“Dawn swift” illuminates origins of swifts and hummingbirds

dawnswiftFrom the spectacular Green River Formation of Wyoming comes a tiny fossil that researchers have identified as a possible relative of both hummingbirds and swifts.

When Eocypselus rowei, whose genus name is Greek for “dawn swift,” died approximately 50 million years ago, it fell into shallow, oxygen-poor water and was covered with fine layers of mud that preserved minute details of its body and plumage. Except for its long wings, the fossil shows few hummingbird-like characteristics. Its stubby bill is more like those of swifts and suggests that, like them, it fed on flying insects. Though about the length of a Magnificent Hummingbird (12 cm, 4 3/4″), its short bill, proportionally larger skull, and longer wing and leg bones would have made it heavier. “Shadows” in the stone surrounding its bones are fossilized pigment structures that would likely have given it a glossy, possibly iridescent black color like many modern swifts.

Though hummingbird fossils have been found so far only in Europe, Eocypselus shows that possible distant hummingbird ancestors did occur in the Americas.

Read the full text of the article here:

Fossil evidence of wing shape in a stem relative of swifts and hummingbirds (Aves, Pan-Apodiformes)

Read more at:

ScienceDaily

AAAS Science Now

Science 2.0

Search of the Week: “why don’t hummingbirds get diabetes”

A male Broad-billed Hummingbird threatens an intruder in his feeding territory.

A male Broad-billed Hummingbird threatens an intruder in his feeding territory.

This week’s featured search topic has been addressed on LB&E previously here and here.

Type 2 diabetes, the disease people are thinking of when they ask such questions (because they’ve been told, wrongly,*⇓ that sugar consumption causes diabetes), is largely a modern human affliction. We eat too much, including highly processed foods full of easily digested simple carbohydrates that flood our bloodstreams with glucose. We exercise too little, contributing to getting fat and staying fat. Our bodies may continue producing insulin to aid in utilization of the glucose in our systems, but over time our cells may stop responding to it.

These issues weren’t much of a problem for our pre-industrial ancestors (even those with a genetic predisposition to diabetes), and they’re still not much of a problem for people living labor-intensive lifestyles and eating traditional diets high in complex carbs, fiber, and other good things.

They’re also not a problem for hummingbirds. More than 40 million years of evolution have adapted these tiny, hyperactive dynamos to a sugar-rich diet. To maintain some of the highest metabolic rates ever measured, hummingbirds must take in enormous amounts of energy. The most energy-dense food available to them is flower nectar. Without it, the tiny, hovering jewels we know and love would never have evolved.

You might say that hummingbirds show three classic symptoms of diabetes: they eat a lot (polyphagia), drink a lot (polydipsia), and pee a lot (polyuria). Of course, these “symptoms” are simply consequences of a high metabolism and water-rich diet. They also have very high blood glucose levels, high enough to cause serious complications in humans, but their absorption and utilization of the sugars in their diet are so efficient that almost none ends up in their urine (as it does in human diabetes patients).

Medical researchers would love to know exactly how hummingbirds avoid the short-term and long-term complications of high blood glucose, but it’s clear that their ability to do so has been honed by natural selection. Any hummingbird that had a serious defect in its ability to absorb and/or metabolize sugar would be dead within days, weeded out of the gene pool.

Here’s an in-depth examination of the issues from the perspective of human health:

Adipose energy stores, physical work, and the metabolic syndrome: lessons from hummingbirds

* Since this post was written, new research has persuaded many members of the medical community that there’s a more direct link between sugar consumption and Type 2 diabetes than decades of propaganda by Big Sugar would have us believe.

Oh pointy birds, oh pointy pointy…


Crested Wood-partridge or Roul-roul
Originally uploaded to Flickr
by Greencolander

Darren Naish has a new blog post on bird anatomy, Clubs, spurs spikes and claws on the hands of birds (part I). The focus is mainly on the pointy bits that don’t originate directly from the digits, but it’s the “normal” bits—claws—that fascinate me.

Anyone into birds knows about the well-developed wing claws on digits I and II of young Hoatzins, but as Darren points out there are a lot of birds with wing claws, even chickens. Most people never notice them, though, because they’re so tiny. In chickens, the claw on digit I (the alula, homologous to our thumb) is reduced to an inconspicuous nubbin that’s easier to feel than to see (if you’re a carnivore, check for it the next time you cook a chicken).

The first bird that I ever noticed a wing claw on was the Crested Wood-Partridge or Roul-roul. I had the privilege of getting to know these exquisite little birds back in the late 1970s when I worked as a zookeeper. A pair that lived in the rainforest exhibit of the bird house occasionally produced eggs, and with artificial incubation one of these produced a chick.

The normal procedure for precocial chicks was to place them in a plywood brooder box with a heat lamp, some gamebird starter mash with chopped lettuce garnish, and a drown-proof waterer and just leave them alone. This works fine with your average gallinaceous bird, but Roul-rouls are not your average gallinaceous bird. “Roulettes” are fed by their parents for the first few days of life, and since the parents in this case weren’t involved, this job fell to me.

Several times a day I would get the chick out of its box, place it on the bird house’s kitchen counter, and present it with succulent morsels of greens, fruit, boiled egg, and chopped mealworm. It was on the first of these close encounters that I noticed something hard and shiny protruding from the leading edge of the roulette’s wing: a long, curved black claw. I was stunned. It could have been a kitten’s claw, except that it was sticking out of a bird’s wing.

Up to that moment in my young life, the evolution of birds had been an abstract concept, based on evidence with which I had a basic familiarity but no personal experience. Seeing the wing claw on the Roul-roul chick was like being smacked upside the head with evolution.

Roul-rouls spend their days on the ground but roost in trees. I wonder if, like the young Hoatzin, the Roulette’s wing claws help it navigate the third dimension of its rapidly vanishing tropical forest home?

Happy Darwin Day!

Before the end of the weekend I’ll post something more substantial in celebration of the 200th birthday of Charles Darwin, but here are two quite different songs testifying to his profound impact on the way we look at our world and ourselves.

Chumbawamba: “Charlie”


Chris Smither: “Origin of Species”

Charge your glass and face the world – we’ll drink a toast to Charlie!

Spiders = Brain Food

I’m almost a year behind on this article in Science Daily, but this might explain something I’ve observed when banding hummingbirds.

In females during the nesting season, I often see what appears to be tiny spiders floating around in the liquid in their crops (the skin and esophageal wall are extremely thin and so close to transparent that a well-filled crop looks like a goth snow globe). The habitat along the San Pedro River is rich in other invertebrates, including gnats and leafhoppers that also show up in crop contents, so are the females hunting spiders preferentially, and if so, why? Maybe to build smarter, more competitive offspring. Hummingbirds have pretty large brains anyway, but feeding them a diet rich in the amino acid taurine, of which spiders are an excellent source, may be a way that mothers build brain quality into their young.

I have yet to find a way to sample what the birds I band are eating without putting their safety at risk, so I’m not certain of either the identification of the critters in their crops or the proportion of one prey item to another, but the article seems to support this casual observation and provide a possible reason behind it.

And speaking of large brains, I have to thank GrrlScientist for leading me to the article cited above through a link to an article on brain size and evolution in her regular Birds in the News feature.

Large brains have long been hypothesized to favor species diversification by giving their possessors the behavioral flexibility needed to exploit new ecological opportunities more rapidly and efficiently than smaller-brained competitors, and now there’s evidence to support this “behavioral drive” hypothesis. Ecologist Daniel Sol of CREAF-Autonomous University of Barcelona and evolutionary biologist Trevor Price of the University of Chicago analyzed measurements of 7,209 bird species and found that those bird families that show the greatest diversity in body size tend to have proportionally large brains.

The use of encephalization as a measure of intelligence is somewhat controversial, but one study found that the brains of hummingbirds averaged 2.5 times as large as those of gallinaceous birds (which include chickens, turkeys, quail, and pheasants). Though we’re still working out how hummingbirds brains are organized and how much space is devoted to the thinking/learning parts of the brain versus those that control the birds’ complex motor and sensory functions, we know that hummingbirds can learn songs, keep track of what flowers they’ve visited and how long they take to refill, and remember feeders and flower patches along their migration routes from year to year.

The natural limits on how large or small a hummingbird can be make the size range of living hummingbird species a poor measure of evolutionary diversification, and diversity of plumage, behavior, and ecology are harder to quantify for comparison to brain size, but these factors plus the large size of the Trochilidae (approximately 330 species, one of the largest bird families in the world) and their long life spans suggest that hummingbirds have seen big-brain evolutionary benefits comparable to those Sol and Price attribute to corvids (ravens, crows, jays, magpies) and parrots.

Ben vs. Birds

With Christian cell biologist and theistic evolutionist Ken Miller returning to The Colbert Report last night (he’s got a new book), one of my favorite episodes of Futurama on immediately afterward (plot: penguins on Pluto), and Expelled!: No Intelligence Allowed opening in Canada next week, I thought I’d compare the box office performance of the anti-science propaganda film starring Ben Stein with two prominent documentaries starring birds, March of the Penguins and Winged Migration. The data were gleaned from Box Office Mojo (thanks, Sensuous Curmudgeon).

The results? The dinosaur descendants deftly defeated the Darwin defamers:

Expelled! March of the Penguins Winged Migration
Release date April 18,
2008
June 24,
2005
April 18,
2003
Domestic Total Gross $7,614,754
(as of 5/29/08)
$77,437,223 $10,764,402
Genre Rank: Documentary 12 2 7
Opening weekend gross $2,970,848 $137,492 $33,128
Opening weekend % of total 39.0% 5.7% 0.3%
Opening weekend theaters 1,052 4 1
Opening weekend avg. per theater $2,824 $34,373 $33,128
5th weekend gross $102,690 $4,382,340 $139,896
5th weekend theaters 210 2,102 21
5th weekend avg.
per theater
$489 $3,086 $6,661
Widest Release
(# theaters)
1,052 2,506 202
Best weekend 1st 7th 12th
Best weekend gross $2,970,848 $7,117,206 $439,461
Best weekend theaters 1,052 1,867 108
Best weekend avg. per theater $2,824 $3,812 $4,069

Expelled! grossed higher and played in more theaters on its opening weekend, but average income per theater for March of the Penguins and Winged Migration, a more accurate gauge of popularity, was about 12 times greater. The stats for each film’s fifth weekend and best weekend show how both bird flicks had serious “legs,” staying in theaters for weeks (23 for Penguins) and growing enormously in popularity. Expelled!, on the other hand, plummeted from that first weekend’s plateau into a bottomless pit of public disinterest, grossing a measly $489 per theater on its fifth weekend. And that’s 2008 dollars; BOM reports that the average price of a movie ticket has gone up $0.85 since 2003 and $0.47 since 2005.

Box Office Mojo only provides dollar amounts for ticket sales, not attendance, but the numbers clearly show that Expelled! simply hasn’t put butts in seats during its U.S. run despite various questionable incentives (according to imdbcom):

The movie is being promoted by Motive Marketing, who have created several novel initiatives to raise interest in the movie. The “Expelled Challenge” will provide schools with $5 to $10 for each “Expelled” ticket stub from the first two weeks of the film’s release, up to a maximum of $10,000. To “maximize your school’s earning potential” they suggest a “school-wide mandatory field trip”. “Adopt-A-Theatre” will provide $1000 to the five largest group ticket bookings. Anyone who took a group of 25 or more to see the movie could send in for a free Ben Stein “bobblehead” doll.

What?? March of the Penguins and Winged Migration outperformed Expelled! without kickbacks or bobbleheads? Wow.

Of course, revenues and attendance aren’t the only measures of a film’s success, but with survey reports indicating that over half of all Americans embrace creationism, plus attendance by both religious and non-religious debunkers of “intelligent design” (in order to know what claims were actually being made), you have to wonder why Expelled! was such a flop. Whatever the reasons, I’m gratified that American movie-goers showed more interest in birds than in junk science, particularly:

  • that March of the Penguins is the second highest grossing documentary in history and won the 2006 Oscar for Best Documentary, and
  • that Winged Migration beat Expelled! so decisively at the box office despite never showing in more than 202 theaters at a time.

Like many biologists, including the film’s director Luc Jacquet, I was appalled when March of the Penguins was co-opted by proponents of “intelligent design” and people who saw validation of conservative ideology in the birds’ behavior. (Contrast veteran film critic Roger Ebert’s review to the comments of conservative critic/pundit Michael Medved.) In retrospect, this response isn’t so surprising. Penguins already rank among the most frequently anthropomorphized birds thanks to their upright posture and “formal wear” plumage, their production of one offspring at a time and involvement of both parents in rearing is also rather human-like, and the filmmakers further emphasized these similarities in the English narration and marketing material. For the parallels to conservative family values to work you have to ignore the existence of nearly equal gender roles, serial monogamy, homosexuality, “divorce,” “kidnapping,” and infanticide in penguin society, but hey, the extra buzz got more people into theaters (and churches) to see a nature documentary, which can’t be a bad thing.

If you haven’t seen March of the Penguins or Winged Migration, do yourself a solid and rent one or both. The extras on the Penguins DVD are worth the rental fee all by themselves. If you decide to give Expelled! a chance to make its case against the scientific establishment, please weigh the film’s message against both the facts of the cases it presents and these chilling cases from the other side of the ideological coin.

Expelled! star Ben Stein is a character actor, television personality, investment advisor, dog lover, and former speechwriter and lawyer for presidents Nixon and Ford. None of this gives him any credibility on matters of biology, of course, but I’m sure the filmmakers were hoping his previous movie and TV credits would attract mainstream audiences while his reputation as an intellectual would bolster their lame premise.

I used to like Ben, despite our many ideological differences. He’s a witty and articulate guy (even if his voice does put me to sleep), and it took guts to risk his giant ego on the MTV quiz show, Win Ben Stein’s Money. He frequently lost to ordinary folks and was often a poor sport about it, which of course made the show all the more entertaining. After it was canceled, Ben seemed to recede to the distant fringes of the pop-culture radar only to reemerge as a surprisingly progressive financial guru who supports universal health care as a “moral imperative”:

Too bad that Ben wasn’t satisfied with this new, more dignified role (plus his gig hosting America’s Most Smartest Model), because his alliance with the “intelligent design” crowd doesn’t speak well of his ability to separate fact from fantasy. Based on an interview with Craig Ferguson on the Late Late Show, he seems pathetically confused over what Darwinism and evolutionary theory actually cover and what Expelled! is whining about. Very sad…