Arrival of Red-Tailed Hawk 24-2154
While the patients presenting to the Wildlife Medical Clinic are typically injured or ill in some shape or form, we do sometimes receive patients that are clinically healthy. This was the case for a juvenile red-tailed hawk who was brought to the clinic on October 3, 2024. This hawk, patient number 24-2154, was brought in after it was found by the side of the road, unable to fly. The finder noted that the hawk still wasn’t moving but seemed to be improving during the drive to the clinic. When we did our initial physical exam on the hawk, everything looked normal, with no signs of any wounds or fractures that might have contributed to its inability to fly. The only thing we found was that the hawk had a very large and full crop. Why would a full crop cause this hawk to not be able to fly? Let’s take a brief look at the anatomy of a bird’s digestive tract to find out why.
Avian Digestive Tract
Birds have a slightly different digestive system than mammals do, especially when it comes to their esophagus and stomach. In general, food will pass from the mouth through the esophagus and its associated crop before entering the two-part stomach and then moving into the intestines. The crop is an out-pouching of the esophagus that is used as a temporary storage location for food. This is an important feature for birds who need to regurgitate their food to feed their young. The storage capacity of the crop is also helpful for birds that want to quickly grab a meal and then move to a safer place to digest it. The stomach of birds is divided into the proventriculus and ventriculus. The first portion, the proventriculus, contains cells that secrete mucus and glands that secrete digestive enzymes and gastric acid. The acidic environment here is especially important for partially digesting bone from the diet, which is an important source of calcium for carnivores. The second portion of the stomach is the ventriculus, which is also known as the gizzard. This portion of the stomach is thicker and more muscular than the proventriculus, and it helps to break down the food into smaller pieces. Many birds will ingest grit, small pieces of sand or stone, to help the proventriculus grind and further break down food material. The ventriculus is also the area where indigestible materials like bones, fur, and feathers are trapped and formed into pellets or casts that will be regurgitated. The ingested material will then pass through the intestines, allowing the absorption of nutrients that the bird needs before it is ultimately expelled as fecal material.
Red-tailed hawk diet
The gastrointestinal anatomy of birds differs between species depending on what type of food they are eating. Red-tailed hawks are a type of diurnal raptor, meaning that they are carnivores who do their hunting during the daytime. In the Midwest, they mostly eat small to medium mammals, such as voles, mice, squirrels, rabbits, and some birds. They are opportunistic hunters, however, and will eat a variety of prey items of different sizes. Red-tailed hawks can swallow small to some medium prey items whole, but in cases of large items, they may instead be taken to a perch to be eaten slowly. These raptors have a crop where they are able to temporarily store food and begin the process of digestion before it reaches the stomach.
Exam Findings
Based on its otherwise normal physical exam and large crop size, red-tailed hawk 24-2154 was suspected to have eaten a very large meal that prevented it from flying away properly. The large nature of the crop and the added weight likely caused some balance issues that made it much more difficult for the hawk to be able to take flight. The patient was kept overnight to monitor if it was digesting its prey appropriately and to make sure there were no other signs of injury or infection present. The patient had a DVM exam on October 4, 2024, where the crop size was back to normal, and the patient was completely healthy. The patient was flight tested outside of the clinic on a creance, which is a long weighted line that was attached to equipment placed through removable anklets we placed on the hawk. The patient exhibited normal, symmetrical flight and was approved for release. The hawk was released the following day near where it had been originally found a couple days prior. While this case involved very minimal interventions, this was still a very rewarding case to work on, as the patient made a quick recovery to normal function and was able to be released back to the wild right away.
References:
https://birdsoftheworld.org/bow/species/rethaw/cur/foodhabits
Ritchison, G. (2023). In a class of their own: A detailed examination of avian forms and functions. Springer Cham. https://doi.org/10.1007/978-3-031-14852-1_5#DOI
Written By: Sarah, Class of 2027
