As extinctions go, the demise of the passenger pigeon was more than usually poignant. The dodo and the sea cow may have vacated the planet without anyone really noticing, but the last rites of a species that had filled the transatlantic skies a generation or two before its decline took place more or less in public. A single female, Martha, remained in Cincinnati Zoo, and her death, in September 1914, was announced to the world in the certain knowledge that no other survivor remained.The wildlife photographer John Aitchison began his elegy to Martha and her kind (10 March) by stressing their original superabundance. It was estimated that a population of between three to five billion greeted the first European visitors to the American mainland. The birds travelled in huge, noisy flocks, who