Jonathan Corum has expanded upon half of the age old question, What is the Airspeed Velocity of an Unladen Swallow?.
Critical to this is his explanation of The Strouhal Number in Cruising Flight. However, as Mr Corum notes, it’s also a bit of a trick answer to ask “African or European,” because 47 of the 74 worldwide swallow species are found in Africa, but only two are named after the continent. Of these, only the South African swallow comes close in its migratory path.
One may further speculate that, given an average body mass of 20g, and with a 28cm wingspan, the European Swallow would be capable of carrying much and that any payload would substantially impact its speed of 22.36 miles per hour, suspiciously close to the impact speed of falling off a 20 foot ladder