Many bird species do this layering or alternating of song as well,
especially if two species have songs with similar frequencies or
patterns that could be confused or that would obscure each other if sang
at the same time. When I first heard it 12 years ago I thought the 2
species were dueting or countersinging but I have now realized that
something else is going on here.
Generally one species dominates the other. An article was published
documenting that Bewick's Wren dominates Wrentit in CA. I have a long
recording wherein a Song Sparrow seems to dominate the Fox Sparrow. The
Fox Sparrow consistently waits until the Song sparrow has finished for a
few seconds before inserting his song in the empty slot. This spring I
noticed the same thing with a Western Meadowlark dominating a Vesper
Sparrow. It seems the louder and more vigorous songster tends to
dominate the sound space and the secondary species fits in his sounds
when the coast is clear.
Kevin Colver
-----Original Message-----
From: Walter Knapp
Sent: Friday, May 23, 2003 3:34 PM
To:
Subject: Re: [Nature Recordists] naturerecordists campout
Rich Peet wrote:
> It was also interesting to see how perfectly the vocal range of the
> Virginia Rail slotted between the calls of the American Toads and
> Spring Peepers who were much louder. The rail was easily heard by
> using this technique and I assume that the bird has always commanded
> this frequency slot and did not change its call to this wetland.
Where we have so many species of frogs down here, it's very noticeable
how different frequencies or timing are used to avoid conflicts. It's
interesting in that it shows that many of the species evolved together.
Even within single species there may be a deliberate effort to slot
between others, or in some cases seemingly a deliberate effort to walk
over other's calls. The long calls in toads, for instance are attempts
to outshout competitors. It's like whoever can call longest wins. Though
I've not seen research to back that up.
Certainly one can watch a bird voiced treefrog call and see how he's
focusing on one particular other bird voiced call. They seem to take
turns listening in between.
Walt
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