First you need to find and identify what is making the big bites :-) Look for slugs or snails and check under the leaves for caterpillars and cutworms. They are often green themselves so sometimes hard to see.

You can bait for the slugs/snails with a safe, environmentally friendly product (Sluggo) and caterpillars and cutworms can be picked off. It is also very possible that what was there causing the holes has now moved on. In which case, you need to do nothing.

I checked under the leaves, and I couldn't see anything. The plants are also in a big pot and I can't see any slugs or snails within or nearby. I can see some weeds starting to grow in the pot and some white spots in the soil - not sure what they are, but that's it. :S I'm so puzzled! I also haven't seen anything webby to suggest spider mites.

One person suggested to me that birds might be pecking at the basil...is that a thing??

When I see big holes this time of year, its often cutter bees. I'm not entomologist, but I believe they live underground in small colonies and don't really do a whole lot of damage, in the overall scheme of things.

Agree completely with the above :-)

Sorry for the delayed response.

Here are some photos of different bites on the leaves. Some are little holes, whereas some leaves have entire halves bitten off. (I couldn't figure out how to rotate the images after uploading, sorry!) The last photo highlights these weird white spots in the soil - is it some kind of fungus?

Thanks so much for the help. I feel better knowing that it's probably harmless.

oh goodness, your basil looks great. Do not listen to the friend who told you to spray for bugs. It is time to pinch off the tips, though. That will help the plants bush out and produce more. And of course, use what you pinch off.

You wouldn't see snails or slugs unless you go out with a flashlight at night, but if it is them, it doesn't look like they are eating more than their share anyway.

Mmmmmm . . . .pesto!