OHIO-BIRDS Archives

September 2010

OHIO-BIRDS@LISTSERV.MIAMIOH.EDU

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Tom Bain <[log in to unmask]>
Reply To:
Date:
Mon, 6 Sep 2010 11:31:16 -0400
Content-Type:
text/plain
Parts/Attachments:
text/plain (92 lines)
The scale of the 'rings' in the video loop is county-scale, hundreds of
square miles. Are there enough swallows, martins, and such in Ohio, if
gathered in one place, to provide reflective density enough to complete just
one of these dense rings? The symmetrical arc subtended by the regular
spread evident in this phenomena does not reflect a living bird
landscape-oriented spread from a roost--a natural spread pattern must be
dendritic as well as diminishing, I think, that's what I've observed at
large roosts in the past, anyway. Migration reflectance is far more diffuse
and numbers of species responding to weather patterns do respond together to
support reflectance over broad areas. I'd be very interested in additional
insights from folks tuned into remote sensing and reflectance. Is the arc
pattern an artifact of reflectance along moisture and temperature
boundaries, or is it living birds, or what?

This is a very good thread for the OOS forum. I will open a thread there for
those interested.

Tom Bain
Delaware County

-----Original Message-----
From: Ohio birds [mailto:[log in to unmask]] On Behalf Of Doug
Overacker
Sent: Sunday, September 05, 2010 9:59 PM
To: [log in to unmask]
Subject: [Ohio-birds] Radar and Bird Roosts

Brian Menker sent me the following link about radar images and bird roosts.
I agree with him that I don't think all of these rings could be due to
Purple Martins. I have never heard anyone reports such large roosts of
Purple Martins in Ohio. The only large roost in the area that I have heard
of is one at Presque Isle, Pennsylvania. Brian's comments are below.

Doug Overacker
Springfield, Ohio

http://www.erh.noaa.gov/iln/research/birds/

They make some interesting observations about radar "rings" that appeared on
several mornings in early August, that they claim are due to roosting birds.
Specifically, they speculate that they are due to huge roosts of Purple
Martins that return to the same places at night and create radar rings in
the
morning as they leave to feed for the day.

I find this conclusion to be highly doubtful.  The number, size, and scale
of
the "roost rings" on their example loops from early August would indicate
many massive roosts of martins that we just don't see.  If there were that
many roosts of Purple Martins numbering in the tens of thousands, birders
would be reporting them.  I don't have my Peterjohn copy handy, but I don't
remember ever hearing of those types of roosts here in Ohio.

I think these rings are artifacts of specific atmospheric conditions and
ground scatter.  They even say that the rings show up in the morning and not
the evening because the atmospheric conditions are more favorable for the
radar beam to hit lower objects.

I wanted to post something on this to Ohio Birds to let everybody weigh in,
but I'm not set up to post anymore.  I know there are discussions on radar
detection of birds from time to time, and I think feedback from Ohio's
birders could help the Weather Service see that their speculations are a bit
wild. Could you at least post the link and throw it out there for comments?

If any bird roosts in Ohio would create a radar ring, I would think that the
crow roost here in Springfield would show up on winter mornings.  There are
tens of thousands of them, and they are much bigger reflectors than martins.
Maybe I'll keep my eye on the radar when they show back up for the winter.

Brian

______________________________________________________________________

Ohio-birds mailing list, a service of the Ohio Ornithological Society.
Our thanks to Miami University for hosting this mailing list.
Additional discussions can be found in our forums, at
www.ohiobirds.org/forum/.

You can join or leave the list, or change your options, at:
http://listserv.muohio.edu/scripts/wa.exe?LIST=OHIO-BIRDS
Send questions or comments about the list to: [log in to unmask]

______________________________________________________________________

Ohio-birds mailing list, a service of the Ohio Ornithological Society.
Our thanks to Miami University for hosting this mailing list.
Additional discussions can be found in our forums, at www.ohiobirds.org/forum/.

You can join or leave the list, or change your options, at:
http://listserv.muohio.edu/scripts/wa.exe?LIST=OHIO-BIRDS
Send questions or comments about the list to: [log in to unmask]

ATOM RSS1 RSS2