Conclusion and Conservation Implications:
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Evidence from this research does not support the need for managing three distinct populations of New Zealand falcon. I did however identify distinct morphological populations correlating with the North and South Islands. New Zealand falcons located in the North Island had significantly shorter wings than those falcons in the South Island. While no significant population genetic structuring was identified in neutral markers there was some structuring present in the population. Larger sample sizes and in increase on marker numbers may shed more light on this in the future. The low level of variation and lack of partitioning suggests a recent origin of morphological
differences in populations.
The largest barrier for juvenile dispersal in falcons in New Zealand is likely to be geographical barriers such as the Cook Strait. Beyond this, habitat differences,
philopatric behaviour and other behaviours such as nest imprinting may play a role in the morphological differences arising in the populations throughout the North and South Islands. It maybe that falcon size is a response to a gradient of environmental conditions corresponding with Bergmann’s rule, but this is may be partially countered by movement within the islands at the juvenile stage to average out the size variation within the islands, resulting in two distinct size morphs.
Estimating genetic divergence among populations is crucial for the conservation of many threatened and endangered species (Allendorf & Luikart, 2007).The Zealand falcons population structure has always been poorly understood and being classed as taxonomically indeterminate/data deficient (Robertson et al, 2013) has meant that they are without a conservation management plan. There are few guidelines on managing New Zealand falcons, as there is currently no Department of Conservation Recovery Group (pers. comm.). We know a number of New Zealand birds show North Island and South Island polymorphism; and that these are usually managed as distinct populations by the Department of Conservation.
Many management programs are concerned with resolving taxonomic uncertainties among groups in order to prioritize the conservation efforts below the species level
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(e.g. subspecies and evolutionary significant units), which is important because much of the existing taxonomy may not reflect the underlying genetic diversity present (Hass et al, 2009). Unfortunately, basic information on population genetic structure is lacking for many threatened species, hindering conservation and management actions such as translocations and reintroductions (Moritz, 1999).
New Zealand conservation managers have used translocations and reintroductions to assist the recovery of many endangered species (Griffith et al 1989, McLean &
Armstrong 1995). Currently New Zealand falcons are bred and released into the wild at only a few sites around New Zealand (Wingspan Birds of Prey Trust, Marlborough Falcon Conservation Trust). Wild falcons are rarely moved except if injured and there is a need for medical attention/rehabilitation and then returned to the wild.
Translocation of individuals among extant populations is an important tool in species conservation that allows managers to supplement dwindling populations and
potentially alleviate the deleterious effects of inbreeding. Ideally, translocations should reflect the historical relationships among populations in order to avoid disruption of existing population subdivision and local adaptation (Avise 1989, Storfer 1999). Managers of blue duck (Hymenolaimus malacorhynchos) have advised to only translocate individuals around neighbouring populations and not between the North and South Islands due to the presence of two genetically distinct populations
(Robertson et al. 2007). Blue ducks are clearly less mobile than New Zealand falcons, generally staying within their catchment area, but like New Zealand falcons little is known on the juvenile dispersal of the species (Robertson et al, 2007). To conserve any local adaptation within the Blue duck populations, managers have been advised to only translocate individuals from within these catchment areas and neighbouring regions (Robertson et al, 2007). New Zealand falcons may also show local adaptation within the North and South Islands (even with the flexible ecology they seem to possess), supporting the current management of not translocating between the North and South Island populations.
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There is also a need to revise population size estimates in the New Zealand falcon, currently the estimates are for each of the three originally proposed morphs (Bush, Eastern and Southern) and subsequently the Southern morph is reported as having very low numbers. Population numbers should be reassessed for North and South Island populations. Further work in falcon population structure may include genetic analysis with larger sample sizes and a larger number of loci and research into juvenile movement using satellite transmitters to determine the extent and timing of natal dispersal. New Zealand falcons have low genetic diversity but expanding the genetic research will provide a better picture of the possible structure within the species and morphological and genetic work with recent fossil falcon bones could be used to gain an insight into the evolutionary history of the New Zealand falcon informing on past genetic diversity, changes in shape and gene flow.
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Allendorf, F.W. & Luikart, G. (2007) Conservation and the Genetics of Populations. Malden, MA: Blackwell Publishing.
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