You would think that birds are happy to live near humans as they can get easy access to food. Unfortunately, this is not the case, particularly for large birds. Sound drives them away. Traffic noise and heavy machinery are the culprits. Larger birds use low-pitched songs to communicate. This is drowned out by engines and clunking machines. Birds and nests were counted near natural gas wells. Compressors on the wells run day and night. The noise is like a reving motorcycle. Thirty species of bird were surveyed. The number of large birds was very low. Small birds have high-pitched songs that can still be heard over rumbling machinery, so their lives are unaffected. http://www.adventure--australia.blogspot.com/ http://www.tysaustralia.blogspot.com/ http://www.feeds.feedburner.com/AdventureAustralia http://www.technorati.com/blogs/ http://adventure--australia.blogspot.com . . . . . . . . . . . . . . . . . . Biology