Birds in Their Habitats

by Ian Fraser

  Photo 24. Yellow-billed Spoonbill, Jerrabomberra Wetlands, Canberra. This bird is preening: running each feather in turn through its bill to clean it and ‘rezip’ the barbules. This is an immense task, which every bird undertakes every day. (Page 146)

  Photo 25. Pied Kingfisher, Queen Elizabeth National Park, Uganda. This is one of many bird species in some 30 Families that breed in excavated burrows. (Page 173)

  Photo 26. Collared Sparrowhawk with House Sparrow, suburban Duffy, Canberra. This little drama took place in our small backyard: it’s amazing what happens in your garden! (Page 177)

  Photo 27. Gimlet (Eucalyptus salubris) woodland, near Norseman, inland southern Western Australia: such woodlands are biologically very rich. (Page 181)

  Photo 28. Darwin’s Rheas, Torres del Paine National Park, Chilean Patagonia. These are ratites: flightless, mostly large, southern birds (the ancestral rhea flew into South America long ago). The male is the sole carer, and they produce many young to increase the chance that some will survive. (Page 183)

  Photo 29. Mealy Parrots, Blanquillo clay lick, southern Peru. The ‘mealy’ (i.e. floury) look is due to an abundance of powder down, a talc-like powder produced by highly specialised decomposing feathers to assist in general feather care. (Page 189)

  Photo 30. Nankeen Kestrel, wind hovering near Canberra: balancing itself against the wind by constantly adjusting wings and tail. The alulas (special feathers on the ‘elbow’ of the wing of every flying bird to break surface turbulence and greatly improve aerodynamics) are quite visible here. (Page 206)

  5

  Wetlands and rivers

  Gum Swamp, New South Wales

  There was something chillingly surreal about that hunt. The hunter sank in the water until not much more than eyes and nostrils were visible, then edged forward slowly with barely a ripple. The effect was eerily crocodile-like. The mother of the intended prey suddenly became anxious, then stood up in the water with flapping wings, yelping loudly and harshly, at which the eight Grey Teal chicks rushed across the surface, either towards her or the nearby reeds. At that moment the hunter also made his own rush across the water surface; when the roiling water and terrified chaos had subsided, the eight chicks were now seven. The male Musk Duck was not to be seen until he surfaced some 30 m away, a limp bundle of downy feathers in his beak.

  This little drama played out at Gum Swamp (and isn’t that an archetypal Australian place name?) on the edge of the historic goldmining and pastoral town of Forbes in the south-western slopes of New South Wales. In general terms, this swamp is in many ways fairly typical of wetlands in modern southern Australia, and indeed beyond. It comprises several hectares of shallow open water fringed with reeds and rushes, with an adjacent area of somewhat degraded woodland. It has a rudimentary, but functional, concrete bird hide, which is by no means a universal accoutrement at such sites. However, the giveaway to the recent nature of its current state is the large number of standing dead eucalypts in the water. This may once have been an ephemeral wetland – in which case the drowned trees are probably River Red Gums Eucalyptus camaldulensis – or it could just have been woodland, but it is now artificially permanent, fed constantly by an outflow of treated water from the adjacent sewage works. There are very few significant wetlands outside the Australian tropics in anything like their original condition. In this land of El Niño, this means ephemeral: filling in the rains, especially of the wet La Niña seasons, and gradually drying as the months and years go by with evaporation exceeding rainfall and subsequent inflow. (Mind you, given our record in draining and choking off natural wetlands, I’m happy for any compensation going in the form of artificial ones, but we also need ‘real’ ones.) The dead trees were mature when they drowned, because many have nesting hollows. Cockatoos use some, but they also support a huge population of Feral Pigeons, which in turn attract regular visits from Peregrine Falcons, a few from Black Falcons, and occasional ones from the mythically rare Grey Falcon (never while I’ve been there though!). Scores of ducks of up to nine species are scattered across the waters, along with grebes, moorhens and coots. Herons and rails patrol the edges where Australian Reed-Warblers and Little Grassbirds sing from the reeds, and ibis and spoonbill perch in the dead trees.

  r-selected breeders: ‘have lots of kids, hope a couple survive’

  The little Grey Teal family tragedy is a daily occurrence in the lives of duckling broods, which is precisely the reason that there are so many eggs in the clutch, and so many youngsters hatching from them (minus the odd egg that falls to an opportunistic goanna or snake or raven).

  In a dead tree across the swamp from the hide is a huge stick nest belonging to a White-bellied Sea Eagle, which has been there for generations and may weigh hundreds of kilograms. They generally have only one chick (if two hatch, the second rarely survives to leave the nest) on which they lavish all their attention, investing hugely in its survival. This, as we’ve discussed elsewhere (page 87), is referred to by ecologists as a K-selected breeding strategy: it is an adaptation to steady conditions over a long period of time. Indeed, K is a mathematical symbol referring to the carrying capacity of the local environment. It has been taken for this usage from a complex equation (complex by my, and possibly your, standards at least!), which was derived in 1838 by Belgian mathematician Pierre François Verhulst to model population changes. K-selected breeding species, such as the Gum Swamp sea-eagle, rely on a stable world in which they maintain their generally low population at a level close to what the environment can support.

  The teals, however, go for ‘the other’ option: they are r-selected breeders. In Verhulst’s equation, r stands for the maximum rate of increase of the population. (I’m sure someone could tell you why Verhulst used a capital K and a lower case r, but I’m afraid that person is not me.) Such organisms have many offspring, with minimal attention to each one, and rely on chance and basic care (or in some cases none at all) to ensure that one or two get through. In an unpredictable environment – such as that provided by a wetland in an El Niño-driven climate – r-selected species with their high rates of population growth and generally unfilled niches are at an advantage. Strictly speaking, if a pair of birds throughout their life only manages to have two offspring that grow up to reproduce they would be breaking even, though it’s likely that they would be behind some of their neighbours in the genetic competition. The eight ducklings the mother teal was trying to protect represents the mean clutch size for the species. Others such as the Australian Wood Duck can have up to a dozen eggs, and the peripatetic Plumed Whistling Duck, which occasionally turns up at Gum Swamp from northern Australia, can have up to 14. Actually, larger clutch sizes are regularly reported, but many ducks have a tendency, especially in drier seasons, to dump eggs in someone else’s nest to be looked after. The nest of a Red-crested Pochard was reported to contain 39 eggs (Carboneras and Kirwan 2017), most of which she had certainly not laid!

  Parasitic ducks

  Digressing for a moment – though can a good story ever really be digressive? – the Black-headed Duck of central South America is an obligate nest parasite: the only duck that never builds its own nest. Amazingly, its hosts include not just other ducks, but coots and gulls are important too; other hosts include ibis and even raptors such as Snail Kites and Chimango Caracaras (the latter being an egg predator!). These ducks are not like cuckoos, demanding to be fed: after hatching, the duckling slips out of the nest and disappears, already self-sufficient. It means that the mother can lay as many eggs as she can produce, not just as many as she can brood.

  However, the real r-selected specialists among vertebrates are fish, which can lay thousands of eggs. Beyond that, insects can have huge broods and plants such as eucalypts can produce hundreds of thousands of seeds.

  Nature, as ever, refuses to sit neatly in the boxes we create for her: they are for our benefit not hers. For this reason, it’s important to remember that it isn’t just a question of a bird being either r-selected or K-se
lected: those are just an indication of the extremes. We could almost certainly find (if we had that much spare time to comb determinedly through the literature) species with mean clutch sizes of every number between the sea-eagle’s one and the teal’s eight. Moreover, the numbers themselves don’t tell a uniform story: for instance, the White-bellied Sea-Eagle produces one egg (occasionally two) a year, but the Andean Condor lays just one every 2 years.

  For the most part, our little brains tend to prefer simple definitions without too much nuance. Bad luck then when our brain is forced to consider a situation such as that of the Letter-winged Kites of the arid desert plains and grasslands of the Lake Eyre Basin and Barkly Tablelands of inland Australia. In ‘normal’ (i.e. dry) seasons, they behave like we expect a raptor to: producing one or two young a year, or none at all in drought times. Then eventually La Niña comes and the rains reach deep into the centre of the continent, flooding vast areas and isolating homesteads and communities for weeks at a time. As the waters recede, the land comes pulsingly alive with unimaginable bounties of grass seeds, flowers and insects and the birds and other vertebrates that feed on them. At this time, the Long-haired Rat Rattus villosissimus breeds in vast numbers – and the Letter-wings’ time has come. With their main food supply now assured, they cast caution to the desert wings, and flip from being a ‘normal’ K-selected raptor to a classic El Niño r-selected bird, producing up to six young at a time. When the land dries again, and the surviving rats retreat to the fissures in the now-cracking black soil plains, the young kites disperse across the country, many dying hundreds or thousands of kilometres from the land of their ‘chickhood’.

  ‘Normal’ really is such a dangerously alluring and comfortable concept to rely upon.

  Grey Teal and breeding triggers

  Indeed, when a remarkable man called Harry Frith turned his attention to Grey Teal (and other waterfowl) in the 1950s, he refused to accept that these children of El Niño were ‘normal’ in the context of Northern Hemisphere understandings of how breeding triggers work.

  Frith had a degree in agricultural science, but his career was interrupted before it had begun, like that of so many others, by the Second World War. He fought in the Middle East and New Guinea, then returned to work in the citrus orchards of the Riverina in southern New South Wales. His heart wasn’t in it, however, and he switched to the Wildlife Survey Section of the Commonwealth Scientific and Industrial Research Organisation (CSIRO), the peak government research body. He taught himself ecology and zoology to such good effect that a decade later he was appointed the first chief of the new Division of Wildlife Research. Frith was instrumental in our understanding of Australian waterfowl and the Malleefowl, and was a great conservationist who played a key role in the declaration of Kakadu National Park in the tropical Northern Territory: one of the world’s great parks (Tyndale-Biscoe et al. 1995). (We may see it as ironic that very many ducks were killed in the cause of conservation, but it was essential to understand what was happening, especially with regard to breeding status and preferred food supplies. The numbers of these deaths were as nothing compared with the impacts of habitat loss and competition from agriculture and other sectors of the economy.)

  In strongly seasonal climes, changing day length triggers the production of hormones that start the courting and breeding cycle at the same time every year, but Frith saw that that wouldn’t work here – it might start waterbirds breeding when there was no water and prevent them from doing so when conditions were perfect. It wasn’t rainfall per se, as he observed that that alone didn’t trigger a reaction. What he observed was that the sight of rising water sparked Grey Teal breeding behaviour in anticipation of the food bonanza that the birds ‘know’ will come. They began displaying within a day or so of this happening, and ovulation began soon afterwards, well before a change in food could be the stimulus. If water rose, then fell again, displays petered out and there was no ovulation (Frith 1967; Andrewartha and Birch 1986).

  I recall my excitement as an impressionable young undergraduate when I heard that story from another giant of Australian ecology, HG Andrewartha at Adelaide University.

  The members of that little family of Grey Teal whose drama I witnessed could have ended up anywhere in Australia if they survived. A waterbird in inland Australia must move when the waters dry up, or perish. Nationally coordinated banding studies – overseen by Frith – showed that, when conditions are tough in the Murray–Darling Basin, as happened in 1958, Grey Teal scattered throughout the entire continent, and as far as New Guinea and even New Zealand. They fly fast and hard in straight lines; if they fail to find water they either reach the coast or perish, as very many do. This is a variation on the nomadism that is key to the survival of inland Australian birds (see Chapter 1).

  Musk Ducks: a story of a duck’s luck

  The more we learn about the southern Australian Musk Duck, the more we realise both that it’s worth knowing and how much there is to know. At Gum Swamp I’ve seen not only the hunt – a very rare behaviour among duck species, most of which are vegetarian as adults – but have also seen a female Musk Duck carrying two chicks on her back. This is also uncommon among ducks, though not for swans. We used to be fairly comfortable in assigning the Musk Duck to a place with the stifftail ducks: a group comprising a genus of six species, including the Australian Blue-billed Duck, which between them are found on every unfrozen continent, plus a couple of South American species in separate genera. Now, however, we tend to cough a bit uncomfortably and suggest that we never really thought that the Musk Duck belonged there …

  The problem is, we don’t really know where it does belong. Maybe its ancestor was one of the stifftails back in a long-ago Gondwanan lake, and isolation has led it down different paths. Or, perhaps more likely, it really is an old Gondwanan with no meaningful foreign relatives, other than perhaps the equally enigmatic Australian Pink-eared Duck (there is some genetic evidence for that) and resembling the stifftails simply because of its similar freshwater diving lifestyle.

  It is one of the few birds named for its smell. Not many individual birds can claim (albeit posthumously) to have unequivocally given their name to the entire species. That, however, is the dubious consolation for an unfortunate male Musk Duck, cut down not only in his prime but at the most inconvenient time of year for him. We know this, not only because he was collected (in 1791 by Archibald Menzies, inland from current-day Albany) at the height of his spring breeding season, but because his post-mortem revenge was to imbue the entire ship with his courtship perfume. This, it seems, had been more alluring to female Musk Ducks than it was to male British sailors. The drake exudes the chemical with his preening oils from his uropygial gland when he most needs to impress his intended. As far as I know, not many birds employ this strategy, which is more often associated with mammals or insects.

  However, it wasn’t just the late duck whose luck ran out; Menzies too was badly short of this commodity. George Vancouver (a veteran of Cook’s Pacific expeditions) was sent by the Admiralty in the Discovery in 1791 to sort out the Spanish who were being a nuisance off the north-west coast of North America. As ever, unofficial British biologistin- chief Sir Joseph Banks made sure there was a scientific presence, in the person of Archibald Menzies, a naval surgeon and botanist. At that stage, the west coast of North America was about as far from England as you could get. If you didn’t want to go via Cape Horn (and who in their right mind would?!) the option was the Cape of Good Hope, east across the Southern Ocean and north-east across the entire Pacific. Vancouver decided that he might as well have a look around while he was in the neighbourhood of south-western Australia. Menzies used his time industriously: he gathered ‘wild celery’ to counteract scurvy, collected many native plants and planted vine cuttings and watercress, and almond, lemon, orange and pumpkin seeds. (The plantings, unsurprisingly, did not survive.) And, in addition to the Musk Duck, he collected specimens of (and wrote in his journal the first descriptions of) the Western
Rosella, Southern Boobook and Red-capped Parrot. Sadly he didn’t ever publish, so others later got the credit. It got worse for him though – he fell out with Vancouver and got locked up on board for 3 months, during which time his carefully collected and tended live plant collection perished. The duck was probably smiling grimly to himself at the time.

  Showing off in the water

  Until his sudden and unfortunate demise, the duck would have participated in one of the most unusual and impressive courtships of any waterbird. Swimming out from the fringing reeds, he kicked powerfully with one foot at a time, each stroke hurling a spout of water behind him. When he got to the open water he stopped, while still hurling the water out behind him (which in itself seems to be a pretty clever trick). With each kick, he raised his wings to meet above his back. This continued for some minutes, while his whole appearance changed. The fleshy lobe beneath his bill distended with blood while he puffed out his neck and checks so that his raised head resembled a ball. At the same time, he lifted his tail and fanned the stiff tail feathers across his back. By now he barely resembled a duck. But just in case no-one had noticed yet (very unlikely), he let the world know in no modest terms, with a series of deep resonant ‘ker-PLONKs’ echoing across the water from his feet. (Humans haven’t really worked out how a Musk Duck does this.) Finally, the whole performance reached a crescendo as he sank in the water, slowly rotating while still hurling gouts of water out behind him, his bill pointing to the sky as he whistled loudly and shrilly for minutes at a time. Such a display tends to attract an audience of both males and females, understandably enough. A successful and brief mating with one of the female admirers marks the end of the spectacle.