Birds in Their Habitats

by Ian Fraser

  Tinamous

  Tinamous fascinate me. They are among the most ancient of living birds, some 50 species restricted to Central and South America. Superficially like big quail, until recently there was some disagreement as to whether they belong in the same Order of birds as the ratites, which are flightless and mostly giant old Gondwanans such as the ostriches, emus, cassowaries, kiwis and rheas, or in an associated Order. Recently, however, the argument seems to have been settled in favour of the former (see pages 184–5). Tinamous, however, have retained their powers of flight, though they fly only weakly and awkwardly for the most part. This limitation is due to several factors, including small wings, the lack of a tail to help with braking and steering, and a surprisingly small heart. All birds are dinosaurs, but tinamous and other ratites have retained some particularly reptilian traits, such as their blood proteins and the structure of their palate, which closely resembles that of Tyrannosaurus rex. Repeated unsuccessful attempts have been made to introduce various species to Germany, France, Hungary and the USA, so that people can enjoy the fun of killing them. Curious creatures – us I mean, not the tinamous.

  Other hard-to-see forest floor birds that came that day to Norbil’s hide included Orange-billed Sparrows, Grey-necked Wood Rails and White-tipped Doves.

  If the only way to see birds was by such habituation, the world would have problems well beyond limits on our birding, but clearly that is not the case for most species, and it’s probable that such approaches wouldn’t work for many species anyway. Norbil’s birds, like Angel’s, are not dependent on the handouts, though they doubtless benefit from them. They most certainly benefit from the fact that their forest is still there and not converted to a coffee crop. Moreover, as with Angel’s neighbours in Mindo, it is likely that at least some of Norbil’s neighbours, as well as others further afield, will be inspired to do something similar. Their lives will materially improve and yet others will see that it is due to protecting the forest and its birds. It’s hard to see any losers in this scenario.

  Acjanaco Pass Road, southern Peru: cloud forest

  My introduction to neotropical rainforests was at the other end of the Peruvian Andes, far to the south, crossing the watershed of the great range north-east of the old Inca capital of Cusco, at Acjanaco Pass, 3500 m above sea level. Here we are in real cloud forest: a stunted high-altitude version also known as elfin forest. It’s a strange and wonderful world, where ghostly streamers might dissipate nebulously, or clarify into ribbons of lichen or moss. Birds appear from the mist, perch briefly and disappear into it again. Giant Hummingbirds, Great Thrushes, Masked Flowerpiercers, Grey-breasted Mountain Toucans all come and go, often in silence. There is a wealth of orchids on the trunks and branches, which also coalesce out of the swirling clouds as we walk among the trees. Behind us to the west from where we came are drier slopes in a rain shadow; ahead of us are lush forests, falling to the vast Amazon basin. The road continues in that direction, descending through changing cloud forest through an endless series of blind switchbacks and along sheer drops into the green depths, past waterfalls and rockfalls. Some 2000 m below Acjanaco, we stopped and walked briefly off the road to a hide – in front of which, inconceivably as it seemed to me, was a group of some of the most outrageous-looking birds on the planet, and another species that I never really expected to see.

  Andean Cock-of-the-Rock: leks

  The Andean Cock-of-the-Rock is like no other bird. It’s a large cotinga: a group of the numerous old South American suboscine passerines, about the size of a domestic fowl. The female is a uniform coppery brown; the male is definitely not! His head and body are bright red here, but orange in populations north of Cusco, both shades being classic examples of showy and expensive red carotenoids. He has a large pearly-grey patch across his lower back formed by the tertial feathers (the wing feathers closest to the body), which cover and protect the flight feathers when they are closed, while the rest of his wings and tail are black. A broad comb-like red crest on his head makes his whole head look ridiculously long, and apparently half way along it the bill barely protrudes from the mass of feathers. His eyes with black pupil and pale yellow iris resemble those of a teddy bear. And then there’s the behaviour … Pairs of males display to each other, bobbing heads, clicking bills, leaping about and flapping wings, while emitting a hoarse buzzing squawk. When a female appears, the displays rise in intensity to a crescendo. This was not only my first experience of this bird, but of a lek.

  The word lek is from Swedish, and was coined to describe the display areas and gatherings of various grouse species. These gatherings comprise dozens of males that have come together to flaunt their often outlandish garb and make themselves loud and conspicuous. (In fact it’s all somewhat reminiscent of certain social situations involving young human males, and the reasons for both are rather similar.) In many leks – perhaps even most, including some human ones – most of the females’ selection process is done for them, as the most successful males work their way via a series of contests to the centre of the display area. It is no coincidence that these positions are the safest, with predators inevitably drawn to the edges of the performance. It is certainly to the females’ benefit not to have to travel far to compare the talent on offer, and for said talent to sort out their rankings for her to inspect. The benefit to successful males is also clear, with guaranteed access to as many females as are impressed by the overall performance of the lek. Unlike in other mating systems, however, the less successful blokes, the majority of the male population, will probably miss out entirely, even if they don’t get picked off by lurking predators (e.g. Fiske et al. 1998).

  In addition to grouse and cotingas, lekking is practised by some members of groups of animals as disparate as hummingbirds, African antelopes, Galápagos Marine Iguanas, frogs, cicadas and butterflies (where the term used is ‘hill-topping’). A variant of lekking is the ‘exploded lek’ where competing males are distant from each other and compete by calling loudly; examples include the tragically endangered flightless New Zealand Kakapo (a parrot), and the Australian Musk Duck, whose splashes and whistles and grunts carry far across the surface of the water (see page 130).

  In the case of the cocks-of-the-rock, a series of one-on-one knockout competitions sees consecutive winners take up the prized innermost perches and, once a female has made up her mind, she simply ignores the also-rans and goes straight to the top. Life, however, is never simple and straightforward (for humans or cotingas). His frantic displays, on top of his high-energy red carotenoid habit, sap his strength – but if he goes for a much-needed fruit snack, he loses his prized and hard-won position and must start all over again. The result for enthralled birders in the hide is that, no matter how rapt we are (and it is hard not to be), eventually we are going to have to walk away while the cocks-of-the-rock continue the eternal contest.

  The next time I went there I received a severe shock. The hide where we’d stood spellbound was a scatter of splintered wood among vigorously regrowing greenery down the slope where it had been hurled. The trees where the vivid cocks had displayed to each other and to us had been entirely swept away. From way up the slope above us a swathe had been cleared through the forest by a shattering landslide, triggered by an earthquake. The Andes are still growing and such cataclysmic events are part of their growing pains. At least nobody had been in the hide, but I could only hope that the birds were as lucky; I console myself that it’s more likely that they had sensed it coming than that we would have.

  Top End, Australia: monsoon forests

  Cloud forests are not the only variation on the theme of rainforests.

  In the tropics there are also forests, usually at low altitudes, which are subject to heavy seasonal rain followed by a long dry season – these have a very different feel from rainforests, being lower and more open, and are known as monsoon forests. In common with rainforests there are many lianas and epiphytes; in fact an alternative name, often used in Australia, is vine forest
. Another, widely used elsewhere, is ‘tropical dry forest’. Often some, or even most, of the trees are deciduous, due to the need to cut back on evapotranspiration to conserve water, which is a very clear difference from true rainforests.

  Pittas: old passerines

  These monsoon forests characterise the Top End of Australia in the Northern Territory, and further west in the Kimberley, in contrast with the always wet rainforests of east coastal Queensland and northern New South Wales. Our most recent visit was in January, far from peak tourist season. Our motive was to experience the habitat in the wet: it’s less comfortable then than it is deep in the dry winter visitor season, but it’s bursting with life. In this we were out of luck in that the wet was very late that year – in fact it barely came at all. On a hot still morning we were sweating our way through the monsoon forest at Darwin’s East Point, ears straining, having watched the day brighten from a vantage point at the end of a walkway in the nearby mangroves. Finally there it was – a hard, ringing ‘WIK WIKAWIK’, coming from higher up than we would have expected. It took a while to locate the source, as the call bounced off branches and made it hard to track down the small stump-tailed black bird proclaiming itself from a branch well up in the canopy, thinned by seasonal leaf fall. Rainbow Pittas, naturally enough, are not just black, however. Through binoculars the red vent shows up, and from side-on the green-gold wings and brilliant blue wing patch glow. Pittas rarely take to the trees except to roost, spending the time hopping over the ground searching for snails, worms and other invertebrates in the litter. Pittas, some 40 species of them in Africa, southern and South-East Asia to Australia are passerines – indeed they are among the oldest groups of living passerines.

  Within the passerines, nearly 90% of species belong to the Suborder Passeri, the oscines, which have the most sophisticated syrinx, the avian ‘voice box’. Another Suborder, Acanthissiti, contains just two living species: the tiny and ancient New Zealand wrens. The third, to which the pitta belongs, is another old group, Suborder Tyrani: the suboscines. These form a tiny part of the bird world – except in South America. Apart from the 40 pittas, the Old World suboscines include ∼20 species of Asian and African broadbills and four of Madagascan asities. But in South America suboscines rule! There are almost 1200 species of them whose ancestors prospered and evolved dramatically during the continent’s long period of isolation between leaving Gondwana and crashing into North America. Astonishingly, by world standards, they outnumber the oscines, which can only muster around 800 South American species. By contrast Australia, whose biological history in most ways is eerily reminiscent of South America’s, has among its nearly 350 passerines just three suboscines: all pittas. (You will have noted too the remarkable discrepancy between the numbers of Australian and South American passerines.)

  Passerines

  There are some 30 Orders of living birds (the imprecision is because we are still uncovering new information as more subtle and powerful tools come to hand, and subsequently are constantly rethinking and fine-tuning our understanding of bird relationships). The most modern – that is, the most recent to have arisen – and most startlingly successful in terms of number of species is the Order Passeriformes, the passerines. This single Order provides 60% (roughly 6000 species) of all birds now on Earth. Alternatively, the other 29 older Orders between them account for only 40%, which is why we lump them somewhat disrespectfully as ‘the non-passerines’, defining them by what they’re not. We tend to refer to the passerines as songbirds or perching birds, but, as you would expect, it’s not easy to find a character that describes 6000 species. Many of them do sing, though we don’t really think of most crows for instance as songsters, and some members of other Orders, such as parrots, can be quite musical. They do perch (but so do many non-passerines), though their method of doing so is instructive, with three of the four toes pointing forward and a usually long one at the back, all at the same level. (Even this characteristic is not unique, however: it is shared by birds of prey such as hawks and falcons, which are not closely related to each other or to the passerines.) However, passerines also have a special mechanism involving a leg tendon and foot muscles, so that when they land on a branch and bend their leg the toes automatically lock around the branch. Asleep, they can’t fall off. There are other characteristics too, but they involve internal structures such as palate bones and wing muscles that can’t be examined without cutting the bird up – rarely practical and never desirable.

  Among the very first birds named by Carolus von Linnaeus, the ultimate architect of our basic taxonomic system, was the House Sparrow, which he called Fringillus domesticus. Two years later, the French zoologist Mathurin Brisson removed it from the Chaffinch genus and coined the genus name Passer for it, meaning simply ‘sparrow’ in Latin. This genus gave its name to the family containing it, Passeridae, and thence to the Order Passeriformes. ‘Passerine’ comes straight from that.

  The South American suboscines comprise two subgroups, both of which we met at Angel Paz’s property. The cocks-of-the-rock represent one group, which includes the South American tyrant flycatchers, cotingas and manakins, while the antpittas (no relation to ‘real’ pittas) front for the others, which are largely ground-dwellers such as antbirds, tapaculos and ovenbirds, as well as the arboreal woodcreepers. As a result, birding in South America represents real challenges to an outsider – it seems that so much of what we’re seeing is entirely unfamiliar and it takes time to get some sort of handle on what we’re looking at.

  Kibale Forest, Uganda: more pittas

  While thinking of pittas, I must revisit an image that stays with me, from the wonderful Kibale Forest in south-western Uganda. We set out on foot in the dark, because it is at dawn that the Green-breasted Pittas call. Our local guides, both called Gerard, were superb, winding without hesitation through a maze of faint elephant tracks in the dark, as easily as we might make our way from bedroom to bathroom at night. They carried old rifles – AK47s I am told – in case we encountered any of the elephants. It would have been a terrible thing if our presence had caused the death of one of them, and I’m not totally sure if the rifles would have been up to it anyway but, fortunately for all concerned, the elephants stayed away.

  I loved watching the forest around us slowly emerge from the dark. Having reached a known pitta territory we waited in silence until Gerard heard the faint distant call, like a wooden mallet melodiously resonating on a hollow wooden pipe. As we crept closer it resolved into a double note, like the very lowest end of a xylophone, with two bars being hit almost simultaneously. Moving more quickly now we (i.e. the Gerards) located the birds on the ground – a pair and a juvenile. The birds were intrinsically gorgeous (as pittas are). A broad buffy-golden eyebrow and nape divides the black head, and a pale olive breast is sharply cut off from a crimson belly. The wings and back are a rich deep green, slashed with three of the vividest blue wing stripes. However, it is the overall context that especially stays with me: experiencing the regenerating rainforest coming to life to start another day. (We went on to spend time with wild Chimpanzees too – this really was a very special day – but that’s a story for another place.)

  Paluma, north Queensland: fragmented rainforest

  On the eastern seaboard of Australia rainforests are scattered in suitable locales, from the steamy tropical stands of north Queensland, to subtropical forests of southern Queensland and northern New South Wales, all the way to cool temperate rainforests of southern New South Wales, Victoria and Tasmania. Certainly, they have been further fragmented since European settlement in the late 18th century, but the original isolation of these pockets of rainforest was due to climate change. For much of its isolated history, Australia was covered in rainforest: in more recent times, cooler rainforest types gradually replaced tropical-type forests in many areas. It was only 5 million years ago that rainforests disappeared from the inland, replaced by woodlands, grasslands and ultimately deserts. A new ice age began 2.6 million years ago, tho
ugh we are currently in a warmer, moister inter-glacial phase within the cycle of glacials and inter-glacials that comprise an ice age. The rainforests shrank into a series of isolated fragments, mostly along the east coast. And in those fragments animals and plants became isolated from their relations, no longer able to interact and interbreed.

  Riflebirds and speciation

  I was thinking about that while sitting in amazed delight on the verandah of a little café in the rainforest at Paluma, in the ranges north of Townsville in the Queensland tropics. On the rail at the end of the verandah, a bird was performing, and the performance was extraordinary. The riflebirds comprise a group of four members of the bird of paradise family; they apparently arose in Australia, where three of them remain, while one has crossed to New Guinea. Victoria’s Riflebird lives above sea level in rainforests from the Paluma Range north to the Atherton Tableland inland from Cairns. This one was attempting to attract the attention of a dusky female that was more interested in the bananas provided for the birds. He’s not a big bird: a bit smaller than a Magpie-lark, but his presence was huge. With a characteristic harsh ‘yaaahhh’, which exposed his yellow mouth interior, he opened his rounded black wings and puffed up his glossy olive underside feathers, then started swinging from side to side, alternately hiding behind his flicking wings and exposing his face. It was like watching a pantomime villain swirling his cloak. An iridescent green-blue triangle on his throat and his shining crown flashed on and off behind the sooty cloak; he carefully aligned himself to make the most of the reflecting sun. I was transfixed, but though I’m sure the object of his desire peeped at him from time to time, her hormones (and his) lost out to her stomach. Had she succumbed, she would have approached him until he could enfold her in his wings before mating. In the end, he accepted that his performance wasn’t impressing anyone that mattered, and he flew up into the trees.