When He and She Look Different; Birds #2

Continuing from last week, which seems to have generated some interest I'm happy to say. I won't reiterate last week's introduction, but will move on to introduce some very dimorphic couples indeed, birds which in at least some cases you'd have to know belonged to the same species. These are not just a question of more and less intense versions of the same colour patterns, but quite different ones. However, having said that, I readily acknowledge that such observations are of necessity subjective, and where one type of dimorphism blends into the other is a very fuzzy line indeed.

Where they are truly distinctive however, and the name is descriptive, as so many names are, it means the bird is named only for the male - keep your eye open for this blatant discrimination as you browse!

Mostly in dimorphic species the male is brightly coloured while his mate is not, but this isn't always the case even in species where the male is the dominant partner in terms of courtship and display (we saw a couple of examples last week where the female was dominant, brighter or bigger). I recently had the pleasure of the company of a pair of birds which demonstrated this impressively, at a beautiful campsite at Gunlom Falls in Kakadu National Park in the Northern Territory.

Shining Flycatcher Myiagra alecto pair, male above, female below, Kakadu NP.
He is the same glorious blue-black below as above.
This monarch flycatcher is generally found near tropical waters, including mangroves and monsoon forests.

 

Another Australian example is that of the widespread, but in most places not especially common, big duck, the Australian Shelduck Tadorna tadornoides; it is not readily possible to state which of the sexes is more brightly coloured - they're just very different!

Australian Shelduck pair, Bethungra Reservoir, New South Wales, male right, female left.
A very poor old pic, my apologies; a slightly better photo of the male below, at Esperance, Western Australia.

 

A related group of birds, the South American 'geese', also have very different male and female plumage, but both are also equally striking.

Above Kelp Geese Chloephaga hybrida, Chiloé Island, Chile and
below Upland Geese C. picta, far southern Chile.
In both cases the males are white and the females are coloured.

 

Other such South American examples can be found among the marvellous hummingbirds.

Green Thorntail pair Discosura conversii, Mindo Valley, north-west of Quito, Eucador; male on the left.

In most of the cases which follow however it's pretty straight-forward - the males have relatively striking colouration and the females are essentially brown, which is an excellent colour to be if you don't want to be noticed while sitting vulnerably on a nest.

Superb Fairy-wrens Malurus cyaneus, male (Canberra) above,
female (Eurobodalla Botanic Gardens, Batemans Bay) below.
One of south-east Australia's best-known and best-loved birds.
Males moult in winter and follow the females into brown obscurity.

 

Many of the Australian 'robins' (which are no more robins than our wrens are wrens!) follow a similar approach. 

Flame Robin Petroica phoenicea pair, taking a break from attacking the invaders in the mirror,
Namadgi NP near Canberra.

Hooded Robins Melanodryas cucullata, central Australia, above and below.
I seem to be incapable of taking a decent picture of this species, but I'll keep trying!

 

The whistlers form another familiar Australian group which shows strong dimorphism.

Rufous Whistler male (Tinbinbilla Nature Reserve near Canberra)
and female (Mt Scoria Conservation Park, Queensland)

Other monarch flycatchers in addition to the Shining Flycatcher featured above show dimorphism, even though the females aren't as strikingly coloured.

Leaden Flycatcher Myiagra rubecula male (Mareeba Wetlands, Queensland) and
female, Namadgi National Park near Canberra, below.

 

Trillers are a group of small cuckoo-shrikes (family Campephagidae) which show strong dimorphism, unlike the larger members of the family.

White-winged Triller Lalage tricolor pair, Longreach Waterhole near Elliott, Northern Territory.
This was part of a large flock moving south to breed - he is still moulting into his full breeding plumage.

Satin Bowerbirds Ptilonorhynchus violaceus, male, National Botanic Gardens Canberra, and
females, Jerrabomberra Wetlands, Canberra.
The day when bowerbirds get their own posting here is surely approaching!

 

Mistletoebird Dicaeum hirundinaceum, male (Milang, South Australia) and
female (Fraser Island, Queensland).
The only Australian Flowerpecker (Family Dicaeidae), whose ancestors arrived relatively recently
here from Asia, but which is now the major vector (spreader) of Australian mistletoes.

 

 

Orange Chats Epthianura aurifrons, Bourke, New South Wales.
Now recognised as being well within the honeyeater family, some of the Australian chats nonetheless exhibit a strong
dimorphism that other honeyeaters lack.

Another group which varies considerably between species with regard to the differences between males and females are the parrots, most of which show no such traits. Some do however.

Superb Parrots Polytelis swainsonii, Canberra, above and below.
A threatened species which flies south from northern New South Wales to breed in woodlands
north of Canberra, but in recent years has taken to feeding in Canberra suburbs, probably prompted by drought.

Red-rumped Parrot Psephotus haematonotus pair, Canberra.
An exquisite little ground-feeding parrot, common in suburban parks.

Red-winged Parrot pair Aprosmictus erythropterus; a glorious parrot found across much of the
tropics and eastern inland Australia, as well as southern New Guinea.

As noted above and last week, ducks are well-represented in lists of dimorphic birds. Here are a couple more strong contenders.

Above Chestnut Teals Anas castanea, south coast New South Wales, and
below, Cinnamon Teals Anas cyanoptera, Arica, northern Chile.

And now that we've returned to South America, let's stay there to finish off today's exploration, beginning with one of the continent's truly iconic birds.

Andean Cocks-of-the-Rock Rupicola peruvianus, males above at a display lek,
female, below, eastern slopes of the southern Peruvian Andes.

 

Austral Negritoes Lessonia rufa, southern Chile, above and below.
These active little ground-feeders are members of the old South American family of tyrant-flycatchers.

   

Thick-billed Euphonias Euphonia laniirostris, Aguas Calientes, below Machu Picchu, Peru, above and below.
Euphonias are members of the huge and colourful tanager family; this species is
found across much of north-western South America.

 

Great-tailed Grackles Quiscalus mexicanus, Puerto Jeli, Ecuador.
These bold urban scavengers are North American blackbirds, whose ancestors arrived in
South America relatively recently, as South America crashed into North America.

 

Finally, trogons are one of the more spectacular bird families, comprising some 40 species across the world's tropical and sub-tropical zones - except for Australia. Many are notably dimorphic.

Masked Trogons Trogon personatus, Andean cloud forests north-west of Quito, Peru.

Well, if nothing else I hope you've enjoyed meeting some pretty impressive birds, with a special characteristic. 

Next time I'll look at a place, probably featuring somewhere from my recent travels in Australia.

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When He and She Look Different; Birds #1

After quite a hiatus, I am back live in my office, and will be for some time, so my usual weekly postings (not pre-prepared as has been the case recently) recommence now. 

It is an interesting phenomenon in the natural world that in some animal species the sexes are externally identical, in others they differ relatively subtly, though consistently, and in still others they look so different that they could be (and in some cases have been) described as separate species. Our own species of course is a case in point - on average (which of course means there are always exceptions) males are larger than females, and there are obvious physical differences. 

Today though I'm going to limit myself to birds, because this is a very large topic - in fact I'm not going to even attempt to complete it today. In species which do differ physically between sexes - ie are dimorphic - it is usually the males which are larger and more colourful. Not always however.

Australian Painted Snipe Rostratula australia, Jerrabomberra Wetlands, Canberra.
The female, on the right, is larger and more brightly coloured.
(Though I'm not entirely certain that the other bird isn't an immature - it is a feature of such species that the less
colourful sex often has very similar plumage to young birds of both sexes.)
This is a rare and seldom-seen species whose appearance here in 2011 generated considerable interest.

Brown Falcon pair Falco berigora, Sturt NP, New South Wales.
The obviously larger bird on the right is the female; this is consistently true for most diurnal birds
of prey - falcons and hawks/eagles, even though the two groups are not at all closely related,
as well as many owls.
In this case the purpose seems to be to divide up the territory so that the two birds are hunting
different-sized prey from each other, utilising the resource more efficiently.
The colour differences here are simply part of a wide variation in this species, and are not sex-linked.

It is a useful rule of thumb that monogamous species tend to be monomorphic - both are contributing significantly to the ultimate breeding success so neither is more expendable. On the other hand a large proportion of polygamous species tend to be dimorphic, with the dominant sex being larger and more brightly coloured; as noted above this is usually the male. It is glib but nonetheless at least partly true that the more brightly coloured a male is relative to the female, the more socially useless he is likely to be!

Perhaps more helpfully, his conspicuous plumage's role is likely to be primarily for attracting a mate (or several mates) - "I can afford to be so easily seen because I'm strong and smart enough to survive, and isn't that what you want in the father of your chicks?". However, in the broader scheme, the same message helps in intimidating rival males and maintaining the territory. It may even be that by being colourful and loud he is attracting the attention of predators who are thus less likely to notice his more subtly-coloured mate sitting quietly on the nest.

We can say that strong colour dimorphism is commonest among species that nest in the open. As ever in nature, it's all a trade-off - be inconspicuous to predators and you're unlikely to appeal to a desirable female. Be too obvious and you'll end up as lunch before you're a father. An extreme example of this is the peacock's ridiculous tail - the longer and heavier it is, the more females are impressed. Simultaneously the more likely he is to be unable to escape the attentions of tiger, leopard or dhole.

However, I'm going to start by introducing some milder, but nonetheless obvious, examples of dimorphism, where the female is similarly coloured to the male, but generally paler and less intense. Where this becomes a different colour as opposed to a variation on the same shade is of course subjective, and some of these examples could as readily have appeared in next week's offering of more dramatic examples of dimorphism. 

Spotted Pardalote Pardalotus punctatus, female above, male below.
(She belongs to the yellow-rumped mallee race, xanthopygus;
I was a bird bander in a past life.)
She is only subtly more different, with buffy spots rather than his strikingly white ones,
and without his yellow throat.

 

Tasmanian Scrubwren Sericornis humilis, Freycinet NP, female above, male below.
Like most other scrubwrens, she's a washed-out version of him.

 

Zebra Finches Taeniopygia guttata, Kata Tjuta NP, Northern Territory.
She, in the centre, lacks his chestnut cheeks and flanks.

Australian Darters Anhinga novaehollandiae, Canberra, female above, male below.
His plumage is richer in colour, especially the chestnut throat and dark breast.

 

Cockatiels Nymphicus hollandicus, Sturt NP, far north-west New South Wales.
This exquisite arid  land cockatoo is the world's smallest.
Again, males are a more intense version of the grey, white and yellow theme.

Cactus Finches Geospiza scandens, Santa Cruz, Galápagos, female above, male below.
He has much more melanin in his feathers, but it's essentially the same pigment.

 

White-browed Woodswallows Artamus superciliosus, Canberra, female above, male below.
Again the difference is evident, but is in intensity of shades.

Ducks are particularly notable in dimorphism (though by no means all of them of course), and several will feature in next week's post of extreme dimorphism. Here are a few more subtle ones.

Australian Wood Ducks Chenonetta jubata, Canberra, male right, female left.

Green Pygmy-geese Nettapus pulchellus, Fogg Dam, near Darwin, female left.
These are not really geese at all, but in the mainstream line of duck.

Chiloé Wigeons Anas sibilatrix, Puerto Natales, southern Chile, male right.
Despite the name, this pretty duck is widespread across southern South America.

Some species are subtly dimorphic in a more specific way - they have very similar plumage except for just one feature. This may even be as discreet as eye colour!

Black-necked Storks Ephippiorhynchus asiaticus, Croydon, North Queensland.
He has black eyes, she yellow.

Galahs Eolophus roseicapilla, Nambung NP, Western Australia.
In this case she has red eyes, while his are black.

Magpie-larks Grallina cyanoleuca, Canberra, female above, male below.
In this case the only difference is in the face colour - black for him, white for her.
(Immatures have a black forehead and white throat and sort it out later!)

 

Magnificent Frigatebirds Fregata magnificens, Galápagos, male left.
She has a white throat, where he of course has the red throat pouch.
(In this case he is flying higher than her, he is not smaller.)

Olive-backed Sunbird pair Cinnyris jugularis, Cairns, Queensland.
It may initially seem that they are very different, but nearly all the difference is in his iridescent throat.

Nankeen Kestrel Falco cenchroides;female, Fraser Island, above, male, near Canberra, below.
Here the distinction is in crown and tail, chestnut for her, grey for him.

 

And that will do us for today. Next week, as I've flagged, I'll conclude this series (for now at least) with examples of more extreme dimorphism, where the sexes are entirely different. 

(By then I hope to have been able to process my photos from my last two Australian trips, to the western deserts and the tropics, so I can share some of those lands with you.)

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