Yes - they can be if you don’t take care with how you site them, particularly for raptors. There is one particular wind farm called Altamont Pass that is notorious for this. But what he is leaving out there is that this is a known issue and that any new wind farm is carefully assessed for damage to birds and there is a lot of work done to make sure to reduce the effects.

Birds also die by flying into buildings, and windows, and in many other ways. So generally the aim is to reduce the mortality. They also die from fossil fuel plants and from power lines, millions a year.And most of all are killed by domestic cats, into the billions a year. For links to research on various ways that birds are killed by our technology, see Pecking order energy’s toll on birds

Cats kill many more birds than wind turbines, but they don’t normally kill eagles. And you want to do what you can to avoid them killing birds anyway.

THE PROBLEM

So first, why does it happen: the thing is that the blades move apparently slowly but at great speed, and they come down at them from above slicing down on them, and they are not adapted to look out for threats like that from above, 80 meters per second (180 mph, 288 kilometers per hour)

SOLUTIONS

However it has a lot to do with the siting of the wind turbine, and its design. By moving it a short distance you can get it out of natural flight paths for the eagles.

The worst wind farm is one at Altamont Pass in the US which is right in the middle of a migratory route, it also uses an older style of wind turbine that is more hazardous to birds.

The main thing that is being done at present is just to check the site carefully and make sure that wind turbines are not built in places where birds are likely to fly into them. They are still hazardous but if they are built in places where birds don’t normally fly then they aren’t going to kill them, or not many.

As an example, the UK bird protection society RSPB has built a bird-friendly wind turbine at its headquarters.

Other approaches include using radar to switch off wind turbines if there is a raptor anywhere near but this has mixed success.

The California Condor is protected in another way - most of them are equipped with GPS sensors - so they can program the wind turbines to switch off within two minutes if there is a California Condor within two miles of the turbine. This 2013 wind turbine scheme combines that with radar to protect raptors. Terra-Gen gets OK on wind farm in wake of condor decision

There are designs of wind turbines that wouldn’t cause any damage to birds at all but these are not in wide use at present.

Truly Eco- and Bird-Friendly Wind Turbine

Also these shrouded wind turbines - they actually spin a lot faster than a conventional wind turbine, but they are more visible to birds

Shrouded Turbine Design is a Step Forward for Wind Energy

VERTICAL AXIS WIND TURBINES

Vertical axis wind turbines are mounted closer to the ground and are less hazardous to birds. However because they are normally mounted close to the ground, and not so easy to mount at height, they may produce less power. Some advantages and disadvantages here: Vertical Axis Wind Turbines

Here are some designs: Savonius vertical axis wind turbine

Darrieus wind turbine

Éole à Cap-Chat - The world's tallest vertical-axis wind turbine, in Cap-Chat, Quebec . It is a Darrieus wind turbine

Overview of several designs:

UNCONVENTIONAL WIND POWER

There are many other ways to harvest wind for power generation. For instance High-altitude wind power using kites or aerostats. High altitude winds are much more stable, so have a lot of potential if they can be accessed.

Airborne wind turbines (similar at lower altitudes) and other forms of Unconventional wind turbines One idea that’s being explored is Crosswind kite power where the kite flies at an angle to the wind, rather like a boat tacking, or someone kite surfing .This lets the kite travel much faster than the wind velocity and lets it use much more wind power than would normally be possible for its cross sectional area, rather like the rotating sails of a conventional wind turbine.

See also Public Kite Power Research

See also Do wind turbines kill birds?