Weekend Highlight - Arctic Tern

It was a fairly long week at work, even though Monday was a holiday it still felt long. All I could think about was waking up early on Saturday and birding the flats at Cupsogue Beach County Park to study some terns. I really wanted to find an Arctic Tern, the furthest traveling migrant in the world. Arctic Terns breed in the Arctic and spend their winters in Antarctica making roughly up to a 44, 000 mile round trip per year. The majority of their migration takes place over open sea, where their buoyant, seemingly effortless wing beats carry them across the ocean. Every year, a handful of Long Island birders get lucky enough to view these birds as they touch down on the island for a quick rest stop. 

Arctic Tern - Cupsogue Beach C.P., 5/20/13 - Note many good field marks
captured in this image. Thin black trailing edge of outer primaries, relatively
short, deep red bill, short legs and an extensive black cap (image captured
with an iPhone and Meopix Adapter through Meostar S2 Spotting Scope).
On 5/20/13, I finally got to study my first, real life Arctic Terns out on the flats at Cupsogue Beach with Shai Mitra. Despite the rolling fog I was able to make out the 2 individuals that Shai had found, both subtly differing from one another. Having Shai’s expert commentary on the sideline was invaluable. I don’t know that there’s one single book that covers all of the tern information that he doled out. The first adult-type Arctic Tern remained on site for about ten minutes past my arrival and eventually took to the ocean, flying directly overhead and lending a few quick “kip” notes. It must have only been 5 minutes until Shai picked out another adult-type Arctic on the flats. I have routinely missed Arctic Tern in previous years since I’ve been birding more intensely. This was a highly sought lifer for me and it was great to finally observe these birds. 

 So as I was initially saying, I was anxious to get out to Cupsogue this past weekend and search for “my own” Arctic Tern. I arrived at Cupsogue shortly at 7:30 AM on the morning of 6/1/13. I started out with a brief sea watch to see if any morning pelagic wanderers were within the reaches of shore. It was pretty quiet with only a few Sooty Shearwaters loitering around just east of the jetty at Moriches Inlet. I decided to cross to the bayside flats and start studying terns. I ran into Steve Walter, who takes dynamite nature photographs and was also out looking for Arctic Tern. After about 3 hours of roaming around the flats we decided to go revisit a group of terns that were frequenting the north end of the flats. Arctic Terns will drop in periodically throughout the day and can really show up at any time. While glassing a large congregation of terns, primarily composed of Commons, I picked out an adult-type Arctic Tern. Picking out an Arctic Tern definitely takes a bit of time and scrutiny as they look superficially like the other 3 members of the Sterna genus or “medium-sized terns”, most closely resembling Common Tern. Carefully examining each and every individual is extremely important. 
Arctic Tern - Cupsogue Beach C.P., 6/1/13 - another adult-type bird. Note the uniform gray primaries, extensive black
cap and a deep red bill showing a bit of a dusky tip. Also notice the small white gap between the upper mandible and
black cap, usually more broad on Common Tern (Image captured with an iPhone and Meopix Adpater though a Meostar S2 Spotting Scope).
Like many birds, terns appear differently depending on their age and plumage cycle. In this instance, I am only focusing on Adult-type individuals. Some clues to look for when searching for an adult Arctic Tern are:

  • Bill Color - A deeper red toned bill (some showing a slight dusky tip). Arctic Terns generally show a shorter bill compared to their other Sterna counterparts but this is sometimes difficult to judge in the field.
  • Head & Face - Rounder headed with black cap extending further down past the eye. White facial feathers between the upper mandible and black cap may appear as a narrow white line. The line or gap may appear more broad on Common Tern.
  • Underparts - darker gray throughout underparts, although in bright conditions this will not always be so apparent. I have noticed that this feature seems better viewed when the bird is in flight. 
  • Leg Length - Arctic Terns will appear short-legged. Another caution that is dependent upon the contour of the ground in which it stands. Other Sternas can appear this way if they’re standing in a small divot, ditch, soft substrate, etc.
  • Tail Length - Outer tips of tail feathers extend beyond wing tips
  • Underwing Pattern - this is a great feature that can be noted in all plumages of Arctic Terns and separates it from the others. The pattern of the trailing edge of the 7-8 primary wing feathers lends the effect of a dark, sharp edge. Commons appear more blotchier and thicker. 
  • Upperwing Pattern - Uniform gray throughout. When sitting, the birds primary extension will appear uniformly gray.
  • Flight - Said to have a more buoyant, effortless flight. 
Arctic Tern - Cupsogue Beach C.P., 6/1/13 - Not the best image but you can
note the darker gray undperparts, thin black trailing edge of outer primaries.
The dark body contrasting with the neck and cap almost creates the look of
a white line (image captured with an iPhone and Meopix Adapter though a
Meostar S2 Spotting Scope).

Arctic Tern - Cupsogue Beach C.P., 6/1/13 - Again, note
the dark gray body, creating the white line effect where face
meets cap. See the outer 8 primaries tipped with black (image
captured with an iPhone and Meopix Adapter though a
Meostar S2 Spotting Scope).


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