So using standard 12 oz. pop/beer cans that are rinsed and dry I find that the consensus is that it takes from 32-35 cans to make a pound. There seems to be no exact number because there are variances by brand. So now we basically know about how many cans one has to gather together to make a pound a make some money.
During a chase, however, speeds increase; ducks, for example, can fly 60 mph or even faster, and it has been reported that a Peregrine Falcon can stoop at speeds of 200 mph (100 mph may be nearer the norm). Interestingly, there is little relationship between the size of a bird and how fast it flies.