The radar pattern tonight is similar to what it was last night. High
reflectivity and high velocity in a NW direction. Does this mean tomorrow will
be birdy or quiet? I can’t say for sure but I’d like to share some thoughts
about it.
Steve brings up the issue of promising radar reports but poor showings on the
ground. The mediocre showing today despite high reflectivity on radar is a
phenomenon I have seen a number of times before. It has been my impression that
this occurs more frequently on nights when migration velocity is high. I have
never seen an explanation for it, but thinking about it today, a theory
occurred to me.
To illustrate the theory, I’d like to use the analogy of rain on a windshield.
Whenever I am driving on the highway in the rain, the faster I drive, the
harder it seems to rain. While driving fast does not increase the density of
raindrops falling from the sky, it does cause many more drops to hit the
windshield per second as you drive into a steadily falling stream.
Perhaps it is the same with bird radar. When birds are flying particularly
rapidly, more of them may intersect with the radar beam per second. This
produces an increase in reflectivity, without an increase in density of birds.
Since we generally assume that high reflectivity is due to high bird density,
the spurious increased reflectivity would make it seem that more birds were up
there than really were. Hence a disapointing showing on the ground the next
morning. This scenario could explain what happened last night.
While I have not heard of this theory before, I doubt I am the first to think
of it. I emailed Cape May radar-maven David La Puma about it today. If he gets
back to me, I’ll let you know what he thinks.
So what about tomorrow? I would just say this. Birds are up there and
migrating rapidly. It's just that the numbers MAY NOT be as high as it appears
based on reflectivities.
In any case, good luck out there,
Peter
On Wednesday, May 2, 2018, 7:17:58 PM EDT, Shaibal Mitra
<shaibal.mi...@csi.cuny.edu> wrote:
Hi Steve and all,
At Robert Moses SP, to the east of Jones beach, I didn't see any Red-headed
Woodpeckers this morning, but I did see 14 Red-bellied Woodpeckers--all
migrating east to west. Those familiar with the barrier beaches, and the usual
absence of most forest "resident" species there, will understand that this was
a remarkable sight. Stephane Perrault has some interesting ideas on the
relationship between these irruptive flights and inter-year variations in the
regional population density.
Southwest winds tonight?--let's get some more Melanerpes data!
Shai Mitra
Bay Shore
________________________________________
From: bounce-122535933-11143...@list.cornell.edu
[bounce-122535933-11143...@list.cornell.edu] on behalf of Steve Walter
[swalte...@verizon.net]
Sent: Wednesday, May 2, 2018 7:09 PM
To: NYSBIRDS
Subject: [nysbirds-l] Red-headed Woodpeckers at Jones Beach
I had two adult Red-headed Woodpeckers at Jones Beach West End this morning,
essentially as fly-bys. The first flew by me while I was in the median and
turned east on the blind side of the tree line. The second, about a minute
later, made brief stops in the higher trees before also moving east and out of
sight. Also, one or two Red-bellied Woodpeckers were around. So it was
Melanerpes Moving Day.
I hadn’t planned on going down to the beach, but an early assessment of the
Queens parks suggested the much anticipated and overdue first big wave had not
materialized – at least not here. I’ve gotten into the radar watching, like
others have. I can’t say that I feel comfortable with what I see – but. The
other day, someone mentioned the radar showing birds. Looking at the referenced
radar image, it didn’t look that way to me. But I do appreciate people looking
at that and offering alerts or opinions. We might figure this out. What I
looked at on radar this morning suggested there was movement along the coast.
So I figured why not change plans and check that out. I can’t say that what I
saw on the ground should have lit up the radar, but there were a variety of
migrants at Jones. Not much unusual other than the woodpeckers, but 5 Baltimore
Orioles in one tree was a sight to see. Maybe the most interesting bird I came
across was an immature Great Cormorant on a piling outside the boat basin. It
doesn’t look like a record late date, but close as far I can see.
So what happened with the migration? It’s May 2, there was no flight of note
recently, and winds last night were SW to WSW. There should have been migrants
everywhere. One thing I had been noting and saying to people is that the trees
have barely begun to leaf out – which would also limit insect hatches. Arboreal
birds don’t want to be in that. Would that retard the migration? Wouldn’t they
actually have to get here to know what the situation is here? Well, SW again
tonight. It can only get better.
Steve Walter
Bayside, NY
--
NYSbirds-L List Info:
Welcome and Basics<http://www.northeastbirding.com/NYSbirdsWELCOME.htm>
Rules and Information<http://www.northeastbirding.com/NYSbirdsRULES.htm>
Subscribe, Configuration and
Leave<http://www.northeastbirding.com/NYSbirdsSubscribeConfigurationLeave.htm>
Archives:
The Mail
Archive<http://www.mail-archive.com/nysbirds-l@cornell.edu/maillist.html>
Surfbirds<http://www.surfbirds.com/birdingmail/Group/NYSBirds-L>
ABA<http://birding.aba.org/maillist/NY01>
Please submit your observations to eBird<http://ebird.org/content/ebird/>!
--
--
NYSbirds-L List Info:
http://www.NortheastBirding.com/NYSbirdsWELCOME.htm
http://www.NortheastBirding.com/NYSbirdsRULES.htm
http://www.NortheastBirding.com/NYSbirdsSubscribeConfigurationLeave.htm
ARCHIVES:
1) http://www.mail-archive.com/nysbirds-l@cornell.edu/maillist.html
2) http://www.surfbirds.com/birdingmail/Group/NYSBirds-L
3) http://birding.aba.org/maillist/NY01
Please submit your observations to eBird:
http://ebird.org/content/ebird/
--
--
NYSbirds-L List Info:
http://www.NortheastBirding.com/NYSbirdsWELCOME.htm
http://www.NortheastBirding.com/NYSbirdsRULES.htm
http://www.NortheastBirding.com/NYSbirdsSubscribeConfigurationLeave.htm
ARCHIVES:
1) http://www.mail-archive.com/nysbirds-l@cornell.edu/maillist.html
2) http://www.surfbirds.com/birdingmail/Group/NYSBirds-L
3) http://birding.aba.org/maillist/NY01
Please submit your observations to eBird:
http://ebird.org/content/ebird/
--
