Do wind turbines kill many birds each year?
An upper estimate might be of the order of half a million birds per year in the USA.
However it seems that hundreds of millions of birds are killed by
collisions with other man-made structures. So wind turbines account for a small percentage of bird deaths attributable to human activity.
Nevertheless this can be a significant threat to the survival of some
important bird species.
at night, or in fog
Wind turbines are hazard to birds (and other avians) in daylight. Bird evolution has evidently not incuded
the necessary millions of years of exposure to non-catastrophic
levels of threat from this type of fast-moving hazard. They are poorly equipped cognitively to recognise danger in any of these and
other man-made hazards.
Per small installation
Some individual wind-turbine operators think even ten deaths per year per turbine is too many:
Primary school forced to turn off wind turbine after bird deaths
"We were told by the manufacturer to expect maybe one fatality a year but it killed 14 in six months so we took advice and made the decision to turn it off.
"If it had happened at night time you could understand that the birds couldn't see the blades, which rotate at 135mph but it was happening at all different times of the day."
Large numbers of birds die every year from other causes, turbine-related deaths are currently alleged to be only a very small proportion of these.
According to a 2002 study A Summary and Comparison of Bird Mortality from Anthropogenic Causes with an Emphasis on Collisions "funded by DOE, with direction and support from the Wildlife Working Group of the National Wind Coordinating Committee"
- Collisions with buildings kill 550 million birds each year,
- Cats kill 100 million birds each year,
- Collisions with wind turbines kill 28,500 birds each year.
So the answer to the question depends on how many is "many".
More recent studies find higher numbers of avian deaths per year.
A 2016 study A preliminary assessment of avian mortality at utility-scale solar energy facilities in the United States
included this table:
Estimated annual avian mortality from various sources
in the Southern California Region and United States.
Mortality source Southern California United States
Utility-scale solar energy
(USSE) developments 16,200–59,400 37,800–138,600 a
Wind energy developments 29,537–48,862 140,000–573,000 b
Fossil fuel power plants 3,561,600 14.5 million c
Communication towers 70,552 4.5–6.8 million d
Roadway vehicles >453,000e 89–340 million f
Buildings and windows >7,800,000g 365–988 million h
a Based on approximately 14 GW total name plate capacity of
utility-scale solar facilities in operations or under construction
across the United States .
b Sources: Loss et al. , Smallwood , Erickson et al. .
c Source: Sovacool .
d Sources: Erickson et al. (2005), Longcore et al. .
e Represents a minimum estimate using only estimated mortality for
paved roadways in the southern California study region.
f Source: Loss et al. .
g Represents a minimum estimate using only estimated mortality
for residential structures in the southern California study region.
h Source: Loss et al. .
I have not checked the dates of the references. It may be that this 2016 study is based on data from older studies.
Effects on endangered species
Deaths for some bird species may be more significant than others: Scientists study wind-farm risks to birds
One survey at Big Horn Wind Farm in Klickitat County estimated that more than 30 raptors were killed during an initial year of operations — more than seven times the number forecast in a pre-construction study. The dead raptors included kestrels, red-tailed hawks, short-eared owls and a ferruginous hawk, which Washington state lists as a threatened species.