Banded Hairstreaks and Hackberry Emperors at Inwood Hill Park

A 1997 article on NYC butterflies (https://www.naba.org/pubs/ab97c/p4.html) described "scores" of Banded Hairstreaks, and other Satyrium hairstreaks covering milkweed blossoms in June at northern Manhattan's Inwood Hill Park. And the late Nick Wagerik's butterfly list from Central Park (last updated in 2007) listed Banded Hairstreak as fairly common (http://edlam.net/B_CP.html).

However, as we've compiled a contemporary list of New York County butterflies based on data from iNaturalist and North American Butterfly Association and Butterflies and Moths of North America reports, Satyrium hairstreaks were missing. No species have been publicly reported from Manhattan in the last decade or more.

This has puzzled me for some time -- did climate change or habitat changes push the hairstreaks out of Manhattan? Or have they simply not been reported, amid 175,000+ reports of nearly 4,600 species from the borough (on iNaturalist)?

On Friday, June 19, I got the answer within 30 minutes of stepping into the forests of Inwood Hill Park. Two small butterflies in a swirling aerial fight caught my eye, and the victor landed on a poison ivy leaflet -- a gorgeous Banded Hairstreak. I saw a dozen individuals that afternoon, often in spectacular aerial combat that lasted for several minutes. When perched, these butterflies were quite bold, unbothered by close human approach along the trails.

So, now we know that Banded Hairstreaks persist in the forests of Inwood Hill Park. I did not find any other Satyrium hairstreaks, and I found barely any milkweed -- just two small clumps of Common Milkweed -- which a nectar plant for this species (the larvae feed on oak and hickory leaves after overwintering in the egg stage). It's hard to picture those two small clumps being enough to sustain "scores" of hairstreaks as reported in the 1990s.

Banded Hairstreak is known to fluctuate in numbers annually and has only one brood a year, with adults flying in late June and July. Now is the time to see them.

I also discovered many Hackberry Emperors -- more than two dozen by my count -- guarding choice common hackberry trees throughout the park. These are bold, pugnacious butterflies that fiercely defend their turf from rivals, and from other butterflies that get too close, like dueling Banded Hairstreaks that dared venture up into the hackberry canopies. This species had been reported only once from Manhattan on iNaturalist -- an individual that landed on someone's window in the Inwood neighborhood.

This experience confirms my hunch that Inwood Hill Park is undersurveyed here on iNaturalist -- and it shows that whole populations of butterflies persist but are virtually unreported in one of the densest counties in the nation. There's still a lot to learn and observe!

Finally, I was also delighted to find the locally scarce Pipevine Swallowtail (https://www.inaturalist.org/observations/50227655 -- a real stunner) and Dun Skipper (https://www.inaturalist.org/observations/50227660) in the park. Clearly, Inwood Hill Park has a lot to offer butterflyers today.

A coda: On Sunday, June 21, I also walked extensively through Central Park's North Woods but could not find a single Banded Hairstreak (which Wagerik reported as fairly common the mid-2000s) or Hackberry Emperor (which Wagerik described as very rare), despite similar weather conditions two days after my Inwood Hill Park visit. Do these species still occur in Central Park? Unclear.

FYI @blkvulture @colbee1 @danielatha @jholmes @joedicostanzo @kasimac @natron13 @nycbirder @sadawolk @spritelink @steven-cyclist @zahnerphoto @zihaowang

Posted by djringer djringer, June 22, 2020 12:13

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David,

Thanks for the details and the links to the NABA article on NYC Butterflies and Ed Lam's posting of Nick Wagerik's 'The Butterflies of Central Park'. Nick was an amazing naturalist and he knew me as a birder and an amateur astronomer and it was always a treat when Nick was around and we had our telescopes setup in the park. He got a great kick seeing craters on the Moon, the cloud bands on Jupiter and the rings of Saturn. He is sorely missed.

Nice find and photos of the Banded Hairstreaks from Inwood Hill Park. I remember a day birding on Governors Island a few years ago and we came across a Banded Hairstreak in Hammock Grove. No photos were taken though.

I looked for an iNaturalist "place" for Inwood Hill Park and the one created by the NYC Park's Department excludes some parts of the park on the east edge and in the northeastern section.

Here's a list using a place I just created that excludes casual observations showing 87 observations of butterflies with 25 species.

Inwood Hill Park (2020): Butterflies excluding Moths

https://www.inaturalist.org/observations?place_id=153659&subview=grid&taxon_id=47224&view=species

A place I used to bird often just south and east of Inwood called Swindler Cove Park has a number of flowering plants on the south side of Sherman Creek including many milkweeds. Here's a project I created a while ago called 'Swindler Cove Park & Sherman Creek Wildlife':

https://www.inaturalist.org/projects/swindler-cove-park-sherman-creek-wildlife

There are only 8 butterfly observations at Swindler Cove of 6 species:

https://www.inaturalist.org/observations?place_id=121942&taxon_id=47224&view=species

This might be a decent place to look on a good day for butterflies.

Ben

Posted by nycbirder about 1 month ago (Flag)
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Interesting post David @djringer
That is pretty remarkable that they would not show up in all of those iNaturalist posts! This is interesting. I was thinking about a recent walk I did along the bottom edge of Highbridge, near the Swindler Cove that Ben mentions above. That was a few weeks back, you have encouraged me to head back there. I will try to work that in.

Jay

Posted by jholmes about 1 month ago (Flag)

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