Birds Breeding No

Tropical Topics A n i n t e r p r e t i v e n e w s l e t t e r f o r t h e t o u r i s m i n d u s t r y Birds breeding No. 52 January 1999 Helpful offspring Notes from the Kookaburras like to chorus, family groups of up to a dozen together producing a cacophony which proclaims their Editor territory. The more birds, the louder the chorus and the The excellent David Attenborough stronger their territorial claim. Kookaburras therefore television series, Life of Birds, (ABC benefit from living in large families. 7.30pm on Sundays) has recently been focussing our attention on the varied Most birds drive their offspring from There are several and often entertaining behaviour of their territories as soon as they are theories and no birds. This issue of Tropical Topics independent, but young kookaburras doubt some are takes a look at some of our local birds continue to live at home for about four valid for some and, in particular, their breeding years. During this time their parents species and some behaviour. put them to good use; young laughing for others. Possibly a kookaburras perform about a third of young helper: Birds are a bit like tropical reef fish. incubation and brooding duties for the • unable to breed and pass Unlike so many other animals, they next generation and supply the on its own genes, does the are colourful, visible, act out their nestlings with over half of their food. next best thing by promoting the lives largely in full view — and move family genes. through space with enviable ease. Kookaburras are not the only birds to • having mated with the breeding They invite our interest and, as breed co-operatively. In fact, child female is (or believes he is) the researchers learn more about them, labour is a feature of least 80 father**. (Females may deliberately they become ever more fascinating. Australian species* including forest recruit helpers by mating with them.) Bird watching can be simply about and buff-breasted paradise- • helps in exchange for ‘pocketmoney’ identification — ticking names of kingfishers, bee-eaters, a number of — the right to remain, and feed, at species on lists — or it can be about honeyeaters, particularly the miners, home. understanding what the birds are fairy-wrens, thornbills, robins, • learns vital childrearing skills. doing, which in many ways is much woodswallows and butcherbirds, to • hangs on, hoping one day to inherit more worthwhile. mention only some. the estate. • finds safety in numbers — more As usual there are many more aspects Why do these young birds hang lookouts give more warning of to this topic than room in the around with their parents instead of predators — and more feeders help to newsletter. Look out for more on bird setting up homes of their own? keep the nestlings quiet. behaviour in future issues. Breeding may well be limited by food • having helped raise a brood can then scarcity, particularly where there is no recruit them into its gang and, with I would like to thank Steve Garnett, seasonal increase (as happens during strong numbers, move out to establish DEH, and Elinor Scambler for their a northern hemisphere spring) to fuel a its own territory. help with this issue. sudden population growth — and more beaks are needed to gather it. Whatever the reason, co-operative Please note breeding seems to be a particularly that you are welcome to photocopy Even if the young birds cannot breed Australian phenomenon — 85 percent Tropical Topics. However, if the by themselves how are they of all bird species which breed co- text is reproduced separately it must persuaded (every human parent with operatively are found here — and may not be altered and must adolescent children may well want to well be a response to Australian acknowledge the Environmental know) to help with domestic chores? conditions. Protection Agency as the source. Illustrations must not be reused *Details vary between species. Some pairs are capable of raising a brood without without permission. Please contact help, but others invariably fail if they try. Some require only a few helpers, while the editor (details on the back page) others may have 20 or more. if in doubt. **Although helpers are often closely related to the breeding pair and nestlings, sometimes they are not (see Promiscuous fairy-wrens, p7). Bowers Mimics Bowers are not nests but display areas, built by male bowerbirds to attract All the Wet Tropics male females for mating. Females choose their mates after carefully inspecting the bowerbirds are known to mimic structure and decorations of each bower (rare items gain bonus points) as well other birds, usually as part of as the male’s plumage, his display and his vocal repertoire. Males with the best their courtship display. Male displays get to mate with the most females — in any population only a few tooth-billed bowerbirds (right) experienced males, with the most impressive bowers, may actually father the can copy the songs of more young. This creates much competition with males actively destroying the bowers than 20 other birds. From September to of rivals and stealing trophies. This forces the victims to spend more time on February each year they enliven the rebuilding and less on seducing females. Following his conquest, the male forest in the vicinity of their stages, bowerbird takes no further interest in the female and his offspring. In contrast giving an impression of countless to their mates’ elaborate structures, the females build rather ordinary cup or species of birds in full song. The males saucer nests made from twigs. sing for much of the day and it is thought that the mimicry component is Tooth-billed bowerbirds’ bowers are The great bowerbird and the satin used specifically to attract females. the simplest. The male clears an area bowerbird build avenue bowers. Thin However, the loud songs also seem to one to three metres in diameter, sticks are neatly arranged in an upright function as an advertisement of returning to exactly the same patch of position, forming two parallel walls, territories to other males since a bird forest floor each season. He then looking almost like a couple of old- will stop now and then to listen for its decorates his stage with fresh leaves, fashioned brooms sticking out of the neighbours. If an adjacent rival is not pale side up, having snipped them off ground with a narrow passage heard, the bird may then mount a quick with his double-notched bill. Each day between. Decorations are mainly raid to steal his neighbour’s leaves! he brings more fresh leaves arranged at each end of this avenue, (sometimes stealing them from the great bowerbird choosing pale neighbours). What the male lacks in objects such as bleached snail shells, bower-building he makes up for in stones, bones and soft drink can ring- mimicry (see Mimics, right) spending pulls as well as green fruits, while the almost every daylight hour at his satin bowerbird prefers blue — bower. feathers, berries, flowers, glass, plastic and so on. Further adornment is added by the males ‘painting’ the inner walls of the avenue with plant matter and Frequency in saliva. The satin bowerbird even uses kilohertz a frayed grass stem as a brush — a rare example of tool use in animals. Time in seconds Time in seconds Interested females enter the avenue, These sonograms show the similarity where mating takes place, after which between calls of three birds (left) and she may be promptly chased away to the male tooth-billed bowerbird's leave the bower free for further mimicry (right). From the top, (left) seductions. white-throated treecreeper, Lewin's honeyeater and pied currawong. Females of the satin and great bowerbirds are also known to mimic The smallest, the golden bowerbird, when disturbed at their nests. They builds the biggest bower. Two towers, usually choose to mimic predatory up to three metres in height, is made birds but can also produce cat and from sticks piled around two saplings human noises. (One great bowerbird, about a metre apart. Often the towers near a quarry, can mimic the noise of are connected by a horizontal perch at rocks being thrown into a trailer and a the sides of which decorations of two-way radio.) Possibly this is done lichens, mosses and pale flowers and to distract a predator by confusing it fruits are added. The beautiful golden with the impression that another male displays on the perch and around individual is present. the area of the bower. The bower may Visiting bowers People are fascinated by bowers — but may unintentionally create a situation last for many decades, often with the Reproduced, with permission, from Emu Vol 96, 1996. same owner, and may be handed down where all the bird’s hard work is in vain. through generations. Bowerbirds put an immense amount of If you want to visit bowers, or take effort into their creations, spending up others to visit them, please put the to 20 years building, renovating and needs of the birds first. decorating. A good bower is the key • Time your arrival carefully so that to a male’s breeding success — as you visit the bower in the middle of long as the females come to visit him. the day. The females visit for mating in Females, however, are shy and if a the morning and evening, so visits bower is frequented by potential between 11am and 2pm will help predators, such as humans, they may minimise this disturbance.

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