Breeding Behaviour of the Wild Budgerigar
Breeding behaviour of the wild budgerigar Melopsittacus undulatus and its application to improving the breeding performance of exhibition budgerigars.
By Rob Marshall 1 and Jean Marshall 2
1. R. Marshall B.V.Sc.,M.A.C.V.Sc. (Avian Health)
2. J. Marshall B.A. Hons (Geology), T.C.
The breeding biology of the budgerigar (Melopsittacus undulatus), a nomadic and opportunistic breeding parrot species inhabiting a vast range across Australia was examined. The budgerigar's range across Australia is largely one of arid and semi-arid zones. Our 5 year ongoing study at five locations; Delmore Downs, Simpson Desert, Finke River, Hammersley Ranges and Lake Tandou showed that it is possible to predict the location of breeding sites and times when breeding activity of the budgerigar is most likely to occur.
High summer temperatures and an unpredictable low annual rainfall is a feature across the budgerigars' range. Budgerigars are nomadic and survive in very dry areas by following thunderstorms. In habitats where little water exists, budgerigars may arrive in explosive numbers after rain. As conditions deteriorate they then move on. Budgerigars do not breed in desert regions but rely upon desert grasses such as hard and soft Spinifex (Triodia species) for their survival during drought. Rainfall initiates breeding behaviour for budgerigars in Nature but a complex set of seasonal, climatic, geographical and geological circumstances is required to bring breeding activity to its successful conclusion. Budgerigars require breeding habitats that provide suitable nesting hollows, water and food supply. These sites can be predicted by geological and soil maps that are known to support nesting trees (river eucalypts) and nearby feeding areas favoured by breeding budgerigars.
Breeding behaviour is rapid in onset but remains an uncommon event because drought conditions dominate the budgerigars' range. Drought conditions may last for several years. Completion of the budgerigar's breeding cycle is determined by a rapid flush of seeding grasses and other desert and semi-desert plants that occurs after a sequential rain pattern. The best breeding outcomes in central Australia result when this pattern sequence occurs from mid-February to mid-March. The Delmore Downs study site represents an ideal breeding habitat for budgerigars across their northern range. Spring breeding is more common in the southern range of the budgerigar where a winter rainfall pattern predominates and temperatures are often too cold for breeding during autumn.
Knowledge of the breeding behaviour of wild budgerigars may be used to improve poor breeding performance of show quality exhibition budgerigars by ensuring they follow the same breeding patterns of the wild budgerigar.
Geology and Soils
Geologically, Australia has been stable for at least 200 million years, with an extensive area of its inland once being occupied by tropical, shallow seas. Structures that originated as sediment in these warm inland seas have uplifted with earth movements and over a long geological time scale these outcrops of hard, mineral rich rock have weathered to release their metallic ions, especially calcium, magnesium and sodium. The resulting soil is extremely rich in nutrients. The MacDonnell and Hammersley Ranges are examples of "upland" areas of rich in nutrients.
Weathering, by wind and water, carries some of the nutrient rich sediments beyond the ranges to the low lying regions below. Sand brought with winds from the northwest of the continent into this lower region combines with the nutrients originating from the mineral rich outcrops to form a soil type that is specific to this region. This soil is fine, rich in iron and reddish brown but less fertile than the soil found in upland areas. More significantly, the soil found in some parts of these low lying areas is rich in calcium. This is a result of the limestone and clay lenses that have been exposed by weathering. Calcium supply, otherwise not available in the upland areas, is a major determining factor in the budgerigar's selection of breeding sites. The availability of calcium is necessary for egg production and thus forms an integral part of the budgerigar breeding cycle. Beyond these areas are the inhospitable sand deserts and gibber plains where budgerigars are unable to breed.
The predominant species across the lowlands are the Acacia shrubs. Underlying and surrounding the Acacias dispersed throughout these lowlands is a diverse range of perennial and annual grasses and forbs. These grasses come into flower following periods of rain and the resulting seed forms a significant part of the wild budgerigar's diet. However, during drought, when these grasses and forbs are unavailable as a food supply, budgerigars may be forced into the deserts as a means of survival. Desert vegetation is specialized for drought conditions and includes tussock grasses, Spinifex and Bandicoot Grass, Blue Bush and Salt Bush. Whilst these grasses provide enough nutrients for the survival of the wild budgerigar, the lack of rain and absence of calcium enriched soils results in an environment in which the budgerigar is unable to breed.
The climate across the arid range of the budgerigar is one of the most unpredictable in the world (Oosterzee 1995). Rainfall is unreliable in amount and season. Budgerigars have adapted to this unpredictable climate by being able to activate their breeding cycle very quickly after rain.
Weather patterns are believed to follow extremely long cycles (in the order of centuries rather than decades) and the breeding success and subsequent numbers of budgerigars seen in the wild will also fluctuate over an equally long period. In the wild, the breeding behaviour of budgerigars follows a distinct pattern. They respond sexually to the coming of seasonal rains that represent the imminent full growing time of plants and grasses. At other times, when food supplies are limited by season or drought, their sex hormones lie dormant and they have no desire and are unable to breed. When food supplies run low they become nomadic, flying vast distances across their tropical range in search of new seeding grasses.
Summer rainfall patterns prevail across the northern parts of the budgerigar's range with worthwhile falls most likely to occur during the second half of the wet season (between December and March. See chart 1). The wet season determines the success of the budgerigar's breeding cycle. Its starting time and duration may vary from year to year depending upon monsoon activity further north and west of Australia. El Nino events, which occur every 4-7 years, also have a major effect on the start and length of the wet season. The consequence of El Nino events varies according to their intensity. An intense El Nino results in drought and a failure of weather conditions that allow budgerigars to breed. "Normal" years result in monsoon activity starting in November and extending through until April. Breeding success and therefore budgerigar numbers in Nature vary according to the intensity of the El Nino and La Nina, events that are thought to follow a 1500-2000 year cycle. Breeding conditions may not arise during El Nino events with a resulting decline in budgerigar numbers. Numbers should be expected again to rise when La Nina events dominate the weather pattern of the Australian continent.
Temperature & Rainfall
The budgerigar has adapted to the climate of arid and semi-arid Australia. Temperature and rainfall govern their breeding seasons. The ability to breed spontaneously after rain is inherent to the budgerigar, although breeding is not made possible only by the presence of rain. It is a combination of rainfall associated with moderate temperatures that brings the budgerigar into breeding condition. Although there is adequate rain, breeding in summer across the northern range is not possible because of extreme temperatures. Similarly, in the southern range, temperatures are too cold in winter to allow breeding even when rainfall is adequate. During the winter months budgerigars may migrate north east into the semi-arid zone of North Queensland where warmer temperatures may allow breeding after rain. The remaining seasons, spring and autumn, are the most suitable times for budgerigar breeding because adequate rainfall and moderate temperatures allow for the successful completion of the breeding cycle. The opportunistic nature of the budgerigar allows breeding to occur at any time when there is adequate rainfall and moderate temperatures. Breeding is not restricted by particular seasons because of the variable nature of rainfall and temperature throughout their vast range.
Water is a scarce resource in the arid centre of Australia and one which budgerigars must seek in order to ensure their survival. It has been estimated that an average of 80% of the desert waters come from thunderstorms. These thunderstorms have a flash flood affect, causing water to flow down the slopes of the ranges and into the dry river beds that cut through the lowland areas. When fed by rain these desert rivers and the waterholes along their length provide an ideal breeding habitat for budgerigars. The filling of the water table after heavy rain enables the growth of Red River Gum (Eucalyptus camalduslensis) and other nesting trees along the banks of the dry riverbed.
The wild budgerigar has adapted to tropical and temperate semi-arid and arid areas of Australia by becoming a nomad, breeding "on the run" and reducing its size. It has adapted to drought conditions that may persist for up to ten years. During prolonged droughts many budgerigars perish and only the fittest survive. On average drought conditions prevail for five out of every ten years across the range.
Seasonal weather patterns determine the breeding activity of budgerigars. Their gonads remain dormant until stimulated by rain. A sequential pattern of rain falling in a breeding environment is required for completion of the breeding cycle. Budgerigars require suitable nesting holes, calcium and mineral rich soils and a sustained supply of food in order to breed.
It is possible to predict where budgerigars breed from knowledge of the geology, soil types, vegetation and water source across their range. Budgerigars may breed on the fringes of but not within desert regions. They may however inhabit deserts to take advantage of desert resistant grasses such as Spinifex and other desert plants that suddenly come to life after rain. Knowledge of climate, seasonal and local weather patterns makes it possible to predict when a breeding outcome is possible. Autumn breeding is more likely in the north and spring breeding in the south of their range.
This study was initiated to learn more about the breeding behaviour of the wild budgerigar in order to improve the breeding performance of the exhibition budgerigar.
Over the past 20 years the standards for exhibition budgerigars have promoted a large bird with "buff-type" feather. Nowadays infertility and breeding difficulties are linked with the best quality exhibition budgerigars. Knowledge of the breeding behaviour of wild budgerigars may be used to improve breeding outcomes for show quality exhibition budgerigar. Improvements can be achieved by ensuring the budgerigars to be paired are first exhibiting signs of breeding condition and that breeding activity is not initiated when it is too cold, too hot, a month prior to the shortest day of the year or during the natural moult period.
The budgerigar (Melopsittacus undulatus) is a small compact bird 18cm in length. The sexes are alike in colour and size. Cocks have blue and hens a brownish cere colour. Budgerigars are highly nomadic and follow flushes of seeding grasses after thunderstorms. They are most active during early morning and late afternoon when visiting waterholes to drink, marching through grass searching for seeds or flying from one tree to the next (Forshaw, Parrots of the World 1973). They feed on seeds procured on or near the ground. Important food items are spinifex (Triodoa) and Mitchell grass (Strebla) (Forshaw 1973). Pigface seeds (Portulaca oleracea) have also been found in the crop of budgerigars (Lea & Gray 1935). During the heat of day they spend their time well camouflaged in trees or tall bushes.
The study sites selected for this research encompass the major habitats of Central Australia. A temperate location in the budgerigars southern range was also included. The major habitats used by budgerigars include riverine woodlands, desert ranges, mulga woodlands, sand-dunes and sand-plains. These habitats are not defined by strict borders and often a number of these environments were contained within the one study site. The Finke River study site was selected as an area of riverine woodland that provided a habitat suitable for budgerigar breeding where food and water were made available following rain. Mulga woodlands were nearby.
The vast sand plains of the Simpson Desert study site play a significant role in the survival of the budgerigar species. In periods of drought the desert hardy grasses found here are the only food sources available to budgerigars. Spinifex, one such desert hardy grass found widely across Australia, is favoured by budgerigars but alone does not facilitate breeding. The Delmore Downs study site, similar to the riverine woodlands of the Finke River proved the most suitable environment for breeding budgerigars. This site is set apart from the Finke River study area by the existence of calcium deposits and clay lenses within a richer soil. At this site the semi-desert iron rich red soils, in combination with calcium from limestone deposits provided an area in which, following rain, budgerigars could find enough nutrients, water and nesting sites to complete their breeding cycle. The nearby mulga woodlands and Mitchell grass plains, rich in grasses for feeding, supplement this zone and further its idyllic breeding nature. The Hammersley Ranges provides an example of a desert range, where rock outcrops have uplifted with earth movements, creating extensive gorges and steep hillsides. During thunderstorms these gullies act as a water catchment zone, which in turn feeds the otherwise dry riverbeds of the surrounding lower lying areas. Riverbeds on the outskirts of Newman provided the study site. Mulga woodland and spinifex heathlands were part of the variable environment near the study site. The Lake Tandou study site, a semi-arid, man made inland waterway in the southern part of the budgerigars range provided a site in which budgerigars were known to breed.
The chenopod shrublands and gibber plains are a major habitat within Central Australia but one in which budgerigar breeding does not take place. Whilst this environment is rich in nutrients, its absence of surface water results in an environment not suitable for budgerigar breeding. For this reason no site within this region was selected for study.
The study covered a vast area and range of environments across Australia. These included Finke River, Northern Territory; Simpson Desert, Northern Territory ; Delmore Downs, Northern Territory; Hammersley Ranges, Western Australia and Lake Tandou, New South Wales.
Finke River, Northern Territory
The study site is located in an area west south west of Alice Springs and extends from Latitude 23.5-26°S. The Finke River originates in the MacDonnell Ranges west of Alice Springs and flows south east towards the Simpson Desert. It forms part of the ephemeral river system of Central Australia and remains dry, except after heavy rains. Flash floods may occur in summer after violent thunderstorms and winds of high velocity carry the sediment over a broad stream area creating the dry and sandy riverbeds of the Finke River and its tributaries.
Mulga (Acacia aneura) and Red River Gums (Eucalyptus camaldulensis) fringe these wide river beds and their deep root systems reach down to the water table. Coolibahs (Eucalyptus coolibah) grow in the alluvial basins and distributary channels. Beyond this, vegetation becomes sparse. The riverbed and its surrounds is an excellent breeding ground where at the time of study (August/September 1998)) there were nests everywhere, ranging from ground level to the near tops of the trees. One nest was observed under a pile of stones.
Budgerigars were observed flying in small groups of 20-30 birds to the south east. Together with many other budgerigar groups they were seen feeding in an area of diverse plant life, ranging from forbs and flowering plants including Billy Buttons (Craspedia charyantha), Daisies (Minuria sps.) and Parakeela (Calandrinia sps.) to a variety of grasses including annuals; Button Grass (Dactyloctenium radulans) and perennials: Native Millet (Panicum decompositum).
Early each morning, with the desert in full bloom, budgerigars were observed flying in small groups from the breeding area in the direction where plant life was prolific. During the study, midday temperatures were recorded at 38-40°C, at which time budgerigars camouflaged themselves amongst the leaves and remained silent. However, later in the week and during the midday heat two budgerigars were observed flying back and forth from the feeding to the breeding area. At the feeding areas there was a continuous but quiet communication as they grazed. Late in the morning small groups of budgerigars were observed drinking at a permanent water sink. They circled, quickly drank, flew off and circled again, then repeated the process before flying off in the direction of the breeding grounds. In captivity similar feeding activity, whereby budgerigars continuously seek food for their rapidly growing feathered nestlings has also been observed. This observation supports the idea that budgerigars in captivity emulate the breeding activities of their wild counterparts.
Further south east, both the vegetation and waterholes became smaller and increasingly sparse. In this area budgerigar populations diminished and breeding activity was not observed.
The Finke River (Maloney Creek tributary) study site provided an ideal breeding environment for the wild budgerigars. The water sink found at the Maloney Creek site together with a nearby feeding area, some 20 kilometres away from the nesting hollows, provided the water and nutrients required for the completion of their breeding cycle.
Simpson Desert, Northern Territory
The study site is a typical sand dune environment, where high winds, moving sands, low rainfall and high evaporation produce sparse and stunted vegetation. The desert extends southwards from about Latitude 21-26°S and is characterized by broad and shallow dry creek beds similar to the Finke River study site. With sparse vegetation to hold the moving sands and no obvious water sinks, breeding budgerigars were not observed.
Our study site was in the surrounds of the Andado Homestead. Midday temperatures were above 40 degrees each day. Here budgerigars were located but not observed to be breeding. They were seen flying westward early mornings. On inspection it was noted that they were utilizing the same feeding grounds and sinks used by the breeding population of our Finke River study site more than 100 Kilometres away.
During drought conditions budgerigars were observed climbing up the stems and eating the tops of the Spinifex (Triodia sps.) on the sand hills, where Kerosene Grass (Aristida contorta) and Bandicoot Grass (Monachather paradoxa) also provided a food supply. Spinifex species are widespread covering 60% of the Australian continent. Hard Spinifex (Triodia basedowii) is the most common species with a geographic distribution of almost half the area of central Australia. Soft Spinifex (Triodia pungens) and Feathertop Spinifex (Plectrachne schinzii) are also widespread throughout the Simpson Desert. The environmental value of Spinifex lies not only in its ability to hold moving sands but also as a food supply for budgerigars and aborigines. After rain or fire aborigines rely upon the presence of budgerigars feeding on Spinifex as an indication that the spiky plant is producing seed.
The Simpson Desert study site did not provide a breeding environment for wild budgerigars because temperatures were too high, there were no suitable nesting trees, no water and food supply was sparse.
Delmore Downs, Northern Territory
Delmore Downs is a cattle station situated on the Bundey River 250 kilometres north east of Alice Springs on the Tropic of Capricorn (Latitude 23.5°S). The Sandover River and its tributary, the Bundey River, have cut down into rock layers and exposed limestone (calcium) residues. These originate from coral reef formations of ancient times when a broad area of Central Australia was a shallow, warm inland sea.
Over millions of years, storm waters from the southern reaches of summer monsoons and local thunderstorms have created a river system that has cut down through the rock layers, forming a narrow and deep river. The surrounds of the Sandover River support tall trees that provide an abundance of nesting hollows. The river beds of Delmore Downs are narrow, deeper and less meandering than the "flash flood" broad, shallow channel country further south and east at the Finke River and Simpson Desert study sites. The resulting effect of this narrow river system is less evaporation than that seen at the southern study areas. Accompanying the natural water holes of the Delmore Downs, there are 18 sinks, originating from the underlying Great Artesian Basin, providing additional and permanent water.
Plant types found in this area are similar to those found in other study sites. However, with two possible wet seasons (spring and autumn) and its geographic situation relative to the tropics the vegetation here is more abundant and larger than further south. Whitewood (Atalaya hemiglauca) and Ghost gums (Eucalyptus papuana) provide excellent nesting hollows along the riverbank. These eucalypts are additional to the Blood eucalypts (Eucalyptus opaca) and other gums found in other study areas. Buffel Grass (Chenchrus ciliares), an introduced species, is widespread across Delmore Downs with thick growth lining the riverbank during summer. Following heavy rain, alluvial flats are predominated by seeding succulents of the Portulaca "Pig Weed" family (Calandrinia remota), an ideal food source when parents are feeding their feathered young. Extending from the limits of the riverbed are the Acacia scrublands. These are predominated by the Gidgee (Acacaia georginae) and Mulga (Acacia aneura) interspersed with Witchetty bush (Acacia kempeana). Further afield there are natural perennial grass plains containing Mitchell grass (Astrelba pectinata) and Wooly Butt (Eragrostis eriopoda) grasses. Mulga and other acacias are found intermittently throughout these vast plains. Highly nutritious annuals such as Wooly Oat (Eneapogon avenaceus), and Button (Dactyloctenium radulans) were found beneath and near these acacias.
We consider this subtropical calcium rich land with clay lenses to be an ideal breeding and feeding ground for budgerigars. The abundance of plant and grass species available to budgerigars following rain in this area provides budgerigars with a plentiful supply of food for successful breeding.
The region is characterized by good soil, low evaporation, abundant nesting hollows, more moderate temperature diurnal ranges, two distinct breeding seasons and following sequential rains, an abundant food supply. Nesting hollows are high up on the branches, overhanging small but permanent water holes and the feeding grounds are nearby. The calcium rich soils and moderate temperatures (with less diurnal temperature variation) during autumn and spring are capable of providing a great variety of nutritious plants and seeds.
Newman, Western Australia
This is a subtropical desert containing clay and limestone lenses located to the north of the Hammersley Ranges. This study site contains a more varied environment compared to the Delmore Downs study site. The environment is variable, supporting Mulga scrubland, Spinifex heath and riverine woodland habitats. The area offers a perfect environment for breeding opportunity. Nest holes are present in a variety of eucalypt species (Eucalyptus camaldulensis, Eucalyptus vitrix, Eucalyptus leucophloia and Eucalyptus aspera) that line the dry riverbeds. Compared to central Australia rainfall is more predictable and droughts are an uncommon occurrence in this region. Annual mean rainfall is 348millimetres of which 275millimetres falls during the wet season (December to March). About 80% of the rains come from afternoon thunderstorms and 20% from cyclones.
There are many suitable breeding habitats for budgerigars but breeding activity is an uncommon occurrence because most rain comes at the height of summer when temperatures are too hot. Average maximum summer temperatures fall between 33-39 degrees Celsius. Humidity is also generally very low (17%-48%) with highest recordings seen in June and July when the likelihood of breeding is low. Over the past 15 years budgerigars have bred only once in the local area. Autumn 1995 was the last occasion that budgerigars were seen to breed here in high numbers (pers. communication David Kaljuste 2003).
Lake Tandou, New South Wales
This temperate semi arid area of New South Wales is situated in the Broken Hill area very close to the Darling River (Latitude 33°S, Longitude 142°E). The Tandou Creek and Lake are man made and part of the Menindee Lakes Scheme. The Tandou waterway joins with the Darling River and passes through flat semi-desert in the form of a chain of lagoons and shallow lakes. It is part of a gravity fed irrigation system on self mulching, grey clays and is protected from flooding from the Darling River system by an intensive levee system made up of two high red soil dunes. The Darling River receives the bulk of its water from the Macintyre River area of Queensland. The remainder comes from monsoonal rains (35%) and from the channel country of Queensland (20%). These waters take about two months to reach the Menindee Lakes Scheme.
The climate of the southern parts of Australia follows a winter rainfall pattern. Most of the annual rain in this district falls in winter. Lake Tandou has an average winter rainfall of 225mm (8"). Winter rain is brought across by westerly winds. During spring and summer desert storms are prevalent. It is an extremely dry area with poor sandy soil that supports specialized plant growth.
The vegetation supported by this flat, poor quality, semi-desert soil completes its life cycle in about four weeks. These dunes are vegetated with Coolibah (Eucalyptus coolibah) trees, Ironwood (Acacia estrophiolate) and other acacia species interspersed with Blue Bush (Chenopodium auricomum), unidentified native grasses and Saltbush species. High temperatures and evaporation during summer prevents the growth of other than semi-arid flowering plants, forbs and trees.
In the past budgerigars have bred in this region during late winter and spring (August to October). This study site was chosen when large flocks numbering thousands were observed moving into the shallow creek and lakes system during October after a heavy storm dropped 50mm (2 inches) of rain. By the time of our arrival in mid-November most birds had left the area. Several nests containing recently hatched chicks were found abandoned. Temperatures at this time were between 40-43 degrees Celsius.
Here, surrounded by water, they were protected from most predators except the Azure Kingfisher. Several nests had been abandoned. Budgerigars were observed nesting within small, deep hollows of dead Black Box trees within the lake. Remaining parents birds were seen searching for food beneath native grasses and amongst dying succulents.
Lake Tandou study site was not considered to be a good breeding habitat for budgerigars. Although the lake system provided a permanent water supply and a plethora of nesting hollows food supply was severely compromised by the semi-desert sandy soil vegetation, high summer temperatures and low rainfall.
A vast area of the inland zone is underlain by a huge artesian basin. Under pressure this water can be lifted to the surface by bores, thus providing a mineral rich, but often hot, water supply for these semi-desert and desert areas. Farmers of this region have implemented such bores in order to provide water for their cattle. This man made effect offers an alternative water supply for breeding budgerigars.
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