South Sister St. Marys, Tasmania

South Sister

bird survey and report

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[Linked images linked on this page were kindly provided by various contributors to whom we are grateful.]

There are many different native birds found in this forest with a marvelous chorus particularly at dawn. There are numerous species found here which reflects the diversity of the food resources such as nectar and insects found in the area. For bird watchers, this area is a real treat and sets it apart from other areas with its diverse array of vegetation and numerous species of birds.

Of particular importance are three endangered species commonly seen flying around the region:

S. Lloyd has provided below a partial list of the 36 species of birds found so far on South Sister.

Sarah Lloyd (Conservation Committee, Birds Tasmania)
26th January, 2005

On January 19th 2005 I visited South Sister to conduct a bird survey at the site designated for logging. Thirty one bird species were seen or heard during the survey and an additional five species seen frequently in the area by local residents are also listed. Additional fauna species observed opportunistically are also noted. (see species list below)

Coupe NI114A at South Sister is dominated by several eucalypt species, mostly E. delegantensis, and has a floristically diverse and dense understorey. There are few signs of past disturbance and the vegetation is in excellent condition. The health of the forest and understorey is reflected in the number and diversity of bird species seen during the survey and the high number of juvenile and immature birds present on the site. The mixture of predominantly wet vegetation interspersed with stands of Banksia marginata, indicative of drier sites, attract a range of wet and dry forest birds and accounts for the high diversity of bird species seen.

The forest trees and the rich understorey vegetation at coupe NI114A provide a year round food supply of invertebrates and nectar for many forest birds. They also provide birds with a range of nest sites and nesting material, and places where they can seek shelter from inclement weather and from predators.

For instance, at the time of my visit many of the eucalypts were flowering attracting nectar feeding birds such as Little Wattlebirds, Yellow Wattlebirds, Crescent Honeyeaters and Swift Parrots.

Swift Parrots (Commonwealth Endangered Species Protection Act 1992 - Endangered) are attracted to sites where flowering eucalypts provide an important food source after the birds have bred. This hollow nesting species has declined mainly because old growth trees with suitable nest sites have been removed from the landscape through land clearing, particularly clearfelling. The east coast of Tasmania is a hotspot for these birds during the breeding season because they are dependent on a good flowering of blue gum E. globulus which triggers their breeding cycle. In years when blue gum doesn’t flower adequately for them to breed, other flowering trees provide them with an important nectar source.

Tree hollows and many rotting logs on the ground are indicative of old growth forests in good ecological condition. Eucalypts take 80 – 100 years to form hollows suitable for small cavity nesting birds such as Striated Pardalotes and hollows for larger birds such as Yellow-tailed Black Cockatoos take an additional several hundred years to form. Regrowth forest at this site following the logging will not provide suitable nest sites for many forest birds for well over a hundred years.

The 100 hectare coupe at South Sister is part of an extensive forested area that extends west along the Nicholas Range. As forests in the rest of Tasmania are being clearfelled, fragmented, cleared for agriculture or becoming otherwise degraded, areas of contiguous forest in good condition are becoming rarer in the state. This is reflected in declines of many bird species. Birds Tasmania (the regional group of Birds Australia) has sufficient long term data to indicate that many bush and forest birds have declined to the extent that they now qualify for listing under the state’s Threatened Species Protection Act. These include birds seen on or near South Sister such as the Yellow-tailed Black Cockatoo, Flame Robin and the endemic Dusky Robin. Birds already listed as rare or threatened in the state, including the Wedge-tailed Eagle, Swift Parrot and Grey Goshawk regularly use South Sister as a foraging site.

Of particular note:

Unusually, all four robins resident in Tasmania were seen during the survey. Once again this indicates a mixture of wet and dry forest types as dry vegetation is favoured by Scarlet Robins and wet vegetation is the preferred habitat of Pink Robins.

Many bird species, including robins, are vulnerable to habitat fragmentation and disturbance. The infrequent reporting of Flame Robins, (a bird considered as 'the most widespread and common of the Tasmanian Robins' by Dr Bob Green as recently as 1995) during the past three years of the Robins and Swift Parrot project, supports data collected during Birds Australia’s Atlas projects. In the twenty years between the 1st Atlas (1977-1981) and the 2nd Atlas (1998-2001) there has been a 51% decline in reporting rate of this species.

While there is often a focus on the threatened species, those birds currently regarded as common should not be seen as any less important. Many are also in decline because of current land management practices, the clearing of large areas of native forest, the conversion of forests to plantations and the degradation of habitat.

Many forest birds require abundant canopy cover and those species that forage on the ground (robins, scrubwrens, and fairy-wrens) require a high density of leaf litter and logs as these provide an abundance of ground dwelling invertebrates on which they feed. Logging and other forest disturbance adversely affects the litter layers by increasing wind speeds and solar radiation, thus desiccating the litter and rendering it unsuitable habitat for many invertebrate species.

The fact that only two species of reptiles were seen during my survey is not a true indication of their prevalence, but rather a result of the cool, misty conditions during my visit. The endemic ocellated skink Niveoscincus ocellatus seen at the site always associates with rocky habitats, which provide an abundance of invertebrate food, rocky sheltering places and the fruits and flowers of understorey plants, (particularly Cyathodes sp.) on which it occasionally forages.

Clearing of vegetation at South Sister will inevitably lead to an increase in invasive species, both plant and animal. When the logging occurs and the understorey is flattened or destroyed, native bracken fern takes over large areas as it has already done under the transmission lines close to the coupe. As well, non-native species such as gorse, Spanish heath and broom, which are already moving up the road from St Marys and invading nearby bush, get a foothold.

An increase in non native bird species also occur at such sites. The carnivorous introduced Laughing Kookaburra, which favours fragmented bush, will have an adverse impact on the reptile and small mammal and bird fauna, and an increase in blackbird numbers, a bird that feeds on fruits of introduced plants, will facilitate the spread of weeds.

The burning of heaps of 'waste' that inevitably follows logging further degrades any remaining habitat of any value.


Key

(be) breeding endemic
(e) endemic
(i) introduced
(m) migratory
* seen in the vicinity of the coupe by local residents

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