my true love gave to me,
four calling birds.
Apparently "calling birds" is a corruption of the original "colly" or "collie" bird, the European black bird; from the Middle English "col", or coal. And the European blackbird (Turdus merula) is really a small thrush with a melodious call, or song.
I'm going to skip any recipes for blackbird pie (it probably tastes like chicken, away), in favor of this nifty wooden mechanical model
from Mechanical Monkey in Cornwall, England (they have ballista, trebuchet, and catapult kits, too).