One Heron, one Cormorant and two Canada Geese - but what species are the ducks?

                                                

During his lifetime, London-based artist and college lecturer Julian Trevelyan (1910-1988) was not noted for his studies of birds, but one of them attracted plenty of interest when it was offered for sale at an auction conducted by auction house Roseberys.  His etching of waterbirds - number 18 of a limited edition of 75 prints - was expected to sell for between £300 and £500 but bidding was such that the study fetched £1,050 including hammer price and 31.2 per cent buyer's premium. The scene is thought to depict the birdlife on the River Thames at Hammersmith where Trevelyan lived and had his studio.