According to the Birds of the World entry, they copulate while floating:
Copulation
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Occurs 2-;4 wk after pair formation, usually on rocks in stream but
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sometimes as birds float downstream (S. Bouricius and G. Evans, personal
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communication). Continues for about 15 s; repeated 3-;4 times within 2 min (
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3 <https://birdsoftheworld.org/bow/species/amedip/cur/references#REF2403>).
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Copulation accompanied by singing and loud *jik* Call Series (10
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<https://birdsoftheworld.org/bow/species/amedip/cur/references#REF2410>;
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see Sounds and Vocal Behavior
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<https://birdsoftheworld.org/bow/species/amedip/sounds#vocal>:
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Vocalizations
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<https://birdsoftheworld.org/bow/species/amedip/sounds#vocal>). Two
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reports of midair copulation: following neck-stretching ritual, female took
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off in slow flight; aerial copulation ensued 5 m over water, then birds
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fell together in free drop to water, continued copulation for 6-;7 s while
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floating downstream through riffles, then separated and preened (3
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<https://birdsoftheworld.org/bow/species/amedip/cur/references#REF2403>;
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S. Bouricius, personal communication).
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The "3" reference in the text is "Bakus, G. J. (1959a). Observations of the
life history of the dipper in Montana. Auk 76:190-207."
HTH!
Preston Mui
prestonmui at gmail.com
http://prestonmui.github.io/
(425) 223-8450
On Sat, Jun 15, 2024 at 12:10 PM Trileigh Tucker via Tweeters <
tweeters at u.washington.edu> wrote:
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Hi Norm,
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This is a fascinating observation! If folks reply to you directly (without
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copy to Tweeters), I'd love to hear any insights you gain.
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Thanks much,
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Trileigh
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*Trileigh Tucker, PhD*
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*Professor Emerita, Environmental Studies, Seattle University*
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*Pelly Valley, West Seattle *
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*Writer, Photographer, Fine Artist*
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*NaturalPresenceArts.com <http://naturalpresencearts.com/>*
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*From: *normandlaura donelson via Tweeters <tweeters at u.washington.edu>
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*Date: *Friday, June 14, 2024 at 5:48 PM
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*To: *tweeters at u.washington.edu <tweeters at u.washington.edu>
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*Subject: *[Tweeters] Dipper Behavior Surprise
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Yesterday I birded the Oxbow Loop Trail, off Middle Fork Snoqualmie River
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Road east of North Bend. New trail for me, and I highly recommend it!
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I took the spur trail down to the riverside, and soon spotted a pair of
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Dippers. They landed on a large rock at midstream, then on a smaller
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nearby rock. There was some fluttering, then I saw the pair of them
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floating downstream, one atop the other! There was still much fluttering
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from the upper bird, as it tried to hold its position. This only lasted
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for a few seconds.
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I can only think they were copulating. Have any of you seen this
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behavior, or heard of it before? The closest I got in a quick online
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search of the literature was a mention of an observation in which
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copulation occurred while the female was standing submerged in the water.
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If this floating copulation behavior has been seen before (and
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realistically, I have to suppose it has), I couldn't find evidence of it.
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I should also note the alternative possibility that it could have been two
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males in Dipper combat, though nothing about the incident struck me that
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way.
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Interested in any observations you may have,
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Norm Donelson
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