State of the world's birds

In Australia, Swift Parrot Lathamus discolor (Endangered) is threatened mainly by loss of its Blue Gum tree habitat (Garnett and Crowley 2000)—only 1,000 pairs remain. With such extensive habitat loss, they have come to depend increasingly on suburban areas as a source of flowering trees, and collisions are beginning to take their toll. During a three-month period in 1997, 40 birds (c.2% of the world population) were killed by collisions with windows and fences while foraging amongst trees in one suburban area (Swift Parrot Recovery Team 2001).

Structures in urban areas are by no means the only problem: the mushrooming of radio, television and mobile phone towers across the countryside of Eurasia and North America poses considerable danger to birds (Evans and Manville 2000, USFWS 2002). Conservative estimates suggest that at least four million birds are killed in the USA each year by collisions with towers (USFWS 2002). In Wisconsin, a single radio tower has caused at least 120,000 bird deaths since it was constructed (Evans and Manville 2000), and there are at least 100,000 large towers of this sort in the USA alone. Moreover, there is a growing likelihood that 1,000 so-called ‘megatowers’ for digital television transmission (including some taller than the Empire State Building) will be erected in the USA (Evans and Manville 2000). In Europe, central Asia and Africa, meanwhile, electrocution on power lines is documented as a cause of mass mortality of raptors, particularly of inexperienced, juvenile birds (Moseikin 2003). For example:

• Spanish Imperial Eagle Aquila adalberti (Vulnerable) loses 30% of juveniles to electrocution on power lines each year. However, simple, inexpensive alterations to the design of power line poles could cut annual mortality by more than 50% (Janss and Ferrer 2001)

• in Kazakhstan, a single 100-km section of 10 kV power line in the Atyrau region caused at least 311 raptor electrocutions in a single year (Moseikin 2003)

• north of the Caspian Sea in Kazakhstan, no fewer than 932 Steppe Eagle Aquila nipalensis were electrocuted along 1,500 km of power line in one survey season (Moseikin 2003).Given that Russia and Kazakhstan hold at least 50,000–70,000 km of this type of power line, this pressure alone may explain a large proportion of the raptor declines reported in this region.