To find out how much less a hummingbird weighs than a U.S. penny, you can subtract the weight of the hummingbird from the weight of the penny.
Weight of a penny: 0.1 oz
Weight of the hummingbird: 0.056 oz
Now, subtract the weight of the hummingbird from the weight of the penny:
0.1 oz - 0.056 oz = 0.044 oz
So, a hummingbird weighs 0.044 ounces less than a penny.