the field-glass," said the Doctor, following the boys along the road
where telegraph wires made bird-perches between the high poles.

"You said a lot of birds came last night," said Nat to Rap; "but how do
you know that they came last night and where did they come from?"

"I know they came last night because they were not here yesterday,"
answered Rap; "but I don't know where they came from, except that it
must be from where it is warmer than it is here, because they went away
just before it grew cold last fall. See, Doctor, there are some of them
now on those fence rails and more up on the telegraph wires. The miller
calls them 'Bee Martins,' and says that they eat up all the honey-bees.
Have they any other name--because I have never seen them catch bees?"

Nat looked at them first with the field-glass, then without it as they
drew quite near the fence, and saw a fine bird, twice as long as his
middle finger. Its back and wings looked dark gray; it was white
underneath, with a touch of gray on the breast, and had a black tail,
with white at the end of it. As Nat looked the bird raised a little tuft
of feathers on top of its head, as if angry, flew into the air, giving a
shrill cry, seized an insect, and returned to its perch.

"That is the Kingbird," said the Doctor; "one of the most useful of the
insect-catchers. Instead of living on honey-bees, as many people think,
he eats very few of these, but kills instead thousands of the bad
robber-fly, which is the honey-bee's worst enemy. This bird is really
king of the air and of all fly-catching birds. See how graceful his
flight is, and how easily be moves!"

"Why did he go away last fall?" asked Nat. "Does he feel the cold