Date: 5/3/18 6:09 pm
From: Gus Keri <guskeri...>
Subject: Re: [nysbirds-l] Radar musings
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&gt;dull green&gt;bright blue&gt;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





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---- On Thu, 03 May 2018 17:21:32 -0700 David Nicosia &lt;<daven102468...>&gt; 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 &lt;<swalter15...>&gt; 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:<drpinky...>]
Sent: Wednesday, May 02, 2018 11:05 PM
To: NYSBIRDS &lt;<NYSBIRDS-L...>&gt;; EBirds NYC &lt;<ebirdsnyc...>&gt;; Steve Walter &lt;<swalter15...>&gt;
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 &lt;<Shaibal.Mitra...>&gt; 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-122535933-11143133...> [<bounce-122535933-11143133...>] on behalf of Steve Walter [<swalter15...>]
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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