A nest is a roost for birds, consisting of a shallow bowl woven of wooden twigs; its “proper” tincture is therefore brown. It’s never found in period heraldry except when a bird is sitting in it, as in the crest of Nobrega, c.1540 [Nobreza xxº]. The illustration shows a dove reguardant sitting in a nest. See also birdcage.
The Order of the Cygnets Nest, of Meridies, bears: A swan sitting in a nest proper within and issuant from an annulet argent.
Danamas of Starlinghurst bears: Azure, atop a demi-wall issuant from dexter base, a starling contourny argent perched in a nest Or.