Likely birds. They generally eat it more for moisture than the fruit itself. Provide a bird friendly fountain (you can make an insect friendly landing area too) and you can reduce the predation while encouraging pollinators and pest eating activity.

got any pics

here's the tomato. The others, both red and green had 1/2 of the tomato gone.

Should I wrap the tomatoes in window screen material?

I put my tomatoes in paper bags after the first one attacked by birds. Mockingbirds are notorious for eating tomatoes. and they're bold too, they're not scared by crap like CDs and bird scare tape. I've had to do the same with my grapes, and i've had great results. Putting paper bags on them helps them ripen slower, so they aren't quite as sour. Also I've started picking mine early while they still have green shoulders and I ripen them indoors. they taste way better. The heat just force s them to ripen too fast and they end up tasting sour.

Could also be bugs that are attacking your tomatoes. I have never been lucky with large tomatoes just for this reason. I only grow the small cherry tomato types.

I grow all kinds of tomatoes and have never seen a bird do that. I also have a ton of birds. I just keep looking at the photo and I don't think a bird did that. Tomato worms will do that, those big beatles will do that. It looks like it started to split and a critter finished the job

Thanks for all the responses. I protected a couple of tomatoes with screen, and they survived. I have my first tomatoes after years of trying.

I did look for the tomato worms, as I've had them in the past, but none are present, so I'm guessing it was birds.

The tomatoes are Pearson, but it does appear they are subject to splitting, just like all tomatoes out here in Phoenix. I'm going to try Solar Fire tomatoes next and see how they take the heat

Try "Heat Master" by Bonnie Plants (HD and I think Lowes has it, too). Specifically bred to flower/set fruit at temps at 95 degrees and over; I planted 4 of them and have NO splitting and excellent fruit production so far. Not as flavorful as some of the heirloom varieties, but I guess we can't have everything. Here's a pic of the latest harvest. And that looks like birds to me, which is why I built a completely enclosed (walls, ceiling, door) steel cage for my veggie garden. Which is a bit extreme, but hey, when you've had enough and just want a lousy tomato - LOL!

I grew Solar Fire last year and they were great - prolific, with no splitting. I tried new varieties this year (especially loved Black Prince), but I'll plant Solar Fire again next year. In this picture from July of last year, they're the larger tomatoes on the right. The others are Husky Cherry, Black Cherry, and Bloody Butcher, which I also have good success with.

I should add to the OP that I had the same problem with birds. I had to put netting up after losing so many last year.

I thought birds too, but am far from an expert. I DID want to say how great your tomato harvest pics are Queenie and Lynne, great stuff! Thanks for sharing the variety names and information. Great job! Happy gardening all!

Thanks all for the responses. I think it is birds. I added some screen around a few tomatoes that were about to get ripe, and they've survived.

While others were completely decimated.

I'll try solar flare too!