The Raptor Research Foundation is an excellent source for the latest information on birds of prey. As their name suggests, they are dedicated to research of birds of prey. This primarily focuses on population topics, such as ecology and biology, but also touches on areas of individual health and welfare. Of particular use is their journal and the free resources they provide on their website. The foundation even offers a techniques manual covering a wide breadth of topics pertinent to avian biologists or veterinarians. Check out their resource page at https://www.raptorresearchfoundation.org/publications/.
Or go straight to the techniques manual: Raptor Research and Management Techniques Manual