The Butterflies of Manhattan: Building a List
Which butterfly species occur in Manhattan? I discovered that this seemingly straightforward question does not have a particularly clear answer, so I started compiling information from publicly available sources in an effort to assemble a list, which is accessible here as a work in progress: https://docs.google.com/spreadsheets/d/1Y2mNKMNXqtk4Ms820YvKXaaTySSYoxtcGlq7znoCjtY/edit?usp=sharing.
The Challenge
Observations documented here on iNaturalist provide a helpful starting point but not a complete picture. Not all species are fully or correctly identified, and Inwood Hill Park, which could have more species than anywhere else on the island of Manhattan because of its remnant forest and marsh habitats, has only a few dozen observations recorded on iNaturalist, out of nearly 5,000 observations for the whole borough. This may mean that some species are not yet documented from the island on iNaturalist. Furthermore, some rare occasional vagrants like Long-tailed Skipper have not been recorded yet on iNaturalist.
As far as other data sources, eButterfly is barely used in New York; there appear to be only four checklists submitted from the entirety of Manhattan. A group of enthusiasts compiled a list of species seen within 50 miles of New York in the 1990s, and Nick Wagerik kept a list for Central Park up until at least 2007. Butterflies and Moths of North America has a number of historical records (without dates or locations) and some contemporary reports from New York County. And periodic reports are submitted to North American Butterfly Association's sightings log.
A small network of knowledgeable observers seems to keep detailed records privately, and occasionally post anecdotal reports on the New York Leps Google Group, but as far as I know no contemporary compilations of this data are published publicly.
The List
I created a spreadsheet attempting to compile data from as many of these sources as possible in order to begin creating a relatively well-rounded and view of species reported from Manhattan historically and, especially, since 2010.
You can view that document here: https://docs.google.com/spreadsheets/d/1Y2mNKMNXqtk4Ms820YvKXaaTySSYoxtcGlq7znoCjtY/edit?usp=sharing -- and the second tab of the spreadsheet contains an explanation of the fields and data, including links to the various data sources and lists referenced.
The results so far include reports of 81 species from Manhattan through time, and 51 species since 2010, with several more reported in the greater New York City region but not necessarily from Manhattan. The reliability of some of these reports or identifications may be questionable, especially for difficult genera, but a picture does begin to emerge when all these data sources are considered together.
It's clear even from this rudimentary effort that some species have become rarer over the last 30 years, or may have even become locally extirpated. On the other hand, some southern species are increasing in frequency and abundance -- for example, Sachems and and even more recently, Eastern Giant Swallowtails.
The Geography
The borough of Manhattan and the county of New York include of course the island of Manhattan, several smaller islands (including Randalls and Wards, Roosevelt, and Governors), and a sliver of the mainland.
Interestingly, some designations also currently include the piers of Brooklyn Bridge Park, apparently because the county line was drawn along the Brooklyn shoreline, but the piers jut out into the East River, over the historical county line. So a search on iNaturalist today for New York County includes observations from the Brooklyn Bridge Park piers.
Some Questions I Encountered While Compiling the List
- What is the status of Celastrina azures in Manhattan?
- What is the status of Northern Crescent, Phyciodes cocyta, in Manhattan?
- Does Columbine Duskywing occur in Manhattan?
- Have several species of skippers, hairstreaks, and satyrids been extirpated from Manhattan in the last 20 years, or are they simply underreported?
The Project
I've created an iNaturalist project to start tracking things more closely -- please join if you want to keep a closer eye on Manhattan butterflies: https://www.inaturalist.org/projects/butterflies-of-new-york-county-manhattan
Tagging a few folks who might be interested: @ansel_oommen @blkvulture @cathyweiner @cesarcastillo @conuropsis @craghorne @danielatha @d2b @elevine @ginsengandsoon @kasimac @kdstutzman @kenchaya @maractwin @nlblock @nycbirder @pawelp @sadawolk @spritelink @susanhewitt @wayne_fidler @zahnerphoto @zihaowang
