Thursday, 15 February 2018

Ibis and Spoonbills; odd-billed oldsters

Whichever continent you live on, you are sharing it with ibis and spoonbills - though only Australia has more than one spoonbill species. There are just six spoonbills in the world, and 29 ibis (though nothing in taxonomy is ever that clear cut and while 29 is generally accepted, there is of course disagreement over the delimitations of some species). While all spoonbills belong to the same genus, the ibis are divided into about 13 genera.

60 million year old ibis fossils from South Africa are identifiable as belonging to two modern genera - that of the African bald ibises, Geronticus, and African and Australian white ibises, Threskiornis.

While the bills differences between the two groups are very obvious and unambiguous, they are actually very closely related and it's not even clear if they represent separate sub-families.
Black-faced Ibis Theristicus melanopis on the rooftop - a common sight - in Puerto Varas,
southern Chile. An ibis bill is long, narrow and distinctly downcurved.
Royal Spoonbill Platalea regia, Jerrabomberra Wetland, Canberra.
This is the typical spoonbill bill, long, broad and straight, with an expanded tip.
'Ibis' is one of the few common English words to come to us from Egyptian (albeit via Latin and Greek). 'Spoonbill' was consciously coined by the great 17th English naturalist John Ray, when he translated Francis Willughby's Ornithologica from Latin in 1678. In doing so he replaced folk names such as shoveller.

Both groups feed with the bill at least partly submerged, in water or mud or even cracks in the grounds; ibis probe while spoonbills constantly sweep the bill from side to side underwater. They can rarely see their prey, but the bill tip and inner surface of the end of the bill are packed with specialised sensors - of at least four types - which respond to a mix of taste and touch, together forming the 'bill tip organ'. When a food item is encountered the bill automatically snaps shut.

For spoonbills in particular the process is generally slow and methodical, like this pair of Yellow-billed Spoonbills Platalea flavipes progressing purposefully in front of one of the hides at Jerrabomberra. They take very small prey and are a large bird, so must forage all day and well into the night.
Spoonbills hunt by kicking up mud and with it small animals as they advance,
then seizing the animals as they sense them.
However recently I was surprised to see a couple of Royal Spoonbills fishing at Jerrabomberra, dashing about in pursuit of the fish, apparently hunting by sight.
You can get a sense of the energetic, almost frantic, pursuit of the fish in these two photos.

All the references I can find refer to very small fish prey, such as mosquito fish Gambusia spp., but the
bird on the left was swallowing something quite sizeable, probably a young European Carp Cyprinus carpio.
There are a couple of further bill adaptations worth mentioning. If you're going to spend much of your time with your bill submerged, you definitely don't want your nostrils perched on the tip of it. Indeed, ibis and spoonbill both have slit-like nostrils at the base of the bill.
This Plumbeous Ibis Theristicus caerulescens, in Brazil's Pantanal, has just had its bill almost
completely buried in the mud, but its nostrils (just visible in front of the eyes -
you may have to click on the picture) were clear.
Moreover the inside edge of the bill of a spoonbill has papillae which are said to act as motion or vibration detectors to assist in locating prey which is presumably away from the bill tip organ. I'm not certain how well-established this assertion is though.
The papillae are quite visible here, though you may again have to click on the photo.
All species have varying amounts of bare skin on the face and even head and neck, again to avoid fouling with mud.
Australian White Ibis Threskiornis molucca, Cairns Esplanade.
Curiously the young of this species has a feathered neck and head, presumably for insulation, but loses the feathers as it forages for itself.
Young Australian White Ibis, Jerrabomberra Wetlands, Canberra, still showing vestiges of its baby neck plumage.
Even younger ibis have straight bills, presumably to facilitate feeding by its parents.
While wading legs would not seem ideal for perching, ibis and spoonbills are regularly found high off the ground in trees, though they tend to move cautiously while so perched.
Yellow-billed Spoonbills, Leeton, New South Wales.
Generally large birds with broad wings, they soar in thermals, especially when migrating or dispersing to seek new water resources.
Straw-necked Ibis Threskiornis spinicollis soaring, Grenfell, New South Wales.
I love the fact that the two birds on the left are carrying out in-flight maintenance.
While in transit they move in long ragged lines or V-shaped flocks.
Glossy Ibis Plegadis falcinellus moving out from roost to feed at dawn,
Kakadu National Park, Northern Territory.
And perhaps it's time to wrap up this brief summary by introducing some of the species, including those who have already modelled for us.
Royal Spoonbill, Jerrabomberra Wetlands. The long head plumes and coloured face patches are
indications that the bird is breeding. Its range is primarily Australian, but it is also found in New Guinea
and nearby Indonesia. During the 20th century it colonised New Zealand.
Yellow-billed Spoonbill preening, Jerrabomberra Wetlands.
It appears an unlikely tool for the job, but seems to work just fine!
The high nostrils are also very evident.
Found only in Australia, it is more solitary than the Royal, and has a longer, narrower bill.
Glossy Ibis Plegadis falcinellus, Coombs, surburban Canberra.
A relatively small ibis, it is the only member of the family to be found across much of the world.
Australian White and Straw-necked Ibises, Kioloa, south coast New South Wales.
They have been probing the oval for beetle larvae; see the depth of the mud on the Straw-necked's bill.
This species nests in colonies of hundreds of thousands.
Both are found mostly in Australia, extending just into New Guinea and nearby islands.
The White Ibis has adapted well to urban living, scavenging at dumps and picnic tables.
Immature African Sacred Ibis T. aethiopicus, Queen Elizabeth NP, Uganda (looking a bit intimidated
among hordes of White-breasted Cormorants Phalacrocorax lucidus).
This ibis gave us the name of the group; the ancient Egyptians saw it arrive with the life-giving
Nile floods, and concluded that the birds had brought the water.
Until recently the Australian White Ibis was thought to be in the same species; they are very similar.
American White Ibis Eudocimus albus, Puerto Jeli, Ecuador. This lovely ibis is found around the Gulf of Mexico
and the Caribbean, and the west coasts of Mexico and of Ecuador. It is very closely related to the
Scarlet Ibis E. ruber and there is some interbreeding where they overlap in Colombia and Venezuela.
Bare-faced Ibis Phimosus infuscatus, Pantanal, Brazil.
Found mostly in swamps (though this one didn't know that, standing in a river) it is found widely in
eastern and northern South America. It is alone in its genus.
Black-faced Ibis Theristicus melanopis, Torres del Paine NP, Chilean Patagonia.
This hefty ibis is ubiquitous and common in the south of the continent.
It and the next species form part of a close grouping of three species in a four-species genus.
Buff-necked Ibis T. caudatus, Pantanal, Brazil.
Like the previous species, this one is mainly found in grasslands, where it probes for a range
of invertebrate and small vertebrate prey.
Plumbeous Ibis T. caerulescens, Pantanal.
This slightly manic-looking ibis is more closely related to the previous two than is immediately obvious;
it is also more aquatic than them. It is restricted to south-eastern central South America.
Puna Ibis Plegadis ridgwayi in the high Andes near Chivay, southern Peru.
A close relative of the Glossy Ibis, the Puna Ibis is generally found above 3,500 metres from
central Peru to northern Argentina, but finds its way to the coast on occasions. I've seen it both in Lima
and at Arica on the Atacama Desert coast of northern Chile.
Hadada Ibis Bostrychia hagedash, Queen Elizabeth NP, Uganda.
This striking ibis is one of the voices of sub-Saharan Africa, with its wild trumpeting laugh, often uttered in flight.
(Here's a sample; I'd suggest the third one of the list - click on the arrow at the left end of the row.)
And it is from this voice that both scientific and common names are derived. 
This was the first bird I ever saw in Africa, from the evening window of my airport
hotel in Johannesburg, many years ago now
I hope this brief introduction to an ancient and intriguing group of birds has been of interest - thanks for reading to the end, if indeed you are still reading!

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Flabmeister said...

I am surprised that neither the Scarlet Ibis nor the Roseate Spoonbill featured in this post. Does your blog have a luridity filter or do the species feature on your bucket list rather than your photographed list?

Ian Fraser said...

Yes to the latter! I did once see the spoonbill flying by rqpidly, but that’s it....

Eric Robert said...