Swift Parrot (Lathamus discolor) Recovery Plan 2001-2005

Swift Parrot Recovery Team (2001)
Tasmanian Department of Primary Industries, Water and Environment
ISBN 0 7246 6283 9

Introduction (continued)

Life History

Breeding

Swift parrots begin to return to Tasmania in early August with most of the population arriving by mid-September. The breeding season coincides with the flowering of Tasmanian blue gum, the nectar of which is the main food source for the parrots during this time. In Tasmania, the breeding range of the swift parrot is largely restricted to the south east coast within the range of blue gum. There is also some breeding in the north of the state between Launceston and Smithton, which is outside the natural range of Tasmanian blue gum. Blue gums have been planted widely as a street tree, in wind breaks, in gardens and plantations and are used by swift parrots when in flower. The size of this breeding population varies from year to year depending on the available flowering resource.

Both sexes are involved in the search for suitable nest hollows which begins soon after they arrive in Tasmania. Nesting starts in late September, however birds that are unpaired on arrival in Tasmania may not begin nesting until November after they have found mates (Brown 1989). Gregarious by nature, pairs may nest in close proximity to each other and even in the same tree. Nest sites may be re-used but not necessarily in successive years. The re-use of a nest site depends on the availability of food in that area.

The female occupies the nest chamber just before egg laying. She will not leave the nest until the chicks are hatched and sufficiently developed. The usual clutch size is four eggs but up to five may be laid (Hutchins and Lovell 1985). The eggs are white, glossy and oval, rounded at both ends. During incubation the male visits the nest site every three to five hours to feed the female. He perches near the nest and calls her out, either feeding her at the nest entrance or both will fly to a nearby perch.

Young swift parrots fledge at about six weeks and the first chicks are usually seen outside the nest in late November and early December. The presence of juvenile birds that appear to have recently left the nest in late January and early February suggests that double brooding may occur in some years. Brown (1989) reported a second nesting attempt at Fern Tree in the 1987/88 breeding season, however it was unsuccessful. At a property near Devonport, two distinct arrivals of juveniles have been reported, firstly in mid-December and a smaller group of young in mid-February. Double brooding has also been reported in captive birds.

Dispersal

Young birds begging for food are seen when they first leave the nest. They remain in the nesting area and gather together in flocks before dispersing. After breeding, most of the east coast population of adults and immature birds moves westwards to the Central Plateau and western Tasmania as blue gum flowering declines and other eucalypts begin to flower elsewhere, in particular stringybark, gum-topped stringybark/alpine ash and white gum/manna gum. The parrots are nomadic during the post breeding period, appearing wherever there is a suitable nectar source in the west and north of the state.

Swift parrots begin to leave Tasmania for the mainland from mid-February and most have left by the end of April. They leave from the north coast between Launceston and Smithton and appear to migrate through western Bass Strait during daylight hours without stopping, arriving on the mainland around Port Phillip Bay including the Mornington and Bellarine Peninsulas. However, records in East Gippsland and the far south coast of NSW at around this time suggest that some birds may fly direct to eastern Victoria and southern NSW.

A small number of Swift Parrot records are received from the Melbourne area in March and April, but most of the birds are not detected until they reach their usual non-breeding range in the box-ironbark region or in coastal New South Wales. Once Swift Parrots reach their core non-breeding range there is no known geographical pattern of movement. Dispersal within the non-breeding range during winter does occur, with the two winter surveys often recording markedly different results for a particular site in a given year. Such within-year dispersal on the mainland is subject to local food resources. As a result, swift parrots may stay at a site for a few days or several months, and changes in food availability may necessitate large or relatively small-scale movements. A small number of records are received from the Melbourne area in late winter-early spring before the birds return to Tasmania.

Some broad temporal changes in the relative importance of various food species are evident in the Victorian box-ironbark region, where the Swift Parrot has been most intensively studied on the mainland. Grey box is a source generally used early in the non-breeding season. Red and mugga ironbark stands are used through much of the winter and yellow gum and white box are of increasing importance towards the end of the winter. There is considerable overlap in the flowering times of these species however, and local conditions play a major role in dictating the timing and extent of flowering in each region.

Food

During the breeding season, swift parrots feed primarily on the nectar from the flowers of Tasmanian blue gum. The intensity of Tasmanian blue gum flowering varies greatly from year to year and the nectar from the flowers of black gum/swamp gum is an important foraging resource in years when there is little blue gum flowering. Black gum flowers in late winter and is the only nectar source available to swift parrots prior to the Tasmanian blue gum flowering in spring.

Post-breeding food resources in Tasmania are mainly nectar from summer and autumn flowering eucalypts, particularly stringybark, gum-topped stringybark, white gum, mountain gum and cabbage gum/snow gum.

Swift Parrots feed extensively on nectar and lerp and other items from eucalypt foliage during the non-breeding season. Mugga ironbark, red ironbark, white box, grey box, and yellow gum are important sources of nectar in the box-ironbark forests and woodlands of Victoria and New South Wales. Grey box, river red gum and white box are major sources of lerps in these areas at times. Swamp mahogany, spotted gum and red bloodwood are important nectar sources in coastal parts of the non-breeding range. Forest red gum and yellow box are used by foraging swift parrots in northern NSW and south east Queensland. There are also several records of the species foraging on lerps in the foliage of blackbutt in the Wollongong area of NSW.

Table 2. Location of principal over wintering forage species used by the Swift Parrot
 
Forest Redgum
Grey Box
Mugga Ironbark
Red Ironbark
Spotted Gum
Swamp Mah'y
Red Bl'wood
White Box
Yellow Gum
Central Victoria   *   *         *
North east Victoria   * *         *  
NSW western slopes   * *         *  
NSW coast *     * * * *    
Southern Queensland *                
South Australia                 *

Reasons for Listing

Small Population Size

There is anecdotal evidence from reports in the past that the swift parrot was once more abundant and that its range extended from the Mt. Lofty Ranges in South Australia to south east Queensland (Hindwood and Sharland 1964, Brown 1989, Higgins, 1999). Swift parrots are now rarely seen in South Australia and are restricted to the Bordertown area on the Victorian/South Australian Border, although they are still regularly recorded in small numbers from south east Queensland. The total swift parrot population is estimated to be no more than 1000 pairs and is at best stable but may be continuing to decline, given the continued mortality of birds and the ongoing loss of habitat. The decline in swift parrot numbers was first reported as early as 1917 by Mathews who summarised its status 'It appears to be exceedingly rare in New South Wales and more common, though by no means now as plentiful as formerly, in Tasmania' (in Brown 1989).

Loss of Habitat

The breeding range of the swift parrot based on environmental domain analysis of the Tasmanian blue gum utilised by the swift parrot during the breeding season is estimated to be 264,000 ha (4% of Tasmania's land mass including the offshore islands) of which 148,000 ha (56%) is forested (Brereton 1997). Of the remaining forested area within the breeding range, only 4% contains potentially suitable swift parrot foraging habitat. This is predominantly grassy Eucalyptus globulus forest, which covers an area of approximately 8,000 ha. The area of potential habitat occurs as a narrow band down the south east coast of Tasmania predominantly between Swansea and Dover including the Forestier and Tasman Peninsulas and Maria and Bruny Islands. This band extends no more than 5 km inland except for an area between Marion Bay and Sorell where the band expands up to 10 km. The environment of this area is characterised by low rainfall, high annual mean temperature, low seasonality of rainfall and temperature, low elevation and relatively fertile soils. Within this area suitable grassy E. globulus forest has a patchy distribution which is related to available moisture and soil depth. The habitat most often used by swift parrots tends to be on deeper soils with higher available moisture particularly on lower slopes and coastal plain.

Breeding success varies greatly from year to year depending on the intensity and extent of blue gum flowering. In years of poor flowering there appears to be little breeding activity particularly in the larger south eastern Tasmania population. The impact of seasonal variability in breeding success on the swift parrot population is being intensified by the loss of habitat within the breeding range. Areas of grassy blue gum forest, which in the past may have contained a suitable food resource in some years, have now been cleared. Approximately 56% of grassy E. globulus forest has been cleared.

The greatest proportion (82%, 7000 ha) of grassy E. globulus dry forest within the breeding range occurs on private land. The amount of habitat within the reserves is approximately 18%, (1500 ha), the majority occurring within the Maria Island National Park.

The environmental domain of the shrubby E. ovata forest used by the swift parrot during the breeding season also occurs as a narrow band down the south-east coast of Tasmania, predominantly between Triabunna and Ida Bay including the Forestier and Tasman Peninsulas and Bruny Island. The environmental domain of shrubby E. ovata forest is wetter and cooler than that of grassy E. globulus forest. E. ovata prefers moist sites and its occurrence is typically localised in drainage basins, soaks and hollows. Shrubby E. ovata forest has been severely depleted by land clearing in Tasmania, approximately 97% of this forest type has been lost.

Habitat loss has also been considerable across the non-breeding range. Box-ironbark forests and woodlands have been extensively cleared for agriculture. It has been estimated that 85% of the vegetation in the box-ironbark region has been cleared in Victoria and New South Wales (Robinson and Traill 1996). The density of large trees has been greatly reduced in the habitat that remains in Victoria (Soderquist and Rowley 1995).

Important vegetation types in Victorian non-breeding habitats are box-ironbark forest (168,200 ha remaining), heathy dry forest (45,100 ha) and a range of low-lying woodlands (12,500 ha). Of this habitat, only a small amount is suitable for swift parrots at any given time. Flowering of box-ironbark eucalypts is greatly variable from year to year, with a stand of eucalypts rarely producing a large amount of nectar in two successive years. The birds must locate the areas of abundant food within this 225,000 ha area of habitat, which is spread in remnants over a total area of 3 million hectares.

In Victoria, only 3% of the box-ironbark ecosystem currently occurs in conservation reserves (Environment Conservation Council 1997). However, a further 184,000 ha of box-ironbark forest has been recommended for inclusion into Victoria's reserve system (Environment Conservation Council 2000). In New South Wales, only 5% of ironbark and woodland communities are reserved (Robinson and Traill 1996).