The Pea; The Pewee

To tell the Pewee from the Pea,
Requires great per‑spi‑ca‑city.
Here in the pod we see the Pea,
While perched close by is the Pewee;
The Pea he hears the Pewee peep,
While Pewee sees the wee Pea weep,
There’ll be but little time to see,
How Pewee differs from the Pea.