[TN-Bird] Re: Active Wood Thrush nest!
- From: "Boves, Than James" <tboves@xxxxxxx>
- To: <Scott.Somershoe@xxxxxx>, TN-birds <tn-bird@xxxxxxxxxxxxx>
- Date: Fri, 20 Aug 2010 14:47:41 -0400
The timing of nesting and survival of nestlings and fledglings is very
interesting to me as well! In general the relationships are not well
understood and could use a lot more research. In studies of Cerulean Warblers
in the Cumberland Mountains we have not seen differences in nest survival (or #
of fledglings produced) as the season progresses (as Scott mentioned), but then
again we don't have a cowbird problem. We actually see a decrease in the # of
fledglings produced/successful nest as the season progresses (possibly b/c of
calcium limitation?).
This year we had several late nests where we observed another potential cost of
late nesting. At 4 late nests this season, the males associated with the nests
completely left the female to raise her young alone. We are not sure if the
males were still present in the general area but just not helping raise their
young, or if they had already left for migration. We had never seen this
happen in over 300 nests monitored previously. Additionally, at about 8 late
nests this season, the young were not exposed to any cerulean warbler song (as
far as we could tell). We hadn't seen this previously either, and it seemed
that the hot weather affected the amount male cerulean warblers sang (which
means that young cerulean warbler males would not learn their appropriate song
- Hooded warblers continued to sing at this time however). Of course this is a
small sample, but these could be additional reasons why early nesting may be
beneficial to individuals.
Than Boves
Knoxville, TN
-----Original Message-----
From: tn-bird-bounce@xxxxxxxxxxxxx on behalf of Scott Somershoe
Sent: Fri 8/20/2010 1:37 PM
To: TN-birds
Subject: [TN-Bird] Re: Active Wood Thrush nest!
Thanks for posting this Melinda. This is a good opportunity to share some
really interesting information on birds. Well, this stuff is really
fascinating to me anyway.
The first round of nesting by songbirds is generally bad. From the projects
I've been involved in and am familiar with in the southeast, the first nesting
attempts get nailed by cowbirds (where cowbirds are abundant) and tend to do
poorly with lots of predators feeding their own young and needing baby birds
for food, etc. A project in Mississippi found that nearly the entire first
nesting attempt of Acadian Flycatchers was wiped out by cowbirds every year.
Second broods were much more successful and had a much lower rate of cowbird
parasitism. Personally, I think predators shift their focus from nestlings to
fruits and other food resources later in summer when there is a lower chance of
finding a nest with chicks to eat. However, nesting early is the best time for
abundant food resources and for growing big, healthy chicks. So you need to
try to fledge young in that first breeding attempt. There's a whole other
story with timing of breeding and peak food resources, but
I'll save that for another day (also very interesting stuff).
In terms of a late second brood, there are big tradeoffs by doing this late in
the season. The one benefit is fledging more young and hopefully passing along
more of your genes to future generations; however the parent birds do not have
much time to raise the young to independence AND molt and prepare for
migration. As a result, these birds that try for a second brood have been
shown to migrate later, get poor territories on the winter grounds and
ultimately have a poor winter season. So in spring, these birds have a poorer
body condition (overall this means less healthy) and arrive on breeding grounds
later, are unable to get or hold a good territory, attract a high quality
female, and raise young.
In the end, you are very successful in raising young in one year, but you may
risk no reproduction the following year.
Males and females often cheat on the mate with whom they have a nest, which
helps pass along genes through others raising your young. The majority of
"socially monogamous" songbirds are not monogamous at all. The dawn chorus
isn't just birds calling and defending their territory and keeping their mate
closeby, but it is a call for, well you get the picture. This is the short
version of a much bigger story.
There is a new book by Bridget Stutchbury called the Private Lives of Birds: A
Scientist Reveals the Intricacies of Avian Social Life. This is a really
interesting book about birds and their social activities with nesting,
cheating, raising young, etc., but is a very readable book. She tells lots of
stories about research along these lines. It is definitely worth checking out.
This is not an ad for this book, but I am promoting an excellent resource that
our users may enjoy:) I don't even know Bridget, but I know some of her former
grad students.
Cheers,
Scott Somershoe
From Melinda:
Fernvale, TN
Williamson Co. 8-19-2010
I was surprised this afternoon when I saw a Wood Thrush with a bill full of
insects on our wooded driveway. I followed the bird for several minutes
before it flew up to a nest directly over the drive. There were at least 3
hungry mouths visible above the rim of the nest as they stretched for their
afternoon meal; the nestling couldn't be more that a few days old!
According to Chuck's Atlas of Breeding Birds of Tennessee, Wood Thrush often
have second broods, and late season nests are often more successful than
May-nests, but August 19th seems incredibly late!!
I'll keep an eye on it and see if it fledges.
Melinda Welton
Franklin, TN
State Ornithologist
Tennessee Wildlife Resources Agency
P.O. Box 40747
Nashville, TN 37204
615-781-6653 (o)
www.tnwatchablewildlife.org ( http://www.tnwatchablewildlife.org/ )
www.pbase.com/shoeman
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=================NOTES TO SUBSCRIBER=====================
The TN-Bird Net requires you to SIGN YOUR MESSAGE with
first and last name, CITY (TOWN) and state abbreviation.
You are also required to list the COUNTY in which the birds
you report were seen. The actual DATE OF OBSERVATION should
appear in the first paragraph.
_____________________________________________________________
To post to this mailing list, simply send email to:
tn-bird@xxxxxxxxxxxxxx
_____________________________________________________________
To unsubscribe, send email to:
tn-bird-request@xxxxxxxxxxxxx
with 'unsubscribe' in the Subject field.
______________________________________________________________
TN-Bird Net is owned by the Tennessee Ornithological Society
Neither the society(TOS) nor its moderator(s)
endorse the views or opinions expressed
by the members of this discussion group.
Moderator: Wallace Coffey, Bristol, TN
wallace@xxxxxxxxxxxxxxxxxxx
------------------------------
Assistant Moderator Andy Jones
Cleveland, OH
-------------------------------
Assistant Moderator Dave Worley
Rosedale, VA
--------------------------------
Assistant Moderator Chris O'Bryan
Clarksville, TN
__________________________________________________________
Visit the Tennessee Ornithological Society
web site at http://www.tnbirds.org
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ARCHIVES
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MAP RESOURCES
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