Well, European swallows, AKA Barn swallows, are pretty small. Couple of ounces. Couldn't carry a 14 pound arrow, not even if 2 of them picked it up together.
If you're talking African swallows, you need to be more specific. There's your West African swallow, Cecropis domicella, your Angolan swallow, Hirundo angolensis, your Ethiopian swallow, Hirundo aethiopica, your South African cliff swallow, Petrochelidon spilodera, and a whole pile of others.
Thing is, most of your African swallows are non-migratory, so they generally wouldn't come across any 14 pound arrows. African arrows tend to be tiny.
Now, you can have your South American swallows, like your Chilean swallow, Tachycineta meyeni, and your Andean swallow, Haplochelidon andecola, which might live in areas where the native people of the Amazon rain forest live, and these people traditionally used these real long arrows.
So I'm thinking, South American swallows would be the biggest of the swallows, so their feathers would make the best fletching. From among the swallow family, anyways.