No, your eyes aren't deceiving you, that is a 15% buffy coat!

It is not, however, made of white blood cells! This hematocrit tube came from a wild fledgling great horned owl (Bubo virginianus) with a severe Leucocytozoon infection. That buffy coat is largely made of red blood cells parasitized by this protozoa, which can been seen on the image of a blood smear taken from the same patient.

While often found incidentally in the blood smears of clinically healthy wild birds, Leucocytozoon can cause illness. Clinical disease and mortality result from anemia, high numbers of the large gametocytes blocking pulmonary capillaries, or parasites invading the endothelium of vessels in tissues (brain, heart, etc.) where they form megaloschizonts that occlude vessels. This disease is spread by insect vectors, namely black flies and midges, and in North America, is most often seen in late spring and early summer. Treatment is challenging and does not usually result in complete elimination of the protozoa.
#AAVWildlifeCases

Did you know that recently grown-in owl feathers will fluoresce under UV light?

This is because the owl feathers contain porphyrins, which fluoresce pink under ultraviolet light. As the feathers age and are exposed to the elements and sunlight, the porphyrins eventually fade. This unique aspect of owl feathers help with age determination. Only juvenile owls will have flight feathers that uniformly fluoresce, because all of the feathers grew in at the same time. Once owls are one year of age or older, they will only molt a few feathers each year, and those new feathers will fluoresce much more brilliantly than the older feathers.

Owls do not have UV-sensitive cone cells in their eyes like diurnal birds, but research suggests that they can still detect UV light. We don't know why owls, or other bird species such as auks, puffins, penguins, nightjars, parrots, bustards, and birds-of-paradise fluoresce under UV light, but it likely help communicates important information between birds.

Did you know? Two vulture clades, Cathartidae (“New World” vultures), and Gypiinae (or Aegypiinae, one of the two subfamilies of “Old World” Vultures) display distal forelimb pneumaticity, meaning bones of their distal wing, including the ulna, are pneumatic and thus continuous with the air sac system. This is clinically significant for avian veterinarians because the ulna is a common site for intraosseous catheter placement; however, this site should NOT be used in many vulture species!

Source: Gutherz SB, O'Connor PM. Postcranial skeletal pneumaticity in non-aquatic neoavians: Insights from accipitrimorphae. J Anat. 2022 Dec;241(6):1387-1398.

Photos: Wing radiograph of a turkey vulture (Cathartes aura), and photo of rehabilitated turkey vulture.
Photo credit: Stephany Lewis, DVM, CWR, DABVP (Avian Practice)

Did you know that if an owl's eye requires removal (due to severe trauma, for example), it is recommended to eviscerate the eye rather than enucleate? During an ocular evisceration procedure, the scleral ossicles can remain in place. This is in contrast to an enucleation procedure, in which the scleral ossicles are removed. Leaving the scleral ossicles in place helps prevent deformation of the facial disk structure, the concave collection of feathers on the face. The facial disk collects sound waves and directs those waves towards the owl's ears, enabling the bird to locate prey by sound. The evisceration procedure is also considered safer, as it decreases risk of traction on the optic chiasm, and decreases risks of trauma to the contralateral eye or brain.

Note that not all wildlife rehabilitators and veterinarians recommend release of owls lacking vision in one eye, though there is some evidence to support this practice with adult nocturnal owls, and most nocturnal owls hunt primarily with sound.

Images:
Barred owl with an eviscerated right eye
Images of Eastern screech owl skulls with scleral ossicles

Electrocution injuries are most commonly seen in large free-ranging raptors. Individuals that are not immediately killed are likely to develop severe burns and tissue necrosis, with injuries often not apparent for several days. Lesions caused by electrocution are usually observed at the two points of contact and first manifest as swollen and edematous skin with a serous exudate. Massive tissue destruction tends to occur with a grave prognosis for successful rehabilitation and release. These injures are presumed to be extremely painful, thus early recognition and/or close monitoring of a suspected electrocuted bird is important to allow for timely euthanasia, if appropriate. Veterinarians and wildlife rehabilitators are required to report all wildlife electrocutions to US Fish and Wildlife Service law enforcement, as well as the electrical company that owns the power line.

Photo is of a Golden Eagle wing on presentation to the author, several days after electrocution. This patient was humanely euthanized.

Did you know? Caprimulgiformes, like this common poorwill (Phalaenoptilus nuttallii) are aerial insectivores and do not self-feed in captivity. This group of species, which includes other "goatsuckers", such as nighthawks, Chuck Will's Widows, and Whip-poor-wills, need to be hand-fed insects or insectivore formula 5-6 times daily while they are in rehabilitation. This order of birds also possess a tapetum to assist with their crepuscular hunting habits, and many species can enter torpor during cold weather to conserve energy. Common poorwills have been recorded to have body temperatures as low as 41 degrees F (5 degrees C)!

You are working with a wildlife rehabilitation center and receive an adult American crow that presented unable to fly. It's physical examination is unremarkable aside from some crepitus in the region of the left shoulder and a left wing "perk" (the left primaries rest more dorsal than the right primaries). You perform VD and lateral full-body radiographs, and obtain the following images of the pectoral girdle. What is your diagnosis? What is the prognosis for return to flight for this patient? What is your treatment plan?

Answer:
This crow has a left clavicle fracture as well as a left caudodorsal coracosternal luxation. Since the left scapulohumeral joint and triosseal canal are unaffected, this patient has an excellent prognosis for a full return to flight. This patient returned to full flight capabilities with normal flight mechanics following 3 weeks of hospital cage rest with analgesics, 1 week in a 12ftx12ftx15ft enclosure with varying perch heights, and 1 month of reconditioning in a 50ftx30ftx20ft flight cage.

An adult wild great horned owl (Bubo virginianus) presents after falling in someone's pool. The bird is in thin body condition, does not make attempts to fly in a flight cage, and has reduced extension of the shoulders on palpation. You take the following radiograph as part of your diagnostic work-up. What is the most likely diagnosis?
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Answer: Synovial chondromatosis!

Synovial chondromatosis is a condition in which the synovial lining of a bursa, tendon sheath, or joint has numerous metaplastic nodules of hyaline cartilage. The nodules may ossify and detach into the synovial fluid. This condition has been described in great horned owls, mainly affecting the scapulohumeral joints, usually bilaterally, and can affect other joints as well. The cause of synovial chrondromatosis in owls is unknown, and no treatment has been described.