I'm filming Trumpeter Swans for a narrated movie I'll post on my YouTube channel (Jo Alwood). I filmed several of them seemingly chasing each other around in the water. Nobody was nipping at another swan, but one of them did have that hook-necked posture that I associate with attack. Do they play with each other? Did one of them chasing another one get all the neighbors stirred up? I'll post a picture of some of the action, though you'd need to see the whole film clip, and I can't get that to post here.
Hi Jo, welcome to the forum, you should be able to post the You tube URL of your film clip on here, just copy & paste the link in reply box! Sorry can't help re behaviour though, no experience but others may be able to, not so busy on here being christmas day!
2013 photos & vids here
eff37 on Flickr
Don't think it possible to help with any more info Jo as you have come on to a UK bird forum and we don't have Trumpeter Swans in the wild, a check on Google on one site says these swans are very territorial! We have some in captivity here ...
https://www.slim-bridge.co.uk/trumpeter%20swan.html
but doubt this will be of much help to you!