, I will recall some previous tracking results, but first present our next bird:  

Ludvig is named after Ludvig Munsterhjelm (1880-1955), finnish zoologist and hunter, who in one of his many travel and hunting depictions ”Sommar i Norra Ishavet: jakt-, djur- och reseskildningar från Ishavet och Spetsbergen” (1911) described how the brent geese, found in June 1910 at Prins Karls Forland (the northwesternmost island in the Svalbard archipelago), occasionally migrated towards northwest over the Arctic Ocean (thus en route towards Greenland). In 1997 during our first satellite tracking study we found that some geese migrated directly from Denmark to Greenland – and in 2001 we had the first example of a goose that migrated via Svalbard to Greenland, as Munsterhjelm had mentioned. Thus it is recommended that scientists occasionally read old books – and thanks to librarian and birdwatcher Mikael Lagerborg, who dug this old information out of the shelves in a library.  
Sources: The satellite tracking studies carried out in 1997 and 2001 have been dealt with in depth by:

  1. Clausen, P., Green, M. & Alerstam, T. (2003): Energy limitations for spring migration and breeding: the case of brent geese Branta bernicla tracked by satellite telemetry to Svalbard and Greenland. - Oikos 103(2): 426-445. 
  2. Clausen, P. & Bustnes, J.O. (1998): Flyways of North Atlantic Light-Bellied Brent Geese Branta bernicla hrota Reassessed by Satellite Telemetry. In: Mehlum, F., Black, J. & Madsen, J. (eds.): Research on Arctic Geese. Proceedings of the Svalbard Goose Symposium, Oslo, Norway, 23-26 September 1997. - Norsk Polarinstitutt Skrifter 200: 227-243.

16 May 2012

16 May: First week with Arner

The first weeks data from the satellite transmitter of the gander Arner show that this particular bird utilises a slightly larger part of Nibe Bredning than the others reported on so far, including some saltmarshes on the north coast of the inlet. 

Arner is named after Arner Ludvig Valdemar Manniche (1867-1957), teacher, ornithologist, zoologist and hunter, who participated in the so-called Danmark-expedition 1906-08. The primary purpose of the expedition was to map the still unknown coastline of Northeast Greenland between 77oN and 83oN, but also to initiate investigations of the meteorology, geology and nature of the region. Manniche contributed with his account of”The terrestrial mammals and birds of North-East Greenland” that was published in 1910 (Meddelelser om Grønland, Volume 45), where he describes the first observations light-bellied brent geese from Northeast Greenland, the Worlds northernmost breeding population of geese.   

15 May: First week with Robert

It's getting a bit boring - Robert has the "same behaviour as Otto, Peter and Abel" - but just wait untill the geese initiate their migration to the Arctic in the last days of May - then we will most likely see a suite of various migration strategies.
Robert is named after Robert Collett (1842-1913), norwegian professor in zoology at the Zoological Museum in Oslo. He might be considered as the 'father' of norwegian ornithology. Through his own field observations and by corresponding with and collecting data from many contributors from throughout Norway in the second half of the 19th century, he compiled the information that formed the basis for the first major description of the occurrence of birds in Norway, published as three volumes in the series "Norges Hvirveldyr", a masterpiece covering  the vertebrates of the country. Collett died before the bird volumes had been finalised, and they were finished by his student Ørjan Olsen and published in 1921. Volume 3 includes a thorough desciption of the contemporary knowledge on the occurrence of the light-bellied brent geese in Norway. 

15 May: First week with Abel

The first weeks data from Abel, as for Otto and Peter, highlights the importance of the saltmarshes on the islets in Nibe Bredning as vital feeding areas for the light-bellied brent geese in the area.
Abel is named after Abel Chapman, (1851-1929). British hunter and naturalist, who in 1889 published his Bird-life of the borders - records of wild sport and natural history on moorland and sea. This book gives the first solid account on the significance of Lindisfarne to larger flock of light-bellied brent geese, especially duirng cold continental winters. Chapman also illustrates a fantastic knowledge about the birds ecology in the book, well worth a read and available online as pdf file.

12 May: First week with Peter

This aerial photo gives the first weeks movements of the gander Peter we caught 3 May. Not particularly different from the movements of Otto in the area.
Otto is named after County Councillor Peter Holm (1733-1817), who in his Forsøg til en Beskrivelse over Lister og Mandals Amter i Norge already in 1794 gave a surprisingly precise desciption of the spring migration of the light-bellied brent geese along the coasts of southwestern Norway. Spring migration patterns are more or less similar tody, except that is is evident from Holms account that the brent geese were much more common in those days - hence underlining how rare they have become today!

15 May 2012

11 May: First week with Otto

This aerial photo shows the first weeks data on the movements of the gander Otto, caught at Valsted Enge 3 May. We only track ganders with satellite transmitters because North American studies back from the 1980s had found that females deployd with radio transmitters failed to breed. Perhaps bacause the antanna interferes with the birds mating behaviour.  
Otto is named after Otto Friedrich Müller (1730-1784), Danish zoologist who in his Zoologiae Danicae Prodromus in 1776 descibed the light-bellied brent goose as being different from the dark-bellied brent goose that Carl von Linné had descibed in 1758. 

7 May: Cannon-netting, isn’t that a major disturbance source?

Off course the birds are disturbed – but this photo illustrates it might be a minor problem. The geese in the background is a flock of light-bellied brent geese which landed on the salthmarsh 200 meters away from us and on the saltmarsh where we had just fired the net half an hour earlier 7 May 2012, and immediately after we had taken the captured geese out of the net. The geese are stored in canvas sacks until they are marked – whereafter they are stored on grass in the tunnel tents, visible in the background. If many geese are caught they would also be placed in the tents prior to handling and ringing. All caught geese are released together so paired geese and any goslings from the previous year have a chance to find each other immediately after release.
Also see our post from 3 May last year: Catching and handling - isn't that harmful?

7 May: How to lure the geese into the net?

The cannon-net we use is 20 meters x 20 meters – and seen from the air that is a tiny stamp on a large saltmarsh envelope. We use decoys to optimise a bit on our catch success. This year we bought new decoys (“specle-belly” = white-fronted geese) which were carefully repainted with spray-paints to look like light-bellied brent geese by our technician Michael Schmidt. We use modern Northamerican robot-painted decoys where one can see each individual feather. Further they have an unusual lifelike nonglossy appearance, which has no reflections in bright sunshine, as old-style decoys usually have. Our immediate impression from the first weeks use is that these decoys function as ‘magnets’ on overflying goose flocks. Combined we patience and our skilled cannon-net operator Jens Peder Hounisen we feel well prepared for catching.
Also see our blogs on last years captures on 27 April and 3 May 2011. 

12 May 2012

Why another Brenttags year?

Actually it was our intension to catch around Nibe Bredning back in 2010 – but we failed. One of the main purposes of the 2012 study is to explore if there is a partial segregation of the flyway-population in a western and an eastern segment. We have followed light-bellied brent geese with satellite transmitters from catchsites in the western Limfjord area in 1997, 2001 and 2011 – and are marveled over the fact that all geese we managed to track on the autumn migration, flew to Lindisfarne in England to winter (1 in 1997, 8 in 2001, 6 in 2011) –  although we know that approx. half of the population winters in Denmark in Nibe Bredning, Mariager Fjord, along the Kattegat coasts of northeastern Jutland and north Funen, and in the northern part of the Wadden Sea around the islands Fanø and Mandø.  It is also a surprisingly big share of the birds that has flown to Greenland (2 in 1997, 1 in 2001 and 4 in 2011 + two that made the journey halfway towards Greenland before reversing towards Svalbard). So we also intend to explore if eastern wintering birds tend to summer in more eastern parts of the Arctic. 

7 May 2012: Starting shot fired for second Brenttags year

Literally! With two cannon net captures 3 May and 7 May 2012 at Valsted Enge, Nibe Bredning, in the eastern Limfjord – we colour-ringed 44 new light-bellied brent geese and deployed 9 satellite transmitters – we hope to follow over the next year. 

Tony Fox and Marie Vissing are colour-ringing a brent goose.
Kevin Clausen seems to enjoy that we caught the geese
Jens Peder Hounisen measures the wing of a goose
.. and your blogger Preben Clausen seems to wonder about "what next ......

3 May 2012: Status after first Brenttags year

Your blogger have been absent the pasts months because I´ve been busy with other duties and fairly little has happened with the satellite transmittered geese. We have lost contact to most, either because they have fallen off or because we have programmed them to download more GPS positions than they actually can manage with the solar power provided by short winter days around the North Sea.

Status for our eight geese caught in spring 2011: 

Ebbe: we still follow. The only goose who has an active transmitter a year after capture. He flew to Svalbard, tried to breed on a nunatak in northeast Spitsbergen, failed and flew to Nordaustlandet to moult. Flew to Lindisfarne to winter. It is uncertain exactly when he returned to Denmark – because we had no signakls between 21 October 2011 through 1 March 2012, but 2 March he was back in the surroundings of Boddum in the western Limfjord area. These movements by 3 May 2012 involves an annual journey off approx. 10,000 km. The maps gives the whole route – where the yellow line shows the spring and moult migration routes, and the blue gives the autumn and winter flights.  

Steve: updates will come asap

Loff: updates will come asap

Fridtjof: updates will come asap

Caretaker: updates will come asap

Niels: updates will come asap

Magnar: updates will come asap

Jan Ove: updates will come asap