[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:

https://ebird.org/view/checklist/S57661005

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

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Eric DeFonso
near Lyons, Boulder County, CO

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