Birds are divided in the Mosaic law into two classes, (1) the clean (Lev. 1:14-17; 5:7-10; 14:4-7), which were offered in sacrifice; and (2) the unclean (Lev. 11:13-20). When offered in sacrifice, they were not divided as other victims were (Gen. 15:10). They are mentioned also as an article of food (Deut. 14:11). The art of snaring wild birds is referred to (Ps. 124:7; Prov. 1:17; 7:23; Jer. 5:27). Singing birds are mentioned in Ps. 104:12; Eccl. 12:4. Their timidity is alluded to (Hos. 11:11). The reference in Ps. 84:3 to the swallow and the sparrow may be only a comparison equivalent to, "What her house is to the sparrow, and her nest to the swallow, that thine altars are to my soul."
Dicionário Bíblico Ilustrado de Easton (Easton's Bible Dictionary)
Dicionário Bíblico (Easton)