Common pochard and small populations are sometimes observed on the River Thames. Large numbers stay overwinter in Great Britain, after the birds retreat from Russia and Scandinavia. These are gregarious birds, forming large flocks in winter, often mixed with other diving ducks such as the tufted duck, with which they are known to hybridise. These birds feed mainly by diving or dabbling. They eat aquatic plants with some molluscs, aquatic insects and small fish. They often feed at night, and will up-end for food as well as the more characteristic diving. In number of countries the population of Common Pochard is decreasing
What Bird is That? according to their usual habitat. The accompanying text included brief notes on distribution, breeding and behaviour. While initial sales were poor, history tells us that Cayley had accurately discerned a market need and successfully responded to it. During WWII sales accelerated and Cayley’s first collection, reprinted time and time again, eventually became a household name among birdwatchers and the book was recognised as an Australian classic. The original sponsorship of "What Bird is That?" proved a great investment for the Gould League, who benefited from the sale of its numerous reprints and revised editions. By 1960, it was rated the