Lots of good discussion on this topic, and I think at the end of the day, it's a personal choice and only matters if you're entering a serious contest or having your work published in venue that requires unretouched work (see
this example of a disqualification for a simple clone vs. a crop).
Specific to this photo, you might look at it this way - had you been able to capture the photo a few seconds/minutes later, perhaps the birds wouldn't have been there. I have this happen all of the time with certain birds to feed in groups (mainly Ibis) and get in the shot when I'm trying to get a portrait of a single bird. If you wait, you might get the clean shot but miss the moment. Again, this is what typically happens to me.
In your photo, I don't think that removing the birds (which are quite distracting) constitutes a change that would alter the meaning or behavior of the subject, so I don't see it as serious change. On the other hand, it is an alteration and you have to decide to either discard the image or alter it.
If it were my photo, I would likely discard it in favor of another photo, unless it was my best shot or the only shot of the subject and I really wanted it. I try very hard to reposition myself or wait for a better moment, but sometimes it just isn't possible. Over the years, I have retouched a total of 3 of my wildlife photos (portraits and commercial work are another topic) because they are 3 of my favorite shots and each shot is a special moment that I tried to capture without distraction but for one reason or another, I couldn't. I wish I could enter these in contests, but I can't. Here they are:
Removed distracting twigs and spider webs from perch
Removed distracting branches and leaves
Removed single blade of grass in front that covered part of the bobcat's jaw
EDIT: Here's a shot that pains me and one I have considered retouching, but haven't. I hate the distracting branch right behind the pelican crossing its beak, but if I remove it, should I remove the rock, shell and other items?: