A Pigeon is left for Roger to release at Strickland Junction in Pigeon Post. Nancy says that Uncle Jim gave us one, and called him Homer because he was a homing pigeon. They got two more for company, which they called Sophocles and Sappho after looking up Greek poets (PP1). When they go camping, Dick has to make the returning pigeon ring a bell to alert Mrs Blackett (PP6).
When Sappho wakes Mrs Blackett at five o'clock Nancy says it was that wretched Sappho although when Titty says she gave her some hemp, Nancy says You must never give them hemp "before" a flight. But I expect she'd have dawdled anyway (PP12). Later when Titty says Sappho's turn Nancy says Better send Sophocles .... you can't depend on Sappho (PP31). At the end although Titty says that you can't count on Sappho, Sappho carries the message which calls out Colonel Jolys and the firefighters (PP31).
At the beginning of The Picts and the Martyrs Dick and Dot go to see the pigeons (PM2). Then with Timothy banished to the houseboat he sends urgent messages to Beckfoot by pigeon post. Sophocles had been lost, so they have only Sappho and Homer (PM10). Returning from their first voyage, the Ds hear the pigeon alarm, which Nancy silences (PM16,18).