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Work continues to radio-tag the red kite in Castilla & León




In late 2015, the Fundación Patrimonio Natural and EDP Foundation launched a conservation programme for the red kite in Castilla & León. The initiative has received investment of €204,000 and will run until 2017. The programme consists of a number of activities aimed at acquiring knowledge about the bird's biology, its population, the main threats it faces and awareness-raising and protection campaigns.

Of all of Continental Europe’s birds of prey, the red kite’s distribution is among the most limited. It is found mainly in Europe to the west of the Urals, particularly in Germany, France and Spain, which are home to 90% of the global population. Spain has a sizeable breeding population and is the largest wintering quarter for populations in more northern regions.

Castilla & León is home to the largest breeding and wintering populations of red kite in the Iberian Peninsula. According to the latest nationwide census, Castilla & León is estimated to have a population of 1,298 pairs (56.14% of the population in Spain) and 25,300 wintering birds (50.30%).

A key feature of this programme is the scientific tagging of specimens with GPS-GSM tracking devices. This measure is aimed at gaining valuable knowledge about the behaviour of the red kite, such as the use they make of the territory, their dispersal movements and their philopatry (the tendency of an organism to stay in the same area where they were born or to habitually return to a particular area to breed or nest) via radio-telemetry, an important research tool that allows the birds to be precisely tracked and located.

These devices have a built-in GPS emitter which records the geographical location (maximum margin of error of 18 metres) on an hourly basis. The devices shut down at night as they are solar powered. The data is then sent in a message using the mobile phone network and downloaded into a server. Under optimum operating conditions (high level of sunlight, optimum GPS coverage), the birds can provide up to 5,000 location signals annually, which will allow researchers to gain vast knowledge of a particular specimen's movements over the course of a year.

In June 2015, four red kites were captured and tagged with trackers, one in the province of Ávila (a female of breeding age), two in the province of Valladolid (a female of breeding age and a chick) and one in Zamora (a female of breeding age).

In 2016, the tagging of red kites was extended to other provinces, such as Burgos, Palencia and León, whose populations are smaller and located in the most northerly section of their distribution area in Castilla & León. After searching for and locating breeding pairs in these provinces, in June 2016, a further breeding female specimen was captured and tagged in Burgos, along with a nestling in León.

The programme mainly aims to tag adult specimens of breeding age to ensure they form part of a particular breeding population. Adults were also chosen to ensure they remained on the database for the longest time possible, given that mortality rates for younger or immature specimens are higher.

A trapping system, which has proven to be harmless and efficient, was used to capture the specimens close to active nests with young chicks, consisting of a DHO-gaza net and a live eagle owl decoy. The systems consists of a net measuring approximately 3 × 3 metres which is placed vertically and suspended from two metal poles fixed to the ground. A live eagle owl is placed at the base of the trap, which should be located some 50 metres from the red kite nest. On detecting their prey, the red kites will attack and become trapped in the net, in which they will subsequently be bagged. Once installed, the net is watched from a distance of 300 metres to observe the behaviour of the birds.

In view of the difficulty in trapping adult specimens, the attempts to capture birds in León and Palencia have not met with success. It was therefore decided to modify the trapping method used in these areas. Feeding points have now been set up to attract the birds so they can be captured using remotely operated traps. The feeding points are being monitored using photo-traps. These new attempts to trap the birds will be carried out in the early days of summer with the aim of capturing and tagging two further specimens, one in the mountainous region of Palencia and another in the area of Bañeza (León).

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