Trumpeter swan Edward Preble wrote of the decline in the hunt with the number sold annually dropping from 1,312 in 1854 to 122 in 1877. Sir John Richardson wrote in 1831 that the trumpeter "is the most common Swan in the interior of the fur-counties... It is to the trumpeter that the bulk of the Swan-skins imported by the Hudson's Bay Company belong." By the early twentieth century breeding trumpeter swans were nearly extirpated in the United States except for a remnant population of fewer than 70 wild trumpeters in remote hot springs in or near Yellowstone National Park. Surprising news came
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