The Tweed Valley Osprey Project (TVOP) said it was behaviour which "wouldn't be out of place on an episode of Jeremy Kyle for ospreys".
The images show the male bird - SS - in the nest along with "squabbling females" Mrs O and FS2.
Information officer Diane Bennett said they hoped it would all end with an egg appearing in the nest.
"Mrs O has not given up her battle to remain as the partner of SS at the main nest even though FS2 has tried to usurp her and steal her partner," she said.
"It seems that having the attention of two females demanding fish and moving in on his territory is all a little too much for SS.
"The squabbling females were both on the nest with SS but rather than make a choice and send one of them packing, he wimped out and flew off leaving the females to battle it out for themselves."
However, she said the male bird took "full advantage of the situation" and mated with "whichever female was alone at the nest whenever he returned".
Ms Bennett said it appeared that Mrs O now seemed to be winning the battle as FS2 had not been seen at the nest for a few days.
"She could be laying eggs which have been fertilised by SS into another nest," she said.
"This is the sort of behaviour that wouldn't be out of place on an episode of Jeremy Kyle for ospreys."
She added that they hoped to see an egg in the nest soon before time ran out for any chicks this season.
The battle of two female birds for the affections of one male osprey has been captured on CCTV in the Borders.