Although my research is on indefinite/terminal hiaitus, I am happy to see my last seminar remains online. It is certainly far from my best – given under circumstances of COVID lockdown, and after I had left my last academic post – but at least there’s a record for anyone interested in Prostanthera pollination.
The seminar was given as part of the special Prostanthera series of events held by the Australian Plants Society Victoria.
Two-fifths of a tennis court. About six car park spaces. Three-tenths of an IMAX screen.
That’s the size of my front yard. Yet despite its limited expanse, and its densely urban situation 10 km north of Melbourne CBD, my yard is habitat for at least five species of native bees.
I began watching the bees closely last year in lockdown. The tiny, faintly metallic Sweat Bees (Homalictus) are most common. They appear first in Spring, visiting the Wahlenbergia, the Oxalis weed in the lawn, the strawberry, and rocket flowers; anywhere there’s pollen.
Later, the bold and stripey Lipotriches turn up. Like rock-climbers gripping an overhang, they lock themselves upside down to the anthers of dangling Dianella flowers, emitting short zip-like buzzes as they work with methodical focus.
Then when Summer days begin to blaze, the hyperactive Resin Bees (Megachile) arrive, with that distinctive ember thumb print on their behinds. They fire around the yard like deranged bullets, collecting pollen and scouting for cracks to nest in.
That such biodiversity endures in this landscape—once grassy woodland, now houses, roads, and light industrial—is a testament to these species’ resilience. But their persistence also begs the question of which species might now be absent, less tolerant of such drastic change.
The White-headed Digger Bee (Amegilla albiceps) is one such bee. Large, rotund, and covered in a pelt of golden and white fuzz, one has not been recorded in Melbourne for at least 70 years, perhaps longer. In a Summer free of travel restrictions, I’ll leave town to seek the White-headed Digger. But for now, I’ll keep discovering the delightful locals. It’s Homalictus season now.
This mini essay was originally written for the Urban Field Naturalist Project
Bees are an effective treatment for depression. Well, my depression. And specifically the kind of malaise that comes from being locked out of our national parks and wild places for a second Spring running.
After monitoring my small front yard last Spring-Summer, I knew there was a set of small but diverse native bees that revealed themselves when the weather was warm and the yard was blooming. This year, I’ve decided to go deep and get to know them a whole lot better.
Getting even a basic knowledge of the 2000 native bees of Australia is a very big task. Getting to know the native bees of a single 50 km2 local government area (where I live) is much easier. So I set out to reconcile all the official and unofficial records for native bees within Moreland City LGA (just north of Melbourne CBD), to build a species list. And after going to that effort, I figured the local community would probably also like to have that information. So here is version one of the ‘Native Bees of Moreland‘ infographic (PDF link):
I started by pulling all of the records for bees in Moreland LGA from Atlas of Living Australia. After taking out the two introduced species, there were 12 species-level identifications plus 52 records for bees identified only to genus or subgenus. I then validated the species identified against their geographic ranges to exclude any obviously erroneous records. After that I reviewed iNaturalist records for bees in Moreland to see if I could identify any species that did not appear in the Atlas records.
My summary from this process is in the table below:
| Species | Status | Notes |
| Amegilla (Zonamegilla) asserta | Reliably present | A. chlorocyanea also possible given distribution, observations in nearby LGAs, and iNaturalist records |
| Lasioglossum (Homalictus) sp. | Reliably present | No species-level identifications confirmed. But the genus is very common. At least two species are in Moreland. Possibly L. punctatus, L. brisbanensis, L.urbanus, L. sphecodoides |
| Hylaeus (Prosopisteron) littleri | Reliably present | Unlikely to be the only Hylaeus species in the area |
| Hyleoides concinna | Rare and present | No record since 1946, however one record from neighbouring LGA, Mooney Valley, 2017 |
| Lasioglossum (Chilalictus) calophyllae | Reliably present | Common and recent records |
| Lasioglossum (Parasphecodes) hiltacus | Historical | No record in the LGA since 1956 |
| Lasioglossum (Chilalictus) lanarium | Historical | No record since specimen from 1894 |
| Lipotriches (Austronomia) | Reliably present | No identified specimens, but iNaturalist observations confirm the genus is present |
| Megachile (Eutricharaea) obtusa | Historical | No record since specimen from 1906 |
| Megachile erythropyga | Reliably present | Pinned specimen from 1987. iNaturalist observations since |
| Megachile (Rhodomegachile) deanii | Doubtful record | Far outside known distribution. Must be erroneous. |
| Braunsapis sp. | Doubtful record | B. unicolor and B. plebeia specimens from 1958. Very far from known distribution. Must be erroneous records. |
Clearly, for a very populous area, there are very few records. This is the case for not only bees, but insects in general. An added challenge is that it is often difficult to diagnose bees to species level. Together, that means it has been very easy to find bees that have never been recorded in the area.
For example, the most common small bee in my yard is a tiny, dark Homalictus with a faint green wash on the thorax. It most closely resembles Lasioglossum (Homalictus) sphecodoides, but this species has never been recorded in the area – presumably because no one with the right taxonomic expertise has collected bees, or examined Homalictus specimens from Moreland. Indeed, no species-level identification for a Homalictus has been made for Moreland at all.
In the first-bee hunting trip I took outside my yard this Spring, I even recorded a new genus for the area. I caught both male and female reed bees – Brevineura sp., flitting around a flowering Diosma in the cemetary.
Then there are those historical records – bee specimens collected 60 – 100 years ago and not seen since. How tantalising! Perhaps they are extinct in the area? Or maybe they are just so rare and scarcely recorded. Well not long after finalising the infographic, I rendered it instantly out of date by finding a Lasioglossum (Parasphecodes) hiltacus for the first time in Moreland since 1956.
In just two short trips outside the house I’ve recorded a new genus to the area and made the first local observation of a species since 1956. While I’m aware that our small, arbitrary local government boundaries bear no influence on ecology, it does make a useful context for illustrating just how under-studied is our urban bee biodiversity.
With Melbourne in lockdown and my change in career, time in the bush has been scarce for me this year. So it was with some relish that I recently headed out to Pyrete Range for a therapeutic communion with some native plants and pollinators. Most of Spring flowering had passed already, but I found a large population of Prostanthera saxicola var. bracteolata in peak flower. It’s a pretty restricted and uncommon shrub, so there are not likely to be many other floral visitor observations that have been made on this species.
I spent a relaxed hour or two on a warm day wandering between plants, making informal observations of flower visitors, and photographing interactions. The most frequent floral visitor was a native reed Bee (Exoneura sp.) which was in high numbers and reliably visiting flowers. I must have observed around 50 or more foraging bouts by reed bees, crawling deep into the flowers for nectar and collecting pollen from the anthers in the upper corolla.
I have known reed bees to nest in fern fronds (in wet forest) and in rushes and sedges (in the high country). Quite where they are nesting in this dry sclerophyll habitat, I do not know. But there is obviously a very large population of them.
Honey bees were also somewhat common visitors, as were some striking iridescent blue-green forester moths (family Zygaenidae). I saw six forester moth visits, but am not convinced they could be effective pollinators. They usually perch on the outside of the flowers, extending their proboscis into the base of the corolla for nectar, scarcely contacting the anthers.
One surprise was a single visit observed by this jewel beetle (Castiarina sp.), which was enjoying a feed on Prostanthera pollen.
Legend has it that skulking on Austalia’s forest floors is a bird which forages for earthworms by farting. The hapless worms are so startled by the sensory assault of a Bassian thrush’s fart that their dismayed writhing puts them in mortal danger. Following a quick toot, the gaseous bird simply plucks whichever vermiform vittles volunteer themselves from their humic harbour.
The Bassian thrush (Zoothera lunulata) is a bird of gullies and damp forest floors. Its predominant distribution is south east Australia. Image by Leo (CC BY-NC-SA 2.0)
Today, for those who believe this marvel of natural history, the world becomes a little less magical.
Having incorrectly answered a trivia question on Bassian thrush farting, I was recently moved to fact-check this suspect nugget. My initial searches found nothing but a few webpages referring to one another, a book without citations, and nowhere could I find a reference to the primary source. A literature search also turned up nothing useful apart from a 2016 paper describing observations of Bassian thrush foraging ecology, yet there was no mention of the birds venting vapour.
Bassian Thrushes fart while foraging for earthworms. I learned this in a trivia Q the other day. Several websites claim it is truth. Yet I cannot find a primary source for this “fact”. Where does this comes from???
— Michael Whitehead (@Mikey_Whitehead) July 23, 2020
Following a plea to Twitter’s sharpest bird and fart minds, the primary source was soon unearthed for all by Alex Berryman.
It is from Edington (1983): White’s Thrush: some aspects of its ecology and feeding behaviour. South Australian Ornithologist 27: 57—59.
[Knowing taxonomic history helps with searches like this!]I’m afraid the observation therein is a lot less rigorous than you might hope. pic.twitter.com/beu7nacY8y
— Alex Berryman (@AlexJB497) July 23, 2020
The original observation appeared in a 1983 paper published in South Australian Ornithologist. The reason I couldn’t find anything was that both the bird’s common name and scientific name have changed since the publication of that article.
So what is the evidence that has carried this remarkable phenomenon into Bassian thrush canon? The paper describes a behaviour of dipping the tail (“vent-dipping”), coincident with a noise “similar to a jet of air”. Probing of the soil surface for worms immediately follows. Between vent-dipping, the birds also “shiver”, and whilst shivering there is audible a “very soft sound somewhat similar to an inhalation gasp”. We aren’t told how many birds were observed doing this, and on how many occasions (the paper records 29 total observations of thrushes), so it is up to the reader to decide how common or deviant this behaviour is.
The speculative leap made from this unusual behaviour is that the fart is a strategy to induce the worms to suddenly convulse in repulsion, and reveal their location to the flatulent forager.
From Edington, JSL. 1983. White’s Thrush: Some aspects of its ecology and feeding behaviour. South Australian Ornithologist, 29, pp.57-59.
“The louder of the two noises described (that accompanied by a downward movement of the vent) may well be a ‘scare tactic’ to induce earthworms to contract reflexly (or other prey to move away) and so betray their presence to the Thrush through noise or litter movement and vibration. That these louder noises were made only during foraging, were antecedent to the probing and were more frequent with more intensive foraging, suggests that they were indeed somehow used to detect prey.”
Further, that shivering serves to reload the bird’s cloaca for another blast.
“If the source of the louder noise is assumed to be from the quick passage of air through the vent, then the softer, antecedent noises (each accompanied by a body shiver) might be explained as aerophagia – the gulping of air.”
Now this sphincter-percussion all sounds a bit bizarre, but is not without some scientific precedent. One expert to chime in on Twitter was Dr Dani Rabiotti, author of the book Does it Fart? The Definitive Guide to Animal Flatulence.
It’s generally accepted most birds don’t fart but I guess, similar to some snakes, they could suck air into their cloaca than expel it. I suspect it may just be a myth though – similar to honey badgers farting on bees to subdue them.
— Dr Dani Rabaiotti (@DaniRabaiotti) July 23, 2020
Dani suggests this could be a case of ‘cloacal popping’, or simply a sick bird.
That sounds more akin to cloacal popping, but given it’s observed from a single individual and no one since seems to have seen it, if it was farting it may just have been unwell 😅
— Dr Dani Rabaiotti (@DaniRabaiotti) July 23, 2020
After scratching through the litter of evidence here, I feel it’s time to clear the air. There is simply no compelling evidence that the Bassian thrush uses farts to scare and catch worms. There are some curious but unquantified observations of a bird or birds at one site making some noises that could be due to aspiration and expulsion of air via the cloaca. There are no observations tying this to success in foraging. There have been no subsequent observations supporting the behaviour described in the original paper.
I’m afraid we, as lovers of truth and nature, must let the air out of this myth. Finally, we must all commit from now on, whenever we see a Bassian thrush, to carefully watch its arse, for science.
I recently put together some material on my work for the University of Melbourne open day. As a teaser for the papers in current preparation, here’s an abstract and some visuals on the project.
While we simply do not know what pollinates many of Australia’s plants, there is good evidence emerging showing Australia to be a global hotspot for bird-pollination. This raises questions about what ecological and evolutionary factors might encourage plant lineages to adapt to use birds as couriers for their pollen. As well, we might ask what the outcomes are when a plant species ties its reproductive fortunes to a bird, rather than an insect.
My project employs custom cameras designed for motion-capture data capture of insect visitors to flowers, in order to demonstrate contrasting bird versus insect visitation in pairs of closely related native shrubs. Fine-scale population genetic analysis in these plants is revealing evidence for systemic differences in the movement of pollen under these different pollinator regimes.
Styphelia stomarrhena is pollinated exclusively by birds.
The video below shows bird visitation by a number of honeyeater species, as well as the way in which floral morphology excludes bee pollinators from accessing pollen or nectar in Styphelia stomarrhena.
Styphelia xerophylla is the sister species to S. stomarrhena and has evolved a tight relationship with a single species of native bee: Leioproctus macmillanii.
The videos below show motion-captured footage of the native pollinator of Styphelia xerophyllum, a female native bee (Leioproctus macmillani).
However the flowers are also visited by introduced honeybees (Apis mellifera).
A quick note on plant names: These species recently underwent taxonomic revision, moving them from genus Astroloma to Styphelia. It is rather new, hence the confusion over these shrubs apparently having two names.
I must have been around six or seven years old, but I vividly remember being captivated by Densey’s work on late 80’s Burke’s Backyard. Her subjects were mostly invertebrates, the natural history of which she brought to life with superb macro and timelapse filmography. (For classic Densey and awesome 80’s music check out this vid about cicadas). It might not even be too far-fetched to draw a direct line from Densey’s work— some of my earliest recollections of a natural history fascination—to my life and work now, preoccupied with the flowers and insects she revealed to me so long ago.
Clyne’s clips of flowers blooming in timelapse made a particular impression on me. In a moment of frustration with a bored and annoying child, I remember Mum sending me into the backyard to wait for a flower to bloom. Soaked in the false impressions of timelapse filmography, I stood staring at a Callistemon for what felt an age before finally conceding defeat and coming back indoors.
In the last couple of years I had the desire and embryonic plan to go and visit her, knowing she was getting on, wanting to meet her and tell her the impression she made on me, and perhaps write up an interview to share her experience and wisdom with others. But I never got around to prioritising it, and now that opportunity is gone.
From the tiniest, dankest little crevices in the bottom of my heart; thanks Densey.
(For more information about her life and achievements, the Port Macquarie news have a nice write-up)
The Great Western Woodlands (GWW) form the largest tracts of temperate woodlands left on Earth. They hold approximately 30% of Australia’s Eucalypt species, and close to 20% of Australia’s plant species overall. This is truly an overlooked gem of Australian biodiversity. Last Spring I was lucky enough to visit for my work on pollination in our native plants.
My target there was Eremophila, a genus of approximately 250 species largely confined to arid and semi-arid Australia. The GWW represents one of the centres of diversity for the genus, and so I chose it as a likely spot to set up a new study contrasting bird and insect pollination.
Eremophila alternifolia was one of about 15 Eremophilas I saw flowering despite the drier than average conditions.
I was joined by perhaps the best kind of field assistant: a trained and accomplished professional ecologist who also happens to be my beautiful wife. After driving 2800km from Melbourne to field sites near Norseman, Western Australia, we spent a little under two weeks observing pollinators, surveying and mapping populations of plants, and collecting samples for population genetics.
One of the many viewpoints south of the Nullarbor Plain.
I left in awe of the scale of these woodlands, in love with the peace and isolation they offer, and a bit concerned over their insecure future. Fully 60% of the GWW is tenured “unallocated Crown land”, unmanaged and open access. With more visitors, and more appreciation of the value of these vast woodlands, I hope we can find a way to secure more of it into ongoing reserve for future generations.
The bluebush understory contrasts dramatically with red sand in many areas. Front left is one of my study species Eremophila scoparia.
The whole region is dotted with salt-pans.
As predicted from the small, violet flowers, Eremophila scoparia was visited by a host of native bees.
Eremophila decipiens has characteristic bird-adapted flowers.
Camera traps being expertly arranged by Samantha. Footage revealed that E. decipiens was being visited by a range of honeyeater species.
Eremophila calorhabdos
This spectacular Grevillea hid a massive bloom of flowers underneath it
The inflorescences are held on stems that grow along the ground underneath the shrub. The very long style with pollen-presenter is suggestive of adaptation to birds, but mammals might not be out of the question.
Eucalyptus loxophleba with daggy botanist for scale
Majestic Salmon gum (Eucalyptus salmonophloia) with Samantha for scale.
The serenity of wandering amongst giant Salmon gums at dusk was magic.
Gleaming bark on Eucalyptus salubris
Elevating on Lake Cowan. Photo: S. Vertucci.
For the second half of the trip I was joined by collaborator and all-round legend Dr. Renee Catullo. I made us walk 10km to collect camp gear following a single poor decision.
Stay tuned as research results emerge. The study should tell us about the way pollen moves under bee and bird pollination, and how those fine scale patterns play out on a grand landscape level.
Australian flowering plant diversity is legendary. Within an hour trip outside of our major metro centres anyone can quite easily witness unique Australian plant diversity in subtropical forest (Brisbane), grassland (Melbourne), and sandstone heath (Sydney). The diversity close to home is fairly well catalogued, and while it is hard to discover a new plant species, merely spending time around our native plants is very likely to reveal something that has never before been documented.
Something like 90% of our native plants rely on animals for pollination in order to set seed. Despite this, we simply do not know what pollinates most of our Australian native plants. The fact that the private lives for many of our native plants remains mysterious is due to their great diversity and the limited time and resources available to document what’s going on every day in the bush.
Two native bees (Hylaeus (Rhodohylaeus) sp.) visiting flowers of the Broom Bush (Eremophila scoparia) in Western Australia.
And these uncharted interactions are totally critical for the functioning of our native ecosystems. Pollination underpins production of seed for the next generation, builds seed banks for post-fire regeneration, and also produces fruits and seeds that are critical food resources for our native animals.
Our ignorance of native pollination networks is therefore vastly out of step with their importance. This is illustrated in the example of bee declines, where we have all heard about the threats impinging on honeybees and pollination service for food crops, yet when it comes to Australian native bees, we lack the basic benchmark data needed to make a solid judgment about whether they too are declining*. It is therefore imperative that we commit effort to recording native pollination networks now, before they are lost to us. While it is hard for long term ecological monitoring projects to attract funding, ongoing development of automated imaging of flower visitors and large scale citizen science projects offer some promise for increased capability in filling this ecological blind spot.
But our ignorance here can also be thrilling. This means that every time you are in the bush, and witness an insect or bird taking nectar or pollen from a flower, there is a reasonable chance it has never been documented before. In my work with University of Melbourne I have been studying several native shrubs to understand their pollination, and for many of these species, it is gratifying to know that my work will be the first documented evidence of what is visiting them. But you don’t have to be a trained scientist to do this, you just need some patience, luck, and some fine weather. And while discovering and photographing an unusual native bee pollinating one of our native flowers won’t win you a Nobel Prize, I guarantee it will provide any enquiring mind with a hit of electric discovery every single time.
Photographed on Mount Buffalo, Ken Walker (Victoria Museum) later identified this bee as the very rare Lasioglossum (Callalictus) callomelittinum. Few photos of it exist. This individual is buzz-pollinating a Fringe Lily (Thysanotus tuberosus).
Links for pollinator observations:
Bowerbird: Nature observations database
Government pollinators repository
*But given native bees need native habitat, and native habitat is being cleared at astonishing levels, we can, with a high degree of confidence, say that native bees are declining too.
The flowers on one of these plants conceal drops of sticky nectar. The other is a cheating orchid, presenting empty flowers and false promises. Can you tell which is which? Even if you knew which one carried nectar, how can you tell the difference between them? The two plants might look a bit different to human high-res optics, but now try blurring your eyes. Pretty similar, huh?
What about this pair?
If it’s difficult for our brains and eyes to discern the difference between the flower with the reward and the one that’s falsely advertising, then what hope does a nectar-hunting fly with low resolution compound eyes and a smear of a central nervous system have?
Specifically, I’m talking about this fly…
If this fly looks embarrassed, its because it has orchid pollen stuck to its face.
Until now, you probably thought lion, or elephant, or rhino were the most impressive animals roaming the grasslands of southern Africa. Well you’re wrong, and it’s ok to change your mind after seeing the majestic long-proboscid fly of South Africa. There are several species of these magnificent beasts, and this one is named Prosoeca ganglbaueri.
That giant proboscis hanging from its face is a tool crafted by evolution for sucking nectar from the bottom of long flower tubes, and it can grow as long as 5 cm (which is longer than the fly’s own body length). Unlike butterflies who coil their proboscises, the long-proboscid flies simply hinge the instrument down, tucking it away underneath their bodies to trail out behind them. And this species isn’t even the most extreme: proboscises in Moegistorhynchus longirostris get up to 8 cm!
Sometimes handling that long instrument can be a challenge…
In some areas of South Africa, P. ganglbaueri is the only creature capable of extracting nectar from flowers with very long floral tubes, and because of this it has become the exclusive pollinator for 20 species of plant. Altogether, the long-proboscid flies as a group bear the great responsibility as the only pollinator for approximately 130 species of plant, making them a truly important creature for the ongoing survival of many South African plants.
Figure 1 from Whitehead et al. (2018): Prosoeca ganglbaueri feeding from a variety of nectar sources. (a) Zaluzianskya microsiphon, (b) Scabiosa columbaria, (c) Agapanthus campanulatus, (d) Dianthus basuticus.
An interesting fact about flowers that are pollinated by long-proboscid flies, is that most of them are pink, or white, or some variation in between (with one blue exception). This strong colour preference is a critical feature directing the evolution of the cheating orchid flowers introduced earlier. For a deceptive orchid to attract this fly, the orchids’ flower colour must match the flies’ colour preference, or the mimicry simply won’t work.
In my recent paper, we asked whether the colour preference of flies was something that they learned, like we learn to associate that perfect golden-brown hue of fried food with a mouth-watering culinary experience, or if it was instead a more hardwired innate response, like a moth drawn to a lamp. The answer is important for understanding ultimately what is driving the evolution of false advertisement signals in mimic orchids. So, for example, if flies had an innate bias to pink or white, then cheating orchid flowers would evolve to match that bias, in the same way that any good advertisements are designed to appeal to the fundamental desires of its audience. On the other hand, if flies learned to associate nectar reward with certain colours, their preference should be determined by the colour of their local nectar diet. Under the learned scenario, orchids should be evolving to match local flowers’ colours, not any intrinsic bias of the fly.
To test this, I took advantage of just how easy it is to bamboozle these flies. With a home-made artificial flower, painted to match the pink and white flowers visited by the fly, anyone can fool a fly into attempting to feed. So I mounted a pink and a white model to my “interview stick”, and travelled across the rugged Drakensberg Mountains to interview various populations of flies. In each location, I recorded whether the local flies preferred probing the pink or white model flower, as well as the colour and species of flower that the flies were using for nectar there.
Figure 3 from Whitehead et al (2018): Pink-white preference for flies at seven sites. The x-axis shows colour preference, with pink on the right, white on the left. Measured preference at seven sites is represented, with the colour of local nectar sources depicted in the small pie charts.
This tells us that the flies are very flexible in their preferences, and the strong implication is that these flies are learning to associate colour and reward. A further result showed that as the variation of colours flies fed from increased, this made them less choosy in the pink-white preference choice. So the bottom line is that the colour of their local nectar-buffet strongly controls a fly’s colour preference.
What does this mean for orchid cheats? Well, the colour of nectar cheats is all important, and what matters most for the success of a deceptive orchid is the colour composition of the surrounding nectar-rich floral community.
Post-script:
Still wondering about which flowers in the opening images were cheats, and which had nectar?
In both cases the deceptive orchid is on the left. The first image features Disa nivea (left), and Zaluzianskya microsiphon (right), the second features Disa pulchra (left) and Watsonia lepida (right).
Reference:
Michael Whitehead 