Birds in Their Habitats Read online

  In such areas, the low stony ranges provide essential oases, especially where gorges form relatively cool refuges. In these gorges, as at our goal on this particular walk, water from summer storms may form deep pools in narrow slots where the sun doesn’t penetrate and evaporation rates are low. These waterholes are wildlife magnets – and, as an inevitable spin-off, they are also irresistible magnets to wildlife lovers such as ourselves. This was June and the temperature was barely into the 30s, but we were pleased enough to leave the plain and climb the shoulder of the hill behind which lies the shaded waterhole. Here we were reminded, however, that wildlife in such a place can take many forms. As we descended into the narrow forest of River Red Gums and were about to enter the gorge, we met a large soot-black bull coming out, water still dripping from his lips. In such a situation, he could have been either a feral animal or station stock but, even if the latter, ‘domestic’ is not a term I’d use for him. His resemblance, with wicked black-tipped horns, to pictures I’ve seen of Spanish fighting bulls added to our unease; we climbed back up the stony hill among the Porcupine Grass, but fortunately he was in a benign mood and ambled off into the trees. Birding isn’t always the genteel pastime that you might suppose!

  We settled onto a shelf of granite rock above a sandy beach and waited for the birds to come. I suppose such birding must be a bit like playing the poker machines – you can’t know what’s going to happen next, but in the case of the birding you absolutely can’t lose. Even if nothing had come, we would have a peaceful hour absorbing the still beauty of a special place.

  As it turned out, this location wasn’t still for more than a few seconds. There are very few places in all of mainland Australia where you can’t find a Willie Wagtail: a bold, nosy and opinionated black and white member of the fantail Family. (The Family, found from India to Australia and New Zealand, was once thought to be related to the Northern Hemisphere flycatchers, but we now recognise them as part of the great assemblage of songbirds which evolved in isolation in our part of the world.) This Willie was a youngster, as attested by its buffy eyebrows; later they will turn white, but this one wasn’t too young to investigate us closely and pass chattering comment in the way of Willie kind. However, Willie wasn’t attracted by the water for its own sake, but by the insects the water also drew. Meat eaters, be their prey insects or vertebrates, don’t often need to drink (though they may sometimes choose to do so), because there is enough metabolic water in their food: this is an excellent adaptation to living in the dry lands.

  Desert seed eaters

  The desert birds that do need to drink daily are those that eat seeds, which have very little water content. In Australia, this overwhelmingly means finches, pigeons and doves, and parrots. And at Warrigal Waterhole it wasn’t long before a familiar tootling chorus, like lots of toy trumpets, brought a shared smile as we anticipated the coming of one of our favourite birds, the delightful Zebra Finches, ubiquitous across inland Australia. In central Australia, the Pitjantjatjara people hear their cheery nasality in much the same terms that we do – to them these finches are Nyii Nyii.

  As they streamed into the bushes above Warrigal Waterhole before coming down, we took in anew their characteristic orange-red bills and legs, white faces bordered by a black streak running down from the eye like errant mascara, and broadly striped black and white tails; in addition, males have barred breasts, rusty cheeks and white-spotted rusty flanks. They are delightful.

  They are also astonishing little calculators, constantly assessing their environment and determining where to roost to be in reach of the morning’s breakfast bar, when it’s time to move on, and when to start breeding. Day-to-day living is tricky enough: as well as needing to drink daily, a ‘zebbie’ needs to eat up to 6000 tiny grass seeds each day, though fewer if bigger ones are available (Zann and Straw 1984). Both water and seeds are not necessarily available in the same place, however; although Warrigal Waterhole will probably always be here in all but the most vicious of droughts, the seeds represent a much more ephemeral resource. If the little finch can’t find both of these things on every single day, it will surely die. So, it must be constantly planning, not just where to roost tonight to be in reach of water and seeds tomorrow, but where it will go for a seamless transition when the pool dries up or the seeds finish.

  Breeding is even trickier, made more so by their choice of baby food. Like many vegetarian birds, some other grass-finches feed their chicks on insects to give them a high-protein kick-start to life, but others, including zebbies, are purists – they start their offspring off as they’ll continue, on seeds. The only concession they make is to provide soft unripe seeds, which aren’t nearly as easy to find as ripe dry ones (Payne 2017; Payne and Bonan 2017). Seeds are not like insects, which appear almost as soon as the rains do, so zebbies planning to breed have to make some pretty complex calculations. If the weather is cool, grasses take longer to grow and set seed than if it’s hot. The soil moisture level must also be taken into account; this is a function of both the time since the previous rains and what the temperatures were in that time. The end result is that the tiny birds must remember how long it is since the rains came and, as a result of what can only be described as complex computations, start to breed anywhere between 4 and 12 weeks later. We have only recently started to unravel this amazing narrative (and for more on zebbie ecology, truly one of the great Australian stories, I’d strongly recommend Morton 2009).

  Other grass-finches joined the stream of zebbies at the water’s edge in the next hour too, among them a few very smart Painted Finches (red and brown above with white-spotted black sides), a couple of owlish-faced Double-barreds (with two black bands across a white underside, blue bills and spotty wings), and some unexpected Long-tailed Finches (red bills, grey heads, black throats and long pointy black tails). Here, the Long-taileds are at the very eastern edge of their range. The grass-finches (Family Estrildidae) apparently arose on the grassy African plains and, like humans much later, expanded east through Asia (or possibly they began in India and spread both west and south). As Australia approached Asia closely enough in the past few million years, new passengers hopped aboard, including rodents, bats, modern crocodiles, swallows – and grass-finches. It seems that they arrived in three waves, the first being the firetails, including the Painted Finch. Next came the ancestors of zebbies and Double-barreds, and most recently another group, including the Long-taileds, most of which haven’t left the tropics. (There is also a Timor Zebra Finch, which may have derived from some perhaps dissatisfied Australian settlers that later made the reverse crossing, or from some that chose to stay there rather than continue south.)

  A bit of a rule of thumb in Australia is that within a group of animals the oldest members are those that have penetrated the deserts, but this doesn’t really hold true with the grass-finches. Of the firetails, only the Painted Finch lives in the dry country, but it survives solely in the sheltering ranges. Of all the Australian finches, only the zebbie has truly penetrated the deserts. (Of course, it could be that this model of the order of arrival in Australia is incorrect too.)

  Meanwhile, back at the waterhole, we were watching the zebbies drink, along with a couple of Painted Finches that had slipped in along the gorge wall. Their approach to drinking is quite different though: the zebbies stick their bill into the water and suck, which is most unusual among birds, while the Painteds more conventionally take a bill-full of water and tip it back, over and over again. The sipping zebbies can get their fill much more quickly than the tipping Painteds, and consequently need to spend less time at the hazardous water edge (e.g. Forshaw et al. 2012). While we were at the waterhole, it’s likely that our presence was deterring predators, but Australian Hobbies, Peregrines and Black Falcons, Collared Sparrowhawks and Brown Goshawks all hang around such watering points waiting to transform an unwary bird into a meal. It seems that a few, mostly tropical, Australian grass-finches are the only ones of their Family to have developed this useful s
ucking skill, despite the fact that many relatives also live in arid lands in Africa and Asia.

  Better known suckers of water are the pigeons and doves, and by now two desert doves were arriving in small groups and creeping nervously to the water. Peaceful Doves and Diamond Doves are found throughout most of the inland, though as seed eaters they too need to drink daily. Both are small and elegant: the Peaceful has a grey barred body and a blue eye-ring; the Diamond has white-spotted brown wings and a red eye-ring. The high-pitched ‘toodle-oo’ of the Peaceful Dove is a soporific sound on a warm afternoon by any creek line.

  Below us little groups of doves dipped their bills in and filled up quickly, whirring off as soon as they finished. Superficially it seems that they’re doing just as the zebbies are, but in fact their approach is quite different again. The finches use their tongues as a double-action scoop, at up to 20 times a second, taking a droplet of water into the mouth, and from there back into the oesophagus and crop, via the pharynx. (The crop is a very useful sack, an extendable side-wall to the oesophagus for carrying seed away to be digested later at leisure and in safety.) The doves, however, create a sort of peristaltic pump by sending waves of muscular contractions along the oesophagus to pull the water back (e.g. Elphick 2014). There is nearly always more than one solution to any evolutionary question and, with enough time, nature will come up with different answers in different situations.

  Eventually, as we had hoped, a flock of another of our favourite birds (of which there are, admittedly, rather a lot) suddenly swirled into the branches above us, like leaves sprouting from the sere twigs. It saddens me how many Australians don’t realise that Budgerigars are not only wild birds or parrots, but even Australian, and can be seen in huge flocks pretty much anywhere in the inland where conditions are good. It saddens me even more to see a budgie in a cage – for a bird that is essentially sociable and flies constantly across the vast plains, solitary confinement must be a harsh sentence.

  No organism, be it bird or farmer, can survive in Australia without adapting to the integral unpredictability of our climate, driven by the El Niño cycle (or, more formally, El Niño–Southern Oscillation, or ENSO to its friends). Budgies are true children of El Niño.

  Budgerigars

  The budgies at Warrigal Waterhole dithered and panicked and eventually mostly moved on, with only a few coming to drink; maybe there was after all a bird of prey loitering with intent, or maybe it was just us. We left soon afterwards and I’m sure they came back.

  El Niño

  In the first decade of the 20th century a young Australian called Dorothea Mackellar who was travelling in Britain and Europe published a poem called ‘My Country’. It is in the form of one side of a conversation with someone who loves the misty European countrysides, acknowledging that love while expressing her own passion for the harsh extremes of Australia. She was from a wealthy Sydney family, but spent formative time on a family property in the mid-west of New South Wales. The poem caught the Australian imagination and was widely printed in newspapers. It has been put to music more than once – most recently, and somewhat mind-bogglingly, by eminent Australian composer Elena Kats-Chernin for the Vienna Boys Choir! I recall singing a version at primary school and the tune is lodged in my brain, though I can’t determine what its origin was. To many of us this is still the unofficial national anthem. In it she characterises Australia as a land of ‘drought and flooding rain’. And there she nailed it: a truth that some people, even among those who manage the country to a greater or lesser degree, still don’t get.

  When, every few years, the winds fail that normally blow west across the Pacific and keep warm ocean water ‘mounded up’ around Australia, El Niño is triggered. A layer of warm water 100 m thick flows ‘downhill’ to South America where it prevents the normal rich cold upwelling of nutrients by the Humboldt Current on the west coast of Peru. The surface algae that need these nutrients die, and the abundant tiny anchoveta fish starve. Normally, they support one of the world’s great fisheries; population crashes of seabirds and marine mammals follow. On the desert coast, storms and floods scourge the land. Meantime across the Pacific the opposite is happening. The waters off eastern Australia cool and the rains fail. Droughts follow and may affect the entire continent; ferocious fires almost inevitably follow. If there is a series of ENSO events, drought can last for a decade, as happened in the 1980s and for the first decade of this century. The final weakening of the system, which generally happens after about a year, follows from the re-establishment of the easterly winds; it is often followed by torrential rain and flooding in inland, as well as coastal, Australia. This is the La Niña part of the cycle. (In South America, La Niña, as we would expect, brings drought.) Of course, other parts of the world are affected too (and other engines drive Northern Hemisphere weather and Indian Ocean systems) but only Australia is affected continent-wide by ENSO.

  This is very much a simplification of a very complex process that we are still yet to fully understand – we only began to do so in the 1980s – but this is the essence of it. In south-eastern and south-western Australia, European concepts of season work some of the time – until ENSO rolls in. In the Australian arid lands, such concepts are never relevant. It may not rain at all, or not meaningfully, for years, then the land may be a vast shallow lake. As the water soaks in, some plants and animals may reproduce for the first time in years. No matter the time of year, you have to be ready to go when the rains finally come. One way of dealing with ENSO is to build populations up when conditions are right, and trust that at least some of the hordes of scions make it through the coming drought to breed again when the rains return.

  The breeding of wild budgies has to be seen to be believed. Along the normally dry watercourses, every hollow in every River Red Gum has a nest; the sky is a swirling shroud of green and the ground is covered with tiny green and yellow parrots garnering seeds. Just one storm during a drought can trigger such a frenzy of activity. If conditions are right, a budgie can begin breeding when just 4 weeks old, so that a 6-week-old bird is already hatching her own eggs (Forshaw 1994). Most birds defer beginning incubation until the last egg is laid (at one per day); until that happens, an egg can stay in ‘suspended animation’ without coming to harm. A budgie begins to incubate immediately she starts to lay (up to eight eggs on alternate days), so nestling development may be staggered by nearly a fortnight (van Dyck 1995), the younger birds being given a more liquid regurgitated diet. This is so that, if the bonanza fades rapidly, at least the early hatchlings might get through. In addition, if the good times are still rolling on, she can start laying again after one clutch hatches (see Photo 2).

  As a result, numbers build up to enormous levels in good conditions, and they die by the millions in severe drought. One central Australian landholder in 1931 removed and burnt almost 5 tonnes of dead budgies from one dam during a heatwave (Chisholm 1958), but the safety net of vast numbers means that at least some hardy, canny or just lucky budgies are around to take part in the next breeding frenzy. This is what ‘droughts and flooding rains’ or ‘boom and bust’ is all about.

  As we walked out from Warrigal Waterhole across the plain, the sun was much higher and so was the temperature, but that was forgotten as out of the Porcupine Grass (widely known as Spinifex) materialised a glorious Spinifex Pigeon. They always seem to perform this trick of emerging from a red landscape by some sleight of feather: a movement changes your focus and suddenly one, two, a dozen exquisite rusty little birds have been there all along. Their ludicrously tall head tufts and red, black and white visages that seem to have come from a child’s face-painting stall are borne swiftly through the stony landscape on legs that give the impression more of whirring wheels. Some birds really test one’s resolve not to be anthropomorphic.

  Near to the vehicle, the Crested Bellbird, which we had failed so dismally to locate despite its constant calling, had apparently tired of the game, and bounced energetically across the ground chasing a flutte
ring moth alongside the track. It’s a funny business, this birding.

  South-west Queensland: locust swarms

  Another year, and further south in Queensland, in the channel country, we were driving through vast plains braided with numerous (mostly dry) stream lines merging and splitting. We had been watching the great swirling clouds approaching, then suddenly drove into one, the windscreen abruptly spattered with yellow waxy material sprouting legs and heads. The Spur-throated Locusts were flying, so I slowed to a speed at which their rocky bodies just bounced off the glass.

  Locusts

  This is a remarkable story in itself. ‘Locust’ is a curious term referring not to a species, but to something much harder to define: some grasshoppers can be locusts sometimes. In Australia, just four arid land grasshopper species can perform the trick, but there are others elsewhere in the world. They are normally solitary and sedentary, but in some specialised conditions they suddenly multiply dramatically and start to move in vast numbers, eating hundreds of tonnes of vegetation per day. Individuals change in colour, size and behaviour when in high densities compared with when they are solitary, which is known as kentromorphism.

  It is all to do with the uncertainties of living in deserts, especially those ruled by El Niño. Normally the female lays ∼40 eggs in a hole drilled into open ground between patches of vegetation, scattered over vast areas. In drought, the ground can be too hard even for them, and they are forced into smaller and smaller moist areas such as at the foot of dunes or in soaks. Eggs are laid closer and closer together, until there may be 3000 holes per square metre (i.e. there may be a thousand million eggs per hectare – that’s a lot of little grasshoppers!). What’s more, they only hatch in favourable conditions (no point in emerging in a drought), so they may sit in the ground for years until the right conditions come along, then all hatch simultaneously. When such large numbers hatch at once, a behavioural change occurs, apparently induced by developing in close proximity to lots of other little grasshoppers. In such circumstances, they seem to need company, which they don’t if they have hatched separately. They also look different – darker pigments form in the skin, so they absorb more of the sun’s heat, so are more active, so in turn must eat more. All this leads to the formation of a swarm and forces them to keep moving, so they must keep eating. Under normal circumstances, these great swarms are driven by the winds into south-eastern Australia; when the wind speed exceeds 11 kph, they move with it. As they move into cooler areas, they stop moving and eventually all die. Meantime they have been laying eggs as they go, which, until the next drought changes things, will hatch as ‘normal’ grasshoppers (e.g. Symmons 1985; Rentz 1991).