原版书书名：Programming PHP, 3rd Edition
The animal on the cover of Programming PHP, Third Edition is a cuckoo (Cuculus canorus). Cuckoos epitomize minimal effort. The common cuckoo doesn’t build a nest—instead, the female cuckoo finds another bird’s nest that already contains eggs and lays an egg in it (a process she may repeat up to 25 times, leaving 1 egg per nest). The nest mother rarely notices the addition, and usually incubates the egg and then feeds the hatchling as if it were her own. Why don’t nest mothers notice that the cuckoo’s eggs are different from their own? Recent research suggests that it’s because all eggs look the same in the ultraviolet spectrum, in which birds can see.
When they hatch, the baby cuckoos push all the other eggs out of the nest. If the other eggs hatched first, the babies are pushed out too. The host parents often continue to feed the cuckoo even after it grows to be much larger than they are, and cuckoo chicks sometimes use their call to lure other birds to feed them as well. Interestingly, only Old World (European) cuckoos colonize other nests—the New World (American) cuckoos build their own (untidy) nests. Like many Americans, these cuckoos migrate to the tropics for winter.
Cuckoos have a long and glorious history in literature and the arts. The Bible mentions them, as do Pliny and Aristotle. Beethoven used the cuckoo’s distinctive call in his Pastoral Symphony. And here’s a bit of etymology for you: the word “cuckold” (a husband whose wife is cheating on him) comes from “cuckoo.” Presumably, the practice of laying one’s eggs in another’s nest seemed an appropriate metaphor.