The primary objective of the study was to determine why established females tolerate new females that join their breeding group and lay eggs in their nest. Previous work on this population has shown that females suffer a cost of joint-nesting in the form of lowered hatching success. Therefore, we would expect female pukeko to attempt to disrupt the reproductive efforts of their co-nesters by ejecting their eggs from the joint nest.
Two hypotheses might explain why this does not happen. The "peace incentive" hypothesis states that females would forego egg destruction to avoid retaliatory behaviour by the other female. Alternatively, females might not destroy the eggs of co-nesters because they cannot discriminate between their own and another female's eggs. To test between these, we experimentally removed the eggs of one of the females from a number of joint nests. In all S(Wen cases for which we have data on the post-removal behaviour of the females, the robbed female showed no response to the disappearance of her eggs and continued to incubate the clutch.
In addition, we added eggs to eight single female nests. Again, the single females showed no sign that they could distinguish between the foreign eggs and their own. The foreign eggs were not buried, ejected, or destroyed, nor were they moved preferentially to the outer perimeter of the clutch.
To perform the egg removal experiments, I needed to correctly group joint clutches of eggs into maternal sib-groups. I evaluated two methods of doing this, one relying on qualitative observer assessment and the other on statistical techniques. I determined genetic maternity using DNA fingerprinting. Qualitative assessment was more effective than statistical techniques for identifying the maternity of eggs. Such an approach may be a useful alternative to expensive and time-consuming molecular genetic techniques for measuring reproductive skew in joint-nesting birds.
Predation rates on pukeko nests at our study site during the 1998/99 nesting season were significantly higher than they had been in previous years (1990-1995). In the intervening years, the local rabbit population crashed as the result of two rabbit control measures: poisoning and rabbit haemorrhagic disease (RHD). We hypothesised that the increase in predation rates was due to rabbit specialist predators seeking out alternative prey after the crash in rabbit populations. Such a scenario is of grave concern to wildlife managers in many areas of New Zealand where rabbits are abundant and threatened native bird species are already under extreme pressure from introduced predators. / Thesis / Master of Science (MS)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/23477 |
| Date | 08 1900 |
| Creators | Haselmayer, John |
| Contributors | Quinn, Dr. James, Biology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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