Diving into the juvenile Marsh Terns identification
Written by Menno van Duijn en Wouter Teunissen

In late summer (August-September) one can see marsh terns like Black-, White-winged- and Whiskered Tern on their roosting and foraging site predominantly along the IJsselmeer and the Wadden Sea. By that time the adults have started moulting to their winter plumage, starting from their heads. These adults often still show the easy features to recognise them but the juveniles are more challenging.

All three can be seen together with Black Tern being the most common. Best sites are along the Afsluitdijk. Large flocks can be found foraging near the locks when the water moves in or out with the tide. And at the end of the day these groups gather at the sand banks to roost. Black Tern is the most abundant but a trained eye can pick out a White-winged Tern or Whiskered Tern.

In order to help you out we’ve made a short list of each species to help you find one of two scarcer species in their juvenile plumage in flight and settled. All three species can be confused with first calendar year Common or Arctic Tern but all are smaller and those two mainly have two-coloured bill (orange base and dark tip) and longer (outer) tail feathers.

More detailed id-article of British Birds

Black Tern

Resting (photo Rico Otten)

  • Grey wing with dark brown markings contrasting to the dark brown mantle (darkness varies);
  • Long and pointed dark bill;
  • On the white chest a dark patch extending from the mantle to the chest;
  • Black cap and white forehead and cheek. The white of the auriculars reaches to the ear but often doesn’t extend from the eye line to the nape.

In flight (photo Thomas van der Es)

  • Distinct dark brown collar extends from the mantle towards the overall white breast;
  • Dark brown mantle and dark brown markings on the upper wing doesn’t create such a contrast compared to the other two marsh terns;
  • All tail feathers are grey;
  • Grey rump, no contrast to the tail.

Juvenile Black Tern, photo Rico Otten

Juvenile Black Tern, photo Thomas van der Es

White-winged Tern

Resting

  • Contrasting grey wings compared to the dark brown mantle (darkness varies);
  • Shorter more compact dark bill compared to Black Tern;
  • Clear white chest, no extending dark patch;
  • Black and white head where the white patch in the auriculars reaches towards the crown (over the eye-line) and more back into the neck;
  • Longer legs compared to Black Tern.

In flight

  • Dark brown mantle contrasting to the grey upper wings with less dark markings;
  • Clear white underparts, lacking a collar extending to the side breast;
  • Grey tail with white outer tail feathers;
  • White rump, contrasting to dark mantle and grey tail

Juvenile White-winged Tern, photo F&S Martens

Juvenile White-winged Tern, photo Kris de Rouck

Whiskered Tern

Resting

  • Looks more like a miniature juvenile Gull-billed Tern then a marsh tern;
  • Clear grey wing with minor markings and a light brown mantle;
  • Short, stubby dark bill;
  • Dark cap on a white head, the white doesn’t extend in the auricular area.

In flight

  • Again a more juvenile Gull-billed Tern like impression;
  • Light brown mantle markings create a contrast to the more clear grey upper wings;
  • Small darker collar extending from the mantle to the breast;
  • Grey tail with white outer tail feathers;
  • Grey rump, hardly any contrast to the mantle and tail.

Whiskered Tern, photo Richard Ubels

Whiskered Tern, photo Claudia Burger