Cape York Peninsula’s palm cockatoo
SCREECH, SQUAWK, SMACK! I couldn’t believe my eyes. I had just witnessed two male palm cockatoos clash in mid-air above a large, hollow tree and viciously wrestle, using their huge beaks, before finally tumbling to the ground. Over years of researching ‘palmies’, I had never seen such intense conflict.
And the tussle didn’t end there – although the tall, tropical grass concealed the rival males from view, for what seemed like an eternity I could hear a horrible, loud growling coming from the now-grounded, brutal battle. This extreme aggression could only mean one thing – whatever they were fighting over was worth dying for.
We’re near the Lockhart River in a remote part of the Cape York Peninsula, far north Queensland. Despite the fact that the nearest city, Cairns, is 700km away, birders flock here from around the world and brave dirt roads and river crossings to see the iconic palm cockatoo in the wild. It’s no wonder, because it is a spectacular species. Cockatoos are found in New Guinea, Indonesia, the Philippines, the Solomon Islands and Australia – and of the 21 known species, the palmy is the heaviest and one of the largest.
On occasion, when their mood is right, their bald red cheeks can flush with blood, turning from pale red to deep scarlet. If that’s not intriguing enough, perhaps more curious is their drumming behaviour. Like no other creature in the world, palmies fashion thick sticks from branches, grip them with their feet and bang them on trunks and tree hollows. This is clearly an example of sticks being used as tools, but unlike Jane Goodall’s famous chimpanzees, which use tools to forage, palm cockatoos don’t obtain treats in return for drumming. So why do it?
Since the discovery of the behaviour in 1984, drumming by palmies has been a mystery to scientists who’ve puzzled over what the behaviour entails and in what context it occurs. These questions and more have been a source of fascination for Professor Robert Heinsohn of the Australian National University in Canberra.
Thanks to a grant from the Hermon Slade Foundation, Rob was able to employ me to do the groundwork and find the answers. Between us, PhD student Miles Keighley and I currently work over more than 10 Cape York sites, recording vocal and display behaviours in an effort to better understand this bird, and determine the extent to which its populations are genetically related.
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Elusive palm cockatoos photographed
Palmies are infamous for being skittish and elusive. Most people are lucky to get a fleeting glimpse of this unique and majestic creature flying overhead. Many birders have to come back to the region around the Iron Range National Park several times before finally getting a decent view and photo of a palmy.
For the past seven years, however, I have been very fortunate to encounter them at close quarters on many occasions – sometimes even having three birds fly into a tree directly above my head. I am often asked how I manage to get so close to palmies without spooking them. I’d like to think that it’s down to ninja-style stealth, but the answer is more likely to do with the birds themselves. They are a highly intelligent species with large forebrains, and probably excellent memories;
I believe they are almost certainly capable of recognising different human faces. Other species – pigeons, crows and North America’s northern mockingbird, for example – have been shown to discriminate reliably between familiar and unfamiliar humans based on facial features, sometimes up to years after just a single encounter. I’ve been spending up to six months in the field, returning to the same study sites for seven years now, and it’s quite possible that the birds recognise me personally and understand that I present no threat to them.
Indeed, it may be this that has allowed me to record rare drumming behaviour on a remarkable 38 occasions over the past two years. Staring into the glaring sun, my tiring arms struggle to keep a 10m-long extendible pole vertical against the gusting wind. Between morning and afternoon sessions spent watching the behaviour of birds, my volunteers and I spend the hottest part of the day doing numerous tree-hollow inspections.
Studying palm cockatoos no easy task
If I’m having a bad day, as the mounted camera reaches a tree hollow for a coveted view of the nest inside, hostile green ants might crawl up my legs from the ground and begin to inject copious amounts of formic acid into my sweaty skin. Clenching my teeth in pain, I try to focus on the task at hand.
It’s an important job because tree hollows are essential nesting sites for these birds – I’d seen firsthand that they were ready to fight to the death over them – and without ready access to suitable hollows in large, old-growth trees, they are not going to survive. The creation of a palmy nest is a very slow process, starting with a century-old tree.
First, this tree needs to be ripped apart by a cyclone, leaving it as a trunk without a canopy. Then, a small fire needs to create a scar at the base, allowing termites, fungi, and bacteria to enter. Eventually, a fully hollowed-out trunk is formed in which a pair of palm cockatoos might nest – if it has the right dimensions and shape and is strong enough to withstand fires and cyclones.
Palm cockatoos are fussy nesters
Despite hundreds of hours checking dozens of hollows in 2014, I only found five active nests. Needless to say, palmies are very particular in their nesting requirements, and their chosen trees are a precious commodity. Palm cockatoos have very low rates of reproduction and reproductive success.
My predecessor on the research program, Dr Steve Murphy, found that these long-lived birds breed on average just once every two years, and invariably lay just a single egg per clutch. This egg has a relatively low chance of hatching (61 per cent) and an even lower chance of reaching adulthood (39 per cent).
In fact, palmies have one of the lowest overall breeding success rates of any parrot (second only to Australia’s eclectus parrot), and computer modelling work by Robert Heinsohn has shown that the Iron Range population is likely in severe decline. Worryingly, the research suggests the population could be extinct within 100 years.
The problem continues to be exacerbated by extensive land clearing for bauxite mines on the western side of Cape York, excavation of quarries throughout the peninsula, and inappropriate fire regimes that can burn down the 200-year-old hollowed-out trees that are vital for nesting. In recognition of these facts, the federal government recently nominated palmies for a review of their conservation status.
They are currently listed as ‘near threatened’ but may soon be moved into the more severe category of ‘vulnerable’, offering them more protection. Rob and I have submitted official comments to the Department of the Environment, and we’re hoping a decision will be made by June this year. If palm cockatoos are willing to fi ght to the death for ideal nesting hollows, perhaps then, for the survival of this striking species, it is worth us fi ghting to keep these old hollowed-out trees in the Cape York landscape.
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This story first appeared in #126 of Australian Geographic
