Bob,

I am not saying a Siberian longipennis race Common Tern is a total 
impossibility here in the east. Among shorebirds, many of us saw the 
Broad-billed Sandpiper at Jamaica Bay years ago and there are multiple records 
of Sharp-tailed Sandpipers in the northeast. I am saying that an aberrant 
hirundo would fit the bill just as well and seems much more likely.

At least the Gray-hooded Gull is from this (Western) hemisphere and it does 
occur together with wintering Laughing Gulls on the north coast of South 
America. You just don’t have that same possibility for a longipennis to take up 
with a northbound flock of hirundo.

Joe

Sent from my iPad

> On Jun 14, 2018, at 10:44 AM, Robert Lewis <rfer...@yahoo.com> wrote:
> 
> Thanks for the thorough reply.   As a long time student of gulls, I am aware 
> of the concepts you delineated about timing and odd individuals that don't 
> fit the norms.  
> 
> As for how did it (they) get here, stranger things have happened, namely the 
> Gray-hooded gull of a few years back.  Ship-assisted?  Who knows.
> 
> Bob Lewis
> 
> On Thursday, June 14, 2018, 9:08:12 AM EDT, Joseph DiCostanzo 
> <jdic...@nyc.rr.com> wrote:
> 
> 
> 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> 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
>> 
>> Index of /lewis/birds/other_long
>> 
>> Bob Lewis
>> 
>> 
>> 
>> On Wednesday, June 13, 2018, 9:01:37 PM EDT, Joseph DiCostanzo 
>> <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
>> 
>> --
>> 
>> --

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