Jalopnik:

Working near a running jet engine is extraordinarily dangerous. A Boeing 737 engine, running at idle power, has a hazard zone of 9 feet to the front and sides of the engine. This means that, even at idle thrust, a human that walks in the hazard area runs the risk of being sucked inside and consumed by the engine. When the engine is above idle thrust, the hazard zone increases to 14 feet or more. Engines on larger jets, like the 777 have much larger hazard zones. It is absolutely critical that ground crews can identify a running engine and stay away from it.

So very clearly, the spiral is an important feature for helping keep the ground crew safe—pretty much every source out there agrees, here, and it makes a lot of sense. As for the bit about bird strikes, there doesn’t appear to be much conclusive data showing that swirls keep the birds away.

To warn ground crew which engine is spinning makes perfect sense but “the swirls fend off the birds” sounds like complete BS.