That's because over time, birds' beaks become specially formed (adapted) to help them eat specific foods in their habitats.
(That; 's; because over time, birds' beaks become specially formed (adapted) to help them eat specific foods in their habitats) (birds' beaks; become specially formed; T:over time)
That birds' beaks
's become specially formed
because over time, birds' beaks become specially formed (adapted) to help them eat specific foods in their habitats
T:over time