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Herons, Egrets, and Bitterns 285

practice perching, balancing, launching, and alighting from waving branches. One good size for an
outdoor flight aviary for up to 20 birds, depending on species size, is 8 × 16 × 12 ft. (2.5 × 5 × 3.5 m).
Flooring may be of deep gravel or removable rubber textured mats. Aviaries can be constructed of
wood or aluminum frame, with hardware cloth or nylon fishnet walls and ceiling, with shade
cloth, plywood boarding, or other screen type surrounding the lower 5 ft. (1.5 m) of wall area, to
diminish animals’ visual stress. Aviaries not situated in naturally shady locations should have
shadecloth drapes over at least 50% of their ceiling area. It is essential that outdoor aviaries have
hardware cloth flooring that is firmly attached to the walls at their bases. Otherwise, young birds
may be exposed to tunneling predators.
In the pre‐release aviary, young birds will be acclimating to outdoor ambient temperatures,
developing their ability to balance on swaying branches, and learning to forage live food from the
cage floor and in water (Figure 17.7). The most economical live food is ambiently available aquatic
fauna gathered from the outdoor environment. These can be supplemented by mealworm beetles,
live minnows or other feeder fish, frozen–thawed fish, pond bugs, and rodents.
Birds should be evaluated for release from the aviary on a regularly scheduled basis, usually once
or twice per week. During the evaluation, it will become apparent which birds are strong, compe-
tent flyers, skilled at balancing on swaying branches, and extremely alert and active. New arrivals

Figure­17.6­ Large indoor cage setup for American Bittern chicks with a nest area and vegetation for
privacy. Source: photo courtesy of International Bird Rescue.