Swan on coots nest

[tigertom]

Hi can any one tell me what was going on hear. A few weeks back on a local lake I was watching the antics of a coot and great crested grebe who both had mates on nests both very close together when young female swan came on the lake close to both the coots and grebes nests, and first tried to get to grebes nest but was attacked from under water by none sitting grebe. But the swan then turned on the coots nest and chased the sitting bird from nest and then seemed to climb on the coots nest and try to brood the coots eggs. The result was some how in all the commotion the coot nest was ok,(went on to hatch 6eggs) grebes nest washed out,(now got new nest up other end of lake) young female swan was in end cheased off the lake by local pair who did not nest this year. Any one no what this young female swan was doing THANKS