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I am not quite sure what a RC plane is, and which objects you want to recognize. Anyways, some hints:

• It is no problem to give just a smaller region of interest (ROI) to any detector/descriptor method in which you want to find correspondences.
• SIFT and SURF are both having a patent, furthermore SIFT is one of the slowest keypoint based methods.
• I recommend you to use a binary descriptor for a fast matching (you can use Hamming-distance then) and for a (typical) low computational cost, e.g. ORB/ORB or BRISK/FREAK, then you also don't need to compute a ROI since these methods are typically fast enough to process the whole image.

However note that all these keypoint based methods work only for images or ROIs which have some structure, so plane objects with no edges won't be detectable since no keypoints will be generated there, but I guess birds are no problem.