You can know a Sandwich Tern by the yellow tip on its bill, as though it’s been dipped into a mustard jar. Mustard. Sandwich. Get it?

I’ve been lazy about learning my terns. So I especially tried to see terns last Saturday (a week ago) for birding’s Global Big Day.

I did a couple of eBird checklists, first along a favorite stretch of beach north of the House of Refuge in the morning, then north of Fort Pierce at Avalon State Park in the afternoon.

I contributed two checklists to the amazing world total. Nice to be a part of the big day, but it reminded me I don’t always enjoy a diligent count of carefully identified birds while also trying to get a few good photos.

Royal terns loafing in the bright afternoon at Avalon.

My husband helped during my afternoon excursion. He had the binoculars and I had the camera and the iPhone eBird app. So I would ask him to count and also check and describe the birds up ahead in that flock on the beach to see if they were a mix of different species or they were all the same.

The Royal Terns were active and plentiful on that stretch of the beach. They are large terns with dagger-like orange bills, black legs and a long, forked tail.

Breeding adults have a full black cap that sometimes looks a bit shaggy and unkempt in a strong breeze. Non-breeding adults look like they have the receding hairline of male pattern baldness.

Non-breeding hairdo.

Forked tail of a Royal Tern with a full black cap.

Caspian Terns are the other large terns along Florida beaches. I will try to get a photo and show the differences between the two.

The medium-sized terns around here: Sandwich. Breeding birds also have a shaggy crested black cap. Non-breeding birds have a partial black crown, as shown above.