Satellite Tracking

This part of the website presents information about a project we started on the cultural behaviour of eagles, using the latest generation of GPS satellite transmitters, which then expanded into a wider study of golden eagles.  We began our satellite-tracking studies in 2007 and to date have tagged 18 eaglets: 13 males and 5 females.

In July 2007, we fitted our first 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 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 would it go?  How far would it travel? Would it return home? If it gets through its first winter where would it summer, and if bird and radio survive for three years where would 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.  This was the first time a GPS radio was used to track an eagle in Scotland and the results of this and our later studies have been fantastic.

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

The transmitters  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.

All satellite-tracked birds are fitted with a BTO metal ring

The transmitter sits on the bird’s back, secured by a harness










The initial project was a partnership between the Cairngorms National Park Authority, Scottish Natural Heritage, Glenfeshie Estate and the Highland Foundation for Wildlife. In 2007 we tagged our first eaglet (Alma).  In 2008 we tagged her brother (Angus) and another eaglet from the Eastern Cairngorms (Tom).  We didn’t tag any in 2009, but in 2010 tagged a further 9 eaglets, and in 2011 another 7.  Many of these eaglets were tagged as part of the RaptorTrack programme, a partnership between the Highland Foundation for Wildlife, the Cairngorms National Park Authority, Scottish Natural Heritage, RSPB and private estates within the park. Funding for the radios came from Scottish Natural Heritage, Cairngorms National Park Authority, Cairngorms Biodiversity Programme, Partnership against Wildlife Crime and the Highland Foundation for Wildlife.






The radios are expensive, costing £3000 each, and for the data for each bird we pay a monthly charge to CLS Argos, approximately £750 per year. We hope to satellite tag another three golden eagles across the Highlands this year and donations would be very welcome for this and future projects. To donate, please click here:


Details of the initial project

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

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%).

These results must be considered within a culture of long term human persecution of eagles in Scotland and the UK.  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  from ospreys in Scotland already 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 no persecution, good food supplies and relatively high human presence.

This hypothesis has been the basis of much of our satellite tracking of young eagles; our aim is to compare the behaviour and movements of young eaglets from areas where they are used to people compared to eaglets from very remote areas.