Geography Reference
In-Depth Information
urban gradient. Three brisk notes, a trill, and a punctual i nish raise new
questions. Each male song sparrow builds a repertoire from the utterings of
his father and neighbors but develops his own characteristic voice. This one
sounds familiar to me, and it is ringing out from a brushy spot where I have
monitored other song sparrows. I stalk him to determine whether it is a bird I
have banded and to see how he is adjusting to suburban life. It turns out that
he is a bird I know well, with the blue and green plastic bands I placed on him
four years ago. Each of the past three years he sang all spring and summer
within this territory and failed to entice a female partner. His reproductive
output, as best as I could discern, was zip. Yet maybe because he had no other
option, he clung to his territory as the forest around him was converted to a
new subdivision. He remained after a northern l icker and Pacii c wren were
forced out. People cut down the l icker's nest tree and cleaned up the protec-
tive brush that held the wren. Feeders may have helped sustain the sparrow,
but he paid a price. I smile this year as I i nd he has a mate, and together they
succeed in raising at least two l edglings.
Is it enough for suburban birds to occasionally win the reproductive lot-
tery? To i nd out how successful they must be to leave a sustainable legacy
requires us to measure their lifetime reproductive output. It's time to hit the
bushes and look for nests.
