Boyd’s Bible Dictionary:

(throat sweller). The common swift or swallow abounds in Palestine, and its habits, according to Bible mention, are such as we observe: building under the eaves of houses, beneath temple cornices and porticos, and in the sides of cliffs, and rapidly circling above their homes in search of their aerial food (Psa. 84:3; Prov. 26:2; Isa. 38:14; Jer. 8:7).

Concise Bible Dictionary:

1. deror. This is interpreted “roving about,” which agrees well with the habits of the swallow or swift. They come and go, and are not domesticated (Prov. 26:2). In Psalm 84:3 it is typical of the wanderer finding rest and protection in God’s house.
2. agur, mentioned with the word sis, translated “crane” and “swallow;” but sis doubtless refers to the swallow, and agur to the crane. The swallow (or perhaps the swift) is mentioned as “chattering,” or having a “garrulous note,” and it is migratory (Isa. 38:14; Jer. 8:7). Several species of the swallow frequent Palestine: the Hirundo rustica, H. rufula, etc. A species of swift finds the Jordan valley warm enough in the winter, and need not migrate.