Non-breeding ecology of New Zealand falcon (Falco novaeseelandiae) in a pine plantation forest : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Zoology at Massey University, Manawatu, New Zealand
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Date
2017
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Massey University
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Abstract
Deforestation and conversion to intensive agriculture historically caused a large
reduction in numbers of the New Zealand falcon or Kārearea (Falco novaeseelandiae),
resulting in its current classification as Nationally Vulnerable. Several studies in
plantation forests have documented the ecological benefits of limited timber
harvesting on diversities of avian species through providing habitat heterogeneity.
New Zealand falcons occur in managed plantation forests. To date, however, detailed
information regarding falcon prey abundance, habitat use, home‐range size, and
breeding behaviour has been limited to their breeding season. Little is known about
their winter use of managed forests and how forest operations affect their survival and
reproductive ability by restricting their mating system.
I investigated a falcon population living in a large plantation forest, Kaingaroa forest
through addressing the following questions: (1) how changes in forest structures
influence falcons’ habitat use and home‐range size in relation to winter prey
abundance and availability, (2) how the reduction in habitat heterogeneity by largescale
harvesting affects falcon’s home‐range size and overlap, (3) the risk of secondary
poisoning from 1080 operations and falcon annual survival, and (4) how constraints by
changes in the forest structure and compositions shape the mating system of the
Kaingaroa falcon population. I used radio‐tracking data to establish the extent and
habitat composition of winter home‐ranges, and monitoring survival of falcons before
and after 1080 poisoning operations. I used transect surveys to assess the availability
of potential prey birds, and behavioural observation to measure pair breeding
activities.
I found that falcons used the ecotone between mature‐pine stands and young‐pine
stands (the edge‐habitat) most frequently followed by their hunting ground (youngpine
stands – 0–3‐year‐old pine trees). Total prey abundance was similar across all
habitats and sizes of open fields. The dynamic changes to forest structure created by
clear‐cutting and its effect on prey accessibility are the most profound factor
influencing falcon space use. Winter home‐range sizes of forest falcons (used
Kaingaroa exclusively) were smaller than those of farmland falcons, which used
farmland > 10 % of total tracking duration. I found that falcons used smaller home
ranges when the forest provided the edge‐habitats that were concentrated among
mature‐pine stands through creating open‐patches less than 3 km2 that are distributed
closely (< 3 km apart). Results indicate that timber forests could hold a greater number
of falcons with these forest compositions. Thirty‐seven adult New Zealand falcons
were exposed to carrot bait 1080 poison during the three winter months (May–
August), and 17 adult falcons were exposed to cereal bait 1080 poison by aerial
droppings in 2013 and 2014, and all these falcons except one survived. One radiotagged
male died and although a toxicology test found not 1080 residues, however,
the possibility of 1080 secondary poisoning was not entirely cleared. The survival rate
of adult Kaingaroa falcons was 80% and that of juveniles was 29%. All divorces (40%)
were initiated by females leaving their territories regardless of reproductive outcomes,
while males exhibited greater mate and site fidelity. A high rate of extra‐pair
interaction occurred by females (71%) but was absent in males. Female’s extra‐pair
interaction implemented as their strategy for securing breeding opportunities. In
contrast, the mate‐guarding strategy may be the most effective male’s mating strategy
in the Kaingaroa falcon population. Male’s vigilant personality likely enhanced mateguarding
performance. Home‐range overlap was greater in pairs that retained partners
than pairs that divorced. Winter courtship displays were used for pair formation (the
process of establishing a social bond) rather than pair bonding (the process of
maintaining a social bond), and also used for intra‐sexual competition over females. A
rapid rotation of habitat quality and sufficient prey availability in the area may shape
falcons’ various mating systems.
A further long‐term continual monitoring that includes the juvenile falcons is required
to measure the effects of 1080 poison on the Kaingaroa falcon population. A welldesigned
harvesting regime could enable the timber industry to contribute importantly
to the conservation of this threatened New Zealand raptor.
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Keywords
New Zealand falcon, Ecology, Kaingoroa State Forest, New Zealand, Karearea, Research Subject Categories::NATURAL SCIENCES::Biology::Terrestrial, freshwater and marine ecology::Ethology and behavioural ecology