My Wings Big Year… an hour each day gnawing away at the question: what is a bird? One aspect of that multifaceted question is: how big are they? Noah Strycker, in “Birding Without Borders,” offers a typical stylish answer: “The smallest, the Bee Hummingbird of Cuba, could perch comfortably on the toenail of the largest, the Ostrich.” Ever since I read that, I’ve pictured that petite hummingbird resting for a moment on the gnarled toenail of an ostrich. Such an image is a much stronger mnemonic than 5 centimeters compared to 2.75 meters.