Saturday, 18 July 2015

Australian Bowerbirds and their Bowers

I've been meaning to put this post together for a while now but have not had the time until today. Last year I was lucky enough to spend a month (November) in Australia, and am incredibly excited to be heading back over there again later this year to lead a Birding Ecotours trip. Details of thetrip can be found here (there are a couple of places left). Whilst on the Queensland leg of my previous trip I saw my first ever Bowerbirds (Family: Ptilonorhynchidae). There are currently considered to be 20 species of Bowerbird across New Guinea and Australia, mainly found in rainforest and drier sclerophyll habitats.

Bowerbirds are medium-sized, compact, robust passerines, mostly with stout and powerful bills. They feed on fruit, berries, leaves, insects and invertebrates. The majority of Bowerbirds are incredibly sexually dimorphic. Adult males have strikingly diverse and often colourful plumage, while the females are generally much duller – presumably because the females are the ones responsible for the nesting duties. Males have an incredible vocal range and are great mimics.

Regent Bowerbird © Seabamirum
(Basically Turdus merula with a bit of added yellow!)

Bowerbirds are famous for the construction of bowers where courtship displays and mating take place and this was something I was really keen to observe whilst over there and I didn't leave disappointed! There are two main types of bowers in Australia and I saw samples of both:
  • Avenue bowers: a double avenue of twigs/grass, secured on a platform of sticks on the ground (Satin, Regent, and Great Bowerbirds); and
  • Maypole bowers: tall single or double columns of sticks built around adjacent saplings, and partly filling the gap between them (Golden Bowerbird).

The male bowerbird deposit natural or artificial objects within the bower, these objects are usually of similar colour, or reflectively, to the bill, eyes or plumage of their own species. During display, the bower ‘owner’ frequently pecks at, and moves around the objects, often appearing aggressive towards them, as if they were intruding males! It is thought that the males display at the bower helps stimulate and synchronise the development of the pairs’ sexual organs for successful reproduction.  The bowers also act as a shop window for females to observe males and select the superior bird to pair with (a bit like Manakins lekking in the Neotropics). Male Bowerbirds are polygamous so will mate with a range of females that visit the bower. Females do all of the nest building, incubation and feeding of young.

Whilst at Lamington National Park, southern Queensland I was able to watch a Satin Bowerbird (of the violaceus race) actually attending to its ‘avenue bower’. The Satin Bowerbird is a large (27-33 cm) glossy blue-black bird, with a pale bill and a bright blue eye. He had an area that looked like a bit of a clearing next to a tree fall that formed the backdrop to the bower, there was one tuft of ‘grass’ in front of the branches, the edges of the grass were flattened down and in front of that was an incredible array of bright blue objects that the male had collected and added on top of the flattened down vegetation. Blue bottle tops (drinks bottles including ‘Sprite’, and washing/fabric conditioner types), blue pens, blue plastic sweet wrappers, blue paper, even a blue Oreo packet was identifiable. Basically any blue litter was collected by this bird to decorate his bower! There were a few bluish leaves and flower stems added to give a bit of a natural look to all of the plastic. This was my first ever bower, and I was seriously impressed, but luckily he didn't try to mate with me, though he was making some interesting noises!

Satin Bowerbird (male) © Andy Walker 2014

Satin Bowerbird (male) and its 'Avenue Bower' © Andy Walker 2014

Satin Bowerbird 'Avenue Bower' © Andy Walker 2014

In northern Queensland I had brilliant views of the Great Bowerbird attending its ‘avenue bower’. A bird of the drier habitats it is not as impressive in colouration as the two species above, or some of the ones further down this post, being a mix of greys and browns. It is a large bird, 32-38 cm, with a short, stout bill. What this bird lacks in colour it certainly makes up with its seriously impressive bower – which is huge!  The particular male I came across was busy raiding a vegetable patch at a school yard. He had a taste for chili peppers!

The bower was a classic ‘avenue bower’, and the entrance was a mat of twigs, covered in mainly pale objects such as stones and snail shells, drinks can ring pulls, and with the ubiquitous plastic bottle tops – this time white or clear ones, he even a couple of coins in the mix! A splash of colour was provided in the form of pencil crayons, chili peppers and flowers.

Great Bowerbird (male) © Andy Walker 2014

Great Bowerbird 'Avenue Bower' © Andy Walker 2014

Great Bowerbird 'Avenue Bower' © Andy Walker 2014

One of the other Bowerbirds I was incredibly impressed with in northern Queensland was the Golden Bowerbird – now this one did have some pretty impressive looks, and even more interesting was its vocalisations – a series of rattles, frog-like croaks and mimicry. It made a sound like it was having an electric current passed through it – very odd noises!  As the name suggests this bird (well the male) is golden, with some olive tones on the face and back, and a bright yellow eye. A bird of rainforest, this bird builds a huge vertical ‘maypole bower’. Sometimes up to 3 m tall! The bird I came across had a decent sized bower, it was way over a metre, and looked like it had been there for some time, though I didn't get too close to this one as he seemed a bit skittish and I didn't want to disturb him – hence the grainy/blurry photos taken in the near dark!

Golden Bowerbird © Andy Walker 2014

Golden Bowerbird © Andy Walker 2014

Golden Bowerbird 'Maypole Bower' © Andy Walker 2014

I saw a couple of other Bowerbird species, such as the glow in the dark Regent Bowerbird mentioned right at the beginning of the post, but didn’t get any decent photos of that one. I also saw the Tooth-billed Bowerbird, this one had a bower with an assortment of leaves, all of which were face down on the ground within the bower, exposing their blue-grey underside. But it was quite dark so I didn’t get any decent photos of these etiher.

Tooth-billed Bowerbird © Andy Walker 2014

Also members of the Bowerbird family I had both Green Catbird and Spotted Catbird. Although Bowerbirds, they do not build bowers and males are not polygamous, instead they are monogamous (pair with one female), defend an all-purpose territory and assist with feeding their offspring. They have amazing calls, sounding just like cats – as you’d expect from the name! Green Catbird was busy hiding in the tree tops at Lamington National Park, while Spotted Catbirds were a bit more cooperative and lower in the vegetation around Cairns.

Spotted Bowerbird © Andy Walker 2014

For a chance to come and look for these interesting birds, and many more besides, check out the exciting Birding Ecotours 2015 and 2016 Australia and New Guinea tours here

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