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Re: Wood Thrush Declines
- To: Kendrick Weeks <musoikos@yahoo.com>,Carolina Birds <carolinabirds@duke.edu>
- Subject: Re: Wood Thrush Declines
- From: Jules <jlfray@ix.netcom.com>
- Date: Sat, 11 Oct 2003 22:45:40 -0400
- Delivered-to: pardo@metalab.unc.edu
- References: <20031012002506.95637.qmail@web13401.mail.yahoo.com>
- Sender: carolinabirds-owner@acpub.duke.edu
Hi Kendrick
On Wood Thrush declines I have read that they also seem to suffer
mortality from collisions with tall buildings and radio/tv towers. With
the proliferation of wireless towers and such in the last decade do you
see this as a significant contributer to the bird's decline.
Jules Fraytet
Charlotte, NC
Kendrick Weeks wrote:
>
> It is very hard to understand population declines of
> Neotropical migrants like Wood Thrush because of their
> complex life cycle. Increases in mortality can occur
> during breeding (nests or adults), both migration
> events, or wintering. Short term trends can indicate
> punctuated mortality (such as several cold fronts
> during the peak of trans-gulf migration) while long
> term trends can indicate gradual mortality (such as
> increased domestic animal predation and cowbird nest
> parasitism). Drought and extremely wet weather has
> been shown to decrease (or increase, depending on the
> species) survivorship of nests. Determining causes
> of population declines requires long term monitoring
> not only of numbers, but also a miriad of factors that
> can affect mortality. Then, complex regression
> techniques must be used to tease out these causes.
> Using only counts of adults makes it difficult to
> determine causation because many factors are
> correlated and there is little data on nest survival
> (see BBIRD at http://pica.wru.umt.edu/BBIRD/).
> Distinguishing between juveniles and adults during
> counts can help but is not practical.
>
> Acid rain is thought to disrupt calcium uptake in
> birds. However, for acid rain to affect a couple of
> species is suspect.
>
> Your later thoughts tend to imply that the drought
> last year and the wet one this year may have resulted
> in a decline of Wood Thrush for this year's count. I
> think that that explanation is as good as any with the
> limited amount of data at our disposal. This is what
> the folks at Patuxent are paid to do. Speculation on
> population trends, short or long term, is just that.
>
> As a related aside, A PhD student at NCSU was able to
> show increased nesting success of Wood Thrush in the
> Smokies by an experiment that supplemented some
> breeding Wood Thrush with meal worms. The
> supplemented birds had significantly (statistically)
> greater nesting success than non-supplemented birds.
> The hypothesis goes that, with increased food there is
> increased nest vigilance, nestling feeding and,
> therefore, increased survival.
>
> By the way, does anyone know where I can get some
> shade grown coffee?
>
> Kendrick Weeks
> Fuquay Varina
>
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