The Forster’s Tern frequents all types of wetlands where it breeds, such as freshwater lakes, inland and coastal marshes and salt-pond dykes. The same thing happened when trying to decide how orange the bill was; a well-lit bill could look light orange (perfect for a textbook Forster’s), and then when the head turned and the bill became shaded, it was suddenly the deep orange bill of a Common Tern. As you mentioned, I have seen them at larger reservoirs, especially in the south. It is rarely found on sand, mud or rocky islets, the most suitable breeding habitat being dense mats of floating and emergent vegetation. apparently the Common Tern Sterna hirundo, commonly called Sterne, but also of the "Hirundo marirui or sca-swallowe, a bird much larger than a Swallow Hirundo rustica, neat, white and fork-tailed. Then look at the leg length. Audubon’s climate model predicts a significantly shifting climate space for this species, especially in summer, with only 19% remaining stable and a large northward and even farther inland movement. However, to repeat, Common Tern is unusual here, unusual enough that local bird watchers get excited if a Common Tern shows up. Forster's Tern: Medium tern, pale gray upperparts, black cap, white underparts. (Actually, although I say that I worked at it, that’s not completely true, since this minor quest became an utter pleasure and was the furthest thing from work.) Then watch the parents when they leave to see if you could identify them in flight. Drat. Like many birders, I struggled with these terns for a long, long time. Overall this can give an impression of Arctics having a small round-looking head; Adult Common Terns can look rather dusky grey compared to the more uniformly pale grey of adult Arctic Terns. Breeding Forster's usually have a white breast, unlike Common Tern's gray breast. Many birders will be able to recognize this bird as one of the medium-sized terns, which here in the eastern US narrows down to Forster’s or Common Tern. Don’t expect it to be entirely clear, especially when starting out. But which is it? Yes, its a tern, but which one? © Steve Tucker | Macaulay Library California, May 06, 2017 The red really popped when I looked at these birds. Now that you’ve read this far, I want to point out that despite having all of these identification points, distinguishing these two species still can be difficult. Compare the photos of soaring birds below. Common Tern has red legs in breeding plumage, but these darken to near black in non-breeding plumage. ), or they were difficult to see (the edging on the tail feathers is seldom apparent even in good lighting, and only in flight). Another field mark of the Common Tern are the wings. Well, Forster’s Tern is supposed to have a light orange bill, whiter body and wings, a tail that extends beyond the folded wingtips, and longer legs, while Common Tern sports a deeper orange bill, gray body and darker wings, a tail extending the same length as the wingtips, and with black on its outermost tail feathers. Many hours were spent scouring images on Google, studying Sibley, etc. Note the relative lack of any black at the tip of the upper wings. Common Terns are usually found out on the larger bodies of water like Lk St. Clair or the Great Lakes… Forster’s Terns are usually found inland in marshy areas… They can be difficult to ID in flight.. This can vary between individuals, but can be fun to follow. By clicking any of the links in the table below, a map will be pulled up on your screen. Status in Tennessee: Forster's Tern is fairly common during spring and fall migration, and rare at other times of the year. For me the folded wingtips are actually more reliable, with the Common Tern having black wingtips and the Forster’s Tern having grayish wingtips. But note the leg length; the Common Tern has shorter legs than the Forster’s, just like the field guides say. It has a black cap, commonly found in terns. Pictures 2 and 3 are the same bird, and 4 and 5 are the same bird. If we start with the bill color, I would have a hard time deciding if this is a Forster’s or Common Tern, perhaps leaning slightly and uncomfortably towards the darker bill of a Common Tern. Leg length is hard to judge when they are not closely juxtaposed like this, but can be another supporting feature to look for in mixed flocks. A succession of kerrs is used by the female as a begging call during courtship. Forster’s Tern in flight. Forster’s Terns are sometimes referred to as “Marsh Tern” because they utilize this particular habitat type for breeding and foraging. Look at the two terns in the photo below and decide what you think they are. Compared to the Common Tern, the streamer-tailed Forster’s Tern nests more inland and farther south, and winters farther north. For me, looking at the lower wing surface or body was frustrating because it was so dependent upon lighting, and with the sun being above, these areas alternated between sun and shade during flight, turning identification into a guessing game. Is that body gray or does it just look gray because it is shaded from the sun? The Forster’s tern’s bill is proportionately long and large, though still within a range that would be termed medium, and black most of the year.
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