Thursday, 9 February 2017

A World of Herons: #2

Here I am again to complete last week's post on herons, a significant component of wetlands and waterways throughout most of the world. Having offered an overview last time, I want to introduce the groups and some representative species. I confess to feeling quite under the weather at present (no, not self-inflicted!), so this might turn out a little sketchier than intended - though concentrating on something as pleasurable as this topic could also take my mind off minor life-annoyances.

The taxonomy of herons is a very fluid situation, with changing understandings - and of course disagreements, that being the proper nature of science - at all levels, from delimitation of some species, to which species belong in which genera, to the basic breakdown of the family into subfamilies. As ever, I rely for taxonomy on the International Ornithological Congress (IOC) list - not because I think it's automatically the 'best' (inter alia I have no qualifications to judge it by) but because we all have to settle on one taxonomy and stick to it, and because they are excellent at keeping their lists updated, with reasons and references. (The IOC list doesn't concern itself with subfamilies, though the order of species they use can help us to deduce relationships to a large extent.) For most of us of course it doesn't really matter, though I find relationships interesting, and for a large family like this one it can help to subdivide. 

Having said that, three of the subfamilies are relatively small, so subdivision per se isn't so useful here for breaking a large whole into more manageable chunks.

Tiger Herons and Boat-billed Heron; subfamily Tigriornithinae
This is an interesting and attractive small grouping comprising three species of South American tiger-herons, plus three somewhat enigmatic and far-flung single-species genera (the Boat-billed Heron from South America, the Forest Bittern (yes, I know it's confusing!) of New Guinea and the White-crested Tiger Heron of central and west Africa).
Fasciated Tiger-Heron Tigrisoma fasciatum Peruvian Amazonia; this species is more
typical of forested streamsides higher in the Andes.

Rufescent Tiger-Heron T. lineatum, Yasuní NP, Ecuadorian Amazonia.
Boat-billed Heron Cochlearius cochlearius, Ecuadorian Amazonia.
A remarkable bird, active at night or evening so not easy to find.
The extraordinary bill is used as a scoop, unlike any other heron's.
It has until recently been regarded as belonging to a separate family altogether, but it is now generally accepted that
it is a true heron, and in the Tiger-Heron subfamily.
Bitterns: subfamily Botaurinae
The bitterns are secretive stocky herons of the reedbeds, 10 small species and four large ones (comprising two separate genera), plus the unusual rainforest Zigzag Heron of the Amazon basin. The large bitterns especially, which between them are found on all continents, emit dramatic booming calls during mating season, which can echo for kilometres. The name derives originally from a Latin term incorporating taurus, a bull.
Australasian Bittern Botaurus poiciloptilus, McKellar Wetlands, Canberra.
When I posted this pretty ordinary picture on the Canberra Ornithologists' Group's email line in 2014,
it was the first photo ever published of this species taken in the ACT.
The last record was over 70 years ago - no-one living had ever seen one here before (I hasten to say
that I wasn't the one who found it).
There are estimated to be less than a thousand left in Australia, perhaps the same in New Zealand,
and apparently none survive in New Caledonia.

Black Bittern Ixobrychus flavicollis, Kakadu NP, Northern Territory.
This is the largest of the small bittern genus, and is found from Pakistan to China to Australia.
It is rather less cryptic, and rare, than the previous species.
The big feet, common among herons for walking on wet ground, are also used by bitterns to climb up reed stems.
Black-backed Bittern I. dubius, Jerrabomberra Wetlands, Canberra.
I only enclose the top photo to give an idea as to what we actually see; below is a close-up.
This species is an Australian endemic, only relatively recently accepted as separate from the Little Bittern I. minutusof Africa, Eurpe and Asia.


Night Herons: family Nycticoracinae
This is the only contentious subfamily - there is some evidence that it should be subsumed into the day herons (below) but it is far from conclusive.

As you'd expect the birds are mostly nocturnal, roosting by day in trees near water. They are voracious predators - aviary birds are very scared when they're around.
Nankeen Night Heron Nycticorax caledonicus, adult and immature, Jerrabomberra Wetlands, Canberra,
in very dim dawn light. Found from Australia to the Philippines.
As well as fish they take eggs and chicks of other herons, terns and ibis, and will turn to hunting mice on dry land,
even in towns, during plagues.
Yellow-crowned Night Heron Nyctanassa violacea, Guayaquil, Ecuador.
This species is found in the Americas, including the Galápagos, mostly in near-coastal tropics and subtropics.

Black-crowned Night Heron Nycticorax nycticorax, Isla de Chiloé, Chile.
This is a bird with a huge distribution, found in every continent except Australia.
Day Herons; subfamily Ardeinae
This is by far the largest heron subfamily, comprising some two thirds of all species. It is dominated by two largish genera, each with around 12 species, though there is still dissent as to which species belongs where. Let's just go through some of them.

          Genus Ardea
The Great Blue Heron A. herodias (here on Santa Cruz, Galápagos) is found throughout North and Central America.
It is one of the biggest herons in the world.
Black-headed Heron A. melanocephala, Entebbe Botanic Gardens, Uganda.
Found across most of Africa, where it is unusual among herons in feeding mostly on land.
Rodents, birds, reptiles, frogs and invertebrates form important parts of its diet.

Cocoi Heron A. cocoi, Manu River, Peruvian Amazonia.
Cocois can be found on almost any non-montane waterway in South America;
the name is from an indigenous name for it from the Caribbean area.
Purple Heron A. purpurea, Limbe Botanic Gardens, Cameroon.
This one has a very wide range across Africa, Europe and southern Asia.
White-necked Heron A.pacifica, Bladensburg NP, central Queesland.
I find this a very handsome big heron, which occurs across Australia; hence the former name
of Pacific Heron was dropped as being inappropriate.
Great Egret A. alba, Jerrabomberra Wetlands, Canberra. This familiar heron is a world-wide species
(though it wouldn't surprise if the American populations were split off as a separate species).
There seems also to be a possibly inexorable move towards placing both this species and the next in their
own separate genera.

Intermediate Egreat A. intermedia, Fogg Dam near Darwin.
Another cosmopolitan species; see comment above re the moves to elevate it to a single-species genus.
Highly regarded authorities have proposed splitting it too, with both African and Australian birds removed
to create three species.
            Genus Egretta
The other large genus in this subfamily, on average comprising smaller species.
Little Egret E. garzetta Cairns, Queensland.
Yet another very widespread species, found everywhere except the Americas.
Where most herons are patient sit-and-wait hunters, the Little Egret dashes about frenetically.

Pacific Reef Heron E. sacra, Fraser Island, Queensland.
Here both colour morphs occur together; to the north most birds are white. with dark ones to the south.

White-faced Heron E. novaehollandiae, Canberra, the commonest and most ubiquitious heron
in Australia, found from desert waterways to farm dams to wetlands everywhere, and on the coast.
It has been suggested too that it is the most generalist heron in the world, feeding in fresh water, on beaches
and reefs, and in dry paddocks.
Immature Pied Heron E. picata, with Eastern Swamphens and Glossy Ibis, Kakadu NP.
Adults have a black cap and nape. A tiny heron, common across northern Australia and in
New Guinea and associated islands.

Little Blue Heron E. caerulea, Arica, northern Chile.
An elegant little heron found from the southern United States to the warmer coasts of South America.
Snowy Egret E. thula, also at Arica.
A very wide American range, covering the southern half of North America and most of South America
except for the Andes. I love the yellow feet!
          Smaller genera of day herons
Finally there are a number (around six) of day heron genera with between one and six species. The largest of these comprises the pond herons, six species of mostly Asian or African small solid herons.

Squacco Heron Ardeola ralloides, Queen Elizabeth NP, Uganda. This is a non-breeding bird,
as the breeding plumage is a rich non-streaked orange-buff.
One population breeds in eastern Europe and western Asia, and ovewinters in sub-Saharan Africa;
here it joins another permanent population.
Western Cattle Egret Bubulcus ibis, Benoué NP, Cameroon.
This species and the next have recently been split, though this is not universally accepted.
This confuses the story of how the species spread throughout the world.

Eastern Cattle Egrets B. coromandus with Water Buffaloes, Sabah (above)
and with domestic cattle, Nowra, New South Wales (below).
These birds are in their lovely breeding plumage.

Striated Heron Butorides striatus Galápagos, adult above, juvenile below.
This species also has a huge distribution, across South America, Europe, Africa and Australia.
(See here for a photo of the Australian subspecies, from last week's posting.)
However until recently this distribution was even greater, with North and Central American birds also included
(they are now known as Green Herons B. virescens).

Lava Heron B. sundevalli, Santa Cruz, Galápagos.
This bird too was until recently included in the same world-wide species
but is now seen as a Galápagos endemic.

Capped Heron Pilherodius pileatus, Yasuní NP, Ecuador.
A little-known and scarce heron, with a wide tropical distribution east of the Andes;
the only one of its genus.
Finally (!), another very lovely single-species genus from the Amazon basin rainforests. The Agami Heron has been placed at times with the Tiger Herons, or even cast from the entire heron family! That is not generally accepted now though.
Agami Heron Agamia agami, Yasuní NP, Ecuador.
This is a bird of which we know sadly little - I feel privileged to have even seen one.
Well I hope you're not sick of herons yet - after all, though I've told you all that I'm going to, there are a lot of them out there to enjoy!

 (And remember that you can get a reminder when the next post appears by putting your email address in the Follow by Email box in the top right of this screen.)


Roman said...

Sorry to hear you are unwell Ian, I hope you have a speedy recovery.

Ian Fraser said...

Thanks for your kind thoughts Roman, I appreciate that. I'll get there!

Susan said...

We get 4 of the above species here in central France -- black-crowned night heron, purple heron, great and little egrets. Hope you feel better soon.