From James A. Secord, "Nature's Fancy: Charles Darwin and the Breeding of Pigeons" (Isis 72:2 [June 1981]: 162-86):
[I]nitially he did not intend to focus on the fancy pigeons. . . . This situation soon changed. By the end of March 1855, little more than a week after the subject first appears in his letters, Darwin had decided to commit himself to a greatly extended study of the domestic pigeon. "Yarrell has persuaded me to attempt it," he wrote, "and I am now fitting up a place, and have written to Baily about prices, &c. &c." By 23 May Darwin had assumed his usual enthusiasm for the subject of a new study. He set up an elaborate pigeon house in the back of the garden at Down, bought birds from John Baily of Fleet Street, one of the premier judges and poultry dealers in England, and began his breeding experiments and observations without delay. Reversing his earlier judgment, Darwin told Fox that "they are a decided amusement to me, and delight to H[enrietta]," his eldest daughter. By November he was deeply immersed in the subject and was observing daily seven or eight pairs. "I will show you my Pigeons!" he promised Lyell, "which are the greatest treat, in my opinion, which can be offered to [a] human being." At the peak of his researches in Juen of 1857 Darwin was keeping almost ninety birds, includign some extremely rare and choice specimens.