From the website of the American Association of Zoo Veterinarians:
“It is encouraged to keep flamingos full flighted when the appropriate facilities are available and hopefully more zoos will be account for this when designing facilities for flamingos in the future.
Pinioning is the most common deflighting method performed on flamingos maintained in outdoor enclosures. Successful pinioning has been performed on chicks from 2-10 days of age. Refer to the Reproduction chapter for further details on animal husbandry issues related to pinioning. The procedure may be performed with simple crushing of the tissue with a hemostat and cutting with a scissors or scalpel. The incision may be closed with tissue glue. General anesthesia is needed if the procedure is performed on adult sized flamingos. For traditional pinioning, the site of amputation is determined by finding the alula and cutting the bone just distal to the base of this structure. Remove the flight feathers at the amputation site. Other feathers should be plucked and the skin surgically prepared. A circumferential skin incision is made, leaving enough skin to close the wound. The major vessels in this area are between the metacarpal bones, which are fused at either end. A figure eight transfixation ligature is placed loosely around the proximal ends of the bone. The bones are amputated with a sharp chisel, a bone cutting forceps or a giggly wire. Once the distal end of the metacarpal bones is freed, the ligature is tightened. The skin is pulled into place to cover the end of the bones and sutured closed. A light pressure bandage is applied to assist in controlling hemorrhage. The bird usually removes the bandage in a day or two. Amputating less bone (i.e. long pinioning) may improve reproductive success, but it is still unclear if some birds are completely inhibited from flight. Tendonectomy is not recommended because it is more invasive and in some countries is forbidden. Birds often develop droopy wings and the procedure frequently does not prevent the flamingo from flying.”
https://www.aazv.org/page/flamingo_health_med_?