Weighing the Hummingbird
Nancy uses a very delicate scale to weigh hummingbirds. Of course the birds won't sit still on the scale by themselves, so Nancy wraps them with a bit of plastic mesh and clips the mesh closed. Before she starts, she calibrates the scale so when just the mesh and clip are on it, the scale reads zero. Then when the hummingbird, the mesh and the clip are on the scale, the scale will show exactly what the hummingbird alone weighs.