There is a double standard in how the energy industry is punished for killing birds, Robert Bryce, a green energy critic, wrote in a Wall Street Journal commentary. He noted how oil companies have been fined hundreds of thousands of dollars for birds killed by oil spills or faulty power lines. Yet wind farms kill thousands more birds each year, many of which are endangered, and wind companies are never fined. For example, a 2008 study estimated that the wind farm at Altamont Pass, Calif., kills about 10,000 birds each year — nearly all protected by the Migratory Bird Treaty Act, Bryce wrote. However, the Wind Energy Association argues that bird kills by wind turbines are a "very small fraction of those caused by other commonly accepted human activities and structures — house cats kill an estimated 1 billion birds annually."