I have been reviewing these radar maps for the last few years, almost on a 
daily basis during migration seasons. I think there are few points to be 
considered during reading these maps: (especially for NYC birders)

(check the archived radar loops on this site as I explain my point: 
http://www.pauljhurtado.com/US_Composite_Radar/ )

1- the location is very important: To see NYC, you need to zoom the map to the 
proper location. During the last two nights (May 1st and 2nd loops), there was 
hardly any bird landing in NYC. All the landing activities were just east of 
the city, in Long Island or west of the city, in NJ.

2- timing of the activities: In the early evening hours, radar shows the birds 
that are taking off. While in the early morning hours (2-4 am) it shows birds 
that are landing. If you zoom over NYC in the same last two nights you can see 
that a lot of birds took off, which means that the birds' overall counts in the 
city went down in the last two days. 

3- I have noticed also that, in the absence of clouds, the green color on the 
radar indicates more birds than the blue color. And the brighter the color, the 
more activities. (bright green>dull green>bright blue>dull blue)



Unfortunately, we can't add photos here for illustration. 

But sometimes I put a link to the "current" radar map that I saw at the moment 
when I wrote the email. This radar map needed to be seen immediately. If there 
is some delay in receiving the email ( and I noticed this can happen, for a 
couple of hours sometimes) then the map will not show the original activity. (I 
will put the exact time of the activity with the archived map next time, if 
needed)



Gus





Sent using Zoho Mail






---- On Thu, 03 May 2018 17:21:32 -0700 David Nicosia 
<daven102...@gmail.com> wrote ----






The radar reflectivity that we see is proportionally to the amount of water in 
a given volume of atmosphere as sensed by the radar. Birds are largely made up 
of water and hence they are highly reflective. Hence, when we see high radar 
returns from birds it is due to the density of birds in that given volume even 
if they are flying faster. Hence, the higher the reflectivity the more birds 
there are in a volume. Larger birds will be much more reflective than smaller 
birds because reflectivity is proportional to the diameter of the target(bird) 
raised to the 6th power.  



When we look at highly reflective  precipitation on the radar and its very 
windy it still correlates to heavy precipitation. There are know known wind 
velocity corrections that are used nor have I ever heard about this in my 27 
years of working radar.



In upstate NY we have seen an amazing transformation from almost birdless two 
days ago to the woods filling up rapidly with new arrivals. Most of these birds 
are breeders. I would say that "true" migrants have been fairly scarce among 
the landbirds up here. For you folks downstate, I imagine the birds keep going 
until they reach either decent habitat or their breeding grounds farther north. 
You need bad weather for migrant "waves" as you probably know, especially 
thunderstorms. I wait for thunderstorms to end and position myself (when I can) 
near a lake or body of water or other migrant trap. This has worked very well 
for me. I am sure many of you have experienced this....  bad weather = good 
birds.  Best of luck. 



Dave Nicosia  






On Thu, May 3, 2018 at 7:39 PM Steve Walter <swalte...@verizon.net> wrote:

I think I might have run into some musings at the Forest Park water hole today, 
maybe even some hallucinations. But once again, numbers surely weren’t as high 
as the radar reflectivity might have suggested. I would say there were more 
birds than there had been, but nothing to write home about (for the younger 
folks, that’s what we did before we had NYSBIRDS to write to). I still wonder 
about the effect of leaf out being late. There seem to be a decent number of 
Black-and-White Warblers in – they of course don’t make their living in the 
foliage. I wore green today to try and make the surroundings more inviting to 
other species. It’s debatable how well that worked. 

 

It seems to me that the early night radar tends to look promising on many 
nights. But I also like to get a look at the radar as soon as I wake up, which 
may not be until dawn some days. To me, that has not looked so good, although 
Peter tells me that may be too late already. In any event, there is stuff on 
the radar now at 7:30 P.M.  – rain. Also some strange stuff well offshore. But 
the rain will move out, and the flow remains southwest. It’s gotta happen one 
of these days.

 

As for species, you know I don’t like to get into species lists. Everyone that 
gets out gets the same stuff. But if I need to mention some species, a 
Yellow-throated Vireo came down to the water hole. Offhand, I can’t remember 
one coming down – even when one is around singing. And for those who like to 
study the waterthrushes, a Northern and a Louisiana were crossing paths today. 
Even without binoculars, they were easily separable by the different colored 
eyebrow stripes (although it’s not always that easy).

 

Steve Walter         

 

From: Peter Reisfeld [mailto:drpi...@yahoo.com] 
Sent: Wednesday, May 02, 2018 11:05 PM
To: NYSBIRDS <nysbird...@list.cornell.edu>; EBirds NYC 
<ebirds...@yahoogroups.com>; Steve Walter <swalte...@verizon.net>
Subject: Radar musings


 

 



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
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