The Orange-bellied Parrot - Colourful but Endanged Aussies

Before starting up this blog I had no idea that so many parrot species (well, just birds in general) were classed as Endangered or Critically Endangered. Partly it's because I never knew there were so many different species out there, and partly because -in the case of parrots- you can walk into pet shops and see them lined up in cages. I used to assume that if they were being sold to the general public, they were clearly in abundance in the wild.

How wrong I was; of the popular cage bird species, several are classified as 'threatened' on the latest IUCN Red List. Amongst those that are Vulnerable is the African Grey Parrot (Psittacus erithacus), and several others are classed as Endangered, amongst them being the Hyacinth Macaw (Anodorhynchus hyacinthinus) and the Red-fronted Macaw (Ara rubrogenys).

The Orange-bellied Parrot (Neophema chrysogaster) (BirdLife, 2013) is an example of a Critically Endangered parrot, but as far as I'm aware these little guys aren't available as pets. It could argued that such a thing is as good as it is bad; a lack of demand for the pet trade means that nest poaching is much less likely, but it also means that there are few people breeding these birds in captivity. The gem coloured birds are incredibly rare; found in Southern Australia and Tasmania, their population in the wild estimated to be lower than 50 individuals, with a decreasing trend. Between 2000 and 2008, there was an observed 12% decline in the number of adult birds at breeding grounds. This is thought to be due a lack of female parrots attempting to breed, which in turn results in a decline in the recruitment of juveniles to the species' population (Holdsworth et al, 2011).

The Critically Endangered Orange-bellied Parrot (Neophema chrysogaster) - image by Ron Knight on Flickr.

A number of factors are believed to be behind the declining population, and the majority of these are anthropogenic. Agriculture and urbanisation, along with industrial developments, fragment and degrade the important overwintering habitats of Southern Australia. Salt-marsh habitat degradation is also classified as a large threat, and worries have been voiced that proposed mining in Tasmania at Melaleuca could significantly damage breeding grounds. Looking at invasive species, various introduced seed-eating finches compete with the parrots for available winter food, and common starlings (Sturnus vulgaris) take-over nesting sites previously used by the parrots.

Random events also impact upon the species' population, though some of these events may become less random in years to come. Death from storms during migration may rise if storm frequency and intensity increases with future climate change. Disease is another danger, especially when the population is so small. Between 2005 and 2006, 40 birds bred in captivity died due to a suspected viral disease. The population was quarantined to prevent any disease spreading to the wild population, but things may not be as lucky in future. Other threats proposed by BirdLife Australia (2012) include the risk of predation by cats and foxes, inbreeding, deaths from collisions with structures such as wind turbines, and threats from noxious weeds.

It all paints a pretty grim picture for the Orange-bellied Parrot, doesn't it? Nonetheless, things may be looking up for these Aussies!

A breeding programme has been in place since 1986, which aims to increase numbers in the wild by releasing birds bred in captivity into the wild (Tasmania Parks & Wildlife Service, 2013). In 2006, $3.2 million was committed to help expand and protect the population and habitat of the parrots. The conservation attempt encompasses many things, including enhancing the captive breeding program in place, conservation of the breeding and nesting habitat in Tasmania, expansion and protection of the winter nesting grounds in Australia, and control of predators in breeding, migratory and wintering habitats (BirdLife Australia, 2012).

21 young birds were taken from nests in 2011, from where they were transferred into a captive 'insurance population' that currently numbers over 200 individuals. To boost the numbers in the wild, 23 members of this population were released this year. It's hoped that these newly released birds will integrate into the wild population and breed in the following years, thus reserving the population decline (Stephen Garnett, 2013). Hopefully this means we'll be seeing some good news regarding orange-bellied parrot in the next few years to come!

Bird Friendly Tuna?

Many albatross and petrel deaths attributed to pelagic long-line fishing for tuna and similar species in the southern hemisphere. In a study of seabird deaths due to pelagic longline fishing in the southern Atlantic Ocean between 2004 and 2008, Yeh et al. (2012) estimated that between 3446 and 6083 birds were killed per year. These deaths lead to many breeding-site populations reducing in number (Roberston et al, 2013).

A shoal of Skipjack Tuna (Katsuwonas pelamis) - image
from Wikipedia Commons.

There are ways to reduce mortality, such as setting lines at night, but this method -and several others- may mean that industries are unable to set their lines at times that optimise catch rates.

Robertson et al. (2013) suggest that focusing on branch-line weighting may be a way of reducing mortality rates of seabirds in the Australian fishing industry. Weights are not a new innovation in longline fishing, but Robertson et al. (2013) carried out experiments that differed from previous weighting methods. In their tests, weights were positioned differently upon the lines; in the first test, a 120g weight was placed ≤ 2m from the hook, and in the second test a 40g weight was placed directly at the hook. The purpose weighting the lines is to reduce time it takes for the hook and its bait to sink, thus reducing risks to seabirds by reducing the exposure of bait at the surface where birds may become caught.

Concern is often expressed that weights reduce catch, but Robertson et al. (2013) found no reduction in catch rates of Yellow-fin tuna; rather, catch rate correlated with bait type. For the other species caught, neither weighting or bait type seemed to have an effect on catch rates.

Though the heaver weighting method had faster sink rates, the authors acknowledged the implications of the extra weight in the gear bins. For this reason, they suggest using the lighter weighting method. They also indicate concerns for the loss of lead weights through shark bite-offs. Though not so much an economic problem, there is some concern that lead weights will become deposited on the seabed, or that they could be swallowed by sharks which may be later caught for human consumption. A way round this dilemma would be the replacement of lead with another substance.

Robertson et al. (2013) also state that loss from bite-offs may be minimised by placing weights on shorter leads; having the weights nearer hook is also safer for members of the fishing crew, as their experiments show such placement to reduce 'fly back' of the weights when hooks are bitten off. Other benefits they raise are reduced labour times for fishing crews due to less tangling and less like breakage (and therefore less repairs) of lines, as well easier line deployment.

New weighting regimes therefore seem like a win-win situation for both seabirds and the fishing industry. I just don't think the tuna will be all that happy...

Bird Extinction: The Pre-Industrial Picture

Extinction as a result of anthropogenic activities is not something that can be confined to the last century or two; as humans have expanded their reach across the globe, they have been contributing to a loss of biodiversity on Earth for at least 50,000 years (Braje & Erlandson, 2013). Human induced animal extinction rates are believe to be up to a thousand times higher than the natural background rate, and are associated with the loss of around 8500 species of bird since 1600 AD alone (Braje & Erlandson, 2013).

Whilst a loss of species diversity can be seen across the globe, some of the most prominent examples are on the many islands of the South Pacific, where Polynesian expansion across the pacific led to the extinction of many animal species (Pimm et al, 2006). Island populations are especially vulnerable to extinction, as their populations are often small, and may be confined to a minimal area of land. Their isolation also often results in the loss of adaptability to pathogens, predators and competitors that may be introduced, and to the rapid environment change often brought about by humans (Grayson, 2001).

The extinction of endemic flightless birds alongside plants and mammals in Australia coincides with the arrival of humans (Braje & Erlandson, 2013), which may have been visiting the country as early as 22,000 years ago (Flannery & Roberts, 1999), as suggest by a rise in charcoal and a change in tree pollen in the sedimentary record. This has been contributed to anthropogenic deforestation through fire, and not down to climate change (Flannery & Roberts, 1999).

The same applies to New Zealand, which wasn't colonised until much later in the 13th Century (Irwin & Walrond, 2012). Prior to humans living in New Zealand, it was home to many species of endemic birds that are now extinct. 21 species of small landbird are no longer with us today, and alongside them were 11 species of Moas (Braje & Erlandson, 2013) (Grayson, 2001). The only birds known to be totally wingless, the enormous Moa were a family of herbivorous flightless birds. The two largest species, Dinornis robustus and Dinornis novaezelandiae weighed over 200kg, and could reach a height of 3.6m (12ft) if they stood with their neck outstretched (Wikipedia, 2013).

Published in 1879; a photograph of Richard Owen, the director of London's Natural History Museum, standing beside a reconstructed skeleton of Dinornis novaezelandiae - Image via Wikipedia Commons

The only natural predator of the Moa was the Haast's Eagle which was also driven to extinction when the Moa were wiped out completely in just over a century since the Maori populated the islands. Their extinction is believed to be a result of multiple factors, but all are attributed to human activities (BBC, 2009) (Grayson, 2001). Before the arrival of our species it is estimated that up to 90% of New Zealand was covered in forested, yet within a few hundred years almost all of the lowland forest had been destroyed, and with it vanished the habitats of the Moa and other animals (Grayson, 2001). Human predation, evidence of which has been gained from many archaeological sites, was another large factor in the Moas disappearance (Holdaway & Jacomb, 2000). Lastly, the unintentional introduction of Polynesian rats (Rattus exulans) is believed to have played a large role in the extinction of birds not only in New Zealand, but across the whole of the South Pacific (Pimm et al, 2006). Whilst it's doubted by many archaeologists that there was direct predation of Moa eggs by the rats, the rodents are likely to have caused competition for food and impacted the vegetation on which the Moa and other landbirds depended (Grayson, 2001).

Madagascar suffered similar losses following human colonisation roughly 2300 years ago; it too was home to two genera of large flightless bird (Mullerornis and Aepyornis) that are often referred to as Elephant Birds which went extinct between 1600 and 1700 AD (Braje & Erlandson, 2013). Aepyornis was the larger of two, and is believed to have reached weights of up 400kg and a height of 3m (10ft). The causes of extinction are less clear, but signs of butchery from archaeological sites suggest humans played a primary role (Burney & Flannery, 2005).

The birds of other remote islands didn't fare much better. Grayson (2001) suggests that, alongside anthropogenic predation, predation by invasive dogs, pigs and Polynesian rats brought to the islands by humans may have been largely responsible for the disappearance of endemic Hawaiian species. Of 17 species of landbird known from archaeological deposits, only four remain on Hawaii today (Braje & Erlandson, 2013). Rats are also believed to be partly responsible for the loss of 6 species of landbird and several seabird colonies, alongside much of the vegetation (through eating nuts and seeds and thus impairing the ability of the plants to reproduce) on Easter island, which in turn contributed to the breakdown of human society on the island (BBC, 2009)(Braje & Erlandson, 2013).

Grayson (2001) raises the possibility that anthropogenic activities may have, in some instances, created habitats for some subsets of bird species which would not be present were it not for such changes. Despite this, the general consensus is that the increased colonisation of Oceania by humans correlates with an increase in avian extinctions. The past extinction of island fauna paints a grim picture; it shows how easy it is for anthropogenic activities to lead to a loss of biodiversity. Unless we try to minimise our impacts and attempt to preserve and conserve the species that have so far survived, many more species of bird may join the mighty Moa. 

New Zealand by Steve Taylor, on Flickr

Cited:

• Extinctions in Near Time: Causes, Contexts and Consequences - Chapter 10: Late Quaternary Extinctions in Australia (T.F. Flannery & R.G. Roberts, 1999)