First we have several photographs of a lovely hummingbird taken by reader Joshua Lincoln:
This is the Fiery-throated Hummingbird (Panterpe insigns). It is from Cerro de la Muerte in Costa Rica. Cerro de la Muerte means Mountain of Death. It is the highest point of the Inter-American Highway in Costa and for anyone who has driven a rental car very much there, the description is fairly accurate. [JAC: When I was taking an Organization for Tropical Studies ecology course in the summer of 1973, we visited this site, which became appropriately named in another way: about half the class contracted a bad stomach bug at Cerro de la Muerte, and many of us became incapacitated, lying like lox in the dormitory.]
The structural coloration (as opposed to pigment) of the hummingbird’s feathers becomes apparent when you see how light waves either add (strong reflection) or subtract (weak reflection) as they reflect back from the feathers to our eyes (or the sensor in a camera). Here are a few photographs of the bird taken seconds apart demonstrating the effect.
Reader Marilee sent a round-leafed sundew:
Drosera rotundifolia photographed on Grand Manan Island in New Brunswick.“The whole upper surface [of the leaf] is covered with gland-bearing filaments, or tentacles ….The glands are each surrounded by large drops of extremely viscid secretion, which, glittering in the sun, have given rise to the plant’s poetical name of the sun-dew.” –from Darwin, Insectivorous Plants, in which he wrote about his experiments with this species, including movements of the tentacles, in great detail.
And another bird (and a plant quiz) from reader Barbara Wilson:
The good news is, I got some close-up photos of a Pine Siskin (Spinus pinus) near a bird feeder in western Oregon. Note yellow in wing. The bad news is that the reason a person can get this close is that the bird is sick, as so many Siskins we see are.
Question: What is the genus of grass, and how do you know?
Answer: Poa, bluegrass, and you can tell because the leaf tips (e.g. near the bird’s flanks) are shaped like the prow of a boat. (You can’t assume it’s a bluegrass because that’s what lawns are made of; in our area lawns are often filled with bentgrass, genus Agrostis.)
Perhaps some readers might know (I don’t) why so many siskins are ill.
“the bird is sick, as so many Siskins we see are.”
What sickness if afflicting the siskins? We see them most winters in Georgia, but haven’t yet this year, but it’s still early and way too warm between Canada and here.
Gorgeous colors and pictures!
In 2015, here in the upper Midwest (primarily Iowa and Minnesota), somewhere between 40-50 million turkeys and chickens died or were killed because of “bird flu.” No one has been able to identify the source of this highly contagious disease, but the usual suspects are migrating birds. Strangely I have never seen a sick migrating bird, and we have feeders and walk a mile daily in a nearby woods/prairie. Ask a regional USDA person whether they would be interested in testing a sick pine siskin for bird flu. We usually get a few at our feeders, but I have not seen any this year. This past fall no bird flu outbreaks were detected despite the usual flights of migrating birds through the area. I am more inclined to think that the actual vector is humans – like the feed delivery people who travel from farm to farm in large trucks.
From Janet Brownes’ excellent biography of Darwin I had read how Darwin became interested in the movements of plants. He was very puzzled about how they do it, and was trying to work out how they might have something like nerves and muscles.
That’s a fine book. I learned so much from it.
It’s on my shelves…beckoning…
I read the 2nd volume and could not put it down. I then immediately bought the 1st volume. But that was back when my work load was less than it is now.
Right now I have too much going on to do much reading of any length. I just finished Faith vs Fact, dammit, page by page. It took several months!
After all these years, I’ve still never seen the second volume in a bookshop. I would presumably snap it up reflexively if I came across it, but anyone who tracked down and bought all the books I wanted to read would be rich indeed.
Rereading F vs F at the moment…
I will add that biography to my wish list. I recommend “Darwin and the Barnacle” by Rebecca Stott.
Darwin wrote several books on plants, with detailed descriptions of his experiments and observations. One book is on the movements of climbing and twining plants. But sundews are covered in his book on insectivorous plants, and he used the same species as the photo above– Drosera rotundifolia.
University of Google tells me the pine siskins are especially vulnerable to salmonella, and easily pick it up from other birds.
Beautiful shots al!
Ouch, the sick bird photo really triggers my empathy.
My experience of structural coloration is limited to thin-film interference on planar substrates, but I am pretty sure that description is flawed.
The interference effects that add or subtract wavelength bands happens in very thin structures, so they do not show up as reflection variation when viewed from afar. [ https://en.wikipedia.org/wiki/Thin-film_interference ] Instead, as the beautiful Fiery-throat photos show, the coloration varies slightly with viewing angle.
However the maximum (and minimum) brightness of integrated reflectance from such a coloration would start to rival that of other types of mirrors, and that is a good give away. (E.g. bright blue head in the first photo, “shadowed” blue in the second.)
Maybe we have some expert on non-planar interference that can tell if I messed up.
The following is an account of structural coloration in hummingbird feathers
Greenewalt CH; Brandt W; Friel DD. 1960. The iridescent colors of hummingbird feathers. Proceedings of the American Philosophical Society. 104: 249-253.
2 other good references can be found here;
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2706478/
and
http://www.sibleyguides.com/2011/09/the-basics-of-iridescence-in-hummingbirds/
From Greenwalt:
“To summarize, hummingbird iridescence is due to interference colors produced by a stack of about three films whose optical thickness is one-half the peak wave length. Each film is a mosaic of platelets of elliptical form. Each platelet is about 2.5 microns long and one micron wide. The platelets are not homogeneous and consist of air bubbles encased in a matrix of refractive index about two. The different hummingbird colors are produced by a combination of effects. The platelet thickness decreases moderately as one passes from red through green to blue, and the air content increases simultaneously. In theory, of course, platelet thickness could remain constant and the color change would arise solely by variation in air content. Conversely air content could be constant and the platelet thickness varied. Nature for reasons best known to herself has elected to vary both factors together.” (Greenewalt et al. 1960:253)
“First, we repeated the examination of barbular surfaces with the optical microscope. We confirmed the presence of the platelet mosaic on the iridescent surfaces of fifty or so hummingbird species. Only the platelets are colored; the interstices are dark. The platelets are minute, about 2.5 microns across the long axis of the ellipse, and one micron across the short axis. Ten thousand of them laid end to end would measure a little over an inch. Their size varies little throughout the hummingbird species which we have examined. The length of 2.5 microns is a good average and the limits of variation would be no more than 30 per cent either way. Along its length the barbule is divided into cells separated by diagonal lines crossing the width of the barbule. At the points where the barbule joins the ramus and where the pennulum develops, the colored platelets disappear and one sees only a few random uncolored or faintly colored ellipses in these areas. The barbule proper then has a surface which is 15-20 microns wide and 100 microns long, divided by diagonal boundary lines into a series of cells which look like parallelograms, each cell made up of a mosaic of 100 or more beautifully colored elliptical platelets” (Greenewalt et al. 1960:250).
While it’s not the best description of structural colours, it doesn’t scream wrongness at me.
There’s a good treatment of the subject in “Seven Deadly Colours”, http://www.popularscience.co.uk/reviews/rev245.htm, which is definitely worth reading.
Hmmm, seems I heard Parker’s name mentoned recently, and thought “I’ll have to make an effort to watch (or listen to) that.” Can’t remember what it was though.
Brilliant colours!! Such is the power evolution!!
Those hummingbird pictures are gorgeous! They are such beautiful birds!
I feel bad for the poor sick Siskin.
The plant photo reminded me of dulse because Grand Manan dulse is the best dulse you can get & I wish I had a nice big bag of it to eat!
Dark Harbour dulse is the best!
I need to visit NB soon again & go to the market at Fredricton to pick me up a couple nice big bags!
Reblogged this on The Logical Place.
Stunning photos!
The hummers immediately reminded me of Christmas tree ornaments.
Yes!
Posted after such a gorgeous set of hummingbirds and the spectacular, lovely plant, my sick siskin looks even sicker.
I’d have had no idea that siskin was sick had you not mentioned it; could easily just be looking down at the moment. Our eastern House Finches are often sick and they look it–eyes closed, bodies puffy, etc. Sorry to hear of the siskin epidemic out there, and hope they recover by next year.
And thanks for the diagnostic tip on Poa–fun fact! My degree is actually in botany, but I’d not learned that! 😀
I am happy to report the siskins flocking my feeder are active and healthy. A major cause of the spread of salmonellosis is dirty feeders. Clean your feeders out and wash with soapy water regularly, or don’t feed at all. It’s a pain.
I read to clean feeders regularly (and beneath them) with a 10% bleach solution.
My wife’s feeders are becoming my headache.
I feel for you. 🙂 I had feeders one summer and what a mess! The birds were fun to watch, but the mess wasn’t worth it, so no more.
+1
I’m quite confident we can be sure Barbara is most aware of this, biologist that she is. (For that matter, the description she provides makes it sound like the feeder this bird was near might not even be hers.)
What a beautiful hummer. And thanks for the interesting info on structural coloration.
Sundews are fairly easy to keep as well. Good light and high humidity and they’ll thrive. I had a bunch in a greenhouse years ago and they worked great at capturing fungus gnats which were a nuisance.
I read that many birds sick with Salmonella get over it in a couple days, but for an unknown reason, Siskins are more susceptible to the bacteria and rarely recover. 🙁
Lovely hummer, my favorite CR species. And a wonderful sundew plant too!
Gorgeous photos, every one of them. Thanks!
Spectacular hummingbird shots, and I also love the epiphyte community in the last two pics.
And the bog species associated with that exquisite sundew are of great interest as well.
Thanks Joshua, Marilee, and Barbara!