They eat cactus seeds, and with the drought the smaller seeds, that are easier to open up disappear fast such that birds with a slightly bigger beak have a significant selective advantage when all that is left are the large seeds (the study included measurements of the seeds!).
(They; eat; cactus seeds) (all; is left; ) (the smaller seeds; are; easier to open up) (all that is left; are; the large seeds (the study included measurements of the seeds!)) (the smaller seeds; to open up; ) (the study; included; measurements of the seeds) (the smaller seeds, that are easier to open up; disappear fast; L:such that birds with a slightly bigger beak have a significant selective advantage) (birds with a slightly bigger beak; have; a significant selective advantage; T:when all that is left are the large seeds)
They all the smaller seeds all that is left the smaller seeds the study the smaller seeds, that are easier to open up birds with a slightly bigger beak
eat is left are are to open up included disappear fast have
cactus seeds
easier to open up
the large seeds (the study included measurements of the seeds!)
measurements of the seeds
L:such that birds with a slightly bigger beak have a significant selective advantage
a significant selective advantage T:when all that is left are the large seeds