[Tweeters] Song onslaught

Wayne Weber contopus at telus.net
Mon Feb 15 21:21:43 PST 2021

Louise and Tweeters,

It is interesting to look at the initiation of song in spring in different
groups of songbirds.

I would say that in the majority of migratory species, at least in North
America, song begins at a certain time of year, regardless of whether the
birds are on breeding territories or not. Singing behaviour is affected by
testosterone, as are many aspects of male breeding behaviour. Testosterone
production increases dramatically in late winter and early spring, as the
gonads themselves enlarge. This is a direct result of changes in photoperiod
(i.e., an increase in daylength). By February 1, many local species of
non-migratory birds are already beginning to sing. This includes such common
and familiar species as Black-capped Chickadees, Song Sparrows, and
Dark-eyed Juncos. Singing increases in frequency later in February and into
March, and is certainly more frequent after the birds have established
territories than before.

In the case of migratory species, many of them begin to sing on the
wintering grounds, before migration has started. Warblers in particular are
known for singing frequently on the wintering grounds and throughout spring
migration. This frequent song helps us to detect them and identify them in
the spring!

Other species, for whatever reason, never or rarely sing during migration,
and with rare exceptions, sing only on the breeding grounds. This includes
most or all of the Empidonax flycatchers, and the "brown thrushes" (Hermit,
Swainson's, Veery, Gray-cheeked, etc. ) Swainson's at least, and perhaps the
other thrushes, do not start singing until well after they have arrived on
the breeding grounds! Most Swainson's arrive in the Puget Sound area from
about May 5 to May 15, but are silent for the first few days, and don't
begin singing until about May 20 or later. In eastern Washington and
southeastern BC, where the arrival is somewhat later (May 20 to 25), they
don't start singing until about June 1-then all of them start singing within
a couple of days! This sudden outburst of song in an abundant species is
quite a dramatic event.

There are a few species, in contrast to the majority, which sing throughout
the winter, although usually rather infrequently. This includes some of the
sparrows like Song, White-crowned, and Golden-crowned Sparrows. The European
Starling sings throughout the winter, as often as it does in the breeding
season! I suspect that the hormonal control of song is different in these
species than in the majority of birds.

When keeping bird notes, I have always noted which species were singing by
including a little superscript "S" after my code for any species that was
singing on that date. If I analyzed all of these data, I could give you more
precise data on when various species sing. However, I haven't analyzed these
data, and it would take a lot of time to do so!

Wayne Weber

Delta, BC

contopus at telus.net

From: Tweeters [mailto:tweeters-bounces at mailman11.u.washington.edu] On
Behalf Of Louise Rutter
Sent: Monday, February 15, 2021 10:08 AM
To: tweeters at u.washington.edu
Subject: [Tweeters] Song onslaught

With the snow starting to melt, the varied thrushes in my yard all decided
to start singing this morning.

I always find it odd when birds sing where they're not going to be breeding.
I suppose they like to get some practice in before they get to the breeding

Louise Rutter


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