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Upland endemic bird species in Far North Queensland are considered at risk from climate change as their habitat warms up. Longer periods of intense heat, coupled with reduced food availability due to drying habitat, is bad news. James Cook University measured reductions in population density of 14 seemingly common Wet Tropics bird species. Their conservation status was upgraded in BirdLife Australia's Action Plan for Australian Birds 2020.
New ratings for Wet Tropics bird species
Brown Gerygone (Wet Tropics subspecies)
Large-billed Scrubwren (Wet Tropics subspecies)
White-throated Treecreeper (Wet Tropics subspecies)
Australian King Parrot (Wet Tropics subspecies)
Eastern Whipbird (Wet Tropics subspecies)
Satin Bowerbird (Wet Tropics subspecies)
As a priority we should be monitoring these species, but counting rainforest bird numbers is very difficult to do reliably, especially the small scrubwrens and gerygones. It requires substantial effort with a large number of surveys to iron out variations. An alternative is to try and count the endemic bowerbirds of the Wet Tropics. These act as sentinel species with relatively repeatable behaviour and distribution.
Golden Bowerbird Bowers and even many Tooth-billed Bowerbird courts remain at the same location for years. Monitoring of the persistence of bowers and courts throughout the Wet Tropics is undertaken on an ongoing basis. The objective is to determine if there are any changes with time.
The Golden Bowerbird has the highest elevation range of any bird species in Australia. Most bowers are above 1000m. As such it is considered the species most susceptible to climate change in our area.
We have found over 100 Golden Bowerbird bowers and a selection are checked every few years. So far there seems to be little change in their area of occupancy (except for one low location at Topaz). The birds are found at almost all traditionally known locations. They are present in low numbers almost all suitable habitat above 1000m from Mt Finnigan in the North to Paluma in the South. We try and check a percentage of new bowers every year and continue to find new ones.
But checking them is hard work. They are all in upland areas, often some distance from walking trails requiring some energy to reach. They are an inconvenient species for easy monitoring.
Golden Bowerbirds construct a large, usually twin tower, structure of sticks decorated with moss and flowers. Many of these structures remain at the same place for years. We know of some over 40 years old. But they do regularly move a short distance if the supporting sticks or dance perch decompose. Mostly they move only a few tens of meters but sometimes 100s of meters. In addition we regularly find various small odd piles of sticks which are practice bowers built by young males. Sometimes these develop into full bowers but usually they are abandoned as the bird tries to take over a main bower. In some areas e.g. Paluma, Kirrama Range, Ravenshoe, Mt Fisher, thick dense regrowth of saplings following cyclones crowds out the bower area pushing Golden Bowerbirds away. This happens some years after the cyclone event.
If you are aware of the location of a Golden Bowerbird Bower, please let us know the details and GPS position. This will be added to a confidential database. We like to try and check known bowers every few years to see if there are any changes. Contact Dominic Chaplin firstname.lastname@example.org
The Tooth-billed Bowerbird is a bit different. To impress the female, the male clears an area of ground in the rainforest. Then they place leaves upside down on the cleared area. This cleared area is not really bower, so we call it a court. After they have built this court, which is often in the same place or close by every year, the Tooth-billed Bowerbird sits beside it, calling most of the day. They are very easy to find by this distinctive call.
Tooth-billed Bowerbirds are at least 20 times more common than Golden Bowerbirds. We have found over 600 courts which are still present across all of their known range from Mt Amos in the North to Mt Elliot in the South. They occur in a much larger area than Golden Bowerbird as they have a lower altitude distribution with courts from around 600m to 1300m. They are easy to detect by their loud raucous call and occur in a good number of easily accessible flat locations.
It is thought they are also susceptible to climate change. So BirdLife Northern Queensland has a slightly different project to monitor them. Counting the actual number of courts in a particular area, often a tangle of Wait-a-while, is not alway so easy. So instead we have a series of 1km walks across the Wet Tropics. All volunteers need to do is walk along and count how many are heard calling. Although there will be some variation during the day it is much easier to obtain useful information by this method.
We have a selection of around 20 different pleasant 1km walks in hill rainforest across the Wet Tropics. All you need to do is walk along and let us know how many Tooth-billed Bowerbirds you can hear calling from their courts (October – December).
Details on the walks are here and a form to fill can be downloaded from here.
If you are aware of the location of a Tooth-billed Bowerbird court, please let us know the details and GPS position. This will be added to a confidential database. We like to try and check known bowers every few years to see if there are any changes. Contact Dominic Chaplin email@example.com
Photos and article by Dominic Chaplin.
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