As I mentioned in my earlier note to the list on this subject (8 Jun 18, copied 
at the very end of the present note), the jury is certainly still out on the 
status of longipennis Common Terns on the east coast. Joe's highly informed 
contributions are a very welcome addition to the process and underscore several 
areas to focus on in resolving the matter. First, it is clearly true that to 
claim an extralimital longipennis, the evidence must be very strong and include 
multiple characters beyond dark bills and dark legs. I have a lot to contribute 
on this front, because I have made a point of studying non-breeding terns for 
more than 20 years, during which time I have collected detailed data on large 
samples of carefully scored first-summers and "second-summer types" (a category 
which, as Joe notes, consists of an odd amalgam of a subset of some but not all 
two year-olds, older adults short of full breeding condition, and very old, 
senescent adults)--not only of Common Terns, but also of Arctic, Roseate, 
Least, Black, and others.

For now I just want to make two very simple points in response to the queries 
Joe raises toward the end of his note. 

First, I'd like to address Joe's skepticism about judging wing length visually. 
I once wrote a long, detailed note to the ID Frontiers list defending the 
critical, visual assessment of shape (i.e., the relative sizes of morphological 
structures; that piece concerned warblers, or maybe willets, or maybe I did it 
separately for both?). I might be able to dig it/them up, but for now I 
remember demonstrating that large samples of in-hand measurements 
counter-intuitively often obscure real differences between similar species, 
males and females, etc. The reason is that handbooks over-emphasize extreme 
data, neglecting quantitative measures of variance and covariance, and because 
most observers are unprepared or unwilling to think quantitatively. At the same 
time, sharp-eyed birders can unerringly distinguish Blackpoll and Pine Warblers 
at a glance by shape, even though practically all their measurements, viewed 
individually in huge samples, overlap. With regard to terns, I can recognize 
visually how the length of an individual's primary projection compares to the 
chord of its dorsum with enough precision to distinguish Common and Arctic 
Terns very confidently. So I would caution against categorically dismissing 
this line of evidence.

Second, the true statuses of non-breeding seabirds remain an amazing mystery, 
and the few glimpses we've had so far have been really exciting. Most 
obviously, the local status of Arctic Tern has been completely re-written in 
the past 20 years based precisely on attention to loafing flocks of 
non-breeding terns. Furthermore, scrutiny of these flocks has yielded many 
other rarities, some of them as unexpected as longipennis might seem: Elegant 
Tern, Cayenne Tern, acuflavidus Sandwich Terns during June, Little Gulls during 
June, etc. My point is that although the improbability of longipennis needs to 
be answered with strong evidence, much stranger things have happened. I still 
examine every Arctic Tern I see with the remote potential of Antarctic Tern in 
mind; the non-breeders hang out together down there, so maybe a few stick 
together up here, too. Ditto for examining first-summer Least Terns for Littles 
and first-summer Black Terns for White-winged and Whiskered.

Brian Patteson recently saw a Tahiti Petrel off of Hatteras!

Shai Mitra
Bay Shore


________________________________________
From: bounce-122637763-11143...@list.cornell.edu 
[bounce-122637763-11143...@list.cornell.edu] on behalf of Joseph DiCostanzo 
[jdic...@nyc.rr.com]
Sent: Thursday, June 14, 2018 9:08 AM
To: Robert Lewis
Cc: nysbirds-l
Subject: Re: [nysbirds-l] Dark billed, dark legged Common Terns on Long Island

Bob,

Molt, (and I am including change in soft part colors such as bill and leg color 
under the term “molt”) is hormonally controlled. There is also considerable 
variation between individuals in the timing of molt. The timing and sequence of 
molt is no where as neat and fixed as many references might lead you to 
believe. Having worked extensively with a banded population, where the age of 
individuals is known from their banding histories, I know how much variation 
there is. I have seen birds with extensive white foreheads (or heavy speckling) 
and extensive carpal bars that I knew from their bands were two years old. I 
have also seen two year olds that were indistinguishable from normal adults. I 
have also seen that I knew were three, or four years old (or older based on 
their bands) that showed speckled foreheads and traces of carpal bars. I have 
seen adults in August at the breeding colony on Great Gull Island that were 
already in full winter plumage (black bill, dark legs, carpal bar). Individuals 
that don’t match the expected are unusual, but they do occur.

As for the lack of a carpal bar on these dark billed, dark legged individuals, 
you are assuming that feather molt (carpal bar) and soft part colors (legs and 
bill) must be in total lock-step with each other. There is no reason they 
couldn’t be out of sync in some instances. As for primary length, this is being 
based on photos, not actual measurements of the bird in hand. How is the 
primary length being assessed? I am guessing versus tail length. How does 
anyone know the tail length?

These dark billed, dark legged Common Terns get reported every year at this 
season, just at the time young Common Terns are coming back from South America. 
Where are these supposed longipennis birds coming from? The race breeds in 
Siberia and winters in the Indian Ocean east to Australia. If longipennis were 
going to occur here on the East Coast, the fall seems a more likely time than 
the spring migration. It seems far more likely that these birds are aberrant 
hirundo retaining aspects of their winter/non-breeding plumage than that there 
is an annual movement of Siberian based longipennis birds through Long Island.

Joe DiCostanzo

Sent from my iPad

On Jun 14, 2018, at 7:59 AM, Robert Lewis 
<rfer...@yahoo.com<mailto:rfer...@yahoo.com>> wrote:

Good points Joe.

Let's go with the null hypothesis: it's an unusual Common tern (hirundo). 
Apparently a Common tern in September can get gray blotches on the underparts. 
During the winter they have a black bill, black legs, and a black cap with 
white forehead, as first summer birds do now. If it is four - eight months late 
in molt (or four months early), maybe that would explain some features. But 
then there should be a prominent dark carpal bar. Instead, there is none. Also, 
how to explain the very long primaries? And the fact that the back is a bit 
darker gray than neighboring Commons, both adult and immature?

I found a number of images of longipennis on the web.  Here are some screen 
shots:

Index of /lewis/birds/other_long<http://home.bway.net/lewis/birds/other_long/>

<http://home.bway.net/lewis/birds/other_long/>

Index of /lewis/birds/other_long




Bob Lewis



On Wednesday, June 13, 2018, 9:01:37 PM EDT, Joseph DiCostanzo 
<jdic...@nyc.rr.com<mailto:jdic...@nyc.rr.com>> wrote:


One thing that has to be kept in mind about dark billed and/or dark legged 
Common Terns seen on Long Island in the spring is that our Common Terns (Sterna 
hirundo hirundo) have dark bills and dark legs in winter (both the young birds 
and adults). The possibility that these birds are just S. hirundo hirundo 
retaining aspects of their winter plumage must be considered. Indeed, given the 
breeding and wintering ranges of S. hirundo longipennis, S. hirundo hirundo 
with retained winter characters seems a more likely possibility.

Joe DiCostanzo

Sent from my iPad

--

Pasted here 14 Jun 2018 from note to NYSBirds 8 June 2018:

Subject: Nickerson Beach - Possible Common Tern (longipennis) Species - 
Comments and thoughts welcome
Date: Fri Jun 8 2018 1:09 am
From: Shaibal.Mitra AT csi.cuny.edu
 

Dear Mike and all,



This is an interesting bird, and well worth careful discussion. The photos are, 
as is so often necessarily the case, not ideal for assessing wing pattern and 
structure, and several other features. To my eye, the combination of adult-like 
plumage, darkish bill, not so dark legs, and not very deeply gray underparts is 
consistent with an early season variation of adult hirundo Common Tern that we 
do see from time to time.



The jury is certainly still out on the status of longipennis Common Terns on 
the east coast, and in the past I have eBirded the ones I've seen under regular 
"Common Tern"--but with lots of notation and documentation. Based on the 
checklists you've linked from Jay and Michael, provisionally specifying this 
form, I agree it might be best to take this approach while we work things out. 
At least it would be easier to collect and access the evidence.



Anyway, two of the best (and earliest in NY) candidates for longipennis were 
birds at Cupsogue on 26 Jun 2011 and 24 Jun 2014. I've aggregated photos of 
these at the following link:



https://flic.kr/s/aHskD7WtGd



As you will see, these birds were not only different in soft parts colors and 
plumage from same-aged hirundo COTE, but also different in terms of structure 
and molt (as explained in part in the note to this listserv from 27 Jun 2011, 
copied at the end of this note).



I've seen a few more also, including these two I was able to find quickly just 
now:



https://ebird.org/view/checkli...

https://ebird.org/view/checkli...



It seems odd that the best candidates have always been second-summer (TY) 
birds, but there are two points worth emphasizing on this front. First, 
subadult terns are definitely proven to be prone to wander; second, these 
longipennis candidates differ very strongly in multiple ways from the range of 
variation I've documented in same-aged hirundo COTE over the past 20 years. The 
links in my copied email are long defunct, but I can direct those who are 
interested to long series of images of TY hirundo COTE from our area.



Shai Mitra

Bay Shore

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