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Wildlife Boxes
and Their Application Across Eastern Australia |
All broad forests types across Eastern Australia would have originally had a
mean density of 10.8 hollow bearing trees per hectare with an average of 2.2
hollows per hectare of these 5.5 of them would have had a diameter of 100mm
or greater. (Smith, Lees 1998)
Depending on species and environmental factors the age of trees with hollows
will vary, for example spotted gum Corymbia citridora will start to develop
hollows at a dbh (diameter at breast height) of 50 cm, these trees are
estimated to be 100 years old in coastal dry sclerophyll forests and two
hundred years old in inland dry forests. The age of hollow formation of
Corymbia citridora is comparable to that of other eucalypt species (Smith,
Lees 1998)
When considering the application of artificial hollows in habitat
rehabilitation it is important to take these factors into account.
Hollows may vary from tiny entrance holes under pealing bark or on the outer
branches to larger holes in the bole of the tree, all are utilised by our
indigenous fauna.
In South – East Queensland we have 87 species of birds, 35 species of
reptiles and 55 species of mammals that will utilise tree cavities for
shelter and/or nesting. Each of these although having different habits and
requirements and can be catered for using a variety of box sizes and
entrance holes and placement variations.
When planning a rehabilitation project it is important to note that many
species utilise several hollows within their home range.
A single colony of Sugar gliders Petaurus breviceps (2-9 individuals) will
use up to 5 den sites within their home range of 0.65-8.55 ha (Quin et al
1995)
The Australian owlet nightjar Aegotheles cristatus will use 20+ hollows
within their 50-100 hectare home range.
Many of the Microchiroptera (Micro-bats) will change roost sites daily
within their home range which will vary with each species (23 different
species in south- east Queensland that use hollows).
In planning a wildlife box program we work on a starting figure of 10 boxes
per hectare with the mix and quantity of boxes depending very much on the
habitat and food source. The majority of boxes will be for the smaller taxa
in keeping with the natural balance of hollow formation.
A ratio of 2 larger boxes if suitable habitat is present
(owl/Kookaburra/cockatoo), 2–4 medium boxes (duck/possum), 4-6 smaller boxes
(small parrot/ micro bat/ forest bird/small glider).
It is recommended that the boxes be monitored on a regular basis (at least
6-12 month intervals) and the density of boxes increased as populations and
species diversity increase. In areas where trees are sufficiently developed
(minimum age of 15-20 years) these can be utilised to place the boxes.
Other areas utilised for box placement may be on poles at the water’s edge
for animals such as micro bats and ducks, depending on the species. Boxes
may be placed randomly or clumped together in areas of suitable habitat. If
habitat is suitably mature but not yet mature enough to form hollows it may
be possible to increase the density of boxes to 20 per hectare.
References:
Smith, G. C. & Lees, N. December 1998. Sustainable Forest Management
Technical Report.Department of Narural Resources. Queensland.
Quinn, D.G. 1995. Population ecology of the Squirrel Glider and the Sugar
Glider at Limeburners Creek, Wildlife Research 22 471-505.
Sources consulted , Gibbons, P. & Lindenmayer, D. 2002. Tree Hollows and
Nature Conservation in Australia. CSIRO. Australia.
Lindenmayer, D. 2002. Gliders of Australia . UNSW press. Australia.
Churchill, S. 1998. Australian Bats. Reed New Holland. Sydney
Australia.
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