Metabolic Bone Disease in Wild Birds: A Nutrition Guide for Rehabilitators

As wildlife rehabilitators, we often see the downstream effects of well-intentioned but nutritionally inadequate supplemental feeding. One of the most preventable yet devastating conditions we encounter is Metabolic Bone Disease (MBD)—a painful disorder that leaves birds with weakened bones, deformities, and compromised recovery potential.

Understanding MBD in Your Patients

MBD results from dietary imbalances, particularly inadequate calcium, excessive phosphorus, and insufficient vitamin D3. While wild birds typically maintain nutritional balance through varied natural foraging, those raised by untrained caregivers or heavily dependent on bread and backyard feeders often arrive at our facilities with advanced MBD.

The disorder manifests as rickets in juveniles and osteoporosis in adults, causing bone softening, brittleness, and structural failure—complications that significantly impact rehabilitation outcomes.

The Seed-Based Diet Crisis

The calcium-phosphorus imbalance: Seeds (especially millet) are severely deficient in calcium, while nuts, grains, and processed foods are rich in phosphorus. This inverse ratio forces the bird's body to leach calcium from bones to maintain critical blood calcium levels, progressively weakening the skeletal system.

Low protein and vitamin A intake further compounds the problem, affecting bone matrix formation and overall structural integrity.

Clinical Presentation

You likely recognise these signs in intake assessments:

• Marked weakness and lethargy

• Inability to perch properly or bear weight

• Abnormal stance or posture

• Soft, pliable beak, keel, or claws

• Visible bone deformities

• Pathological fractures with minimal trauma

• Egg binding and poor shell quality in females

  
  

By the time these clinical signs are apparent, significant bone demineralisation has already occurred.

Prevention and Nutritional Intervention

MBD is almost entirely preventable through proper nutrition. While our patients receive adequate UVB exposure for vitamin D3 synthesis during rehabilitation, the dietary component requires careful attention:

For Birds in Your Care:

1. Know your patients' natural dietary habits and formulate species-appropriate diets that include adequate protein, vitamin A, and proper calcium: phosphorus ratios

2. Ensure the correct calcium ratios are given immediately upon intake

3. Eliminate seed-only diets as primary nutrition

4. Monitor skeletal health throughout rehabilitation, especially in juveniles

   
   

Education:

When releasing birds or counselling the public, emphasise that supplemental feeding should never replace natural foraging diversity. Compare unbalanced feeding to "constructing a building with only sand and no cement"—the structure appears intact until stress reveals its fundamental weakness.

The Rehabilitator's Role

Every bird we successfully treat and release is an opportunity to prevent future cases. By educating finders and the public about proper nutrition, we can reduce MBD admissions and improve outcomes for the birds that depend on us.

When nutritional needs are met from the start, we provide our patients with the strongest possible foundation for recovery and a return to the wild.

Article Written By

Mandy Robertson – Retired Rehabilitator