Surely, for kids who can read words like ""maple,"" and ""caterpillar,"" and even ""Baltimore oriole,"" it ought to be possible to write something that is simple without being sing-songy. The maneuvers of this backyard pair -- ""They fly around the yard. They call back and forth. They feed each other caterpillars. They mate."" -- are on the dull side, and we were most impressed by the baronial old house of their unindividualized human hosts. Higginbottom's gold and blue-green drawings have a certain ruddy realism, and this is by far the easiest of bird lives, though also far less interesting than, say, McClung's Redbird.