Posts Tagged ‘Common tern’

Common and Roseate Terns in Flight

August 17, 2020

Juvenile Common Tern (left) and juvenile Roseate Tern, West Haven, CT August 2020 (composite: Julian Hough). Note the stout, blackish bill and hood of the Roseate and the body proportions compared to the Common Tern and the paler mid-wing panel, broader white trailing edge to the primaries and the diagnostic whitish outer web to the outermost tail feather on the Roseate. Click to view hi-res.

A good number of juvenile terns are mixing in with the post-breeding flocks at Sandy Point, New Haven, CT. Juvenile Roseates are not frequently seen here, but several have been present and afforded me a nice chance to study them.

On the deck

  • Standing juvenile Common Terns have pale orange bill bases and pale orange-flesh legs with a clean white forehead.
  • Juvenile Roseate Terns have dark blackish-brown legs, a complete black bill and a finely streaked blackish forehead that often extends all the way to the bill base, giving them a characteristic “hooded” look.

In Flight

In flight, especially at a distance, they can be hard to identify in a large mixed flock of flying terns. Their distinctive, di-syllabic “Chrr-uitt” call is often a clue to their presence and it is definitely a call any would-be searchers should memorize.

In flight, like adult Roseates, juveniles often look a bit skinnier and more “pure white” compared to Common Terns. With experience, they look slightly longer-necked, narrower winged and longer-tailed behind the wing (probably due to their shorter wings than longer tails) compared with the more even proportions of Common Tern. The more whiter plumage, especially the rump and tail and the paler mid-wing contrasting a bit more on average with the dark outer wing may be noticeable. These features will be hard to discern in a mixed flock, flying around, so look for the more rapid, shallow wingbeats of Roseate that is often helpful with experience. The dark, hooded look should also be noticeable at a distance helping cement any identifications.

On closer views, some minutiae, that helps differentiate these two species are:

  • the outer web to the outermost tail feather is blackish-gray in Common Tern and white in Roseate (both adult and juvenile). If the tern you are looking at has a dark outer edge of the outermost tail feather it isn’t a Roseate.
  • on Roseate, the tips to the secondaries and particularly the primaries are broadly edged white unlike in Common Tern.
  • the upperpart markings in Roseate are more contrasting, giving a “black and white” pattern formed by broad blackish “c” marks to the rear scapulars. In Common, the dark subterminal marking are less dark and often the whole mantle is washed with ochre-brown.
  • the outer primaries often contrast with a paler mid-wing panel in Roseates while in Common Tern the whole wing tends to be a more even gray.