It looks as though it is quite plausible that the Red Knots were wearing radio tags, although I'd dearly love to get a better look at them.
Barry Truitt is a Chief Conservation Scientist with the Nature Conservancy. He is involved in tagging Red Knots and was kind enough to answer my questions about Red Knots and radio tagging. Here, in part, is his reply to me.
It indeed does appear that at least one of the red knots in your photo is trailing a radio antennae. It is unclear to me that the other bird is trailing a radio antennae as the wire doesn't appear long enough to be an antennae. Like you, it would be hard to imagine two radio tagged birds flying together but stranger things have happened.
Yes indeed we did radio tag red knots (approximately 20) in Virginia this spring as part of a project looking at their migration stopover ecology here. I also believe that other researchers in Delaware might also be radio tagging red knots there. Radio tags are only adequate for close range tracking (5 to 10 kms) and last about 60 days before the battery dies or they fall off the bird so we are not presently following or tracking these birds.

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Very cool to see that antenna, and to get the info on the antennae. I haven’t even seen many banded birds, so one with telemetry attached would be really, really exciting.
By the way, my ipod is currently playing “From Clare to Here” – a different Clare, but still a long way from here. 🙂
Hi Wren,
It was pretty serendipitous for sure. It has generated a fair amount of interest amongst the shorebird recovery people down the eastern seaboard.
I’ll have to search out that song on iTunes.