July 2017 – A cloud of cockies
February 2017 – Eggplants, wasps and crunchy beetles
March 2017 – The paddock tree conundrum
April 2017 – Our splendid rosellas


Build it and they may, or may not, come

Many people are aware of the dependence of our wildlife on tree hollows. Losses of mature trees without timely recruitment of young trees could well provoke a second housing crisis in Australia.  So, what should we do? Studies have shown that it is possible for artificial nest boxes to help endangered wildlife such as Leadbeater’s Possum and the Turquoise Parrot.

It is certainly a most appealing idea to provide nest boxes for various species to raise their young when they might not otherwise have had the opportunity owing to a lack of natural hollows. Eleven years ago we installed an owl box (given to us by a kind friend) and three years ago, at great expense, we installed two boxes designed for Sugar Gliders.  The thought that these specially designed constructions would provide homes for species that we knew were around Gang Gang made us feel pretty good.

However, as with most things ecological, there are more complications associated with nest box provision than is reasonable. Our owl box had a rather startling warning accompanying it “Nest boxes will not attract wildlife”.  Well, one might ask of the manufacturer, why bother to even sell them?  I think what they were trying to say is that if the relevant animal does not already inhabit your patch of bush, it is unlikely to be attracted to it by the nest box.  This makes some sense of course, as owls, for example, need to find enough food, feel secure and find a mate before they are going to even think about breeding.

So, this raises the first consideration. Are the species which you are trying to attract:
1) Actually living in the vicinity?
2) Doing well enough to be able to breed?
3) Experiencing a shortage of nesting hollows?

You may be able to answer 1) and 2), but perhaps 3) can only be tested by providing boxes designed for that species. If you install them, make sure that the boxes are more than a few metres above the ground and on a protected side of the tree, away from prevailing wet-weather winds.

The second consideration is the maintenance of the box. If it gets taken up by Indian Mynas, Starlings, or House Sparrows this may not be very satisfactory, as some of these birds are aggressive and tend to destroy the nests of native species and drive them away.  This is a worse situation than before the nest box went up, so it would be incumbent on you to persistently check the boxes and remove the nest/eggs/hatchlings of unwanted species.

Colonization by honeybees is also common, and they are a much more challenging proposition to remove. While bees are useful pollinators, they were not the reason for which you installed the box, and a hive might have been better.

Aggressive introduced birds are more of a problem in small patches of bush and near urban areas. Brush and Ringtail Possums also tend to dominate box occupation in urban areas, which may not be what you are after in any case, as they are already super-abundant in the suburbs.

The third consideration is the fact that disappointment is likely. In a Gippsland (Victoria) study, 240 boxes were installed at two different sites totalling 4 ha.  The site that had fewer natural hollows had greater occupancy of the boxes, but it is noteworthy that there was a lot of moving around of species – a species did not simply take up residence permanently.  Quite a lot of animals used the boxes at one time or another (5 mammals, 4 birds, 2 reptiles and a frog) but there were 20 other hollow-dependent species that did not use the boxes at all.[1]

The most important finding, and one that should lead to a lowering of expectations, is that the average number of boxes that were occupied on on inspection was only 7%. If you translate this finding to our three expensive boxes at Gang Gang, we would need 14 boxes to have one occupied at any one time.  This might explain why we have not had any evidence of animals using our boxes, which have been up a number of years now.  Not even a bee colony!  So by all means have a go with boxes if you are keen, but you might want to install them in large numbers.

[1] Menkhorst, P. W. (1984) Aust. Wildl. Res., 255-64.


Eggplants, wasps and crunchy beetles

It was a late January morning on my break-of-day meander with the dog, when I noticed her ferreting around in the shrubbery and snacking on something crunchy. I eventually worked out she was eating shiny, iridescent brown scarab beetles, about the size and shape of a plump prune.  The beetles were dropping like heavy raindrops from the eucalypts, where clusters of them were voraciously stripping the new leaves.

Leaving our dog’s strange eating habits to one side, my thoughts flashed back to the vegetable garden in late November. Our freshly planted-out, vigorous eggplant seedlings were being  felled by monster root-eating grubs.  Nearly one plant a night, cut off at the knees, so to speak.

This devastation reminded us how important it is to carefully dig through the soil of the vegetable beds immediately before planting to remove the rather revolting large white beetle larvae (curl grubs) with the brown heads – scarab beetle larvae. In the case of the eggplants, the bed had been dug early in the season, giving the scarab larvae time to  move in.

There are many of species of scarab beetle, including the more multi-hued Christmas Beetle, but they share the lifestyle of the soil-dwelling, root-chewing larva alternating with the eucalypt leaf-eating adult beetle.

According to the NSW Department of Primary Industries, clearing the native vegetation and replacing it with improved pastures has created conditions that favour scarab grubs.

Their numbers are regulated by weather conditions, disease, birds and natural enemy insects. Control of root-feeding scarab grubs in pastures with insecticides is not economic. Nor is it terribly helpful for the numerous other useful insects in the vicinity, or the scarab grub eaters such as Magpies and Straw-necked Ibis who spend a lot of time on the ground digging out scarab larvae with their very large beaks (we exclude these birds from our vegetable patch, and miss out on this useful service).

A number of species of wasp hunt scarab larvae, including the Flower Wasps and the elegantly named Hairy Flower Wasps. The adult wasps, which are themselves nectar feeders, seek out these big scarab larvae to paralyse and lay their eggs on.  The wasp larvae then eat those huge juicy morsels and grow into an adult wasp. One that has been very conspicuous in our vegetable garden mid-summer has been a large, deep, metallic-blue Hairy Flower Wasp.  They have been seeking out scarab larvae, but were too late to save our eggplants.

The proportion of native vegetation in the landscape is very important to the control of dieback of eucalypts, and the reason is understood in the case of scarab beetles. The trees are needed as habitat for birds, and to provide  food for predatory insects.  The adults of the useful parasitic wasps require nectar, and native shrubs such are Bursaria spinosa are considered particularly important for their survival.

The treed slopes of the Yass Valley are testament to the principle that landscapes with significant amounts of native vegetation support healthy tree populations.  They contrast with the isolated trees on the valley floor that are progressively dying.

The paddock tree conundrum

Last month I drove down the western slopes from Armidale to Gundaroo during the heatwave, and saw a distressing sight. Endless paddocks with barely a eucalypt, and hot sheep crowding into the shade of the remaining few trees. In extremis, I saw them lining up in the shade of a fencepost.

A sheep farmer who was once asked why he did not have any trees in his paddock replied something along the lines that the sheep should be out there eating, not loafing in the shade. But he could not have been more wrong.  The reality is that when there is a heatwave and livestock get too hot, they go off their food and production declines.  Eating and digesting food generates heat, so stopping grazing when feeling hot is an obvious behavioural adaptation for livestock.

Both cattle and sheep pant to keep cool, and for the owner this is the easiest way of detecting heat stress. Above 150 breaths per min in cattle, and above 200 in sheep indicates severe heat stress.  In addition, sheep use their wool for insulation against the heat, counter-intuitive I know.  As well as panting, cattle sweat to keep cool.  The tropical breeds of cattle (Bos indicus, e.g. Brahman) sweat more than the temperate breeds (Bos taurus).  The latter reach their maximum sweating rates at 30oC while the tropical breeds are able to increase their rates of sweating up to 40oC, a considerable advantage in keeping cooler during heatwaves.[1]

As important as any hard-nosed production argument is compassion for the animals’ well-being and comfort. The need to provide enough shade for all the animals in a paddock seems obvious.  They also need air movement to generate the evaporative cooling made possible by all that panting and sweating.  A recent heatwave advisory I read from the Central Tablelands Local Land Services, pointed out that dense tree plantings and sheds may not be suitable because they block the movement of air and causing stock to overheat.

In contrast I can assure you that scattered trees in paddocks do not block air movement under them and are a darn sight cooler than a hot tin roof.

Paddock trees provide a high-quality cooling service, as well as many other functions – recycling of nutrients from deep in the soil profile, water table control, improved soil infiltration, wildlife habitat. There are many reasons for keeping viable tree populations in paddocks.  And they do not need painting.

The problem is that when masses of livestock crowd under a tree for hours on end, they do no service to the tree. They wee and poo, smash up the tree’s fine surface roots and sometimes even chew the bark.  All these things can result in premature death of a tree.  Decline is accelerated by the use of fertilizer in paddocks.  Scattered trees are part of our cultural identity.  They are also just plain attractive to have about, and have taken hundreds of years to gain their great presence.  They should be treasured.

There is a solution. Tree survival is a numbers game.  The more scattered trees there are in a paddock, on average, the less the impact a mob of livestock will have on each tree.  If you are down to the last handful of trees, GET MORE IN THE GROUND, or they will quickly disappear.

Usually “more in the ground” means the creation of dense, fenced tree lines, which helps with the neither aesthetics, nor the air-conditioning. An alternative strategy is Greening Australia’s WOPR project:

This involves lines of direct seeding lines through paddocks and has had some terrific results. Provided the eucalypts are not sown too densely, large open-grown trees can be established throughout paddocks.

There may be alternative methods of planting and protecting paddock trees, but some creative thinking is required on behalf of land managers. The hardest thing seems to be motivating people to do something about our vanishing trees.
[1] Silanikove, N. (2000) Effects of heat stress on the welfare of extensively managed domestic ruminants. Livestock Production Science 67, 1–18.

Our splendid Rosellas – April 2017

By all objective measures, a large bird that is deep crimson in colour with bright blue wings and cheek patches, is a stunning sight. Being abundant and easy to observe in bush and garden, the Crimson Rosella is sadly regarded as a ‘rubbish’ bird in birding circles. Commonness devalues birds as it does most things.

The Crimson Rosellas in the district seem to have just had a very good breeding season. A flock of about a dozen juveniles, more than usual, have been visiting our bird bath all through March.  They extravagantly splash water around, really enjoying a good soak. These are the crop of young birds that hatched last spring and have become newly independent.  Juvenile Crimson Rosellas look quite different from their parents.  They have the distinctive blue cheek patch, but the crimson colour is restricted to irregular red splashes, and much of the body is green.  They ‘ripen’ to red at about 15 months.

Rosellas eat insects and seeds of eucalypts, shrubs and grasses. They can be seen feeding both on the ground and up in trees.  They are also fond of sweet eucalypt blossoms, and their presence in eucalypt crowns may be indicated by the rain of plant pieces falling onto the ground, as they nip their way through masses of flower buds.

Like most parrots, rosellas depend on tree hollows for nesting, but judging from their abundance, Crimson Rosellas seem to be pretty successful in the competitive race for suitable apartments.

Crimson Rosellas belong to a complex of blue-cheeked sub-species, which includes the Yellow Rosella of the Riverine Plains, in which the crimson is replaced by yellow, the Adelaide Rosella which is mostly orangey-coloured and the Green Rosella of Tasmania which is yellow with green wings.

A completely different species complex is the ‘white-cheeked’ rosellas, the local variant being the Eastern Rosella. This is a smaller bird than the Crimson – about 5 cm smaller.  But it makes up for size with a colour scheme that is more than spectacular.  Forget the white cheeks – check out the symphony of lime-green, yellow, red, and blue, with striking yellow and black scalloping on the back.  An Eastern Rosella glowing in the sunlight is one of the finest bird sights anywhere.

It is a gift that they are still quite common in the district.

Easterns prefer more open country than the Crimson Rosella, which is regarded as a forest bird. But they do overlap in habitat.  At Gang Gang the rosellas demonstrate these different habitat preferences.  The Easterns predominate on the upper slopes of the property where there are widely scattered trees.  The Crimsons are most common in the sclerophyll forests and more densely treed grassy woodland.  However, in late summer the Easterns come down into the thicker woodland after breeding, where they seem to happily co-exist with the Crimsons.

Confusingly, the Crimson and Eastern will sometimes interbreed. As I write, there are two rosellas at the birdbath that look like young Easterns at first glance.  On closer inspection, it is apparent that the cheek patches are pale blue, revealing their hybrid nature.

A very famous brand of tomato sauce has been made under the banner of the Eastern Rosella since 1899. It seems that the brand has been more important than the sauce, as the trademark has been passed through five different companies over that time.  It has been a favourite of mine since my childhood, but who could not be won over by such a handsome bird.