Sam calls his falcon "Frightful" because of "the difficulties (they)...had in getting together". Sam had to scramble up a mountain and tussle with the young bird's mother when he stole her from her nest (Chapter 7).
"The Baron" is a weasel Sam catches in a trap. Despite his discomfiture at being so ignominously treated, the weasel maintains a noble bearing, "as stately as royalty" (Chapter 9).
Jesse C. James, is a young raccoon, a masked bandit who reminds Sam of the notorious Jesse James. His middle initial, "C", stands for "Coon" (Chapter 12).
When Sam is watching the chickadees, he thinks of his neighbors on Third Avenue. Mr. Bracket used to sit on his front step and chase everyone who approached his apartment away, so Sam names a most cantankerous chickadee after him. Mrs. O'Brien, Mrs. Callaway, and Mrs. Federio always went to market together on Third Avenue, talking and pushing as they went. Sam names "three busy chickadees...(who)...flit and rush around and cluck and fly", after these three ladies (Chapter 18).
Sam discovers that "when you don't have a newspaper or radio to give you weather bulletins, watch the birds and animals...they can tell you when a storm is coming". Sam observes the behavior of a little nuthatch, whom he names "Barometer", in particular, and "when he hole(s) up, (Sam) hole(s) up" (Chapter 19).
The baron weasel-he named him this because the baron was the lowest of the noblemen and that is the definition of baren