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Dr Sarah Pryke from Macquarie University delves into the fascinating world of the endangered Gouldian Finches.
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Gouldian Finches are strikingly coloured birds from the top end of Australia. Male Gouldian Finches are more brightly coloured with more ultraviolet in their blues, greens and purples, making the females less vibrant. Unusually, Gouldian Finches have three distinctly head forms (head morphs) that are genetically controlled in a similar way to the hair colour in people. The three different colours of the head feathers are red, black and yellow and careful study shows that there are large behavioural differences between them.
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| Both male and female red heads are very aggressive and will attack black heads and yellow heads, as well as each other. This makes them very competitive in gaining access to the best nesting holes, an important part of the breeding process.
Sustaining such aggressiveness has its down side however.
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| The high levels of testosterone required to maintain the rage makes them very stressed, meaning they are more susceptible to other life-shortening factors such as parasitic infestations. Male red heads are so preoccupied with fighting they spend very little time raising their offspring, so the female red heads are more like single mothers.
The black heads, which account for some 70% of the Gouldian Finch population, are far more easy going but will still attack the yellow heads. They may not get the best nest sites but they tend to live longer than red heads and the males invest a lot more time in looking after their offspring.
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| Among the Gouldian Finches the yellow heads are the most submissive and tend to completely avoid any interaction with the other head morphs both of which aggressively attack them.
They are easily out competed by the black and red heads and and have the greatest difficulty in finding nesting hollows.
They occur at very low frequency in the wild (less than one per thousand or more) and part of Dr Pryke’s research is to look at what factors have prevented the yellow heads from becoming extinct and continuing to survive at such low population levels.
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One of the most surprising aspects of Gouldian Finches is the ability of the females to manipulate the sex of their offspring depending on the desirability of their male partner. If the partner is desirable then more male offspring will be produced whereas less desirable males will end up with more female offspring. This is related to the sex linking of the three head morphs. Red headed Gouldian Finches can produce all three head morphs and yellow heads can produce black or yellow while black heads only contribute black. So if females have partnered with the more attractive males (for example, a red head) she will tend to produce more males and females partnered with less attractive males seem to produce more females, thus preserving the dominance of the male red headed Gouldian Finch.
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Dr Pryke is also looking at the historical data of the head morphs for the last 100 years. This is possible because the trapping of these birds was not made illegal until the 80s and there are records from the trappers. As well, Gouldian Finches are prized exhibits in museums and private collections all over the world so there is quite a lot of data to collect.
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| A growing problem for all Gouldian Finches is the loss of their particular habitat. They need a diversity of grasses such as sorghum and spinifex. In Queensland Gouldian Finches are virtually extinct because the growth of agriculture has cleared these habitats and in Western Australia the huge Kimberley bushfires destroy grasses as well as nesting sites. Dr Pryke says that Gouldian Finches are literally starving to death, since they cannot adapt to other food sources.
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Part of Dr Pryke’s research is to try and understand the sustainability of the current wild population and how well they are breeding. | A major problem is the loss of more and more suitable nesting sites as old trees are destroyed by the raging bushfires in the Kimberley that burn across such vast areas that they can be seen on satellite images of Earth.
Right and below: the researchers checking nesting sites and boxes.
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Another part of the research is to look at the changing populations of Gouldian Finches and a competitor – the Long-tailed Finch.
Numbers of the Long-tailed Finch seem to be increasing while Gouldians are falling. Whilst the Long-tailed Finch is of similar size, lives in the same areas and uses the same breeding hollows, it has two important differences.
The Long-tailed Finch eats a wider variety of seeds and will swap to eating insects when it needs to, such as the beginning of the wet season when the seed sources become scarce. It is also much more aggressive than even the red headed Gouldian Finch. The Long-tailed Finch will actually go into occupied nest site and chase out the Gouldian Finches.
Sarah is hoping that if her team can put up enough nesting boxes there will be plenty for all comers - Long -tailed and all three Gouldian head morphs.
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Clearly Gouldian Finches are as startling as their colouring and hopefully the research will enable them to have a sustainable population.
Text:V.B. Photos: Sarah Pryke
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