4 April 2011

Satin Bowerbird... in decline. Photo by Alan McBride

The decline in numbers of some bird species in the Sunshine Coast region over the past 30-40 years, and increase in others, may be related to climate change.

An isolated population of the Eastern Bristlebird occurred in the Conondale Range, the northern limit of its distribution. However, just one or two birds survive, and the population appears doomed to extinction.

The Spotted Quail-Thrush was formerly seen with regularity at sites such as Widge, Eudlo, Wild Horse Mountain and Brooyar State Forest. The species is now rare or absent at these sites.

The Crimson Rosella was formerly common across the region in rainforest and wet sclerophyll forest at all altitudes. It is now found only in the highest parts of the Conondale and Blackall ranges, and in much small numbers than previously. For instance, at Booloumba Creek in the 1970s, Crimson Rosellas were common, but they do not occur there now.

A similar story applies to the Satin Bowerbird. The population of this species is similarly concentrated in the highest parts of the Conondale and Blackall Ranges. The bowerbird was formerly a regular winter visitor to lowland sites where it has not been seen for many years. In places such as Little Yabba and Booloumba creeks, where it was once common, it is now scarce.

The Red-browed Treecreeper, though always uncommon, is now decidedly rare in the region. It is found occasionally in the Blackall and Conondale ranges but is absent from many of its former haunts.

What these five species have in common is that they are close to or at the northern end of their distribution in south-eastern Australia, although the rosella, bowerbird and quail-thrush have isolated populations in north Queensland.

Observers have noted steep, parallel declines in populations of several formerly common mammal species in the region such as Boebuck, Red-legged Pademelon and Greater Glider.

Warmer temperatures and drier conditions may be related to the decline in populations of these mammals and birds. In the case of the bristlebird, inappropriate vegetation management by state authorities may have been a factor it its demise.

Conversely, numbers of some essentially tropical species are expanding in the Sunshine Coast region. The Fairy Gerygone was not formerly known south of Gin Gin but it is now regular in vine scrub in coastal dunes.

The Dusky Honeyeater, another tropical species, is also more widespread today around the Sunshine Coast than it was in the 1970s. While it was formerly restricted essentially to rainforest in the Conondale Range, the honeyeater is today seen in a variety of habitats across the region.

Similarly, numbers of White-eared Monarchs appear to have increased. The monarch was thought to be a summer visitor but it may now be resident.