Swallow - (Easton's Bible Dictionary)
(1.) Heb. sis (Isa. 38:14; Jer. 8:7), the Arabic for the swift, which "is a regular migrant, returning in myriads every spring, and so suddenly that while one day not a swift can be seen in the country, on the next they have overspread the whole land, and fill the air with their shrill cry." The swift (cypselus) is ordinarily classed with the swallow, which it resembles in its flight, habits, and migration.
(2.) Heb. deror, i.e., "the bird of freedom" (Ps. 84:3; Prov. 26:2), properly rendered swallow, distinguished for its swiftness of flight, its love of freedom, and the impossibility of retaining it in captivity. In Isa. 38:14 and Jer. 8:7 the word thus rendered (augr) properly means "crane" (as in the R.V.).