Raptor Cages

Tips On Building a Raptor Flight Cage in Central Florida

Nancy Murrah, President, Raptor Center of Tampa Bay, Inc.

Preface

After a great deal of research, the Raptor Center of Tampa Bay has pulled together a document which outlines requirements for flight cages dedicated to Bald Eagles and other raptors native to central Florida. The Center contacted several experts with flight cage knowledge and experience,  and has included in this document their valued expertise and advice. Thanks to Bill at the Avian Reconditioning Center, Sue at the Audubon Center for Birds of Prey, and Missy at C.R.O.W. (Clinic for the Rehabilitation of Wildlife) for their valued assistance. 

Introduction

The goal of using a flight cage is to train raptors for successful release back into the wild. Success can be better achieved by taking the shortest possible amount of time with limited human contact. Preparing a bird for release requires replicating the outdoors within the cage, thereby reducing the stress of captivity. High perches, sufficient room to exercise, and, for raptors in particular, the opportunity to capture live prey are the best ways to ultimately achieve the goal of release: all while keeping the occupants safe.

Predators

One of the goals of a successful flight cage is to keep the birds safe by keeping predators out. The cage exterior and interior should be checked regularly to make sure there is no pathway for predators to get in. Hardware cloth can be installed on the outside of the cage to help prevent predators from getting in.

Cage Materials 

Wooden slats are the preferred cage material for raptors as it helps to maintain feather quality. The wooden slats, when positioned on the interior perimeter walls of a flight cage, assist in preventing direct contact with the outside world and should isolate them from building material used to keep predators out.

The floor of the cage provides protection for the birds from digging predators (such as rats) and to keep the raptors' feet healthy. A variety of materials are acceptable for use as substrate (flooring), and proper drainage needs to be provided: the birds should NEVER be standing in stagnant water in the bottom of the cage. Gravel, such as pea gravel, has rounded edges and is easier on raptor feet. By providing a rock gravel substrate it will help minimize sand-burrowing predators like rats, as well as increase drainage. 

Sand, such as coarse grade builder sand, can also be used. A variety in substrate, such as gravel and sand, is also a good option to provide variety for the raptors feet. During the rainy season, both sand and gravel are needed to even out sitting water in any areas of the cage. Gravel helps to insure drainage, is easy to clean, and maintains its effectiveness longer than any other material.

Cage Types

Rehabilitation for raptors can be divided into three main areas: Clinical, Hunt Training, and Pre-release/Flight Conditioning. Each needs a specific type of cage interior. 

Clinical areas provide an injured raptor with a next step after recovering from their injury in an indoor cage. This is where they take the time to recover and start the process of building up their bodies, and re-acclimating to the weather.  This is done at the Raptor Center.

Hunt Training is crucial for young raptors who rely on their parents when learning how to hunt. The rehabilitators’ job is to prepare orphans for life in the wild by providing a place for to learn how to hunt live prey. A crucial element needed in the cage at this time is a contained area scattered with leaf litter where live prey can hide, but cannot escape, thereby giving young birds the opportunity to practice and perfect their hunting skills. We also receive injured adult raptors who may have sustained head, eye, or ear damage. To ensure all senses are functioning properly after apparent recovery these birds are also tested with live prey. This is done at the Raptor Center.

Pre-release/Flight Conditioning is the last stage of rehabilitation and helps to increase stamina and muscle mass. This is where the 100 foot flight cage at Circle B Bar Reserve will help to create a safe environment for both flying and taking off from the ground. The longer the flight path, the better for the bird. The best use of this space is when perches are only available at each end of the flight path, negating short hops from perch to perch.

Size of the cage is important as USFWS requires Bald Eagles, Black Vultures, Osprey, Peregrine Falcons, Turkey Vultures all be flight conditioned in a cage that is a minimum of 20' x 100' x 16'. 

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Flooring or Substrate

Pea gravel can make an excellent mew or flight cage flooring. It lasts a long time, is easy to clean with a hose and is relatively cheap. As with all flight cages, or mews, any castings or left-over food debris should be picked up immediately to avoid rotting, which attracts bugs and/or predators. One advantage with the gravel is that it allows the birds to rangle: a process of ingesting a small piece of gravel to aid digestion. Pea gravel, sometimes referred to as river bed gravel, should be 1/4 to 1/2 inches in diameter and smooth - unlike jagged driveway gravel (crushed gravel).

Sand

Sand can be readily available and work for many raptor cages. It is easily cleaned and raked, and easy to manage. However, sand will reflect a considerable amount of heat. If a bird is fed on sand, the particles can be ingested and possibly impact in the Gastro Intestinal tract. 

Dirt or Grass

Dirt or grass floorings can be easy to care for and manage. Grass in Florida tends to grow rapidly and maintaining the grass can be quite an issue. This is a natural environment for the bird. Dirt can be raked and contains microbes which help break down leftover food particles. Dirt can also become impacted in the GI tract when ingested. Also, soil types that are more clay-like will tend to dull the talons. While soil types that consist mostly of sand will tend to sharpen the talons. 

Astroturf

There are many different types of material referred to as 'Astroturf'.  When perches are covered in Astroturf they make excellent padded surfaces and protect the bird's feet. Birds that perch in the same spot in a cage develop sores on their feet. The texture of the Astroturf  helps to prevent this.

Shavings

Shavings may work well enough for a flooring in cold climates, but should be avoided in warm or moist climates. Because they're fine, they produce an amount of particulate matter in the air and when they hold that moisture they can grow mold (sawdust is worse). But perhaps more importantly, they are small enough for a bird to ingest them: especially if food is dropped onto the floor. Shavings in the system will cause an impaction and can be difficult to diagnose and treat.

Sawdust

Sawdust is too fine for a flooring because it holds moisture, molds, and can become air born when thrown into the air and inhaled by the bird. Avoid sawdust.

Straw

Straw is the perfect substrate for mold spores. It likely has some mold already in it from the moisture and spores from harvest, then it has been bundled up and the mold has been allowed to grow. Being an organic material it should be avoided at all costs. Even straw that is placed NEAR the mews should be avoided since the propensity is high for developing Aspergillosis, a common respiratory infection that develops from fungus.

Water

Adequate fresh drinking water must be provided. Drinking water should be easily accessible to minimize disturbance. Pools must be a minimum of 2-6 inches deep and wider than the length of the raptor. The water pool within the cage needs to be evaluated for best use.  It is too deep to fill with water even for an eagle. We may consider adding rocks and one additional small shallow concrete pool with a sloping entrance that we can build on-site.

Conclusion

The needs of raptors present several challenges to achieve successful release. Generally, these birds are large predators that hunt on the wing. Appropriate conditioning is crucial not only for foraging, but for territory defense and other behaviors.  Pre-release/flight conditioning is best achieved when the flight cage contains 2 high perches on either end of the cage. This forces the birds to fly (i.e. exercise) from one end of the cage to the other. The perches should span the entire width of the cage and be set up on the highest vertical beam. They should be covered with Astroturf and mounted securely. The floor of the cage should be a combination of gravel and sand, giving the birds a variety of feeling and texture to maintain healthy feet and overall healthy feather condition. Fresh water should always be readily available.

Sources

1. Principles of Raptor Cage Design. Treehouse Wildlife Center's Raptor Rehabilitation Complex, 2021

2. The Modern Apprentice. @modernapprentice.com, 2021

3. United States Fish and Wildlife Service. Resee Collins, Bald Eagle Coordinator, 2021

4. Avian Reconditioning Center. Interview, 2021

5. Audubon Center for Birds of Prey. Interview, 2021

6. C.R.O.W. Captive Rehabilitation of Wildlife. Interview, 2021

7. International Wildlife Rehabilitation Council, Minimum Standards for Wildlife Rehabilitation, Third Edition, 2000