The swimming isn’t what you think. It’s also called the diving reflex for good reason: https://en.wikipedia.org/wiki/Infant_swimming#/media/File:Ba...

As a baby I fell into a pool and needed to be rescued. I didn’t inhale water, but as generally happens I very much did just sank to the bottom. Babies can be taught to float at around 5 months, but it’s not reflexive.

Infants do have a "diving reflex" but that is very different from knowing how to swim. If you throw a baby in a pool, the baby will drown and die.

There are undoubtedly similar reflexes that assist fulmars in learning to fly quickly, but that doesn't mean that rapid learning isn't also required.

I mean they kind of have to when they're part of a species that's curious enough that they'll hear 'babies can swim' and throw babies in a pool en masse to see if it is be true.