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The article was initially published on Suomen Hyötytuuli Oy’s web pages. Suomen Hyötytuuli and Arenso work together at the forefront of arctic wind energy production.

Petteri Mäkelä, Environmental Engineer at Suomen Hyötytuuli

Suomen Hyötytuuli Oy has been leading the way in understanding and mitigating the environmental impact of wind power, consistently going above and beyond what is required by law and developing new practices and technologies at the forefront of wind energy production. This translates into a strong vision combined with hands-on experience as well as a proactive approach to developing new environmentally friendly innovations.

A wide collaboration network

Examples of Suomen Hyötytuuli’s pioneering work on this topic include recycling the dismantled turbine blades at the Reposaari wind farm, the use and development of avian radar technology at the Tahkoluoto offshore wind farm, long-term noise measurements in all onshore wind projects as well as underwater noise measurements at Tahkoluoto, and continuous monitoring of breeding birds in the Pori archipelago.

In order to improve the integration of nature and environmental considerations in the wind energy sector, Suomen Hyötytuuli engages in active dialogue with its network of stakeholders and authorities. During 2024, we have participated in projects such as the WindLife project of the Natural Resources Institute Finland, a project on bird and insect migration using weather radar data of the Finnish Meteorological Institute, a project on the publication of wildlife data from project surveys, satellite monitoring projects for endangered birds and a project on the nature-positivity of renewable energy.

A unique opportunity to observe the behaviour of a golden eagle at a wind farm site

A new, active nest of a golden eagle was recently found just two kilometres from the nearest wind turbine, in the vicinity of one of Suomen Hyötytuuli’s wind farms. Metsähallitus, the conservation officer of the species suggested fitting a satellite transmitter to the male bird of the nesting pair. Since the nest is most likely the closest active nest to a wind turbine in Finland, this would be a unique opportunity to collect data on the behaviour of a golden eagle near wind turbines.

We were lucky enough to catch the right bird and harness it with a transmitter at the first attempt. We had anticipated this to be a challenge, as there were at least five different eagles visiting the same carcass, even on that very morning. We were aware that it could take up to a couple of years to capture the right golden eagle.

Satellite monitoring becoming more rare

Golden eagles are usually lured with a carcass and can only be trapped outside the breeding season in late autumn or in winter, so as not to disturb nesting. A game camera is placed near the carcass to see when the eagle finds the carcass. Once the eagle has accepted the carcass, it is allowed to use it in peace for at least a week. Once the eagle’s visits to the site are regular and the weather conditions are suitable, a trap is set on the carcass. The situation is monitored from the hide, and when the eagle is suitably positioned, the trap is triggered. The eagle is immediately released from the trap, its age and sex determined, its condition checked and biometric data collected. A satellite transmitter backpack is attached to the bird’s back by a harness and the bird is released. The backpack is designed so that the harness will come off by itself in a few years. If the transmitter is still operational after this time, attempts will be made to retrieve it to find out whether the transmitter has become detached or whether the eagle has died.

There have been several studies on the impact of transmitters on the condition and life cycle of birds. The effects are demonstrably scarse, albeit varying slightly between different species of birds. In some species, transmitters have been found to reduce chick production or the number of eggs laid. In addition, the capture itself is always a minor risk and cause of stress for the bird. For this reason, it is nowadays rare for golden eagles to be tagged with satellite transmitters in wind energy projects. However, in special cases such as the one described here, the authorities may request that monitoring be carried out.

The results of the monitoring

The satellite transmitter has produced ample data suggesting that the golden eagle was successful in nesting in 2024 (the result of the Metsähallitus mandated nest survey is not yet known at the time of writing). Based on the data collected, we can already see that the eagle tends to avoid the area of the nearby wind farm. When flying over the wind farm, the eagle reaches altitudes of 300–400 metres, well above the sweep height of the wind turbines.

During the winter, the eagle moved around very little. It spent most days flying between the nest and the carcass, often only a few hundred metres a day. On clear days in early spring, the eagle would venture a few kilometres distance to survey the area. In summer, during the presumed feeding period, the eagle’s foraging expeditions were within 20 kilometres of the nest. Daily foraging flights ranged from a few kilometres to up to 100 kilometres.

The data collected by the satellite will be analysed in more detail during the winter 2024–2025. Particular attention will be paid to its movements in relation to the wind turbines in the area, taking into account weather conditions and possible neighbouring territories.

Pictures: During the winter period, the golden eagle stayed mainly near the carcass. During the busiest feeding period, foraging flights were often within 20 kilometres of the nest.

Pictures of the golden eagle: Olli-Pekka Karlin