Roseate Terns

After a couple of sporadic seasons, the tern colony at Sandy point is bustling with activity with a good post-breeding flock in evidence. It is this time of year that Roseate Terns can be found hanging out with the local Common Terns. They are an uncommon breeder in CT, and many of the coastal Roseate records relate to wandering adults from breeding colonies at Faulkner Island in Long island Sound.

One of the challenges can be picking out these uncommon visitors from the masses of similar looking Common Terns. Simply put, Roseate’s are slightly bigger, ‘whiter’ with a longer, more tapered bill that is often (but not always) blackish. Since many adult Common Terns are acquiring a darker, more blackish bill now as they begin their moult to winter plumage, bill color may be of limited use when trying to pick out a Roseate.  The masses of Common Terns can often mask the other more subtle features and make picking out a Roseate a little more difficult, especially if birds are distant.

Adult Roseate Tern and Common, Sandy Point, West Haven, August 2012 (Julian Hough).

One of the best ways of locating an adult Roseate Tern is to look at the wingtips of sitting birds. Common Terns have mostly dark, worn blackish primaries. Adult Roseate’s often show a very pale and contrasting panel on the inner primaries that contrast with the dark outer webs. Once you find a bird exhibiting this feature, you can check other features listed above.

Wingtips in Common and Roseate Tern.
Note pale, contrasting primary panel on Roseate. This is due to most of primaries being pale grey with white fringes. Longer tail streamers extending past tail often obvious.

Some Roseate’s in breeding plumage develop a red base to the bill that can be extensive and can be similar to Common Tern. Typically the dark is more extensive and the division between red and black is less clear cut on Roseate, but they can retain this into August, so not every Roseate will have a blackish bill. The gonydeal angle of the bill on Roseate is closer to the base of the bill which results in a more fine-tapered bill.

Adult Roseate Tern (Julian Hough). Note bill is quite red on this bird. Also, note that the dark trailing edge often obvious on Common Tern is reduced in Roseate due to the pale fringes of most of the outer primaries. Also, the dark outer web of the outer tail feathers on Common tern is absent on Roseate Tern.

Roseate’s have tail streamers that project beyond the tail, a result of them having shorter wings than Common Tern rather than longer tail streamers. Their flight manner is different with shallow, rapid wingbeats. Their call is a Semipalmated Plover-like “chuwit”, quite distinctive once learned.

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One Response to “Roseate Terns”

  1. penny solum Says:

    Excellent! Thanks, Julian, Penny

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