This photo was rejected. Why? I just started posting my photos to Adobe. Please let me know.

Wildlife photography is one of the hardest to succeed in, with birds at the top of the subject list. The subject's eyes absolutely have to be in sharp focus. You need to be completely in command of your camera settings and choice of lenses. With your zoom maxed at a 300mm focal length, you need to use a tripod. Maybe you did but you can see at 100 percent view that your image is completely soft and you've lost all the details in the vulture's body which might have been extracted in the raw processing if it was in focus.

If you intended to make wildlife a specialty of your stock photography pursuits, be sure you’re deeply familiar with the settings of your camera and your lens capabilities. The other important factor is timing your wildlife shots for just after sunrise and just before sunset, known as the golden light hours. I hope that's helpful and keep working at getting better!