With fewer than 160 birds alive, kākāpō are critically endangered. One reason for their dwindling numbers is that they only breed every few years, when native trees produce masses of edible fruit or seeds.
Our research suggests that the birds’ breeding success depends on oestrogen-like hormones (phytoestrogens) found in these native plants.
Hormone boost from plants
Our study included kākāpō (Strigops habroptilus) and two other New Zealand native parrots, the endangered kākā (Nestor meridionalis) and kea (Nestor notabilis). All three have infrequent breeding success.
Kākāpō in particular have a low reproductive rate and together with the kākā, only breed successfully every three or four years, during mast years, when mass fruiting of native trees occurs.
2016 was a mast year and a record breeding season for kākāpō – the best since New Zealand’s Department of Conservation began managing and monitoring the night parrots 25 years ago.
This link between the parrots’ successful breeding and high levels of fruiting in native plants has focused our investigations on potential stimulants present in their food plants that might activate or improve reproduction.
One hypothesis is that steroid-like compounds in the fruits of certain native plants provide a trigger for breeding. It proposes that kākāpō don’t produce enough of the hormone oestrogen to make a fertile egg, but by eating these fruits and the phytoestrogens they contain, the birds supplement their own hormone levels.
This increases the production of egg yolk protein, which in turn leads to eggs that have a better chance of being fertilised successfully.
We know from other studies that kākāpō seek out the fruit from the native rimu tree (Dacrycarpus cupressinum) during mast years. We believe that this is how kākāpō get extra oestrogen from their diet, and that rimu and other native plants provide a hormone boost that is key to kākāpō reproduction.
Parrots more sensitive to oestrogen
In our current study, conducted by PhD graduate Dr Catherine Davis, we examined the receptivity of New Zealand and Australian parrots to a range of steroid compounds, including oestrogens, and compared it to those of other birds.
We tested various native plant species for oestrogenic content and we found that indeed there is a high amount of phytoestrogens in some of New Zealand’s native plants.
We then looked at the receptivity of parrots to this plant hormone. We studied the genetic makeup of the receptor that is activated by oestrogens in kākāpō, kea, kākā, kākāriki, the Australian cockatiel, and compared this with those in the chicken.
We found that the parrots’ oestrogen receptor was different. All of the parrot species have a unique sequence in the receptor gene, which may make them more sensitive to oestrogen, compared to other bird species, or humans.
In parrots, this receptor contains an extra eight amino acids in the region that binds the hormone.
By adding this amino acid sequence to a computer modelling programme based on the human oestrogen receptor, we have shown that this difference in the parrot-specific receptor would change the strength with which it binds to the oestrogen hormone.
The down-stream effects of this may be an increased sensitivity to plant oestrogens in parrots. This research supports the notion that the parrots’ oestrogen receptor responds differently to oestrogenic compounds in native trees in New Zealand during mast years.
We have previously confirmed the presence of oestrogenic activity in key compounds present in rimu and tōtara (Podocarpus totara), as well as extracts from a number of New Zealand plant species that kākāpō are known to graze. However, the chemical structures of the oestrogenic materials of most New Zealand native plants are not known.
The question remains why the rate of successful breeding of kākāpō in mast years is lower than that of other parrot species. The identification of plant chemicals capable of binding to the parrot oestrogen receptor together with information about plant grazing behaviours of parrots may provide new insights into the conservation of the species that are in decline.
With further research, we are hoping to identify the specific compound in native plants that elicits these oestrogenic properties. This information may enable us to synthesise this compound in the lab. It could then be administered in some way to increase the fertility of our native parrots.
The word “pigeon” evokes thoughts of gentle cooing, fluttering in rafters, and poo-encrusted statues. The species responsible for the encrustation is deeply familiar to us, having ridden waves of European expansionism to inhabit every continent, including Australia. First domesticated thousands of years ago, urban pigeons have turned feral again.
Less familiar are the native species that are not your stereotypical pigeons: a posse of pointy-headed crested pigeons in a suburban park, or a flock of topknot pigeons feeding in a camphor laurel.
The future of Australia’s native pigeons however, may depend on our domestic pigeons. Australia’s domestic pigeon population — both feral and captive – is large and interconnected by frequent local and interstate movements. Pigeon racing, for example, involves releasing captive birds hundreds of kilometres from their homes only so they may find their way back. While most birds do navigate home, up to 20% will not return, of which some will join feral pigeon populations. Birds are also traded across the country and illegally from overseas. These movements, together with poor biosecurity practices, mean that captive pigeons can and do mingle with feral domestic pigeons.
And here’s a paradox. Could Australia’s feral domestic pigeons become the vector for a dramatic decline of columbids – native species on which Australian ecosystems rely?
Emerging viral epidemics
In recent years, two notable infectious diseases have been found to affect our captive domestic pigeons: the pigeon paramyxovirus type 1 (PPMV1) and a new strain of the pigeon rotavirus (G18P). These diseases are notable because in captive domestic flocks they are both spectacularly lethal and difficult to control.
PPMV1, although likely to have originated overseas, is now endemic in Australia. This virus has jumped from captive to feral domestic pigeon populations on several occasions, but fortunately has yet to establish in feral populations.
The movements of captive pigeons, and their contact with their feral counterparts, can be the route through which virulent and lethal diseases – such as the PPMV1 and the G18P – may spread to Australia’s native columbids.
What have we got to lose?
Fortunately, neither PPMV1 nor G18P has crossed over to Australia’s native columbids. We can’t say how likely this is, or how serious the consequences would be, because we have not previously observed such viral infections among our native pigeons.
If the viruses prove equally lethal to native columbids as they are to domestic pigeons, we could see catastrophic population declines across numerous columbid species in Australia over a short period of time.
Should these viruses spread (via feral domestic pigeons), the control and containment of losses among our native pigeon species would be near impossible. Such a nightmare scenario can only be avoided by predicting if and how these viruses might “spill over” into wild columbids so that we can prevent this in the first place.
Protecting our pigeons
Agricultural poultry is routinely screened to check their vulnerability to threats like the PPMV1 and G18P. Such screening is an appropriate response to protect our agricultural industry.
For our native pigeons and doves however, no such similar testing is planned. Based on progress in veterinary vaccine development and advancements in understanding of feral pigeon control, the knowledge and technology required to mitigate this threat should be relatively inexpensive. The threat for these species can be actively managed, now, by improving our biosecurity and vaccination programs for captive domestic pigeons, and eradicating feral domestic pigeons.
The protection of our native columbids however, ultimately relies on valuing their ecosystem functions in the first place.
Male superb fairy-wrens change colour every year, from dull brown to bright blue. But being blue may be risky if you are a tiny bird that is easily spotted by predators.
Published today, our new study found that male fairy-wrens adjust their risk-taking behaviour after undergoing colour change, becoming more cautious while brightly coloured.
Colour and risk
For many males, having beautiful colours is important for attracting choosy females. Researchers think attractive colours come with a cost, so that only the highest quality males can afford to display them. This may be helpful to females looking to select the best mate.
A relationship between bright colours, predation risk and cautious behaviour may seem intuitive; however this is difficult to test. This is because different coloured animals may also differ in their age, size,escape tactics and personality, which can influence both their behaviour and actual predation risk.
To address this, we tested whether individuals adjust their response to risk according to changes in their plumage colour.
Superb fairy-wrens are small, charismatic songbirds. They live in groups with a dominant male and female and, often, several younger males.
These birds are vulnerable to predators such as kookaburras, butcherbirds, currawongs and goshawks. When a group member spots a predator, it gives an alarm call to warn the others. In response, other group members may race for cover, or ignore the alarm and continue about their business.
Male fairy-wrens change colour by replacing dull brown feathers with bright blue, black and indigo ones prior to breeding, turning brown again after the breeding season is complete. Individuals change colour at different times of the year, ranging from the Australian autumn (March-April) to late spring (October).
Although female fairy-wrens have a stable, social partner, when egg-laying time comes, they briefly leave their territory under the cover of darkness and “visit” the male who became blue earliest in the year. Many of the females in the surrounding area prefer the same male, who may father around 70% of the offspring in the neighbourhood. These attractive males are blue for longest (remaining blue for 10-12 months of the year) and so may face the greatest risk of predation.
We gave fairy-wrens different coloured leg bands, allowing us to follow the same individuals over time.
We compared the behaviour of the same males while they were brown and blue, as well as males that remained brown or blue throughout the study. This meant we could test for the effect of colour on responses to perceived risk while accounting for individual differences and possible seasonal changes in behaviour.
We estimated cautiousness in the birds by testing their response to alarm calls. This involved sneaking up on unsuspecting fairy-wrens in their natural habitat and broadcasting fairy-wren alarm calls from portable speakers.
We used two types of alarms: a low-danger alarm, which warns of a moderate threat, such as a predator that is far away, and a high-danger alarm, which signals an immediate threat.
Low-danger superb fairy-wren alarm call. Robert Magrath48 KB(download)
High-danger superb fairy-wren alarm call. Robert Magrath73.1 KB(download)
Costs of being blue
Responses to the low-danger alarm included fleeing for cover, an intermediate response (such as ducking or looking skywards) and no response, when the alarm was ignored. Fairy-wrens fled immediately after hearing the high-danger alarm, but differed in the time taken to return to the open.
We found that fairy-wrens were more cautious while blue; they fled more often after hearing low-danger alarms and took longer to emerge from hiding after fleeing in response to high-danger alarms. Blue fairy-wrens also spent more time scanning their surroundings and less time foraging compared to brown wrens.
This suggests that fairy-wrens perceive themselves to be at a higher risk of predation while bright blue and adjust their behaviour accordingly.
Intriguingly, fairy-wrens also adjusted their behaviour according to the colour of other wrens in the group. When a blue male was nearby, wrens were less responsive to alarm calls and devoted less time to keeping a look-out.
Perhaps this is because fairy-wrens view blue group members as colourful decoys in the event of an attack. This could occur if predators are biased towards attacking the most conspicuous animal, which reduces the predation risk for surrounding individuals. Brown wrens could also be taking advantage of the greater time blue males spend scanning, allowing them to lower their guard.
Being blue for longest gives males the best chance of attracting females, but they need to be extra careful lest they get eaten before it comes to that.
Coauthors on this research are Annalise Naimo, Niki Teunissen, Robert Magrath and Kaspar Delhey.
People who oppose wind farms often claim wind turbine blades kill large numbers of birds, often referring to them as “bird choppers”. And claims of dangers to iconic or rare birds, especially raptors, have attracted a lot of attention.
Wind turbine blades do indeed kill birds and bats, but their contribution to total bird deaths is extremely low, as these three studies show.
A 2009 study using US and European data on bird deaths estimated the number of birds killed per unit of power generated by wind, fossil fuel and nuclear power systems.
wind farms and nuclear power stations are responsible each for between 0.3 and 0.4 fatalities per gigawatt-hour (GWh) of electricity while fossil-fuelled power stations are responsible for about 5.2 fatalities per GWh.
That’s nearly 15 times more. From this, the author estimated:
wind farms killed approximately seven thousand birds in the United States in 2006 but nuclear plants killed about 327,000 and fossil-fuelled power plants 14.5 million.
In other words, for every one bird killed by a wind turbine, nuclear and fossil fuel powered plants killed 2,118 birds.
A Spanish study involved daily inspections of the ground around 20 wind farms with 252 turbines from 2005 to 2008. It found 596 dead birds.
The turbines in the sample had been working for different times during the study period (between 11 and 34 months), with the average annual number of fatalities per turbine being just 1.33. The authors noted this was one of the highest collision rates reported in the world research literature.
Raptor collisions accounted for 36% of total bird deaths (214 deaths), most of which were griffon vultures (138 birds, 23% of total mortality). The study area was in the southernmost area of Spain near Gibraltar, which is a migratory zone for birds from Morocco into Spain.
Perhaps the most comprehensive report was published in the journal Avian Conservation and Ecology in 2013 by scientists from Canada’s Environment Canada, Wildlife Research Division.
Their report looked at causes of human-related bird deaths for all of Canada, drawing together data from many diverse sources.
The table below shows selected causes of bird death out of an annual total of 186,429,553 estimated deaths caused by human activity.
Mark Duchamp, the president of Save the Eagles International is probably the most prominent person to speak out about bird deaths at wind farms. He says:
The average per turbine comes down to 333 to 1,000 deaths annually which is a far cry from the 2-4 birds claimed by the American wind industry or the 400,000 birds a year estimated by the American Bird Conservancy for the whole of the United States, which has about twice as many turbines as Spain.
Interest groups have regularly cited this endangered bird when trying to halt a range of developments.
These include a chemical storage facility and a boating marina. The proposed Westernport marina in Victoria happened to also be near an important wetland. But a professor in biodiversity and sustainability wrote:
the parrot copped the blame, even though it had not been seen there for 25 years.
Victoria’s planning minister at the time, Rob Hulls, described the Bald Hills decision as blatantly political, arguing the federal conservative government had been lobbied by fossil fuel interests to curtail renewable energy developments. Hulls said there had been:
some historical sightings, and also some potential foraging sites between 10 and 35 kilometres from the Bald Hills wind farm site that may or may not have been used by the orange-bellied parrot.
Perhaps the final word on this topic should go to the British Royal Society for the Protection of Birds. It built a wind turbine at its Bedfordshire headquarters to reduce its carbon emissions (and in doing so, aims to minimise species loss due to climate change). It recognised that wind power is far more beneficial to birds than it is harmful.
Simon Chapman and Fiona Crichton’s book, Wind Turbine Syndrome: a communicated disease, will be published by Sydney University Press later this year.
De-extinction – the science of reviving species that have been lost – has moved from the realm of science-fiction to something that is now nearly feasible. Some types of lost mammals, birds or frogs may soon be able to be revived through de-extinction technologies.
But just because we can, does it mean we should? And what might the environmental and conservation impacts be if we did?
Without an answer to “where do we put them?” — and to the further question, “what changed in their original habitat that may have contributed to their extinction in the first place?” — efforts to bring back species are a colossal waste.
These are valid concerns, and difficult to consider in light of the many competing factors involved.
We’ve recently outlined a deliberate way to tackle this problem. Our new paper shows that an approach known as “decision science” can help examine the feasibility of de-extinction and its likely impact on existing environmental and species management programs.
Applied to the question of possible de-extinction programs in New Zealand, this approach showed that it would take money away from managing extant (still alive) species, and may lead to other species going extinct.
Solving complex problems
The potential to reverse species extinction is exciting from both a science and a curiosity perspective. But there is also great concern that in the passionate rush to implement new technology, we don’t properly consider environmental, economic and social issues.
Decision science methods simplify complex problems into parts that describe the benefit, cost and feasibility of the different possible solutions. They allow for “apples to apples” comparisons to be made about different but essential aspects of the projects being considered.
Decision science in action
When applied to de-extinction projects, decision science lets researchers:
compare different possible outcomes of de-extinction approaches
better understand future expected costs and benefits, and
see impacts of using de-extinction technology on other species that we care about.
Over the past decade their management agencies have built on a decision science approach to prioritise their conservation efforts, and increase the number of species they are able to put on the road to recovery.
New Zealand in particular is a prime candidate for considering de-extinction because they have had many recent extinctions, such as the huia.
A recent study took the process that was developed to rank New Zealand species according to priority for action, and included 11 possible candidates for de-extinction in the ranking process. These were birds, frogs and plants, including the little bush moa, Waitomo frog and laughing owl.
By applying a decision science process, the authors found that adding these species to the management worklist would reduce their ability to adequately fund up to three times the number of currently managed species, and essentially could lead to additional species going extinct.
The study also showed that private agencies wishing to sponsor the return of resurrected extinct species into the wild, could instead use the money to fund conservation of over eight times as many species, potentially saving them from extinction.
Crucially, this study could not examine the initial costs of using genetic technology to resurrect extinct species, which is unknown but likely to be substantial. If it could have included such costs, de-extinction would have come out as an even less efficient option.
Could de-extinction ever be the right option?
The New Zealand example is not a particularly rosy picture, but it may not always be the case that de-extinction is a terrible idea for conservation.
Hypothetically, there are situations where the novelty and excitement of a de-extinct species could act as a “flagship species” and actually attract public interest or funding to a conservation project.
There also is an interesting phenomenon where even just the possibility of having a management action such as de-extinction may change how conservation problems are formulated.
Conservation management currently aims to do the best it can, while operating under the constraint that biodiversity is a non-renewable resource. With this constraint we can apply theory that is used for managing the extraction of non-renewable resources like oil or diamonds to determine the best strategy for management.
However, if extinction was no longer forever, the problem could be considered as one that would be managing a renewable resource, like trees or fish.
Of course, the ability to revive species is nowhere near as simple as regrowing trees, and a species being revived does not necessarily equate to conservation.
But changing the way that conservation managers think about the problem could present conservation gains in addition to losses.
Theoretically, different methods may be used for conservation benefit and there may be different strategies to produce the best outcomes. For example, species that could easily be de-extinct may get less funding attention that the ones for which the de-extinction technology isn’t available, or are too costly to produce.
This research does not advocate for or against de-extinction, rather, it provides strategies to deal with alternatives from the start with a clear representation of the trade-offs.
This work aims to step back and take a realistic look at the implications of new technology, including its costs and its risks, within the context of other conservation actions. Decision theory helps to do just that.