Four turned into 5!! WOAH!! Now that's tricky. Like skipping all the calving business magic stuff!! Maybe @farmerjan would want in on that secret and more!
I'd have then penned somewhere, fed some hay, and then if not claimed in a certain amount of time, they would be sold.... you are entitled to any money spent, as well as compensation for time, etc..... Your local sheriff/deputy should be involved.... and if they have traveled any distance, an owner may never be found....
Each county/state is probably different... if you have them penned on your land, and are feeding them... and after a certain period of time... the finder keeps the money... It is the letting the "authorities know" ... that is the key... if the county has to try to find housing etc... then I don't know. Here... if there are loose animals, and they are gotten into the closest/nearest field... say to get them off the road or something... then if the owner cannot be found they are considered abandoned and they belong to the finder..... But.... you report them so that if someone comes looking... it does not look like they were stolen... and I honestly don't know what the time frame is....
Since most of us are farmers, we will run them into a field... usually with some of ours.... make a bunch of phone calls to let someone know we found xyz cattle and where... and usually within a few days/ a week or so... an owner is found.... and the same when we are missing something... we call adjoining nearby owners and let them know we are missing such and so..... because we get along with most all farmers and renters of places near places we run cattle too... everyone looks out for each other pretty much....
Like the heifer we had that got in with the neighbors steers.... was there for over a month or so....she was bucket trained so she actually helped them to get the steers "led" into the pen and across the road... and we helped haul his steers to town and I just brought her back home....you do these kind of things as a good neighbor... hope someone will do the same for you in return....
There you go Mike - report them immediately and then corral them up and see if the owner shows up and claims them. If not and you can keep them, you are now in the cattle business.