You're using visual mods. In an unmodded game, those are sea gulls.
I added one new visual mod relatively recently but I didn't know it changed the birds -- or indeed any animals at all, the frogs and squirrels and rabbits have all been the same -- only some of the landscaping. That still makes me kind of happy, but not the same way it would if they showed up occasionally as a secret surprise in the original/vanilla. (I've definitely seen the seagulls many times.)
I added a couple new mods recently despite being late game because the attempt to maximize production to acquire a golden clock for perfection is feeling kind of grindy and against my play style (I do NOT typically play to maximize profit or strictly make money; no offense to those who do, I'm kind of impressed with how some peoples' projects work out, but it seems like you get to the point of having *enough* money for all other game purposes without getting into maxing, if you aren't trying switch gears from "I'm doing what feels cool right now in this season" to "acquire 10 million in under 2 years without adding money-maker cheat mods or warping my farm past recognition".) Changing the landscape made forage wandering more fun when I have a couple of hours after doing all the money-making on-farm or GI stuff, but didn't leave enough time for a dedicated mine trip.
(Although I was actually on the beach in the *morning* for that pic, however dark the storm makes it look, after ending up hitting the beach obelisk by accident when trying to grab a battery from the nearest lightning rod. Graceful I am not...)
