Corn Bunting Miliaria calandra, Bruant proyer.
AWW 2 5 7 p Then my dial goes not true. I took this lark for a bunting.
Medieval and later periods of cultivation with little woodland and extensive, open hedgeless fields would have suited buntings well.
It must have been common to find buntings in the traps set for larks, hence the proverb - To take a bunting for a lark (TILLEY, B722) - which illustrates the disappointment it was to realize that in the trap there was a bunting instead of a lark.
Shakespeare reversed the proverb, the image is then all the more efficient as a commonplace was expected. Instead of giving an illustration of overrating, Lord Lafeu acknowledges an underestimation:
Then my dial goes not true. I took this lark for a bunting.
(AWW 2 5 7 p)