This gentle, entrancing description of Macbeth’s castle has it providing a home for house martins to build their nests, giving no intimation of the horrors to come.

This guest of summer

The temple-haunting martlet, does approve

By his loved masonry that the heaven’s breath

Smells wooingly here: no jutty, frieze,

Buttress, nor coign of vantage, but this bird

Hath made his pendant bed and procreant cradle:

Where they most breed and haunt, I have observed

The air is delicate.

Not for long…

The martlet, a mythical manifestation of a house martin which never lands on the ground, was depicted in heraldry as being without feet. 

Source: Shakespeare, Macbeth, I.vi