Wedge-tailed Shearwaters of Mutton Bird Island Nature Reserve.

David Page
 

Aims and significance of the project:

Mutton Bird Island

Location: Mutton Bird Island, Coffs Harbour

Objectives: To study the seabird population on the island, looking at mean weights of chicks and burrow densities:
1) population demography
2) movement patterns
3) morphometric data

Methods: The main method for trapping is by hand. Burrow densities undertaken by a one metre grid method.
 

Summary of banding data:

Discussion on gaps in knowledge:

I would like to highlight a number of gaps in knowledge that require further investigation. The question of lights and the impact on chicks has been a long ongoing topic. This year I did some literature searches on the topic and came up with only one paper on a similar problem:

Reed J. R., Sincock J. L. and Hailman J. P., 1985: Light attraction in Endangered Procellariiform birds: Reduction by shielding upward radiation: The Auk 102: 377-383. April 1985.

This paper discusses the problem of thousands of individuals of seabirds being found on the ground in the vicinity of bright lights near the coast on the island of Kauai, Hawaii. I think it is important to consider the population size of the shearwaters on Mutton bird Island with estimates of between 6000 to 9000 breeding pairs and numbers of young that find themselves in problems each year. The question is: is the number that come ashore statistically above the average of normal mortality for fledging seabirds? The study in Kauai give numbers of 1,133 to 1,451 birds per year. The other interesting point raised is that “TV Towers in Florida may not be due to light-attraction; birds may simply strike the tower and support wires because they cannot see the structures in the dark” (Reed J. R., Sincock J. L. and Hailman J. P., 1985). It is interesting to note that the location of the yachts in the Jetty area is closest to the island. These yacht’s masts and wires could play a role in the numbers of fledging shearwaters that come into problems

I believe that shielding to the eastern lights along the break wall would play a useful option but the argument of whether lights in the whole of the Jetty area cause problems needs further study before such a conclusion could be made. In fact some comments in the past could lead to some theories being taken as fact without proper scientific facts. There maybe more than one factor playing a role in this issue and caution is needed.

The other gaps in knowledge that needs further research is where the shearwaters of Solitary Island group are feeding while breeding on these islands. This work is needed to determine their feeding grounds and what impact, if any, fishing or global warming is having on population numbers. The work I am undertaking on mean weights shows that over three years the mean weight has not changed significantly but over the long term such studies would be a useful indicator of trends in food resource for this species. The other aspect that needs further study is the impact of humans, native and feral animals on the shearwater breeding success. To date there has been limited work undertaken on these topics and further scientific studies are needed to compile the full picture on shearwater breeding activities. Work to date has answered the question of shearwater migration from Mutton bird Island. The retrap data below shows clearly the species travels north to Asia.

I believe strongly that because of the easy access to Mutton bird Island and past research on the island that universities should be approached to encourage post-grad studies into this population.