One of the most interesting things learned about birds in 2012
posted April 21st, 2013
For our 2013 Members’ Nights at the museum, I decided to include specimens of two birds, Cinereous Mourner (Laniocera hypopyrra) and Brazilian Laniisoma (Laniisoma elegans) in what I brought out to show people. Humans have too little time or appreciation for natural history these days, but sometimes, someone discovers something that is so cool that people need to hear about it. These birds illustrate an example of that. In the September 2012 issue of the Wilson Bulletin, Fernando Da’ Horta and co-authors Guy Kirwan (a Field Museum Bird Division Research Associate) and Dante Buzazetti published a paper entitled "Gaudy Juvenile Plumages of Cinereous Mourner (Laniocera hypopyrra) and Brazilian Laniisoma (Laniisoma elegans)." I wonder how many ornithologists flipped through this issue without realizing how amazing what was described in this article was. Cinereous Mourner is a fairly common mid-story bird found throughout the Amazon Basin. The tumbnail for this post is a handheld individual netted during our field work along the Rio Japurá in western Amazoinan Brazil. We have 26 Cinereous Mourner specimens in our collection (and 5 Brownish Mourners, L. rufescens its geographic sister species from Central America). It is fair to say that such dull-colored birds are often overlooked for their more colorful cousins. In this case, there were clues, but no one realized what they meant. The species gains a small amount of notoriety because it occasionally has a few orange feathers in the body plumage that are broadly tipped with black (see the photo of a specimen that Doug Stotz collected in southern Amazonia and a photo of a Brownish Mourner specimen I took at the Western Foundation last Fall). This species was described by Vieillot in 1817, so we’ve known about it for about for 186 years, but until Fernando saw an adult feeding a juvenile no one realized the significance of those occasional orange feathers. The painting is of the scene that confronted him in the forest one morning. The juvenile Cinereous Mourner is covered in these orange feathers. Thus, the juvenile is as brightly colored as the adult is gray.
A painting of a juvenile and adult Cinereous Mourner by Tomas Sigrist.
A Cinereous Mourner specimen (FMNH #344130) showing the occasional orange feathers that have long been known to show up in the species.
The black tipped feathers on the breast of this Brownish Mourner specimen (WFVZ) are remnants of a juvenile plumage that has yet to have been seen in this species.
This is simply amazing. Juvenlies and chicks of most species are camouflaged, presumably to avoid detection by predators, and here is a species in which the young is orange with black spots, and because of the feather structure, it looks almost hairy. The authors speculate that it could be aposematic coloroation, meaning that the juvenile Cinereous Mourners have some sort of noxious chemical in their plumage or tissue that makes them unpalatable. Another interesting possibility could be that they have evolved to mimic a poisonous caterpillar. This kind of mimicry is termed Batesian Mimicry (I am unrelated to this Bates as far as I know). It is pretty neat to think that a bird might have evolved to mimic an insect. Here is a link to a photo I found of the kind of an Amazonian caterpillar that might be involved in such mimicry.
I’ll make the claim that had this discovery been associated with a dinosaur, it would have made the cover of the journals Nature or Science. I guess this is just professional jealousy from an ornithologist, but I really do think this is just such an incredible discovery that I am excited to bring it up here. It took scientists working in the Amazon Basin over 180 years for this basic aspect of a common and widespread species’ biology to be uncovered and still it has only been seen once.
The interesting aspects of this story do not even end there. The authors recognized that there was another interesting example of juveniles with bright colors. This was from two specimens of Brazilian Laniisoma that had been collected in 1893 and were housed in the British Museum (see image below). Brazilian Laniisoma (Laniosoma elegans) is an enigmatic green and yellow bird from the Atlantic Forest and the Andes. And wouldn’t you know it, the higher level systematics projects on suboscine birds had uncovered a deep, but well supported sister relationship that had never before been suggested between Lanisoma and Laniocera.
The story went over well at Members’ Nights, as people appreciated the fact that even with birds we have known about for hundreds of years, there are still important and fascinating aspects of natural history that we have yet to learn about.
Check out the original paper:
Fernando Mendonça D'Horta, Guy M. Kirwan, and Dante Buzzetti (2012) Gaudy Juvenile Plumages of Cinereous Mourner (Laniocera hypopyrra) and Brazilian Laniisoma (Laniisoma elegans). The Wilson Journal of Ornithology: September 2012, Vol. 124, No. 3, pp. 429-435.
The original depiction of the guady juvenile plumage of Brazilian Laniisoma based on two 1893 specimens at the British Museum.