Note to Macbeth, Act 1, Scene 6, line 4: "temple-haunting martlet"

Act 1, Scene 6, line 4.
The martlet, now commonly called the "martin," belongs to the swallow family. It builds its nests in high places, such as the sides of cliffs or buildings. Thus Banquo calls it "temple-haunting," not because it "haunts" in the way a ghost does, but because it is most commonly seen in the vicinity of churches or cathedrals, which were in Shakespeare's time the tallest buildings in any community.

Image Source: Scottish Wildlife TrustImage Source: Wikipedia: Fairy Martin