Wind turbines have been installed by almost all countries as an alternate source of energy. Though this source is highly beneficial, the threat it has posed to birds cannot be ignored.
A Cause of Concern
According to the American Bird Conservancy, 600,000 birds succumbed to death in 2012 due to collisions with wind turbines. A 2000 ABC report documented more than 550 Yellow-billed Cuckoo deaths at just 17 towers.
Wind energy is the cleanest form of energy, and thus, you will find large wind farms which fill up our other deficient energy reserves. The moving part of the turbine, i.e., the blades are a major threat, which collide against the birds, thus killing them.
During nighttime, the blades are hardly visible, and if the birds happen to hit the blades, then due to the high RPM of the blades, they hurt their wings, thus falling to their death. Although, many tall buildings and towers can also cause their death, the fact that the blades are a moving part increase the chances of causing death.
Factors Causing Bird Death
Wind turbines can be grouped into lattice and tubular. Lattice structures look similar to mobile towers. Due to their open structure, birds are attracted to them and fall prey to the blades. They build nests on the bars of the towers.
The wind turbine itself shakes when it rotates at the maximum speed, thus killing the eggs. Thus, in the recent years, lattice towers are replaced by tubular towers. As the name suggests, it is a tube-like structure sans the bars of the tower.
Such towers eliminate the risk of birds building their nests on the tower. Also, as compared to the lattice ones, the tubular towers have longer blades. These blades rotate at a slightly lower speed, so a few birds get saved.
Birds have a fixed path that they follow while migrating. Thus, if this path is spared, many birds can be saved. For the new wind farm location, areas which are migrating flyways are excluded. This means, less number of birds will be killed.
Also, the areas where bird population is high should not be chosen as locations for installing wind turbines. Of late, many companies are opting for offshore turbines. Due to the offshore location, fewer birds are killed due to collisions. Wind farms have a huge surface area with many turbines located in close vicinity.
So, if a bird ventures in this area, it is bound to be hit by a turbine. Thus, turbines should not be built in areas around bird sanctuaries or zoos either.
Difficult to Spot at Night
If birds die due to collisions during the day, at night the scenario can be worse. In many areas, there are more bat deaths than any birds. Bats venture out at night, and often collide with the blades in the dark. Many turbine manufacturers are looking into this matter and have made a few changes to the turbine, so that it becomes bird-friendly.
The barotrauma effect is the sudden alteration of the air pressure. The fast-swept vertical-axis rotor blades create vortices and turbulence, and due to this, there is a sudden change in the air pressure. In case of bats, this rapid pressure change causes tissue damage.
Another fatal injury that happens to these birds is internal hemorrhage. Bats have a highly susceptible respiratory anatomy than other birds. Thus, due to the pressure differences, the fatality rate among bats is the highest.
As there are a lot of endangered birds (including golden eagles and bald eagles) being killed due to the wind turbines, wind turbine manufacturing companies have taken a few measures to avoid these deaths.
✇ It would be better to switch to tubular towers and offshore wind farms. This will not only reduce the bird mortality rate, but also help the turbine manufacturers in increasing their output grid value.
✇ Proper wind farm siting is very necessary. Select a region which is clear of a bird’s migrating path.
✇ At the tip of the blades, radium stickers can be placed so as to highlight them during nighttime.
A group of PhD students at the Loughborough University carried out a study to determine the effect of the turbine color on the insects. For this, they placed different-colored cards on a 13m three-blade wind turbine. They found out that purple-colored paint attracts far lesser insects than the regular white and light gray.
The inference they drew from the study was that the use of purple color paint would attract less insects; hence, birds and bats will not come closer to the blades. As a result, the mortality rate will reduce.
Tree-roosting birds, Sage Grouse, Sharp-tailed Grouse, Lesser Prairie Chicken, Greater Prairie Chicken, bats, songbirds, golden eagles, etc., are the most vulnerable species. Most of the preying birds are attracted to vegetation around the turbines. By selecting the appropriate area for wind farms, the mortality rates can be reduced to a great extent.