The Tawny Frogmouth (Podargus strigoides)

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The Tawny Frogmouth (
Podargus strigoides), a #BeakoftheWeek contender from last year,  is a weird and wonderful member of the Podargidae family.

Adult tawny frogmouth, perching in daylight, Queensland

Adult tawny frogmouth, perching in daylight, Queensland

Alongside oilbirds, potoos and some nightjars, frogmouths are part of the wider order of birds known as Caprimulgiformes. Literally meaning ‘goat-milker’ in Latin, this peculiar name is said to have derived from folk tales regarding the feeding habits of the European nightjar, thought to surreptitiously suck the milk from goats in the depths of night!

The Tawny Frogmouth was first described in 1801 by the great English naturalist John Latham who was able to study and name many species of Australian birds from specimens finding their way into England’s growing natural history collections at the turn of the 19th century. In his first great ornithological work ‘A General Synopsis of Birds’ he actually focuses on the unusual bills of these then so-called ‘goatsuckers’ as follows: 
“The bill in this genus is very short, and hooked at the end. Gape vastly wide: on the edges of the upper mandible seven or more stiff bristles.”

Tawny Frogmouth 2

Ornithological painting from the Natural History Musuem’s collection of First Fleet artwork: “Strigoid Goatsucker”, native name “Birreagal”

One of the earliest known images of these birds is part of the collection of artworks created during the First Fleet expedition of the 1780s that saw the formation of the first European colony in Australia. Over half the natural history artworks focus on birds, with a number acting as iconotypes (where an image has survived but the specimen it was taken from (usually the earliest known to science) has not).

This fantastic painting, noted as a type and labelled around its time of creation as depicting a ‘Strigoid Goatsucker, native name Birreagal’ was re-examined in 1970 and confirmed as being detailed enough to accurately identify as Podargus strigoides.

Tawny frogmouths can be found throughout Australia and Tasmania and are known to live in most available habitats- from forests and woodland to heaths and urban areas. Known for their ‘cryptic plumage’, their colouration is variable, but usually consists of greyish upperparts, streaked with barring and vermiculation in blacks and brown with females usually having darker feathers.

Frogmouths have often been confused with owls, seemingly as a result of their nocturnal habits, brilliant camouflage and expressive faces alongside some quirks of historic synonymy. Confusingly, some of the most commonly used names for the Tawny Frogmouth are ‘Birreagal’ and ‘mopoke’, a name also shared by the boobook, a small Australasian owl. The Latin name strigoides itself reiterates this, with strix meaning owl, and oides meaning form. Many resources continue to refer to frogmouths as ‘false owls’ or simply ‘tawny frogmouth owls’ for good measure; there are however a number of key differences between these taxa.

Unlike most owls with their strong legs and curved, pointed bills for killing prey, the tawny frogmouth has an extraordinarily wide, chunky bill ideal for catching and consuming insects. So too, during daylight hours frogmouths tend to perch on branches, utilising their extraordinary camouflage to blend in with their surroundings and avoid detection. Unlike owls, they gather most of their food by ‘pouncing’ from low branches to the ground where they mainly feed on worms, slugs, snails, reptiles, frogs and small mammals.

Tawny Frogmouth family- these birds have some of the most fantastical looking chicks.

Tawny Frogmouth family, New South Wales. Frogmouths have some of the most fantastical looking chicks.

Tawny Frogmouths breed between August and December with both sexes sharing incubation duties. Their nests are fairly loosely formed structures, primarily comprised of sticks and usually creating a platform between forked tree branches to safely raise their young  (having an average clutch size of 2 to 3 eggs) from the ground. These birds have distinctive ‘soft and low’ pitched calls, most commonly sounding like sequential bursts of ‘oom-oom-oom’ sounds, and are known to loudly bill-snap when threatened:


You can find out more about which species are related to the Tawny Frogmouth at OneZoom. For now though, I’ll end this post with a passage from another historical text, The Birds of Australia of 1911, which brilliantly captures the appearance and character of these birds:

‘The Frogmouths are beautifully soft-plumaged birds, with a motley of grey, brown, black and white markings. In the coloration then they resemble the dead bark of the bough on which they sit. To render it still more difficult of detection, the bird does not sit across the bough, but along it, assuming the stiff attitude of a rugged branch broken off short. The eyes are large and adapted to the diminished light of night, the brighter light of day seemingly making them dazed and inert. In both these characters they resemble the Owls. Their disposition is however, much milder, and they can be handled by day without attempting to offer any resistance. They are invaluable insect feeders, and capture their food, Cicadas, Phasmids and Beetles, &c., on the branches of the trees. After swallowing an insect they bring their mandible together with a loud snap, as if in satisfaction over the tit-bit.’

References
Handbook of the Birds of the World Alive, Podargus strigoides: http://www.hbw.com/species/tawny-frogmouth-podargus-strigoides (accessed April 2016)

White, John, A General Synopsis of Birds: Vol 2, Part 2, London, Printed for Leigh, Sotheby, & Son (1801). Available via Biodiversity Heritage Library:  http://www.biodiversitylibrary.org/item/105238#page/7/mode/1up

The First Fleet Expedition and Collections, Natural History Museum London- Library and Archives Collections: http://www.nhm.ac.uk/nature-online/art-nature-imaging/collections/first-fleet/art-collection/index.dsml (accessed April 2016)

Australian Museum, Podargus strigoides factsheet: http://australianmuseum.net.au/tawny-frogmouth (accessed March 2016)

Lucas, Arthur Henry Shakspere & Le Souëf, W. H. Dudley, The Birds of Australia,  London, Whitcombe and Tombs Limited (1911). Available via Biodiversity Heritage Library:
http://www.biodiversitylibrary.org/item/114952#page/9/mode/1up

Images and Audio

Adult tawny frogmouth, Queensland by Tatters is licensed under CC BY 2.0

“Strigoid Goatsucker”, native name “Birreagal” from the Natural History Museum’s collection of First Fleet artworks, available online: http://www.nhm.ac.uk/nature-online/art-nature-imaging/collections/first-fleet/art-collection/nathist.dsml?sa=1&lastDisp=gall&notes=true&beginIndex=264&desc=true

Tawny Frogmouth family, New South Wales by tinykettle is licensed under CC BY-NC 3.0

Audio recording of Tawny Frogmouth (Podargus strigoides) call, XC150467, by Marc Anderson. Accessible at: http://www.xeno-canto.org/150467

 

Lab Updates April 2016

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Data Collection in Tring: 3D Scanning

Overall we have scanned 67% of the world’s birds! You can view many of these 6700 species on our MarkMyBird gallery.

Yellow-throated Longclaw (Macrornyx croceus)

Yellow-throated Longclaw (Macrornyx croceus)

Our current target is to scan every species from our list of ‘island bird families’. The remaining island families we are yet to complete such as fantails, monarchs and drongos are quite difficult to scan owing to their dark shiny bills, and rictal bristles that obscure the sides of the gape of the bill and so this has slowed down our progress a little. However, we have also been targeting some easier to scan bird families to keep things moving such as the pipits and wagtails (Motacillidae). As well as having bills that are easy to scan, many have incredibly long hind claws (such as the aptly named yellow-throated longclaw, Macrornyx croceus) which are thought to be an adaptation to help them walk through grass.

To date we have scanned:

  • 6688 (66.93%) of species
  • 3153 (77.81%) of species from island families
  • 3532 (59.20%) of passerines
  • 3153 (78.30%) of non-passerines

Data Collection in Tring: UV and Visible Photography

Ribbon-tailed Astrapia (Astrapia mayeri)

Ribbon-tailed Astrapia (Astrapia mayeri)

On the photography side of the project this month we have been lucky enough to work on the birds of paradise. With such an incredible variety of colours, amazing iridescence and some of the most extravagant feathers, this plumage is incredible to see up close (and a practical challenge to image at times!).

It’s particularly fascinating to see first hand just how vivid much of this structural colour remains in historical skins and it will be of particular interest to see how these photographs fare in our later analysis.

We continue to progress through the Passerine families and are currently working our way through the bright and colourful Oriolidae.

To date we have reached:

  • 51 (26.29%) of families completed
  • 2108 (21.09%) of species
  • 9583 specimens: we are selecting up to 6 specimens of each species, both male and female
  • 57498 photographs: six photographs- dorsal, ventral and lateral in both UV and human visible spectrums- of every selected specimen

Mark My Bird

Our crowdsourcing site markmybird.org has now exceeded 790 registered landmarkers. The fantastic efforts of these citizen scientists has seen our overall landmarking progress reach 40%, contributing vital data as we proceed further into the analysis stages of the project.

This doesn’t mean the chance to contribute to the study is over, far from it! There are still thousands of these fantastic 3D models of bills in need of landmarking. With new species being added as each family is scanned from museum specimens, you can learn more about this research or join in and have a go yourself by visiting our website www.markmybird.org.

We have a new mailing list for MarkMyBird where we send out a monthly research highlight for our landmarkers. This month you can see how accurate your shoebill mark up was! You can sign up to our mailing list here.

Publications

Raptor skull change with size

Raptor skull change with size

Jen was lead author on a paper published this month in PNAS investigating shape change in birds of prey. As the skulls of birds of prey increase in size, they do so in a predictable way. The bills are tightly linked to this change in skull size – one cannot change without the other – indicating a constraint on how the bill can evolve. If this constraint is broken, it could have important implications for avian groups that exhibit high bill diversity, such as the passerines, particularly in families that have undergone rapid and explosive radiations, including the Darwin’s finches and Hawaiian honeycreepers. You can read more on the University of Sheffield’s press release, or by reading the full paper below:  

Bright, J.A., Marugán-Lobón, J., Cobb, S.N. and Rayfield, E.J. (2016). The shapes of bird beaks are highly controlled by nondietary factors. Proceedings of the National Academy of Sciences.

Twitter and #BeakoftheWeek

Our twitter competition #BeakoftheWeek has continued every Wednesday, with Tim Blackburn and Paul Sweet remaining at the top of our leaderboard- all are welcome to have a go and perhaps even beat our current contenders to the top slots!

We post regular blogs about some of our favourite species chosen for the weekly challenge over on our website, this month including the fabulous Grey-necked Picathartes (Picathartes oreas).

Images
Yellow-throated longlaw (Macrornyx croceus) taken by Carmelo López Abad is licensed under CC BY-NC-SA 3.0

Ribbon-tailed Astrapia (Astrapia mayeri) by markaharper1 is licensed under CC BY-SA 2.0

MMB banner (c) Jen Bright

Raptor gif (c) Jen Bright