Parrot Oddballs part V: The Eclectus Parrot

Today’s subject in this series of articles on parrots with unusual characteristics is the beautiful Eclectus parrot. Eclectus are most famous for their odd colour patterns: the males are green and the females are either red and cobalt/purple or completely red (in a few rare subspecies).  Their mating behavior is unusual as well, because some breeding groups in the wild are polyandrous.

I wrote an article about these fascinating parrots for Parrots International Press and am reposting it below.

The Evolution and Behaviour of the Extraordinary Eclectus Parrot

By: Jessie Zgurski

Eclectus Enigma

High in the canopy of the dense rain forests of Australasia lives one of nature’s most extraordinary and beautiful birds, the Eclectus Parrot.  Although their strange behavior sets them apart from other birds, they are most well known for their brilliant and unusual colors.  The handsome males are a vibrant emerald green, while the elegant females are a dark ruby red, usually with a vest of violet or cobalt feathers.  The two birds are so different that it wasn’t immediately apparent to biologists that the males and females belonged to the same species.  The males were first discovered and described by a Western biologist, P. L. S Müller, in the spice islands of Indonesia in 1776.¹ However, the females, who are harder to see in the wild than the males, were not described until 1837.¹ It wasn’t until 1874 that the two sexes were finally united under the same scientific name, Eclectus roratus.¹

That the males and females are completely different colors makes the Eclectus an oddball among its kin.  While there are other parrot species that have males and females that look different, (are sexually dimorphic) none show such extreme colour differences between the sexes.  For instance, mature male Ringneck Parakeets (Psittacula krameri) have a black ring around their necks while the females do not.  And, in most sexually dimorphic parrot species, males do not develop their adult plumage until they have molted a few times.  Eclectus are different in that the chicks are very easy to sex as soon as their feathers start appearing: boys are green and girls are red.

The form of sexual dimorphism seen in Eclectus Parrots is strange even when they are considered against all other bird species.  It is not unusual for male birds to be much more extravagant looking than females – peacocks are the perfect example of this – but in the Eclectus, neither sex is really more colorful than the other, although it’s the female who would stand out more in nature due to her red colouring.  Males would blend in well against green, leafy tree tops.  The reasons for the differences among male and female Eclectus Parrots eluded biologists until very recently.  In fact, one of the most influential evolutionary biologists of the 20^th century, the late Dr. Bill Hamilton, was so puzzled by the Eclectus that during lectures, he would often show a slide with a photo of a male and female Eclectus and proclaim that once he knew why one was green and the other one red, he would be ready to die. ² Dr. Hamilton often talked about this most unusual parrot species and despite having contributed to solving many difficult problems in biology, he could not explain why Eclectus are colored the way they are.

However, a long term project investigating the behavior and ecology of Eclectus Parrots was started in 1997 by Dr. Robert Heinsohn of the Australian National University.  Dr. Heinsohn was alerted to the unsolved mystery surrounding the Eclectus by Dr. Bill Hamilton’s lectures, and he decided to study this species because they display a form of sexual dimorphism unparalleled in the bird world.  Since no one could satisfactorily explain why this is, it was a perfect biological mystery just waiting to be solved.

Few field biologists had done much work on wild Eclectus Parrots before the start of this project, likely because studying Eclectus Parrots in the wild comes with many logistical difficulties.  Eclectus nests are usually situated very high in trees, at an average of 22.2 meters off the ground.³ Additionally, Eclectus nest holes are often situated very far apart, and for Australia’s population of Eclectus, there is only one suitable nest hole per square kilometer of forest.⁴ That means that any biologist interested in studying Eclectus Parrots must be willing to travel across many miles of dense rainforest, and up trees that tower tens of meters above them, all in an oppressively hot, humid environment.

Dr. Heinsohn decided to take on this challenge, and he and his team managed to find forty Eclectus nests in his first two field seasons studying the birds in a thick rainforest on the Cape York Peninsula of the northeastern tip of Australia.  Traveling around a rainforest is difficult work and the researchers had to rely on creek beds and ridge lines to get around.  The fact that Eclectus can be very noisy around their nests can help people spot them, although the birds often flee once they spot people.  Time spent in an aircraft also helped Dr. Heinsohn find potential nest sites because Eclectus like to nest in tall, emergent trees that are easy to spot from the air.

Once nest sites were found, more grueling work began.  Since Eclectus nests are typically 15-30 meters up trees, Dr Heinsohn and team had to use single rope technology to climb up the trees to examine the nests, take small blood samples from nestlings, and take any shed feathers left by the female.  These feathers were used as a source of DNA.  Climbing ropes in a humid, hot tropical forest is incredibly physically demanding and Dr. Heinsohn estimates that if one stacked up all the trees he’s climbed end to end, he’s climbed the equivalent of a tree ten times taller than Mount Everest.  Climbing the nest trees can get one access to Eclectus chicks, but catching the adult males so they could be banded to allow for individual identification was also a big challenge.  Dr. Heinsohn and team had to string mist nets about thirty meters above the ground to catch adult Eclectus Parrots. And, once caught, the adult parrots were not easy to handle.  As any parrot owner knows, they can bite very hard!  The researchers also had to build viewing blinds 20 m off the ground up in trees so they could observe the birds without disturbing them.

In the end, all that exhausting and challenging field work allowed researchers to gather data that demystified many of the unusual traits of Eclectus Parrots.  Dr. Heinsohn first tested hypotheses regarding the evolution of different colors in male and female Eclectus Parrots by taking optical measurements of the birds and their surroundings using a spectroradiometer.⁵ This instrument measures various properties of the light reflected or emitted off of objects. It was important to make objective measurements using such an instrument because parrots do not see the world the way humans do.  Parrots can see light into the ultraviolet spectrum, which is invisible to people.  This means that an object which blends in with its environment to a person may actually be very conspicuous to a parrot.

The optical measurements indicated that male Eclectus, with their largely green plumage, blend in well with the leafy treetops they forage amongst.  This makes them inconspicuous to the raptors that prey on them.⁵ Males spend several hours each day foraging because they need to feed not only themselves, but a female or two, and possibly some newly fledged young.⁶ Females do not have as large a need to be camouflaged, since they spend most of their time in or near a nest hole they can hide in should a predator show up.  Additionally, the females actually do need to be quite conspicuous at times.  They must compete for nests with other Eclectus and with Sulphur-crested Cockatoos, who often take over Eclectus nests. ³ Female Eclectus will display outside their nests by calling and drawing attention to themselves,⁶ and their colour makes them stand out very well against a leafy canopy.⁵ By being very conspicuous, a female can let other parrots know that her nest hole is taken and that they should stay back.  This often works to prevent conflicts, but even so, females still sometimes have to fight off intruders, primarily other parrots.  Fights between Eclectus can be very intense; and even fatal.⁵

The spectroradiometer measurements revealed another aspect of Eclectus biology that would have remained a secret had not such an instrument been used.  While male Eclectus are difficult for predators to see against green leaves, they are quite conspicuous when seen by other parrots outside of a nest hollow.⁵ Green does show up well against a brown tree trunk, but the measurements from the spectroradiometer showed that an Eclectus’ feathers also reflect ultraviolet light that other parrots can see but that humans and many of the Eclectus’ predators cannot.⁵ So, while Eclectus look brilliant to people, they look even more brilliant to each other.

Bizarre Breeding Behaviour

The very different parental roles of male and female Eclectus Parrots explains why they are different colors.  The males do the foraging and need to be camouflaged against leaves so predators can’t detect them, and females must guard the nest hole and can be conspicuous since they have a nest to hide in.  They must also stand out so they can warn other parrots to stay away from their nests.  However, their coloration isn’t the only unusual characteristic of this extraordinary parrot that has baffled biologists. The breeding behavior of Eclectus Parrots is also very strange for a parrot.  While most parrots are monogamous, Eclectus Parrots are polygynandrous, which means that both males and females may have multiple mates.  A female Eclectus may be courted and fed by up to seven males at once.⁷ The males are not monogamous either, and will sometimes court and feed more than one female.⁷

There are other bird species where females will mate with more than one male, although the behaviour of Eclectus is very different from the behaviour of these other polyandrous birds.  In most polyandrous birds (such as phalaropes and sandpipers), the male will care for the young while the female goes off and finds another mate.  In such species, it is often the female that is the more colorful sex, so the sex roles are essentially reversed.  However, this is not so in the Eclectus, because the female will guard the nest hole and her young while multiple males will feed her.  She will then feed any nestlings present, and he will feed the young once they have fledged.  The female does not abandon the eggs after they are laid as do the females of many other polyandrous bird species.

A female Eclectus can stay at the nest because one or more males will feed her.  But why will multiple males often tend to a single female?  In many animal species, if a male cannot find a mate, he may simply go without one and live as a bachelor.  In other birds, young males and females who cannot find a mate may stay around and help their relatives – usually their parents – raise young.  This is because natural selection shapes animals to act in ways that help them pass their genes on to a new generation.  Of course, an animal can do this by bearing young, and its genes will be passed along through them.  However, an animal can also propagate its genes by helping its parents raise more of its siblings.  This is because identical copies of half of any animals’ genes are also present in their siblings because they share the same parents.  The theory that animals can pass their genes on by helping close relatives produce more young is called “kin selection,” and this idea was developed, in part, by the aforementioned Bill Hamilton.  In many bird species, young birds who cannot find a territory or mate will often stay with their parents and help them care for young.  The presence of these helpers often increases the number of young a pair can raise, and the helpers also benefit by gaining valuable experience in caring for young.  Such helping behaviour has been well-studied in Florida Scrub Jays and African Bee Eaters.  It’s possible that Dr Hamilton’s insight on helping behaviour in animals may explain some of the Eclectus’ breeding behaviour.

One way to test the hypothesis that male Eclectus are helping their mothers raise more young would be to collect DNA from a female Eclectus, her chicks, and her suitors and see if they are closely related.  Dr. Heinsohn and his team did exactly this and it turns out that male Eclectus are generally not closely related to the females they court.⁷ So, kin selection does not explain why more than one male may court and feed a single female.  There must be another reason for this odd behaviour.

In the end, what Dr. Heinsohn did discover is that the Eclectus’ unusual breeding behaviour is the result of a sex ratio that is biased towards males, along with a shortage of suitable nest holes.⁷ Young females have a higher mortality rate than males, so there are simply more males out there than females.  There are also females that may not be able to breed because they cannot find good nest holes.  Good nest holes are rare, because it is not simply enough for an Eclectus to find a tree with a hole in it.  It must be one that either does not flood during rainstorms or one that dries out quickly because Eclectus chicks can easily drown if their nest hole becomes flooded.⁸ Eclectus usually nest in holes that have entrances that face sideways, rather than straight up.  The lack of quality nesting holes means that there can not be enough females with nest holes for every male, so each female ends up with more than one partner.

The fact that multiple males may mate with any one female means that, in any given season, there is a good chance that a given male Eclectus will be helping to raise young that he did not father.  However, a male Eclectus needs to court a female, even though she may be being actively courted by other males, if he is to have any offspring.  As time goes on, he will become more likely to actually father young.  This can take years because some males are far more successful than others in fathering young.⁷ Some male Eclectus will also mate with more than one female to increase his chances of fathering young.  In one instance, a male had young with two females situated 7.5 km apart.⁷ He must have been an extremely busy bird!

One more mystery to solve

Aside from their unusual form of sexual dimorphism and bizarre breeding behaviour, Eclectus parrots have another odd trait that biologists struggle to explain.  Some female Eclectus parrots will produce many offspring of one sex before switching to producing chicks of another sex.⁹ However, the overall sex-ratio of fledgling Eclectus parrots in a population is usually close to 50:50.  Currently, no one knows for sure why some Eclectus produce runs of one sex of chicks.  However, one hypothesis that Dr. Heinsohn plans to test is that the females produce more males when they have higher-quality nest holes and are being fed by many males.  Since male chicks in the wild are bigger and require more food, females may raise them only when they have access to plenty of food.  This strategy is used by Kakapo parrots, which are a critically endangered, flightless parrot from New Zealand.  When female Kakapo are given supplementary food by biologists, they are more likely to raise male chicks, which are bigger and require more food than females.¹⁰

Conclusion

Biologists now have an answer to one of ornithology’s biggest mysteries: how the Eclectus got its unusual colors.  We also now understand why they have such an unusual breeding system, thanks to the ten years of work done by Dr. Heinsohn and team.  He is currently working on demystifying the habits of another unusual parrot species: the magnificent Black Palm Cockatoo.  These cockatoos are well-known for the drumming display that males perform by their nest hollows.  They will take a large stick and bang it on the edge of the nest entrance, like they are playing a drum.  Dr. Heinsohn and his team are working on developing methods to identify individual cockatoos by their voices and are interested in determining why this species has such a low reproductive rate, which is one of the lowest for all parrot species.

Acknowledgements

I want to thank Dr. Rob Heinsohn for providing information about his work on Eclectus Parrots and for answering my questions about them.

References

1. Marshall, R, and Ward. I. 2004.  A Guide to Eclectus Parrots as Pet and Aviary Birds, (revised edition). ABK Publications.  South Tweed Heads, NSW, Australia.

2. Grafen, A.  2000. Biologist who died after Congo expedition was leading Darwinian theorist who explained how natural selection acts on social behaviour.  The Guardian. March 9.

3. Heinsohn, R., Murphy, S., and Legge, S.  2003.  Overlap and competition for nest holes among eclectus parrots, palm cockatoos and sulphur-crested cockatoos.  Australian Journal of Zoology, 51, 81-94.

4. Legge, S., Heinsohn R., and Garnett, S.  2004. Availability of nest hollows and breeding population size of eclectus parrots, Eclectus roratus, on Cape York Peninsula, Australia. Wildlife Research, 31, 149-161.

5. Heinsohn R., Legge S., and Endler J.A. 2005. Extreme reversed sexual dichromatism in a bird without sex role reversal. Science, 309, 617–619.

6. Heinsohn R, and Legge, S.  2003.  Breeding biology of the reverse-dichromatic, co-operative parrot, Eclectus roratus. Journal of the Zoological Society of London, 259,197-208.

. 7. Heinsohn R., Ebert, D., Legge, S., and Peakall R.  2007.  Genetic evidence for cooperative polyandry in reverse dichromatic Eclectus parrots.  Animal Behaviour, 74, 1047-1054.

8. Heinsohn R.  2008.  The ecological basis of unusual sex roles in reverse-dichromatic eclectus parrots.  Animal Behaviour, 76, 97-103.

9. Heinsohn, R., Legge, S., and Barry, S.  1997. Extreme bias in sex allocation in Eclectus parrots.  Proceedings of the Royal Society of London Series B – Biological Sciences, 264, 1325-1329.

10. Clout, M., Elliott, G., and Robertson, B.  2002.  Effects of supplementary feeding on the offspring sex ratio of kakapo: a dilemma for the conservation of a polygynous parrot.  Biological Conservation, 107, 13-18.

Sidebar One

Sidebar: Why are many male birds so extravagant?

In sexually dimorphic bird species, males are usually very showy in appearance while the females are very dull. This is because female birds often prefer to mate with flashy, brightly-coloured males since male birds must be healthy and good at foraging to maintain colorful, vibrant feathers.  Additionally, in some species, biologists have shown that brightly-colored males are more resistant to parasites than duller males.  Bright colors or gaudy feathers also act as a “handicap” to the males that sport them, and any male bird that survives despite being very conspicuous must have excellent predator-evasion skills.  If a female bird mates with a beautiful, showy male, her chicks could inherit his good foraging ability, his ability to resist heavy parasite infestations, or his superior predator-evasion skills.  The females of sexually dimorphic species are usually choosier than males because females put more energy into reproduction than males since they need to produce large eggs. A female who mates with a “dud” may incur a bigger cost than a male who chooses a poor mate.