However, the larger populations of birds that thrive in the city's oasis are not the same as those in the desert, but are less diverse in species, with "generalist" native and non-native species (such as mourning doves, grackles and English sparrows) being favored over many of the more highly specialized birds found in the natural desert.
"What we've found is that some species are missing, while others, in fact, are enriched," said Redman. "What you have, in fact, is the creation of an urban ecosystem which is quite distinct but not necessarily impoverished."
One study in the project, for example, found that Abert's Towhee, a mid-sized bird that is relatively uncommon in the desert, thrives in Phoenix because the city is crisscrossed with canals, which mimic the riverbanks the species normally frequents, and giving the birds ready access to lawns and golf courses which are ideal for its ground-feeding habits. There are also populations of birds not normally found in the low desert at all, including Ravens and Peach-Faced Lovebirds.
While any birder can see that the diversity and abundances of birds are different, to the researchers, a more important detail is something that is practically invisible -- a major shift in the environment's food web what ecologists call the "trophic structure" making the city's biology systematically different from the desert's.
"We've been monitoring and assessing the nature of trophic structure of Phoenix's wildlife the big animals, the smaller animals that they eat and the plants that they eat," Redman said. "You're spreading water all over the environment, and this is one of the prime reasons for the
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Contact: James Hathaway
hathaway@asu.edu
480-965-6375
Arizona State University
3-Jan-2005