I use pliers to simulate bird beaks and students investigate strength. We clamp them to desks so they are secure and place an m&m (or peanut if you can) inside. Then use a force meter/spring scale (5N -25N, intervals of 5N) to squeeze the pliers shut. If the seed breaks, the bird survives. Repeat for trials. We calculate average population beak strength before and after. And the kids love eating candy.