Impacts of wind and solar power plants on birds and mammals - facts and comparisons

Annual mortality of birds and mammals caused by HPPs and PV plants in the Czech Republic

• Wind turbines (WTGs): in the Czech Republic, wind turbines cause only a fraction of the total human-caused bird mortalities. Estimates from abroad suggest that each turbine kills an order of magnitude of birds per year. In the UK, for example, the estimate is 10-100 thousand birds per year for the whole of the UK (vetrnyparkrasnice.cz) (where there are several thousand turbines). The Czech Republic has only a few hundred wind turbines, so in our country it will be at most hundreds to lower thousands of birds per year (in the order of magnitude). In addition to birds, bats (mammals) may also be affected by turbines - studies in Germany and elsewhere in Europe show significant numbers of bats killed, but in the Czech Republic the absolute numbers will again be in the order of tens to hundreds of individuals per year (proportionally to the smaller number of VTEs).
• Solar Photovoltaic Power Plants (PVP): direct bird collisions are very rare in ground-mounted solar parks - unlike wind farms, there is no moving part and the panels are easily visible. There are no significant reported cases of bird mortality due to collisions with solar panels in the Czech Republic. Thus, the main potential impact of PV is more likely to be indirect (land take and alteration of the native environment). Overall, solar power plants have almost no direct fatal impact on birds and mammals - recorded mortalities of individual birds are rare (practically zero compared to other impacts).

Comparison with other causes of animal mortality

For comparison, we present estimates of how many birds are killed annually by selected human activities in the Czech Republic. The table shows that wind and solar power plants are among the least common causes of mortality - many more birds are killed, for example, on roads, on power lines or by predation by feral cats:

Notes: for wind turbines, most often it is birds in flight colliding with the rotor; mammals (bats) are also affected, see above. For solar parks, bird collisions are at most sporadic (e.g. a water bird may mistake a large shiny area for the water surface). Road traffic kills both birds (collisions with vehicles) and mammals - from small (hedgehogs, hares) to large species. For example, around ten to fifteen thousand accidents involving large mammals (roe deer, deer, etc.) are reported annually in the Czech Republic, but the actual number of animals killed on roads (including small ones) will be many times higher (in the order of hundreds of thousands). Domestic cats mainly hunt small birds; there are about 1.4 million cats in the Czech Republic, and even if only one in ten of them hunts a single bird a year, this corresponds to 140,000 birds killed per year (ekolist.cz) - so in reality cats probably kill several hundred thousand birds a year. Cats also hunt small mammals (e.g. mice, voles) in large numbers. Overhead high-voltage power lines pose another significant threat - an estimated 115-340 thousand birds are killed annually by striking wires or electrocuting poles in the Czech Republic (birdlife.cz). Crashes into windows and glass buildings have a similarly large impact - ornithologists estimate that hundreds of thousands of birds (especially urban and migratory species) die here each year(birdlife.cz). These figures show that the contribution of wind and solar power plants to overall bird mortality is negligible compared to other factors.

For context: For example, in the USA (a country about 125 times larger than the Czech Republic), wind turbines killed an estimated 1.17 million birds in 2021, while car collisions killed ~60 million birds and collisions with buildings killed ~100 million birds(vetrnyparkrasnice.cz). In the United Kingdom, wind turbines kill 10-100 thousand birds per year, while domestic cats catch up to 55 million birds per year(vetrnyparkrasnice.cz). These international figures illustrate that wind turbines cause only a fraction (under 1%) of the number of bird deaths compared to car traffic or cats.

EIA measures to minimise impacts (CHP and PV)

Strict nature protection measures are applied in the planning and construction of wind and large solar power plants. The Environmental Impact Assessment (EIA) process includes an assessment of impacts on birds and mammals and sets out conditions to minimise these risks:

• Site selection: the wind farm proposal is assessed in advance in terms of the sensitivity of the area. Turbines are not placed near the nesting sites of rare or endangered species, important gathering places (roosting, wintering sites) or in the main migratory corridors of birds (birdlife.cz). Similarly, it is checked that no colonies of bats or other specially protected mammal species live nearby (eon.cz). If the proposed site is unsuitable from a zoological conservation perspective, the project may be rejected under the EIA before implementation.
• Detailed biological survey: the preparation of a wind farm includes a long-term ornithological survey, typically lasting at least one full year(birdlife.cz). This survey maps bird presence on the site during breeding, spring and autumn migration and wintering to determine how birds use the area at all times of the year. The data collected is used to assess the risk of the project before construction is permitted.
• Technical and organisational measures: Measures to reduce the risk of collisions shall be applied in the design of the project. For example, the power lines connecting the wind park are preferably routed through underground cables to avoid adding new wires that could cause injury to birds (eon.cz). Modern turbines are also designed to improve their visibility to birds; for example, consideration is being given to painting one of the rotor blades a contrasting colour, which studies have shown can reduce the number of collisions by up to 70%(vetrnyparkrasnice.cz). Wind turbines can also be fitted with artificial intelligence camera systems that detect approaching birds and temporarily stop the turbine - first tests show a reduction in bird mortality of more than 80% this way (vetrnyparkrasnice.cz). Emphasis is also placed on ensuring that the construction work and operation disturb the surrounding landscape as little as possible - after construction, the terrain is reclaimed to its original state and, for example, the fencing of the site is designed so as not to impede the migration of small animals (game hatches, etc.).
• Monitoring and traffic restrictions: After the wind farm is commissioned, a 12-month monitoring of bird (and possibly bat) collisions with the turbines is usually carried out (birdlife.cz). Should it become apparent that excessive mortalities are occurring, operators are obliged to take additional measures - limiting or stopping the operation of turbines during the most risky periods (birdlife.cz). In practice, this may mean, for example, shutting down selected turbines at night during the bat migration season or in poor visibility, when the risk of collision is highest. These conditions tend to be enshrined in decisions and permits for the operation of wind farms.
• Compensation measures: Compensation is required if certain negative impacts on birds cannot be avoided even if the above principles are followed. According to the AOPK/CSO guidelines, negative impactsmust be compensated by implementing specific compensatory measures(birdlife.cz). This may be, for example, the promotion of the population of the species concerned in another suitable location, the installation of replacement nesting sites, the modification of the surrounding landscape to improve conditions for the fauna, etc. The aim is that the net impact of the project on the population of protected species should be zero or minimal.
• The procedure for photovoltaic plants: for large PV parks the procedure is similar - the EIA assesses whether there is any interference with valuable habitats or disturbance to fauna. Solar parks are located outside the most naturally valuable sites, often on areas already anthropogenically affected (e.g. brownfields, field margins, etc.). When they are permitted, conditions are imposed to limit impacts - e.g. maintaining green belts around the site as shelter for animals, gentle mowing of the grass under the panels (to avoid the massacre of small animals by machinery), and appropriate fencing to prevent large animals from entering (to avoid entrapment or injury), but allowing small animals to pass. Thanks to these measures and careful site selection, the direct impacts of PV plants on birds and mammals are minimised to such an extent that the construction of solar power plants is generally considered acceptable from the point of view of fauna.

Summary: The EIA and subsequent permitting process emphasises the prevention and mitigation of impacts on birds and mammals. Wind farms are planned and operated with the surrounding ecosystem in mind - from careful site selection, to technical measures (underground cables, turbine modifications) and monitoring, to possible restrictions on operation or compensation. Solar power plants by their very nature have little direct impact; permitting is mainly concerned with ensuring that they do not destroy valuable habitats and allow the movement of animals through the landscape. Thanks to these measures, it can be said that the impacts of VTE and PV on birds and mammals in the country are effectively minimised and many times smaller compared to other common risks (traffic, HV lines, cats, etc.).

Sources.eon.cz.