Effects of translocation on kokako (Callaeas cinerea wilsoni) song and its application to management : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Conservation Biology at Massey University, Palmerston North, New Zealand
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Date
2009
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Massey University
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Abstract
This thesis fills a research gap in our knowledge of kokako song by looking at how song
evolves in multi-dialect areas. Kokako only exist in small remnant populations separated by
large tracts of unsuitable land. Kokako are very poor flyers, only able to fly for
approximately 100 metres at a time. In order to prevent inbreeding and a loss of genetic
diversity in the remaining kokako populations, managers are carrying out translocations to
establish new populations, maintain gene flow and prevent inbreeding. However, these
translocations have the potential to be unsuccessful because kokako exhibit
macrogeographic variation in their dialects, and tend not to breed with individuals who do
not share the same dialect as them. If the purpose of the translocation is to enhance genetic
diversity by having kokako from different areas breed then song is an important factor that
must be dealt with. Song is extremely important to kokako for a number of reasons.
Chiefly, it is hypothesised that song is their primary means of territory defence. A kokako
gains all its resources from its territory, so it is imperative that they successfully defend it.
Their duet song functions in territory defence, but also acts to form and maintain pair
bonds.
In order to try and address the problem that song causes in translocations I studied if and
how song evolves in a multiple dialect area. I conducted research at Pukaha Mount Bruce,
where there is a population of kokako originating from two different source populations,
and thus two different dialects, Northern Mapara and Mangatutu. I looked at the Northern
Mapara dialect, and recorded kokako belonging to three groups; kokako currently living in
the source population, kokako that were translocated to Pukaha and kokako that were born
at Pukaha. In order to determine how the song may be changing I looked at element
repertoires, the levels of sharing between groups, the number of unique elements in
repertoires and the syntactical and temporal characteristics of phrases.
This study shows that translocation into multiple dialect areas can affect kokako song.
Translocation did not affect the size of the kokako repertoire, but it seemed to affect the
amount of sharing within and between different groups of kokako. Currently the level of
sharing within the groups at Pukaha is lower than the level of sharing within the source
Mapara population, indicating that the song may be diverging. There also seem to be more
unique elements found at Pukaha, which in part explains the lack of sharing. There appears
to be microgeographic variation at Pukaha, with birds clustered around the second
(Mangatutu) dialect sharing less with the source population than do those kokako whose
territories are lower down in the reserve. The phrases which are used are also evolving,
with only one phrase truly shared among all groups. There are other phrases which show
additions or deletions of elements, and so are evolving. The main change found in the
phrases is the timing between elements, with six out of seven phrases examined showing
changes.
These results have repercussions for future kokako translocations, and the future of the
Pukaha kokako. A low amount of phrase and element type sharing combined with changes
of intra-phrase timing could lead to the Pukaha kokako’s inability to successfully defend
their territories. This research shows how kokako song can give conservation managers
information on the status of their populations in regards to interbreeding and raises
questions which can be answered by further research, both at Pukaha and in other mixeddialect
kokako populations.
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Keywords
Kokako, Callaeas cinerea wilsoni, Bird song, Conservation biology, New Zealand