In most bird species, even those whose adults are gaudy and colorful, the juveniles are inconspicuous and dull. That seems reasonable, for much bird coloration is sexually selected (males are colorful, females less so), and although being colorful might attract predators, it attracts even more females of your species. But chicks aren’t at the stage of choosing mates and so avoiding predators trumps sexual selection.
But there are a few exceptions, and two remarkable ones are described in a new paper in the Wilson Journal of Ornithology by Fernando Mendonça D’Horta et al. (full text behind paywall). These are two species of birds in the family Laniisominae that are found in Amazonia. In this case, the adults are far less conspicuous than the juveniles, which are bright orange-red with dappling and, in one case, long crests. The two species appear to be each other’s closest relatives (“sister species”), and so the bright juvenile coloration probably did not evolve independently in each.
Here’s the juvenile of one species, Laniocera hypopyrra. This single specimen was collected in 2002.
The authors note the striking crest, which apparently isn’t present in the adult:
A remarkable feature of the crest is the feathers in which there are distal extensions, composed by up to six orange filaments 15 to 22 mm long, possessing white distal and proximal portions (Frontispiece, Fig. 1). The crest, including these filaments, reaches 40 to 48 mm. The same structure is exhibited by some of the dorsal feathers.
Here’s the second species, Laniisoma elegans, for which the authors collected the first juvenile known of the subspecies L. elegans elegans.
Apparently the dichromatism of adult and juveniles in L. elegans was known before, as it’s depicted in this plate from 1880.
Of course, one wonders immediately what the difference in color means, especially since it reverses the common pattern of cryptic chick/showy adult. Earlier workers had suggested that the chicks “had evolved to appear like moss covered by fruits,” but it doesn’t look that mossy and fruity to me.
The authors suggest instead that the chick is warningly colored (i.e., “aposematic”) because it is somehow toxic or distasteful to predators, or, alternatively, that the chick mimics some toxic and unpalatable species that predators have learned to avoid (i.e., the chick is a “Batesian mimic”). Of these two, the latter possibility seems more likely to me, for if the chick is distasteful and avoided by predators, why shouldn’t the adult also keep that pattern? Also, if the chick gets its distastefulness from its diet, well, the parents feed it, and could also have that diet. (Of course, the chick could endogenously manufacture a toxin, but why wouldn’t the adult do that, too, and keep the color?)
It is possible, of course, that the chick’s smaller size plays a role in its resemblance to some other toxic model. In truth, we simply have no idea what’s going on here.
Lest you think that birds can’t be toxic and aposematically colored, there’s at least one example, and it was discovered by Jack Dumbacher, a graduate student in our department. Jack found that the hooded pitohui of New Guinea (Pitohui dichrous), which is black and orange, has a neurotoxin in its skin and feathers. (Jack discovered this when his hands became numb and tingly when handling the bird.) The pitohui may acquire its toxin from eating beetles that contain the poison.
Here’s a hooded pitohui (photo from the NIF blog):
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D’Horta, F. M., G. M. Kirwan, and D. Buzzetti. 2012. Gaudy juvenile plumages of Cinereous Mourner (Laniocera hypopyrra) and Brazilian Laniisoma (Laniisoma elegans). Wilson J. Ornithology 123:429-435. DOI: http://dx.doi.org/10.1676/11-213.1
“Also, if the chick gets its distastefulness from its diet, well, the parents feed it, and could also have that diet. (Of course, the chick could endogenously manufacture a toxin, but why wouldn’t the adult do that, too, and keep the color?)”
I wonder why more birds, and animals in general, don’t manufacture toxins and advertise the fact. Sure, there would be a cost, but surely it would be outweighed by increased reproductive success.
Reblogged this on Beacon of Aquarius and commented:
Reblogged by Beacon of Aquarius July 2 2013
A toxic bird named a ‘pitohui.’ It that onomonopaeic for the sound you make when you try to eat it?
My wife and I conducted our PhDs in the lowland forests of Bolivia, and were constantly amazed at the diversity of brightly coloured caterpillars with a variety of unpleasant hairy coverings. The first thing my wife and I thought when we saw this was the possibility that it is mimicking a caterpillar to ward off being eaten, perhaps one of the caterpillar species that clusters in furry colorful piles.
A possible explanation?
I think Batesian mimicry of a distasteful caterpillar is exactly what’s going on. Check out this amazing video of a chick in the nest: https://www.youtube.com/watch?v=VuedaG61Vik#t=4m06s
The movements it makes when approached sure look very caterpillar-like to me!
I think the adults don’t need this coloration because they are no longer helpless and can escape predation by flying away, which the chick obviously cannot do.
Grabbed the paper when I got into work today. The authors also raise this possibility of Batesian mimicry of a caterpillar.
“However, we consider the patterns observed in the juveniles of these two species (and the nestling of Laniisoma) strongly suggest either a chemical defense (toxic and/or unpalatable) or Batesian mimicry (e.g., of a large, hairy
caterpillar).”
Great video Nick! Thanks for sharing.
That movement certainly helps to reinforce the caterpillar explanation.
Would be nice to know whether there is a specific caterpillar species being mimicked, or if it’s possible for the furry, wriggling, warning colouration alone to act as a generic warning against predation.
I concur with the caterpillar mimicry idea— exactly the same thought sprang to mind on seeing these creatures wriggle about in the nest. Many caterpillars have highly irritant hairs in addition to their general toxicity. This species is also accounted in the Field Museum’s site at http://fieldmuseum.org/users/john-bates/blog/one-most-interesting-things-learned-about-birds-2012
Indeed! I completely forgot that John had blogged about this and it was where I first learned about the video! I work down the hall from him, so I feel quite guilty about not linking to his blog post. 🙁
Wow, I had no idea this bird had such distinctive babies. L elegans lives here where I live, in very “mossy” forests. Actually the “moss” isn’t moss but fancy branched liverworts, and at these elevations they are often golden-orange. My bet is that the juvenile is blending into the “moss” since it probably is stationary more than the adult, who works hard all day to bring food to the fattening baby. Kind of like the age-dimorphism we saw a few days ago with the tapirs.
Compare the juvenile with the pattern of a Golden Tanager, which specializes in foraging along thicker branches covered in “moss”.
http://www.flickriver.com/photos/24201429@N04/8441269899/
If you look at this bird in a photo or in a museum drawer, you would think it is gaudy and you might make some explanation for its conspicuousness. Yet when these things are clinging lengthwise to branches during foraging, nearly buried in thick golden-orange “moss”, they are practically invisible. I have seen them hundreds of times and am always impressed by how cryptic they are in their actual habitat when they are feeding. I think the L elegans juvenile is doing the same. I haven’t read the article but I wonder if this person actually made observations in the wild, or only in museum trays.
Reblogged this on Mark Solock Blog.
Or are they so coloured for mum&dad to find them? (I prefer my grandkids to wear distinctive & brightly coloured tops when I take them to the local park)
Would it not be judicious to examine the birds under different light eg UV or infrared? Perhaps that might be illuminating (pardon pun)?
Could it be that the parents used to be brightly coloured as well in the ancestral species but lost that due to natural selection or genetic drift?
In a siliar way, the tapir offspring have a startling pattern compared with (most) adults of most species?
These two species was grouped under “subfamily” Laniisominae (Barber and Rice, 2007).
Great post Jerry,
As Gammara-Toledo noticed, they belong to the Laniisominae subfamily, and Titytidae family. Also, they are not restricted only to Amazonia, the are found in some Colombia areas too.
Cheers