Compelling research and hi-tech nest-boxes help wild Swift Parrots

October 10th, 2019 | by David Waugh
Compelling research and hi-tech nest-boxes help wild Swift Parrots
Conservation projects
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Recognising that the wild population of the migratory Australian Swift Parrot (Lathamus discolor) was in free-fall, in 2010 the Loro Parque Fundación began supporting a vital research initiative to unearth the principal threats and to devise effective measures to combat them. Since then, a cooperative effort of several in-country institutions has been led by Professor Robert Heinsohn of the Fenner School of Environment and Society at the Australian National University. The research includes the ecology of the species in the south-east of mainland Australia during the Austral winter non-breeding season, and in Tasmania where core team member Dr. Dejan Stojanovic and colleagues have been studying the parrots during their breeding season in the Eucalyptus-dominated forests. The remarkable detective work of the researchers is revealed in several recent publications, and surely nobody back in 2010 could have predicted all the twists and turns in the life of this little parrot.

Logging of forest in Tasmania (c) E. Capp

At the inception of the research, the Swift Parrot was already in the ‘Endangered’ category of the IUCN Red List of Threatened Species, but the researchers found the population decline so rapid that the species was soon up-listed to ‘Critically Endangered’, with a maximum total of 2,500 individuals, and possible as few as 1,000. The most immediate serious threat was found to be the nocturnal predation of nest-contents, including adult females, by Sugar Gliders (Petaurus breviceps) introduced on mainland Tasmania (not the smaller satellite islands).

Satellite image of Tasmania showing forest loss/disturbance between 1996 and 2016 (red) and potential swift parrot breeding range (yellow line). The enlargement shows the Southern Forest study area. (c) Webb et al., 2019

The research team surveyed Sugar Glider occurrence at 100 sites within about 800 km2 in the Southern Forest, a key breeding area for Swift Parrots. They found a very high detectability and occupancy of Sugar Gliders, with naïve occupancy (i.e. the proportion of sites in which Gliders were detected) of 79%. Predictions of occupancy indicated higher levels in areas with greater cover of mature forest (best quality breeding habitat for swift parrots), those areas with almost 100% cover suffering nearly complete occupancy by Sugar Gliders. Furthermore, the research revealed high rates of occupancy of available forest habitat throughout the heavily logged study area, such that even when mature forest cover was less than 10%, Sugar Glider occupancy was more than 50%. Therefore, the risk of predation by Sugar Gliders for Swift Parrots and other small birds may be widespread across logged Tasmanian forests. The researchers are now working to determine whether population densities of Sugar Gliders vary with forest cover, and whether this may affect the frequency of predation (Allen et al., 2018).

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Total loss of eucalypt forest (ha) between 1997 and 2000 (grey bar). Cumulative loss of eucalypt forest each year from 2000 to 2016 (black line). (c) Webb et al., 2019

There has been another disturbing effect of the Sugar Glider’s behaviour. The high predation on females not only causes severe population decline, but also produces strongly biased adult sex ratios (more than 73% are male) in a normally monogamous species. The research has shown that 50.5% of Swift Parrot nests had shared paternity, although the birds remained socially monogamous, and that shared paternity increased significantly with the local rate of predation on breeding females. This suggests that rates of shared paternity increased when the adult sex ratios became more biased. Nests not predated had fewer fledglings as the local adult sex ratio became more male‐biased, possibly due to more harassment during nesting from unpaired males. Analysis of population viability predicted that the Swift Parrot population would decline by 89.4% over three generations if the birds maintained the lowest observed rate of shared paternity, but reductions of 92.1–94.9% under higher rates of shared paternity. In short, shared paternity is very costly and can lead to changes in the mating system and negative impacts on both individual fitness and long‐term population viability (Heinsohn et al., 2019).

Dejan Stojanovic checks a nest-box (c) Dejan Stojanovic

That the Swift Parrot faces a severe extinction risk is further supported by evidence from a population genetic analysis using samples obtained over six years from across the breeding range of the species. The analysis showed no evidence for genetic differentiation across the samples both spatially and temporally, indicating a lack of population genetic structure and that the species is a single panmictic population, i.e. where all individuals are potential partners and there are no mating restrictions. It supports the premise that Swift Parrots act as a single conservation unit. This is a key difference from sedentary or site-faithful species, because unpredictable resources (flowering Eucalyptus) can stimulate large scale movements of nomadic Swift Parrots away from predator-free offshore islands towards mainland areas with many Sugar Gliders. The researchers conclude that island nesting alone may be insufficient to offset extinction risk from high mainland predation rates and that conservation action in predator-infested mainland habitats will be critical to prevent extinction of the Swift Parrot. Action must include limiting deforestation in breeding habitat, protecting parrot nests in Sugar Glider-infested forests, and augmenting nesting habitat on islands (Stojanovic et al., 2018a).

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The hi-tech nest-box door excludes a Sugar Glider. (c) Dejan Stojanovic

In light of the afore-mentioned findings and recommendations, it is reasonable to expect that existing conservation plans could be implemented, and even improved. Regrettably, failings in forest policy and management still allow Swift Parrot breeding habitat in Tasmanian forests to continue to be logged. Positive changes require that official recommendations for the management of threatened fauna be binding on the relevant government agencies, instead of voluntary as now. Also, Swift Parrot habitat requirements must be used to identify areas for exclusion from logging from those areas designated to meet legislated timber quotas. Finally, budgetary provision must be made to compensate for forestry curtailment on private land (Webb et al., 2019).

Thus, if habitat loss continues it will be for socioeconomic reasons, not uncertainty about the species’ requirements. Not to lose time, practical action by the researchers is underway to address conservation needs of the Swift Parrot. Because it is a nomadic species, its unpredictable settlement patterns could make its conservation problematic because of the difficulty to identify where to implement action. However, the research shows that flower bud growth is the primary cue for Swift Parrots to select an area and the parrots settle wherever bud abundance is highest, including the Southern Forest study area. Using this knowledge, the researchers created artificial nests of two types, nest-boxes and carved cavities, at three predicted breeding sites before the birds arrived. The subsequent occupancy of artificial nests was greatest at the site with abundant historical natural nesting sites.

A brood of Swift Parrots in a nest-box. (c) Dejan Stojanovic

The average temperature of nest-boxes (12.8oC) was cooler than natural cavities (14.1oC), the average absolute maximum temperature of nest-boxes (15.6oC) was lower than natural cavities (17.6oC), and the average absolute minimum temperature of nest-boxes (11.0oC) was also lower than natural cavities (12.0oC). Despite these significant temperature differences between artificial and natural nests, differences in clutch size, brood size, or body condition of Swift Parrots in each were not significant. Average clutch size in nest-boxes was 4.55 (+0.85) and in natural cavities 4.33 (+1.02), and brood size in nest-boxes 4.22 (+0.75) and natural cavities 4.06 (+0.98) (Stojanovic et al., 2018b).

A skilled arborist carves an artificial nesting hollow. (c) N. Whiting

Perhaps the most remarkable aspect of the nest-boxes is the incorporation of hi-tech to exclude Sugar Gliders. The box has a light sensor which, as soon as it’s daytime, automatically detects that there is ambient light and triggers a small motor to open a door over the entrance to release the adult Swift Parrot to continue its normal daytime activity. As the light fades at the end of the day and the Swift Parrot is back in the box, the sensor triggers the door to close for the night. Trials with the nest-boxes have shown that the parrots are not at all disturbed by the light-triggered door. Each nest-box is expensive, but the researchers are crowd-funding to be able to install as many as possible. Similarly, the artificial nesting hollows have proven popular with the Swift Parrots. Carved by volunteer skilled arborists, only two weeks after their completion seven pairs of parrots had claimed hollows and three eggs had been laid.

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Stages in the creation of an artificial nesting hollow. (c) DELWP

Therefore it seems that these techniques will help to provide a much-needed breathing-space for the Swift Parrot, during which time it is hoped that forest conservation policy will take due note of the research, and that practices will improve to avoid the extinction of this little nomad.

References

Allen, M., Webb, M.H., Alves, F., Heinsohn, R. & Stojanovic, D. (2018) Occupancy patterns of the introduced, predatory Sugar Glider in Tasmanian forests. Austral Ecology 43: 470–475.

Heinsohn, R., Olah, G., Webb, M., Peakall, R., & Stojanovic, D. (2019) Sex ratio bias and shared paternity reduce individual fitness and population viability in a critically endangered parrot. Journal of Animal Ecology 88: 502–510.

Stojanovic D., Cook H., Sato C., Alves F., Harris G., McKernan A., Rayner L., Webb Matthew H., Sutherland W. J. & Heinsohn R. (2018b) Pre-emptive action as a measure for conserving nomadic species. Journal of Wildlife Management 83: 64–71.

Stojanovic D., Olah G., Webb M., Peakall R. & Heinsohn R. (2018a) Genetic evidence confirms severe extinction risk for critically endangered swift parrots: implications for conservation management. Animal Conservation 21: 313-323.Webb M. H., Stojanovic D. & Heinsohn R. (2019) Policy failure and conservation paralysis for the critically endangered swift parrot. Pacific Conservation Biology 25: 116–123.

Author: Dr. David Waugh, Correspondent, Loro Parque Fundación

Title photo: Swift Parrot and Eucalyptus flower buds. (c) J.J. Harrison

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One Comment

  1. Hello,
    I’m a little french breeder, and I’m in love with this specie.
    Is these a way to help or participate in this program ? Make a donation to nest purchase ?
    Do you know if a program of reintroduction in the nature of female Latham is planned ?
    Thinks for your answers.
    Sarah.

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