Date: 6/28/19 6:29 am
From: Jan G <jangorski...>
Subject: [cobirds] Re: Common Nighthawks, Smith Reservoir, Costilla (story, no rarities)
What an amazing encounter Eric! You might consider taking a video of this
behavior if you see it again!

Jan Gorski
Highlands Ranch, Douglas, CO

On Thursday, June 27, 2019 at 8:14:08 AM UTC-6, Eric DeFonso wrote:
> Hi all,
> Indulge me if you will, I want to share a very lengthy but hopefully
> entertaining account of what for me was an unusual and astonishing
> experience with a common species...or at least one that many COBirders have
> been lamenting this year as not being as common as usual.
> I was setting up to camp at Smith Reservoir SWA in Costilla County, near
> Fort Garland. Around 7pm I was on the SE corner of the reservoir with
> magnificent early evening light behind me illuminating the place, when I
> spotted a Common Nighthawk (CONI) bounding in the northerly breezes over
> the water. It's always a delight to catch sight of a CONI flying relatively
> low and close, allowing for nice looks in the scope, especially in that
> nice light.
> A few moments later, I noticed a second CONI flying near it, also doing
> the same bounding flight in the breeze. I watched them both carefully, and
> thought for a moment that I should check to see if by chance one of them
> might be a Lesser Nighthawk (LENI). Neither fit that description, but I
> kept checking anyway just to be sure. My one Colorado LENI was seen with
> the delightful pair of Coen and Brenda over in Nucla a few years ago, also
> coursing over water with a bunch of CONIs, so it seemed proper to be alert
> to it here too.
> I scanned the rest of the reservoir as well, looking for ducks, herons,
> and any other waterbirds that might be of interest. I've not spent much
> time over the years in Costilla County (and apparently not all that many
> other Colorado birders either, judging from eBird), so county lifers were
> fairly easy to come by that day. I went back to check on my nighthawks, and
> now there were 4. I mean 5! Cool. All of them doing the same thing,
> bounding in the breeze, and working their way towards the middle of the
> reservoir. I noticed at that point that they'd get to about the middle of
> the water, and then let the strong breeze blow them all the way back to the
> south shore, at which point they'd start the process again of working their
> way to the middle. It was a kind of "conveyor belt" of CONIs, as they
> hoovered up low-flying insects over the water in their version of a feeding
> frenzy. Again, I kept checking to see if any of them were LENIs, and none
> of them fit the bill, but my attention was drawn in now and I kept checking
> each bird anyway every minute or two, because "you never know".
> After several more minutes, I counted the CONIs once more and now there
> were 10! Wow, that's cool, I'm not used to seeing all that many in one
> place at one time. Oh sure, maybe when they've just arrived after migration
> and they are accrued in a few concentrated spots, but I hadn't seen that
> myself in quite some time, so it was again neat to see. And all of them
> again engaging in the same "conveyor belt of CONIs", providing a bit of a
> scanning challenge when they peeled off to start over but also providing a
> chance for steady viewing if you followed one in the scope as it slowly
> coursed its way to the middle of the reservoir.
> After another several minutes, I counted 16! Wow, now I was getting close
> to seeing as
> many as I've ever seen at one place and time. Still checked for LENIs as
> best I could, but all of them sported very pointed wings. I should mention
> that the scene was pretty quiet except for the sound of the steady breeze
> blowing. It was cool to watch all this bird activity occurring in silence.
> The Eared and Western Grebes seemed curious to see this growing number of
> CONIs flying over them and foraging so differently from their preferred
> subaquatic style.
> Around 7:30ish it seemed like there were more than 16, so I carefully
> counted again and now there were 40! Holy cow, that's definitely way more
> than I've ever seen at once. I figured that seeing that many at once may be
> typical of a migration flight. but that's something I'd not personally
> witnessed, so this began to feel like an extraordinary occasion. I thought
> back to those COBirds posts about the disappearance of CONIs from various
> local spots in the Front Range, and thought, well, no shortage here at
> least. I should mention that the surrounding terrain is largely
> sage/rabbitbrush shrubland and ag areas.
> It was quite a challenge at this point to keep track of any individual
> bird even in the scope. There was no shortage of choices of birds to watch
> of course, but like trying to watch a single swallow among a cloud in
> binoculars, a single CONI in the scope proved elusive simply because of all
> the other choices that were moving about in the scope's field of view. A
> happy problem to have of course, but it didn't make the search for a
> possible LENI any easier.
> Some minutes later, I thought to count once again. By the way, my method
> of counting such a dynamic, shifting bunch of birds was to start at the
> southern end of the water and slowly scan in the bins northward as the
> birds were slowly making their way there. That way I thought I'd reduce the
> chance of double-counting since I could count the birds I was scanning past
> easily (they were flying slow, into the wind), and then count the ones
> zipping by quickly on their way back to the beginning of the conveyer belt,
> knowing that I hadn't counted them yet. It was still a rough count because
> so much is happening pretty quickly but I felt confident in my end result
> to within +/- 10%. Now I was certain there were at least *93* nighthawks on
> the reservoir!
> Looking with the naked eye, it was clear there were dozens and dozens and
> dozens of them. Again, all bounding silently in the breeze above the water,
> but presumably ravaging the insect life in the process with calm, cool
> efficiency. I definitely had never seen that many CONIs at once. I started
> to wonder, when does this end? How many birds are going to show up here??
> Will anyone believe me?
> By 8ish the light was starting to lessen. It was still nice with sunlight
> streaming over the water, but not as bright as it was an hour earlier. I
> was still scanning for LENI, but at this point it didn't really matter
> because it was so amazing to see that many CONIs engaging in this
> gregarious feeding event, all low over the water and all in easy viewing. I
> thought for a moment that I really wasn't going to be able to do counts any
> more, since it was tiring and getting tougher. But I didn't want the late
> hour (I needed to get to sleep soon for a very early start the next morning
> with a bird survey) to keep me from knowing *just how many CONIs can fit
> above a reservoir*, and I also right then began to envision how I might
> share this remarkable event with the COBirds listserv.
> The next count yielded 160 CONIs! At this point I was starting to count by
> 10s, as quickly as I could before the mass of birds rearranged themselves
> significantly over the water thus making counts fraught with potential
> double-counting errors. Again, I didn't doubt my result since it was a
> veritable cloud of CONIs. The scope field of view at any one time had no
> fewer than 10-12. I had to be careful too about not counting swallows,
> because at this point they were getting in on the hoovering conveyor belt
> action, and in the diminishing light it was getting easier to conflate the
> numbers of nighthawks and swallows. But even allowing for some amount of
> counting error, it was clear that there were ever-increasing numbers of
> CONIs present.
> I wondered, "Where are they all coming from??" I looked at the south and
> west edges of the reservoir and noticed that one or two at a time were
> regularly joining the scrum from the bordering shrublands. It was as if the
> CONI call-to-action had been sounded and they collectively were fully aware
> of what a bonanza Smith Reservoir could be.
> Quarter past 8 and the light was fading. The sun had set but I could still
> resolve individual birds coursing about. Time for one last count before I
> surrender. *210* this time! So many CONIs, it was truly a spectacle. I wish
> I could have photographed it somehow, but how do you capture that many
> birds in this circumstance in a way that people will believe your big fish
> story? And the birds themselves... how could there be enough for them all
> to eat in this one spot? Where did all these birds roost? How far had some
> of them come? Was it like this over all the large SLV bodies of water? Is
> it like this over other large reservoirs in Colorado, and I'd just never
> noticed? I have lots of questions, and haven't really had time to look up
> answers.
> The eBird quantity filter tripped at around 100 birds, so at the moment my
> checklist for the evening doesn't show on the public results, and won't
> unless it gets confirmed. But for those curious, this is the link to my
> submitted checklist:
> I don't know if the CONI frenzy continues every night there, but I will be
> heading back to that area in mid-July for another survey and I plan to camp
> there again. I would love to hear any stories or accounts of dozens or
> hundreds of CONIs observed in one place and time, especially over
> reservoirs. Birds of North America Online says the following about CONI
> foraging:
> "May forage in large groups at local areas. A flock of about 110
> individuals observed foraging in an urban area west of Toronto, ON, in a
> 1-km2 area; individuals spaced about 20 m apart (Ewins 1993a
> <>)
> and similarly near Regina, SK near dawn in spring (RMB unpub. data). Flocks
> of 1000's reported in Kansas (Cummings et al. 2003). At Okanagan Falls, BC,
> 50–300 birds foraged over a 100 m stretch of a river every night (Brigham
> and Fenton 1991
> <>
> , Brigham and Barclay 1995
> <>
> )."
> For those discouraged about low numbers of nighthawks in their areas of
> residence compared to past years, at least be heartened by the fact that at
> least in the SLV, hundreds of them are gathered and making a good living
> there this year.
> Thanks for reading this far!
> Eric
> -----
> Eric DeFonso
> near Lyons, Boulder County, CO

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