Christmas beetle cocky feast

Early one morning last week, I was wandering up my street (bird watching) and noticed a group of Sulphur-crested Cockatoos on the road under a large eucalyptus tree. They were clearly feeding on something on the ground. Closer inspection revealed their interest was in Christmas beetles. There were ten cockatoos on the ground, a further three in the outer foliage of the tree and a couple more on prominent perches nearby (possibly sentinels?).

The birds on the ground were feasting on fallen beetles – some alive and still crawling, many barely alive, and many more quite dead. The birds in the tree were clambering about the outer foliage deliberately seeking out and ‘plucking’ the beetles feeding on the fresh young foliage. 

In both situations, the cockatoos manipulated the beetles, using both beak and feet, in the same way they would an equivalent-sized fruit, or acorn; the softer inner parts of the beetle being scooped out and eaten before the exoskeletal husk was unceremoniously dropped, adding to the carnage below. From the remnants, it appears the muscle tissue inside the thorax was possibly the main attraction.

The following morning, a slightly smaller group of cockies again arrived on the scene and began helping themselves to the dwindling supply of beetles. They seemed a little less engaged, or a little more distracted, and were soon dispersed when a small dog showed up. Some of the cockatoos moved off down the street to feed on the under-ripe fruit of a flowing plum tree for desert.

My interest and surprise in these events was twofold. 

Firstly, the sheer number of Christmas beetles was impressive, particularly in times when the incidence of these beetles seems to be reducing year by year. I estimated at least several hundred beetles on the ground, and many more were visible in the foliage. As far as I could discern, all were Anoplognathus chloropyrus, the Green-tailed Christmas Beetle, even though several different species of Christmas beetles occur in Canberra.

Secondly, animal material is a rare component of the diet of Sulphur-crested Cockatoos. HANZAB (Handbook of Australian, New Zealand and Antarctic Birds - the Australian ornithologist’s ‘bible’) and another authoritative book on Australian parrots mention a few instances of insect material being consumed, including the larvae of longhorn beetles from dead trees, and the larvae and/or eggs of Diptera (fly larvae), Hymenoptera (ant eggs) and Orthoptera (grasshopper larvae and eggs). Christmas beetles are not mentioned. Indeed there is no mention of adult forms of any kind of insect being eaten, let alone such large, crunchy, heavily sclerotized ones as Christmas beetles (not that this would be an issue for the cockies’ massive bills).

When available, Christmas beetles are readily eaten by a range of other birds in the area, including the Australian Ravens that breed each year in the tree in question, Pied Currawongs, Australian Magpies, Noisy Friarbirds, Dollarbirds and so on. But this appears to be the first instance, at least that I am aware of, of Sulphur-crested Cockatoos exploiting this food resource. It seems this might be quite an unusual occurrence, and quite possibly related to the severity of the ongoing drought.

I hope enough of the Chrissie beetles survived to procreate and produce the next generation...

Twin-spot Hunters find Canberra

It was Saturday afternoon and 40 degrees outside. I was in the relative comfort of the study, the fan blowing a cooling breeze, when a report came through on the online Canberra Nature Map (CNM) of a Unicorn Hunter – a type of dragonfly that, in the ACT, frequents sand or shingle beds along some of the lower altitude rivers. As a moderator for dragonflies on the CNM platform I logged in and had a look at the photo. An initial cursory glance showed a tell-tale yellow double band at the 7th abdominal segment, then I looked at the antehumeral stripe to ensure it was ‘attached’ to the collar – it was; but something about the spots on the side of the final abdominal segments, and the pattern of the yellow patches on the side of the thorax, just didn’t seem quite right. Then I looked at the location of the sighting. It was all wrong. It was from open woodland, though not too far from a few small ‘farm’ dams. But nothing like the sandy-edged river locations preferred by Unicorn Hunters.

The photograph submitted to Canberra Nature Map, initially suggested to be a Unicorn Hunter.

So I took a closer look at the thoracic and abdominal patterns against the various other ‘hunters’ in the Theischinger & Hawking field guide, and it became very apparent that the photo was in fact of a thing called Austroepigomphus praeruptus or Austroepigomphus melaleucae, the Twin-spot Hunter.

This species pair has a bit of a confused history. The original A. praeruptus was described by Selys, in 1858, based on a single specimen from South Australia; but the specimen was lost and has never been relocated. Meanwhile, in 1909, Tillyard described a very similar species from Queensland and called it A. melaleucae. Although the vast majority of known records are from Queensland and northern NSW, it seems that the species has now been accepted as A. praeruptus and A. melaleucae has been relegated to junior synonym status.

There are close to a hundred records of the species in the Atlas of Living Australia (ALA), generally from inland south-eastern Queensland and inland north-eastern NSW, but with some more coastal records, including as far north as Cairns and as far south as Sydney. Interestingly, there is a 1976 record from Elanora Heights in the bushland of northern Sydney, less than a kilometre from where I grew up and where I was a teenager at the time! There is also a tight cluster of three records by Reiner Richter, from January/February 2016, from a small drying creek between Shepparton and Euroa in northern Victoria.

Distibution of the 92 Atlas of Living Australia records (Jan 2019).

In a personal email, Reiner indicated to me that a record, in iNaturalist, is of, finally, a recent record of the species from South Australia. This was of an individual in a very poor state from the Adelaide hills. 

So the finding of an individual of this species in the ACT is an important and, for me personally, very exciting outcome, and fills a sizable gap in the species’ distribution. I got onto John Bundock (the naturalist photographer ‘colleague’ of mine who found the dragonfly and submitted the record) immediately by phone, quizzing him on details such as was it just the one individual, how far was it from the nearest water, did it hang about, did he have any other photos of it etc, etc. It seemed to take a while, but I eventually convinced him of the significance and excitement of his find and we agreed to go out together in the morning to try to gather further evidence.

Next day, Sunday 27 January 2019, dawned quite overcast and we were even subjected to the occasional brief shower as we searched the first dam. Not the greatest dragonfly hunting weather. It remained cloudy for several hours but eventually gave way to more extended sunny periods and reached a temperature of 30 degrees. We searched the woodland where John had seen the dragonfly, now three days prior; we searched another couple of nearby small dams, all of which had relatively low water levels. Blue Skimmers and Common Bluetails were particularly evident, and we also recorded a few Red & Blue Damsels and a single Blue Ringtail, but we found no evidence of any Twin-spot Hunters.

We decided to head deeper into the woodland reserve to a couple of other small dams that I’d been wanting to survey for a while, and as we went, photographing any other insect life that caught our attention, my mind started to formulate a possible scenario. If this species is known to inhabit “sluggish streams and rivers, including isolated riverine pools”, it may well be likely that the species has adapted to a nomadic lifestyle. This might go some way to explaining its very patchy distribution through eastern and south-eastern Australia, and the individual John had seen may well have been an itinerant or wind-blown ‘traveller’. Fine as a theory, but not great for my personal aspirations of seeing the species which I desperately wanted to do.

At the other dams there were lots more of what we’d already seen and we added Tau Emeralds, an Inland Hunter and Wandering Percher. But still no twin-spots. So finally, defeated by lack of success and the heat, we decided to head back towards the car. We did a bit of a loop past another drying dam before rejoining the main track just above one of the dams we’d checked earlier that morning. As we approached, I noticed a Royal Tigertail perched on a small emergent branch just out from the bank. We hadn’t seen this species earlier, so I raised my camera and, even through the viewfinder, I realised fairly quickly that this was no Royal Tigertail. I mentally checked off abdominal banding and spots and thoracic markings and knew straight off this was in fact a Twin-spot Hunter. Yes! We spent about half an hour scanning the dam and taking hundreds of photos, eventually seeing three of the twin-spots together.

When we dropped down to the next dam, the one we first surveyed in dull showery conditions, we tallied no less than eight individual Twin-spot Hunters, all along one edge of the dam, perching mainly on logs and emergent submerged branches, but also occasionally on the stems of rushes or on the gravelly bank. What a difference a bit of sunshine can make.

This completely changed things. These were not blow-ins, but in all likelihood had emerged locally. The species was a ‘resident’, at least for one season, of the ACT.

Now we need to monitor over the remainder of this season, and more importantly, check other potential sites in the region, and see if they show up again next season.