🩺 Health & Disease · 7 min
Diet-caused disease
Why this matters
Metabolic bone disease and cramp are entirely preventable, entirely caused by the falconer, and they kill young birds within days.
By the end of this lesson you will be able to
- Explain the calcium to phosphorus problem in a meat-only diet
- Recognise metabolic bone disease and cramp in a downy eyas
- State how both are prevented
The ratio
Muscle meat alone is very high in phosphorus and very low in calcium. Hamburger runs about 1:20 calcium to phosphorus; the appropriate ratio is 2:1. That is not a small deficiency, it is an inversion, and one meal is enough to start metabolic changes.
Feed whole prey with bone. A meat-only diet in a young growing bird leads rapidly to improper calcification of bones and fractures.
Metabolic bone disease and cramp
Both names describe the same calcium, phosphorus and vitamin D imbalance, and both are a primary cause of death in eyases taken in the downy stage, and occasionally in larger downies fed badly.
The clinical picture, as the manual describes it:
- A downy eyas that feeds greedily but cannot sit up, sprawling on its breast, repeatedly trying to right itself and voicing distress. Pain calls begin.
- About the third day after the pain calls, the long bones of the legs visibly arch from muscle spasm, more rarely the wings too.
- The bird becomes unable to walk and will crawl to move.
- Death usually follows.
Hawks and falcons fed only lean meat, classically lean beef, acquire this reliably.
Prevention
Feed small bones as soon as the young bird can assimilate them. The falconer removes the head, crop, viscera and feathers of prey and grinds up what remains, bone included. Ground whole prey, not muscle meat.
Stargazing
A bird with stargazing syndrome has inflammation of the brain and stands with its head up or arched back over its shoulders. A similar picture appears with severe head trauma.
- The most common cause in raptors appears to be a vitamin D3 deficiency, and the preferred treatment is sunlight and vitamin D3.
- Where the cause is a different dietary deficiency, vitamin B1 (thiamine) supplementation is the recommended treatment.
The exam asks both versions, so read the stem carefully: "if stargazing is caused by a dietary deficiency" points to B1, "the preferred treatment for stargazing syndrome" points to sunlight and D3.
From the field
You are raising a downy eyas on chunks of rabbit muscle because it is what you had. On day four it starts calling and cannot stand. What happened, and can you fix it? Metabolic bone disease from a calcium-starved diet. Get it to a vet immediately and fix the diet to ground whole prey with bone, but understand that the arching bones mean the damage is already done. This one is won at the feeding table, not at the clinic.
This lesson is part of the NY Falconry Exam course. Open it in the course to answer the retrieval checks that go with it, track what you have read, and quiz the whole unit. Lessons, quizzes and the glossary are free.