ML609118933
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Observation details
After spending some time at the St. Croix River Boat Ramp and Boomsite/boat launch I was alerted to a call that, in the moment, I not readily familiar with. A high pitched, grating “kee-are”. After a moment of scanning I located the bird in flight and initially I could see it was a large, slim and “gangly” tern. Deep wing-beats and calling constantly, I immediately took a recording and a few photos through the trees as it made the first pass overhead. I stuck with the bird as I noticed the bill was a yellow-gold color rather than a blood-red, or even orange for that matter. The bird made a lazy circle around the launch and I was able to get a look at the head and bill from a better perspective. I could see there was a distinct, white, break in the forehead from the bill and a light peppering of coloration on the head followed by dark band from the eye to the back of the head, forming a slightly crested look. The wings were noticeably pale, specifically, lacking any color along the underside of the wing where you would normally see black for a Caspian; this bird only showing a thin trailing edge. I notified a few local Facebook groups that I may have had something worth investigating as the field marks and calls were not lining up with Caspian Tern. The bird continued to drift to the north and after a brief hiatus of around 5 minutes the bird made a large lap south and flew over the boomsite a second time. Again, continuously calling and a little further out, I was able to redeem photos from a shallower angle and additional looks at the bird and field marks deviating from Caspian. In a state of incredulity, myself and others concluded that the bird was likely a Royal Tern in non-breeding plumage. Losing daylight fast, the bird drifted and circled to the north again and eventually lost sight of the bird. The bird was once again observed by a few birders flying down river around sunset before disappearing out of sight all together. Further discussion and consultation with birders with far and away more experience with terns than myself concluded the bird was indeed a Royal Tern. Similar species- Caspian Tern- Being the most likely suspect at any time of the year. I arrived at the conclusion that the bird was not a Caspian Tern after viewing it the second time. Overall structure of the bird was thinner, wings not as broad, and proportionally appeared different. Underside of the wing had a dark, thin trailing edge with pale inner primaries rather than a more complete, darker under wing as a Caspian would show. Vocalizations were higher pitched than any Caspian Tern I’ve heard and prompted me to investigate the bird further. In addition, bill color was incorrect for Caspian at any age or plumage as it was yellow-gold and not blood-red or orange. Bill thickness was noticeably thinner than a Caspian as well. Elegant Tern - Bill structure was comparatively too thick and not as “droopy” for an Elegant, ideally, the thickness was better fit for Royal which would land in between Elegant and Caspian.
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