Tuesday, July 24, 2012

Joe Neal's Purple martin saga: Birds gather in stages to head to their roosting area after sunset

Purple Martins are already on wires when I arrive at 7:10 PM, but there are only 8, plus many more starlings. I've decided to watch how the pre-roost gathers itself before heading off to the night roost only one mile south. By 7:20 the number doubles, but still far short of thousands here last night.

Welcome to southeast Springdale, heart of northwest Arkansas's busiest industrial area, adjacent the Springdale airport. We've had a 101 degree day and I'm in the welcome shade of an 18 wheeler, part of the fleet maintained by Northwest Technical Institute for teaching and testing potential drivers. I'm constantly scanning for new martin arrivals during the next 20 minutes. 

This mostly flat country is part of the former Osage Prairie. Native Indians from what is now Missouri hunted bison here. And in a region otherwise dominated by the rugged terrain of the White River, settlers preferred open lands and bountiful prairie grass, as did builders of the pre-Civil War telegraph and Butterfield stage, both not far from where I'm sitting. It may also be why martins of the post-breeding season gather here.

At 7:40 I've only seen 40 birds, but suddenly at 8:03 there are a couple of hundred! First they swirl, then settle down and arrange themselves tightly on wires, mainly folded wing-to-folded wing. Orderly ranks, like soldiers on parade. 

So how long have there been these high summer martin gatherings here? I don't have an answer, but just south there's a shady trailer residential area called Whistler Park. Main road in: Purple Martin Drive.

As the sun drifts toward setting over Springdale, 8:15 PM, martins are pouring in. My current count: at least 1,275, give or take 100 . . . or so . . .  like counting/estimating winter blackbirds . . . and more arriving.

Sundown at 8:26 seems a trigger. Wires and tree tops are leafed-out with martins, but then suddenly, as on cue, well-ordered martin ranks lift off, transformed into energetic swirls. Like someone among the martin hosts has yawned and said she's ready for bed. Martins are steadily slipping south. At 8:30 I can see that only half of the sundown swirl returns to perch.

At 8:36 there's another bail-out, with most wires empty. But it's no single big flight to roost, no single leader and a bunch of followers, more like a flowing stream than a flood. But they steadily abandon the 18-wheeler lot. Thin swirls and individuals head the one mile south. By 8:40 I can see maybe 200 birds.

8:41 PM, and all is now mainly quiet here on the martin pre-roost front. Inevitably, there is the putative last of the last of martins to leave pre-roost for night roost. The place seems empty, but nearby, dogday cicadas rage on in chorus, raging, raging for this wonderful summer evening.

It's been one hour and half since I arrived. Zero is the number of martins I see at 8:45, but I can hear a few calls of what I assume are stragglers. Why is the first the first to go roost and why is the last the last?
Why choose this busy industrial hub rather than say, a pristine uninhabited island in Beaver Lake? Is some Methuselah-like collective martin heritage recalling days of Indian grass, sawtooth sunflowers, and hordes of native pollinating bees and flies, ripe and ready for aerial plucking by hungry martins?

8:50, slice of moon up and mainly dark. I'm considering as I fold up my chair and head home, well
entertained, and with many questions. JOE NEAL written about July 23, 2012 experience.

The big Purple Martin roost in northwest Arkansas that Bo Verser first saw on NEXRAD radar July 17 is within Springdale city limits, about two miles north of Lake Fayetteville. David Oakley and I found the roost last night right at dark. It is in Springdale's industrial area, with birds using mid-sized trees in an older, densely developed residential neighborhood.

Prior to locating this roost, Joan Reynolds and I estimated we saw between 6,000 to 9,000 birds July 21 on Parsons Road, approximately 3 air miles northeast of the actual roost. Last night David Oakley and I located another pre-roost north of Parsons Stadium in Springdale about 1 mile from the actual roost.

Birds on Parsons Road were watering at a big open pond adjacent powerlines. Many birds near the stadium were taking advantage of a limestone gravel parking lot, perched on the ground and possibly collecting limestone grit, either to aid in digesting insect exoskeletons or as a calcium supplement.

Martin numbers near Parsons Stadium were easily as high as on Parsons Road. It appears martin numbers using the roost may range roughly between 12,000 and 18,000.

This morning's NEXRAD showed the Springdale martin roost dispersing mainly to north and east, which would send at least part of this flock out over the lower parts of Beaver Lake -- Lost Bridge, Indian Creek, and the dam site.  The radar also shows big rings at Tulsa and the Lake Ouachita. JOE NEAL written about July 22, 2012 experience.

Last night, Joan Reynolds and I estimated a minimum 6000-9000 Purple Martins vocalizing energetic  BREETS and CHURS, and packed shoulder-to-shoulder, on low trees and high wires crossing big open fields at Sonora east of Springdale. As birds came in they made low passes over a big farm pond, rippling the water surface, maybe getting a last drink before roosting.

I was absolutely certain they were about to roost in trees along Parsons Road. That was around 8 PM as the sun was going down. Time for high fives, but then, off they went in ragged swirls, mainly east, toward the old Butterfield Coach Road (265) on Springdale's east side, to roost . . . somewhere . . .

Bo Verser sent me an email on July 17 with a weather underground image of a "martin roost ring" showing up on radar northeast of Fayetteville, maybe on Beaver Lake. He wrote,  "Of course it takes thousands of birds exploding skyward as they leave their roost to create these radar rings."  We're talking about an enormous, donut-shaped swirl. I was unaware of this martin concentration until Bo's email.

The ring appeared on NEXRAD (Next-Generation Radar), a network of Doppler weather surveillance radars operated by National Weather Service. The other ring he'd seen involved the huge and well-known Purple Martin roost on Lake Ouachita.

My Beaver Lake friends Bob and Patti French at Lost Bridge were still seeing good numbers of martins near their nest boxes, but nothing like thousands. I ran this by Joan, who lives near the lake and she checked with others including biologist Alan Bland of the Army Corps of Engineers. He hadn't seen anything, either. I emailed Flip Putthoff, outdoor editor for the Morning News. He wrote back that he'd been on Beaver Lake at Rocky Branch in recent early mornings and had seen no martin swirl.

Were last evening's thousands the whole roosting flock, or just a part that pre-roosts at Sonora? Is the roost just east, or miles further away?

This morning I again looked at the NEXRAD link Bo Verser supplied. Again, Purple Martins are exploding from the roost in a vast swirl, but not mainly southwest toward Fayetteville, but northeast seemingly over Beaver Lake. Somewhere.   JOE NEAL written about July 21, 2012 experience.

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