Jane Elizabeth Stolka, age 8, of Utica, N.Y., for her question:

Do birds migrate on the same day?

In the fall, we watch the birds gathering on the telegraph wires. They chirp and twitter as if they were talking over their plans. Then suddenly they have gone, flown away south for the winter. Maybe a whole flock of birds leaves on the same day. But chances are another flock will leave a few days later. A few stragglers may not get started for a week ox two.

All the migrating birds do not leave on the same day. A flock or two of songbirds may leave every day, but it takes two or three weeks for all of them to leave. Some will meet up with other birds, and huge flocks of them fly south together. When spring comes, a few robins appear first. In a few days there are more, and the last of the slowpokes may not arrive for another three weeks.