Hawaiian Crow
Hawaiian Crow, Corvus hawaiiensis
I collaborated with Dr. Patrick Hart, Dr.Richard Switzer (at Keauhou Bird Conservation Centre), and Ann Tanimoto to assist with cataloguing and examining the vocal repertoire of the 'Alala, (Hawaiian Crow).
Cataloguing the Vocalizations of the `Alala (Hawaiian Crow)
The Hawaiian Crow has been federally protected since 1967. Since 1970, a captive flock has been maintained. Between 1993-1998, 27 captive raised juveniles were released into the wild. Of these, 21 died and 6 were recaptured and returned to captivity. Currently, the highest priority in the recovery strategy is to maintain and expand the captive flock without further loss of genetic diversity (U.S. Fish and Wildlife Service 2010).
Articles on the Hawaiian Crow/ Hawaii bird conservation
Hawaii endangered bird conservation program
Why Study `Alala?
Attention to behavioural detail, such as acoustic communication, could aid in developing effective habitat management and population recovery programs (Bechet et al. 2004; Norris 2004). Reintroduction of captive Hawaiian crows into the wild has had limited success, which may be due to the fact that all currently available habitat is degraded. Moreover, captive-reared birds may lack foraging and other skills that were culturally transmitted in wild flocks (U.S. Fish and Wildlife Service 2003). Vocalization in corvids can be culturally transmitted. In a study of raven vocalizations (Enggist-Dueblin & Pfister 2002), the repertoires of 81% of all individuals were composed entirely of calls shared with others. Because bird vocalization is culturally transmitted it is a rapidly evolving trait. However, this also means that vocalizations can also be rapidly lost.
Decreasing population size may also result in decreasing song repertoire within a population, which may translate to loss of song culture. This has strong implications for population recovery programs, in that birds released from a small population may have a decreased song repertoire, and perhaps a decreased ability to communicate with conspecifics. Cultural transmission of songs in ravens is transmitted within sexes, as well as between pair partners, neighbours and more distant pairs. Further, individual raven's repertoires are restrained to a small set of vocalizations existing in a population (Enggist-Dueblin & Pfister 2002).
Studies have shown that avian communication systems can be altered by habitat loss (Holland et al. 1996; Seibt et al. 2002). The Hawaiian Crow habitat has been substantial altered by human activity, to the point that habitat loss was speculated to result in death in juvenile crows. These changes may have also limited nesting resources as well. Yet, food resource remained plentiful as the crow is an opportunistic feeder (Sakai et al. 1986). A previous study on Dupont's Lark found that the occurrence of anthropogenic habitat barriers seemed to hinder cultural transmission of song types over distance (Laiolo & Tella, 2005). Alterations to the habitat may result in alterations to avian communication, which may render the 'alala more vulnerable to extinction.
Little is known about the reproductive biology of the Hawaiian Crow in the wild. No information exists on courtship, reproductive behavior, nesting and incubation patterns (Harvey et al. 2002). A previous study quantified behavioral interactions between a captive pair at the nest, but this study did not include data on vocalizations (Harvey et al. 2002). To date, nothing has been published on song repertoire of the Hawaiian Crow. Hawaiian crows have been recorded in the wild and in the aviary (1990-2000). We have digitized a fraction of these recordings and have produced digital audiofiles and spectrograms using Raven 1.3 (Cornell Lab of Ornithology) of over 65 different crow syllables. We plan to continue to digitize the rest of the analog cassette tapes before they further degrade. Further, we plan to identify song types and calls associated with different social situations.
Literature Cited
Bechet, A.; J.F. Giroux and G. Gauthier. 2004. The effect of disturbance on behavior, habitat use and energy of spring staging snow geese. Journal of Applied Ecology 41: 689-700.
Enggist-Dueblin, P. and U. Pfister. 2002. Cultural transmission of vocalizations in ravens, Corvus corax. Animal Behaviour 64: 831-841.
Harvey. N.C. ; S.M. Farabaugh; and B.B. Druker. 2002. Effect of Early Rearing Experience on Adult Behavior and Nesting in Captive Hawaiian Crows (Corvus hawaiiensis). Zoo Biology 21: 59-75
Holland. J.; P.K. McGregor and C.L. Rowe. 1996. Changes in microgeographic song variation of the corn bunting Miliaria calandra. Journal of Avian Biology 27: 47-55.
Laiolo, P. and J.L.Tella. 2005. Habitat fragmentation affects culture transmission: patterns of song matching Dupont's lark. Journal of Applied Ecology 42: 1183-1193.
Norris. K. 2004. Managing threatened species: the ecological toolbox, evolutionary theory and declining population paradigm. Journal of Applied Ecology 41: 413-426.
Sakai, H.F.; C.J. Ralph, and C.D. Jenkins. 1986. Foraging Ecology of the Hawaiian Crow, an endangered generalist. The Condor 88: 211-219.
Seibt, U.; W. Wickler; H.U. Kleindienst and E. Sonnenschein. 2002. Structure, geography and origin of dialects in the traditive song of the forest weaver Ploceus bicolor sclateri in Natal, S. Africa. Behaviour 139: 1237-1265.
U.S. Fish and Wildlife Services. 2010. Revised Recovery Plan for the Hawaiian Crow (2010)
USFWS Photo
USFWS Photo
Spectrogram and waveform (in Raven Pro 1.3 window) of calls from the
Hawaiian Crow
Spectrogram and waveform (in Raven Pro 1.3 window) of calls from the
Hawaiian Crow