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Satellite Tracking of Golden Eagles

This part of the website presents information about a project we are carrying out on the cultural behaviour of eagles, using the latest generation of GPS satellite transmitters.

In July 2007, we fitted a GPS radio transmitter to a chick at Glenfeshie Estate in the Cairngorms National Park as part of a conservation project to try to examine the cultural behaviour of eagles (see project proposal below) and to research the home-range use of the Cairngorms and surrounding mountains by a young eagle bred in the area. Using high quality GPS data collected at hourly intervals we hoped to study how the young bird uses its parents' home-range and then to follow its movements into other eagles' home-ranges. Where will it go? How far will it travel? Will it return home? If it gets through its first winter where will it summer, and if bird and radio survive for three years where will it start to settle down at a breeding site. We had hoped to place a second transmitter on a chick from another nest, but the chosen nest sites failed to have young because of the bad weather in 2007. We intend to track more in 2008. This the first time a GPS radio has been used to track an eagle in Scotland and the first year's results have been fantastic.

The up-to-date daily log of detailed information, landscape maps and photographs has proved to be of real interest and excitement to people who are interested in eagles or know the Cairngorms.

The transmitters being used are 70 gram Argos GPS solar transmitter manufactured by Microwave Telemetry in the United States. They have a three season variable program which can collect hourly data from dawn to dusk. The data is a GPS map co-ordinate accurate to 20 metres, flight speed and heading when the bird is flying, and the bird's altitude above sea level. This data is transmitted to satellites of the Argos CLS system and we obtain the results from them through our computer. The co-ordinates are then mapped, kind courtesy of the GoogleEarth Plus system which has revolutionised our ability to present geographic mapping of bird movements.

The project is a partnership between the Cairngorms National Park Authority, Scottish Natural Heritage, Glenfeshie Estate and the Highland Foundation for Wildlife. Funding for the radios has come, so far, from the Cairngorms National Park Authority (two radios), Scottish Natural Heritage (one radio), Glenfeshie Estate (one radio) and the Highland Foundation for Wildlife. We have also had offers of help with the purchase of additional radios and have in stock a radio purchased by the the Alladale Wilderness Trust for use on their estate in Sutherland.

Alma was satellite tagged in 2007 ( so there are 2007, 2008 and 2009 pages); Angus is Alma's brother from 2008 while Tom is a young golden eagle tagged in 2008 in the Eastern Cairngorms.

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Management of Golden Eagles in the Cairngorms National Park; through experimental testing of cultural behaviour of the young.

Introduction. Conserving and enhancing the special natural qualities and furthering the understanding and enjoyment of these special qualities are objectives of the draft park plan. An important issue in the National Park is understanding the effect of visitors, and probably increasing numbers of visitors, on sensitive rare breeding birds. Golden eagles are particularly sensitive to human disturbance and there is a legal requirement to protect this species from deliberate or reckless disturbance. It is important that the National Park maintains a viable population of breeding eagles secure from reckless and deliberate illegal persecution and encourages the re-occupation of vacant home-ranges, and gives visitors a good opportunity to see this iconic species.

Golden eagles in Scotland have already been affected by human disturbance and it is known that eagles have abandoned nesting sites because they are too close to walking routes which have become progressively popular. In the northern Cairngorms, a pair which used to breed in Glenmore moved further away, and then about 30 years ago deserted that alternative nest as visitors increased, and moved even further away from people. Using data from the 1982 Golden Eagle survey in Scotland, Watson and Dennis analysed golden eagle fledging success in relation to the accessibility of nest sites by people. Nests that were most inaccessible fledged young on 50% of occasions, and were significantly more likely to be successful than pairs in the most accessible sites (35%).

Of course, these results must be considered within a culture of long term human persecution of eagles in Scotland and the UK. Eagles must know that if you nest in accessible eyries there is more chance of being persecuted. Golden eagle behaviour has evolved , through trial and error, to avoid humans at as great distance as possible. This behaviour is reinforced in the young by them being reared without sighting humans. Although illegal persecution still takes place, most large raptors are now carefully protected and individuals can live long numbers of years at the same nest, instead of being killed prematurely. These long lived adults will in theory continue to pass on long held behavioural traits to their young. This is a relatively little understood feature of bird conservation. But a parallel is the ‘tameness’ of breeding ospreys and bald eagles in North America, where there was no long history of persecution, compared to the ‘shyness’ of ospreys and white tailed eagles in Scotland and Europe.

Evidence already from ospreys in Scotland shows, that without persecution, individuals become more used to people passing by regularly at a safe distance, and this distance is becoming less. This leads to the view that young birds, which are reared in nests where they can view people without threat, are more able to breed at new nest sites within human-used landscapes. In my view a cultural change is taking place and this could be managed to encourage raptors to breed in areas of nil persecution, good food supplies and relatively high human presence.

Experimental management. Techniques for studying birds such as eagles have dramatically improved in recent years, and the latest satellite transmitters are able to record daily data on an individual’s location, direction of flight and even the speed of its travel. This information can be received from the tracking station. We recommend an experiment where two young golden eagles fledging in the northern part of the National Park are fitted with specialist transmitters. One young will be from a nest which has the absolute minimum of human presence; a hidden eyrie where the young, while they are in their nest, cannot see people. The second radio will be placed on a chick in a nest from which the young can see people regularly.

The young will then be tracked to see if there is any difference in the way that they use land within or close to the National Park; the radios can transmit for 3 years. Some people will be worried that the bird that has been conditioned to humans may put itself at more danger from human persecution. To counteract this our intention is that once the young birds are flying, and without disclosing the location of the actual nest, a continuous up-dated record of the two birds movements will be presented through public websites, and will be publicised. The website of the Highland Foundation for Wildlife already carries migration studies of raptors from the Scottish Highlands, but it would be extremely good to have the information on the Cairngorms National Park Authority website and to encourage local schools to adopt the individuals. This publicity would be undoubtedly beneficial to golden eagles within the National Park and elsewhere.