Darwin in the middle of the dry – a tepid version of a southern winter – is a tough time for birds.
For this immature Blue-faced Honeyeater Entomyzon cyanotis it is just about the toughest time of year – few plants are in flower and the insect count is low.
The battle for access to these scarce resources starts at dawn and will continue all day – only the onset of warmer weather in a month or two will relieve these pressures. Perhaps of all of Darwin’s Honeyeaters the Blue-faced is my favourite – loud, and brightly coloured, they can often be seen around a banana plant – either picking through the tightly-packed flowers or stabbing the ripe fruit with their long and powerful beaks.
Last weekend I was up with the dawn chorus to catch up with the birds that would be catching a feed on a flowering Bats-wing Coral Tree Erythrina vespertilio – a deciduous tree of the monsoonal north often found in thick vine forests.
I’ve been keeping an eye on a few specimens in the grounds of my alma mater, the Charles Darwin University, and noted that while those down by the creek were still shrouded in the bright green bat-winged cloak that one tree – higher and dryer up the hill – had dropped most of it’s leaves and was in flower.
In the past when I’ve checked these trees there has been a wide variety of birds at the flowers. Now – perhaps because such resources are rare or for other reasons less obvious – one species dominated – the garrulous, aggressive and common White-gaped Honeyeater Lichenostomus unicolor.
While a few other species – a brace of Spangled Drongos, a few Friar Birds – called into to sample the sweet offerings of the Bat-wing Coral Tree, the White-gaped Honeyeaters drove them all away in short shrift and for most of the few hours I spent peering through my long lens they were the only species feeding on the Bat’s-wing’s bright flowers.
A few hours later – after my own breakfast at the Roma Bar in downtown darwin – I went prowling around town looking for more floristic resources. Along the top of the rocky escarpment near Darwin High School I came across more than a few trees hosting the obligate hemi-parasitic Mistletoes. More than any other plant in Australia, the Mistletoes perform a range of important environmental services – including being an important off-season source of food for birds and animals through their fruits and flowers.
As my friend Dave Watson, a senior lecturer at the Charles Sturt University, points out in this research paper, Mistletoes are perhaps key species in Australian biodiversity:
There is widespread support for regarding mistletoe as a keystone resource, and all quantitative data are consistent with mistletoe functioning as a determinant of alpha diversity. Manipulative experiments are highlighted as a key priority, and six explicit predictions are provided to guide future experimental research.
The facts which kept me longest scientiﬁcally orthodox are those of adaptation—the pollen-masses in Asclepias—the misseltoe, with its pollen carried by insects and seed by Birds—the woodpecker, with its feet and tail, beak and tongue, to climb the tree and secure insects. To talk of climate or Lamarckian habit producing such adaptation to other organic beings is futile. This difﬁculty, I believe I have surmounted.
From a letter to Asa Gray by Charles Darwin, 1857.
There I caught up with another common bird – smaller but no less aggressive a defender of scarce resources than the White-gaped Honeyeater Melithreptus albogularis – feeding on the many clumps of Misteltoe (sorry but I couldn’t key out the species) living on a small Acacia bush.
White-throated Honeyeaters are common and found across northern and eastern Australia and New Guinea.
That’s all for today – this weekend I’ll go for another cruise around town and beyond and keep you posted. And I welcome your thoughts, comments and observations – please drop any tips about similar food-resources around the Top End as you please.