Faithful golden bowerbird an indicator of climate change
Golden bowerbirds are known for their faithfulness: often the bowers constructed by these birds remain the same for up to 30 years. But when these intricately constructed twig formations start disappearing, scientists can tell something might be wrong.
EXPERTS SAY that golden bowerbirds (Amblyornis Newtonianus)— those bright yellow birds that build artistically superb structures, known as bowers, for their display of courtship— are important indicators of climate change because of their location loyalty: the position of each birds bower can remain the same for up to 30 years.
Despite being the smallest of the ten different bowerbirds in Australia at just 240mm and 79 grams, the golden bowerbird builds the largest bower. Its maypole-type bower is built between two trees approximately a metre apart and separated by a fallen branch or vine which is used as a horizontal perch.
Two vertical columns woven of small twigs bound together by fungus are constructed around the trees, rising to three metres. During breeding season it is decorated with green lichen, orchids, seeds or ripe fruits.
(Image Credit: Paul J Newman)
Of concern to scientists is the recent disappearance of bowers previously known to local birders.
A new set of surveys being conducted by BirdLife Australia, looks to shed light on their dwindling numbers. “The aim of the survey is to locate golden bowerbird bowers at all altitudes so we can see if there is any particular pattern as to when they disappear,” explains Graham Harrington, former president of Birds Australia and a former CSIRO scientist who is running the survey.
“The reason that we fixed on bowerbirds for this survey is because they are so faithful to their bowers. We know that they come back year after year and if the male fails to survive the winter then another bird will take over that bower straight away. If a male bowerbird gets killed during the breeding season, the bower is taken over by another male within hours.”
The first of several planned surveys recruited 31 volunteer birders. Organised along an altitudinal gradient from 740 to 1200 meters the volunteers listened for the rattling, metallic call that is distinctive to the male. The survey will be repeated at other sites during the September to January breeding season now that the success of the method is proven - 13 of the 42 sites surveyed recorded golden bowerbird calls.
Research by Professor Stephen Williams at James Cook University suggests that the faithful bird is in the firing line of climate change. “When you take into account not just the spatial distribution but also the biology, it would suggest that the golden bowerbird is one of the most endangered species from climate change in the region.”
As William’s told AG, “about 50% of species [of rainforest birds] that we have enough data on have already declined.”