Captive propagation and reintroduction programs for rare and endangered species rarely have the luxury of testing methods and techniques prior to initiating recovery efforts. From 1993 to 1996 I used Common Ravens (Corvus corax) in southwestern Idaho as surrogates for the endangered Hawaiian Crow (Corvus hawaiiensis) and Mariana Crow (Corvus kubaryi) to experimentally test the effects of rearing social, altricial birds with or without a puppet. Puppet-rearing uses a conspecific, parental model (puppet) to reduce sexual and filial imprinting on human caretakers. Traditionally, puppet-rearing has been used when parent-rearing or fostering is not an option.
Rearing ravens with a puppet did not affect social behaviors prior to release or dispersal from the release area. Similarly, integration with wild birds after release was not affected by puppet-rearing. However, ravens raised with a puppet were more fearful of caretakers and were more vigilant prior to release. This appears to have translated into improved survival within the study area after release. Rearing with a puppet is not necessary for appropriate sexual imprinting if social, altricial birds can be raised with conspecifics. Therefore, it is important for researchers to consider the species and the desired pre- and post-release behaviors to determine if rearing with a puppet is appropriate for their recovery efforts. This can be accomplished by using a surrogate species prior to recovery efforts and adaptive management approaches in the initial phases of an endangered species recovery program.
Despite good intentions and vast resources, the success rate of reintroduction efforts for endangered species is poor. To improve the success and credibility of reintroduction programs, techniques must be experimentally tested. This can be accomplished by using surrogate species that are closely related or behave similarly to an endangered species. From 1993 to 1995, I used three common species of corvids as surrogates for endangered Hawaiian Crows (Corvus hawaiiansis) and Mariana Crows (Corvus kubaryi) to determine if raising a bird with a wild, older, conspecific tutor would affect behavior and improve survival. I used 161 Common Ravens (Corvus corax), American Crows (Corvus brachyrhynchos), and Black-billed Magpies (Pica pica) as surrogates because they bracket the range of behaviors and body mass of the two endangered species. Raising a bird with a tutor did not significantly affect social or vigilant behaviors prior to release. However, ravens raised with a tutor bad increased evenness of vocalizations and dispersed the release area sooner than ravens raised without a tutor. Crows raised with a tutor gave more alarm vocalizations and had higher survival between the day of release and the day of dispersal from the release area. However, raising a bird with a tutor did not affect survival or reproduction after dispersal from the release area.