You expect outstanding graphics from Firefly Books, but Extreme Birds also excels at wit. It’s a sort of illustrated Guinness Book of Ornithological Records, highlighting the birds with the biggest eyes, heaviest testes, and warmest nests. Some of the delight is in the author’s choice of categories: Pallas’s sandgrouse, native to central Asia, wins the “snuggest underwear” prize for the thickness and coverage of the downy feathers beneath its decorative plumage. But Mother Nature provides plenty of wit herself. The “funniest forager,” for instance, is the bassian thrush of eastern Australia, which farts repeatedly when feeding. The flatulence, we are told, startles earthworms into revealing their location. As with so many of the feathered factlets in this book, who knew?