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384 Hand-Rearing Birds

condition in which the tip of the wing turns up in an unnatural position. It is a permanent disabil-
ity, and results in the bird being unable to fly, if not caught when a slight change in the wing
feather growth is noticed. Angel wing can usually be corrected if caught very early, by bandaging
the wing in a natural position for 2 days. Wing wraps must not be left on longer than 2 days due to
the fast growth rate of a crane colt. Usually, one treatment is effective to correct the condition (Ellis
et al. 1996).
Angel wing is commonly caused by feeding white bread to young colts or waterfowl. Wild crane
colts hatched near parks or other recreational areas that bring humans into contact with young
wild cranes can be affected by the human need to feed bread to birds.

Feather­Problems

Quality of feathers is often underestimated in evaluating suitability for release of both captive-
raised cranes and those that have been rehabilitated. Attention to feather quality (stress bars, dull
or dirty, broken feathers, and issues such as barb defects) is essential. Feathers are responsible for
maintaining waterproofing to prevent hypothermia, as well as for flight. Feathers directly affect the
survival of a bird living in the wild. Malnutrition or other conditions can cause feather changes
and indicate that the bird is not ready for release. Birds that fit this description should be retained
and given supportive nutritional care. Feather damage can be so severe as to delay the release of an
otherwise releasable crane until molting occurs.
Broken primaries can occur with injury, or because of a viral infection. Feathers can also be bro-
ken or in poor condition due to even a short time period in inadequate or inappropriate housing.
Primaries can be imped, a process by which replacement feathers are fixed artificially into existing
feather shafts, with the same methods as those used for raptors.

­ Imprinting­and Habituation

Imprinting and habituation are very different behaviors. Imprinting is the permanent alteration of
sexual identity and species orientation. Imprinted birds can be imprinted to humans, objects, or
even another species when cross-fostering techniques are used. During early efforts to save the
Whooping Crane from extinction, Sandhill Cranes were used to cross-foster Whooping Crane
colts. The result was that the young Whooping Cranes never learned the courtship behavior
expected of a Whooping Crane and were rejected by them. Sandhill Cranes also rejected the young
Whooping Cranes, likely due to vocalization variations (Ritchie et al. 1994; Baughman 2003).
The process of imprinting begins soon after hatch and continues at least through the first month
of life. Recent evidence suggests that imprinting can occur in birds with a long lifespan and slow
maturity post-fledge. Imprinting is thought to be associated with food delivery during the first days
or weeks of life. It is at this time that the young bird incorporates and retains important sounds and
behavior clues that become a permanent part of its identity. Imprinting aids natural reproduction
in terms of recognizing or attracting a mate. Vocalization development of imprinted birds may be
impaired, with chick calls being retained for a lifetime. Aggression often occurs in imprinted birds,
particularly when they reach breeding age. Imprint aggression can be extreme. Imprinted birds
should be considered dangerous and unpredictable. Human-imprinted birds can pose a danger to
humans and should never be released to the wild or used in wildlife petting zoos due to the unpre-
dictable nature of this aggression. If they are maintained in captivity, they should be handled by
only the most experienced handlers.