I subsequently learned(2015),that my supposed comment was nearer the mark,than I could ever have realised.The ponds,there are two,are not stream fed.So,when the swans were introduced,there being just mum and dad,that was ok.there was sufficient "food" for the pair,but when the cygnets arrived,any food in the ponds was quickly consumed,leading to fights betweeen the growing young ones and the parents.So,sadly,the RSPB,were summoned and the swans were re-homed.