Question

Black-bellied seedcrackers are a species of bird found in central africa. they live in various habitats where individuals eat either hard, large seeds or small soft seeds. individuals with thick, shorter beaks can eat the harder seeds. individuals with thin, longer beaks can eat softer seeds. individuals with beaks of intermediate thickness and length cannot really eat either type of seed very well. if you measured beak width and length in populations of black-bellied seedcrackers, what type of selection would you expect to find?

Answer 1

It's an example of disruptive selection/ diversifying selection.

In disruptive selection  the extreme values for a trait are favored over intermediate values. In this case, the favored traits are long beaks because they have seeds they can eat and the short beaks, for the same reason.
The intermediate type of beak is the less fit for this environment.