Geography Reference
In-Depth Information
There are l urries of success here—exceptional reproduction by sparrows
and juncos, for instance. But mortality or movement is greater than repro-
duction by most species, so their populations decline during the construc-
tion of subirdia.
Established developments provide the resources that juncos and song
sparrows require to be sustainable. Bewick's wrens also perform best here,
and our highest estimates of their vital rates suggest they will prosper. Pacii c
wrens l edge many young in developments, but extremely low survivorship
quickly eliminates them from this environment.
Reserves of forest in the sea of suburban development likely hold the key
to sustaining many of the birds that live in subirdia. Robins, towhees, Pacii c
wrens, and Swainson's thrushes are sustainable when breeding there. The
young produced in these bits of nature wander widely, feeding on the bounty
of suburban neighborhoods. This ability to nest away from residents but to
visit their gardens and bird feeders increases the survival of adults and espe-
cially their teen-aged of spring. For avoiders such as Swainson's thrushes and
Pacii c wrens, forest reserves are critical. But they are also important to the
persistence of some adapters, such as robins and towhees that harvest the best
of the natural and built worlds, which together form subirdia.
Amanda Rodewald and her students at The Ohio State University
reached a similar conclusion. They banded nearly two hundred Acadian l y-
catchers and scrutinized their survival and annual productivity. These small,
slightly crested migrants are classic urban avoiders that, like our Swainson's
thrushes and Pacii c wrens, also frequent urban settings. Sustainable popula-
tions in nearby rural areas guarantee their presence in subirdia. It is in these
wilder places that l ycatchers settle i rst, breed longest, and produce the most
l edglings. The l ycatchers in subirdia are mostly young and small—backups
to the big leaguers that live in forest reserves. Suburban lands alone are ade-
quate for many adapters and probably most exploiters. Rodewald found this
 
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