Translocation implications for the song repertoire of the kōkako

The North Island Kōkako, Callaeas cinerea, use song in year-round territory defence and strengthening monogamous pair bonds.  Sandra Valderrama and co-workers described song repertoire in six natural populations, and two translocated populations on New Zealand's North Island to describe how population size affected this important behaviour.

They found that pairs in smaller populations have lower song diversity and higher shared song phrases than larger populations.  In many cases translocated populations are very small relative to the size of natural populations and this study was no exception – the two translocated populations consisted of only 18 and 20 individuals. Higher numbers of founding members may be helpful in accelerating population growth through more efficient pair formation and territory establishment and defence.

Their findings also have implications for selecting individuals from natural populations for translocation.  Translocations using individuals from multiple donor populations may result in individuals from smaller populations being at a disadvantage due to a smaller song repertoire and therefore, reduced ability to find mates. This may have knock-on effects for the genetic mixing of individuals from different donor populations – if the birds from smaller populations cannot find a mate due to a lack of the right ‘vocabulary’, their genes will not be represented in the newly created population.

Valderrama, S. V., Molles, L. E., & Waas, J. R. (2012). Effects of Population Size on Singing Behavior of a Rare Duetting Songbird. Conservation Biology, no–no. doi:10.1111/j.1523-1739.2012.01917.x