Geography Reference
In-Depth Information
chickadees expertly work bird feeders and readily take to nest boxes. They are
also models of contemporary, adaptive, cultural evolution that i ts their songs
into the new urban environment. Loud, low-frequency noise in major Euro-
pean cities favors short, fast, and high-frequency song. In the noisier neighbor-
hoods of Leiden, The Netherlands, tits sing at higher frequencies than they do
in quiet ones. Song sparrows in Portland, Oregon, make similar adjustments,
raising the minimum frequency of song and directing more energy to the high-
frequency components of song in the noisy parts of the city. Even urban jun-
cos trill at higher frequencies than do mountain juncos.
Taste in music is one of the fastest evolving aspects of human life. When I
i rst played “In-A-Gadda-Da-Vida” by Iron Butterl y, my parents were posi-
tive the record player was broken. And whenever they played Andy Williams
singing “Moon River,” I
wished
the record player were broken. Similar changes
in song perception by birds are occurring within our cities. In the Presidio of
San Francisco, California, cultural evolution has changed the voices of white-
crowned sparrows. From 1969 to 2005, as trai c noise increased, so too did
the pitch of sparrow songs. This adaptive response to the masking ef ects of
city noise occurred over time, just as other studies had demonstrated changes in
song frequency between urban and rural or noisy and quiet locations. Rather
than inheriting the song from their parents' genes, young males in increas-
ingly noisy environments changed their tunes because they could better hear
and copy the higher pitched songs of their fathers and neighbors. Low-pitched
songs faded into the background and did not stimulate learning. They were
also less stimulating to established, territorial males. When scientists dug into
their archive of bird sounds and played sparrow songs from the Presidio that
were recorded in 1969 to resident sparrows in 2005, the response was tepid.
But when sparrows heard the 2005 rendition of territorial song, the modern
males lit out in search of the intruder. White-crowned sparrows have about
as much appreciation for their ancestors' tunes as my kids have for my parents'
music.
