Common or Roseate Terns - Connecticut (1 Viewer)

[Parrots]

Hi. As a beginner, I'm having a bit of trouble differentiating Roseate and Common Terns in cases where certain field marks (all white tail of Roseate, etc.) aren't readily visible. I've attached some photos from a location in CT where both species are present -- I saw a few Roseate juveniles and adults feeding them, while Common Terns were much more common. This was my first time seeing Roseates.













Any help in identifying these would be much appreciated. Thanks! Had a great time watching them.

 

[Butty]

My first quick guess would be that (all of?) these are Forster's terns. What features lead you to thinking they're roseate terns?

 

[Parrots]

My first quick guess would be that (all of?) these are Forster's terns. What features lead you to thinking they're roseate terns?

This site is a post-breeding location for Common and Roseate Terns, and juveniles of both species were present -- I'm just a bit stumped when I can't see the white tail (Common Terns from what I understand have black outer tail feathers). Forster's are locally uncommon/rare for this location. Given that it's late summer, most of the Roseates have a half/half red/black bill rather than a solid black bill. Here's an example bird that I think was a Roseate:



Here's another where the tail length is more visible:




In the cases above, I don't yet have much of a sense of the species' general impression when the tail isn't a give-away, especially when the ratio of the bills' red/black shades are approaching those of Common Terns in some cases.

 

[Butty]

Common Terns from what I understand have black outer tail feathers

Not that simple. It's only the outer web (which is very narrow) of the outermost feather which is black.

Given that it's late summer, most of the Roseates have a half/half red/black bill rather than a solid black bill

But the 'red' should be dark red - not orangey, as here. Orangey bills are normally an indicator for Forster's tern.
Roseate tern is a pale bird - and especially strikingly so the wings, in flight.
But terns are tricky, no doubt.

 

[Parrots]

If I had to guess on the initial pictures, and I could definitely be very much off, I'd say Common for the final one (tail doesn't seem to exceed the length of wings by much, black wingtips), Roseate for the one above it (tail looks to be solid white but that could be the angle), Common? for the one above that (dark shades in the tail possibly?), totally unsure about the fourth up (hard to determine tail length/color), Common for the fifth up (tail even with wingtips when folded), possibly Roseate for the one above that (bill looks darker than the average for Common, hard to see tail but looks to possibly be white and slightly longer than wings), no clue about the one in flight, and the first two seem tricky (tail possibly white for the first, bill fairly dark for both, but for the second the tail doesn't look much longer than wings).
Hoping to find some more marks for telling these apart -- in a couple cases the plumage looked much whiter for Roseates but in others I couldn't tell much of a difference.

 

[Parrots]

Not that simple. It's only the outer web (which is very narrow) of the outermost feather which is black.


But the 'red' should be dark red - not orangey, as here. Orangey bills are normally an indicator for Forster's tern.
Roseate tern is a pale bird - and especially strikingly so the wings, in flight.
But terns are tricky, no doubt.

That is very helpful. I think it could also be the camera? (or variation in bill color?) to some extent though as some of the other pictures look orangey.

 

[Butty]

The flying juvenile in no. 3 of the last batch looks like a common tern (dark secondaries and inner primaries).

 

[Parrots]

Yup, the adult scared it off while feeding young -- meant to illustrate the orangey looking adult Roseate bill

I think it could be the lighting -- the Common Tern bills can look orange rather than red as well, here's one feeding young:





In other cases they look a slightly darker red:


That last one definitely shows how narrow the black outer web is

 

[Brian J Small]

Parrots

You have a mix of Common and Roseate and posted a lot of photos, but the first four perched birds on post 1 are all Roseate.

Post 5 - agree all Roseate apart from front left on image which doesn't have the lovely contrast in the primaries between silvery white (moulted and newer) inner primaries and the black outer that can characterise Roseate.

To illustrate this, in post 1 compare the silvery white inner primaries on the first four perched birds (Roseate) with the largely darker primaries of the last 3 on post 1 (Common).

Brian

 

[birdmeister]

Parrots

You have a mix of Common and Roseate and posted a lot of photos, but the first four perched birds on post 1 are all Roseate.

Post 5 - agree all Roseate apart from front left on image which doesn't have the lovely contrast in the primaries between silvery white (moulted and newer) inner primaries and the black outer that can characterise Roseate.

To illustrate this, in post 1 compare the silvery white inner primaries on the first four perched birds (Roseate) with the largely darker primaries of the last 3 on post 1 (Common).

Brian

Agree with Brian. Just wanted to add that presence of metal as well as colored leg bands/rings is a supporting feature for a range-restricted breeder like Roseate in my opinion.

 

[Parrots]

Thanks for the help! I'll keep an eye out for those marks in the future.

 

[njlarsen]

On flying birds, one of the things to look out for is absence (Roseate) vs presence of black tips to primaries when wing is seen from the underside.

Niels