Speed of a swallow

Question: What is the airspeed velocity of an unladen swallow?

Answer:

I'll ask the usual ones back.
What kind of swallow?
Is the swallow in horizontal flight?
Young or old bird?
Maximum or average speed?
Relative to the air or the ground?

However to be serious for a moment:

It seems that the average speed of an unladen swallow I horizontal flight is somewhere between 18 m/s and 23 m/s (40 to 50 m.p.h).
Greatest speed of a bird is probably the peregrine falcon in a dive although estimates vary wildly here from 100 m.p.h to over 180 m.p.h.