A report by Birds Australia says there is mounting evidence that climate change will have, probably already is, having an impact on our bird species. The way they breed, migrate and feed are undergoing great changes even though the measurable increase in temperature in recent decades seems minor. Experts forecast if temperatures rise between 2C and 5C more than they were in 1990 by 2070 extinctions for some species will occur following a progressive collapse of regional populations. It is thought this collapse may already be happening.
The report is a collection of papers by scientists who say tropical and subtropical seabird breeding colonies in northern Australia are in decline. In an area of the Great Barrier Reef numbers of the Brown Booby have crashed by 85% since the 1980’s. In another area the numbers of 2 Tern species have fallen by 30%. The increasing incidence of El Nino weather events is causing the problems as warmer seas reduce fish availability as well as other foods for seabirds, it is thought the food is forced into deeper water. During the 2002 El Nino event the mortality of Wedge-tailed Shearwater chicks on Heron Island was 100%. Two thousand  adult birds also died.
The report identifies the birds of the savannas and rainforests of northern Australia as being among the most at risk from climate change with 55% of the 387 species recorded anticipated to suffer big population declines. In the wet tropics of north Queensland a suite of species that are confined to high altitude rainforests face extinction as temperatures rise. The Golden Bowerbird is one under particular threat. Chowchillas and Fernwrens habitat is also contracting upland at a steady rate.
It is believed the rise in temperature will cause sea levels to rise, ultimately vast areas of the wetlands of Kakadu and Gulf of Carpentaria will be covered by salt water, this will destroy the habitat of Magpie Geese and other freshwater birds. Elsewhere in the north hotter and more frequent fires will put pressure on other endangered birds such as Golden-shouldered Parrots and Gouldian Finches, an expected increase in the frequency of cyclones will impact on Cassowaries.
The warming is altering feeding behaviour and creating problems, Kookaburras are moving into higher mountain areas once too cold for them, they are feeding on Alpine Skinks who make no attempts to hide as the new arrivals are not considered a predator by the skinks. This species of skink is being wiped out.
Thirty one birds are considered to be at high risk of extinction, they include the Mallee Fowl, Orange-bellied Parrot, Albert’s Lyrebird, Hooded Plover and Fairy Tern.
The report goes on to say many birds that may have been able to adapt to climate change will be at risk because their habitat has been fragmented by land clearing. The report explains that temperature changes affect bird populations because climate regulates the geographic limits of their distribution; it sets boundaries of environmental conditions within which a species can function. Climate provides the energy and water inputs that determine rates of plant photosynthesis, growth and decomposition. Small changes in temperature may mean the habitat of a particular bird is no longer suitable for its needs. Noted climate related habitat changes in recent decades affecting bird populations include eucalypts encroaching into rain forests and woody weeds into inland woodlands; a 40% reduction in snow depth and the spread of trees into alpine meadows and glacial retreat in the sub Antarctic and Antarctic.
The report comments that all is not as gloomy as it may sound as warmer waters further south are boosting the numbers of temperate seabird species, eg. Australasian Gannet population has increased threefold in the past 2 decades in Bass Strait.
The warmer weather has led to northern bird species spreading south, Figbirds and Common Koels unknown as far south as Sydney are now seen in Victoria. Pied Butcherbirds, White-headed Pigeons and Pheasant Coucals have expanded their range south, their southward journey continues at a rate of between 100km to 150km a decade. This indicates some species have the ability to adapt. Others don’t.
Migration patterns established over thousands of years have markedly changed in a little more than a decade. White-throated Nightjars and Little Bronze-cuckoos, strict summer visitors to some areas now arrive earlier and stay later.
Breeding behaviour is changing, this is probably due to a combination of the warmer temperatures and decline in rainfall over the past 10 years. Studies of Masked Lapwings show birds are nesting 2 days earlier a year in north Queensland and one day later in southeast Australia. Breeding success of this species in Tasmania is declining by 1.5% a year.
Introduced weeds will prosper in the warmer temperatures, fire adapted weeds will accelerate the frequency and severity of fires. The Queensland government warns their extensive savanna woodlands in the north could end up as treeless plains. Invasive species are the big winners from climate change, this is not good for many birds. Increased levels of carbon dioxide are expected to reduce nitrogen levels in eucalypt leaves, reducing the populations of lerp insects. These lerp form a major portion of the diet of honeyeaters and many other bush birds.
Ed note : Over the past 10 years Garry and I have noticed a huge drop in the number of individual birds and the number of species in our region. As for the Lerp on eucalyptus trees, haven’t seen any for years, our gliders in care miss out on that treat each season.