As Many Exceptions As Rules: As A Bird

Mr. Carlson and Herb Tarlek had to deal with the

aftermath of bombing Cincinnati with live turkeys.

The line about turkeys being able to fly is one of the

most famous in TV history. But he should have at least

questioned whether they could fly, there are more than

50 species of flightless bird alive as we speak.

In a famous 1978 episode of the TV sitcom, WKRP In Cincinnati, station manager Arthur Carlson releases turkeys from a helicopter to a waiting crowd below as part of a holiday publicity stunt. The birds crashed to the ground (off camera), as intrepid reporter Less Nessman described the carnage. You can find the entire episode here; it’s as funny now as it ever was.

This comedy had a 1940’s parallel in real life, when the town of Yellville, Arkansas dropped Thanksgiving turkeys off the courthouse roof for several years in succession, and then from low flying planes. They didn’t seem to have any qualms about the flight problems of the domesticated turkey.

In contrast, the North and South American wild turkeys would have survived the stunts. In the genus Meleagris, there are several species of wild turkey, and they can and do fly short distances. In fact, they spend their nights perched in the low branches of trees from Maine to Peru.

The Aztecs introduced the Spanish to Southern Mexican turkeys (Meleagris gallopavo gallopavo), who took them back to Europe in the 1520’s. The Spanish trade capital at the time was Turkey, and from there turkeys spread all across the continent by the 1550’s. Therefore, the English called them turkeys, because they thought the birds originated in Turkey.

The Meleagris g. gallopava birds brought back to Europe were domesticated and became the eating turkeys of today. They were bred for large breast muscles, and being raised in domestication caused them to lose much of their flying musculature; the domesticated turkey is flightless and mimics a bowling ball when released from a helicopter.

Here’s proof for you city folks that turkeys can fly.

Their perch is bird-like, drawing up one leg. This might

be to conserve heat, or to change their outline and

make them look like a plant in order to avoid predation.

Truly, that is one hypothesis… I mean it….really I do.

In animals, only birds have a vertical extension (keel) on their breastbone to allow for attachment of the large breast muscles required for flight. Birds are also the only animals to have fused collarbones, called a furcula. This bone attaches to the muscles important in the down stroke of wings, and also helps to pump air into the lungs - we know this structure as the wishbone. The furcula is more massive in the middle, and can flex and act like a spring during flight.

We use the furcula as a sign of good luck, but for domesticated turkeys it is just an unfortunate reminder that they used to have a fighting chance at avoiding a gravy bath. It's ironic that breeding to increase the size of their flight muscles is exactly why the domesticated turkey can’t fly.

Over many generations, the domesticated turkey’s muscles have become too big to allow it to fly and its legs have becomes shorter, so it has a hard time running. In fact, they are so large and cumbersome that they can’t even mate; they are inseminated artificially in order to breed them further. Many have been bred for white plumage, so that the small pin feathers left after plucking are harder to see.

But the noble turkey (Benjamin Franklin suggested the turkey as our national bird) can trace its line back to about 1100 CE, with the Spanish entering the picture about 400 years later. But new evidence suggests turkeys were raised in captivity much earlier than either of these estimates.

A recent study based on excavations of Mayan ruins shows that as early as 300 BCE there were male, female, and juvenile M. gallopava within the settlements, and some reduced flight morphology suggests that they had begun to be domesticated by that time. What is more, the native turkeys in southern Mexico were M. ocellata, not M. gallopava (from northern Mexico and America), suggesting that trade in the animals with the north had already commenced by this time period.

All this traveling suggests that by the time the pilgrims landed in Massachusetts they were already familiar with the turkey, and its inclusion in the first Thanksgiving feast was probably not a surprise to them. There is no evidence that turkey was the served at the first Thanksgiving, but it makes sense; both cultures were familiar with the bird. American Indians even had tribes named for turkeys and believed that their feathers had mystical powers; Central American Indians had turkey gods.

I find it a little odd that the turkey was revered as a god, considering its looks – that is truly a face only a mother could love. It has appendages and little growths everywhere. If a turkey spins its head around when startled, it could slap itself silly! But as nature proves again and again, everything has a purpose – or did.

You can see the differences between wild turkeys and those bred

for lots of meat. True, the domesticated version is puffed up in

a display, but he is much bigger weighing twice as much as

the wild version on average (16-50 lb.s/7.25-22.5 kg for domestic).

The fleshy appendage around the head a throat of many bird species is called the wattle. In turkeys, the wattle hangs from under the beak and down the throat, but in pheasants it is located around the eye and cheek. Another name for this structure is the dewlap, and many animals have these. Even your grandmother might have a dewlap under her chin or upper arms!

The wattle is a mark of sexual dimorphism in many birds (di = two, and morph = shape). The males and females look different in species that are sexually dimorphic. It is hypothesized that birds’ wattles are a form of ornament for mate selection. A male with a larger wattle may be seen as more fit and a may have more reproductive success. The hypothesis states that a large ornament is energetically costly, so only the strongest, most disease resistant males will be able to survive the cost of a large ornament and still live to reproduce.

In terms of the female turkey, picking a male with a bigger wattle would be the same as picking a male with stronger genes. Indeed, a 2010 study in pheasants showed that there were different immune genotypes (MHC, major histocompatibility complex) associated with wattle size. The functional difference between the different MHC genotypes is not known, but they did show a significant difference in the genotypes of males with larger wattles, and those are the more highly preferred mates, so it may also represent stronger MHC types.

But domesticated turkeys don’t worry about selecting mates or appearing healthy, all decisions are made by the breeder, so why do they still have wattles? It may be because their breeding is anything but true natural selection, but it may also be that the wattle has another function. Being highly vascularized (having many blood vessels), the wattle can release body heat by placing a large amount of blood close to the surface, thereby acting as a physiologic control.

Use this picture to memorize the parts of the turkey’s

head. Cousin Eddie asked Clark to save him the neck

in National Lampoon’s Christmas Vacation, but I doubt

that anyone ever specifically for the snood! There are

no snood recipes - believe me, I looked.

On top of a turkey’s head and down its wattle are smooth surfaced growths called caruncles. At the base of the wattle are larger growths called the major caruncles (not very imaginative). The exact function of the caruncles is not known, but they are significantly larger on males than on females, so sexual ornamentation might be one of their functions. Together, the wattle and caruncles are also a mood detector. When threatened or ready to mate, the wattle on a tom turkey will turn bright red.

The strangest part of a turkey’s head is the snood. The English word “snood” was around long before the English were aware of turkeys. It referred to a decorative hair net or bag worn by women on the back of the head to confine their hair. The resulting mass of hair does look something like the snood that hangs over a turkey’s beak, and this might be where the name came from (see below).

While many animals have wattles, and several different kinds of fowl have caruncles, the turkey is the exception in that it is the only animal with a snood. Its functions may be similar to those of the wattle and caruncles, as they are much larger in males than in females. The snood length in males is linked to testosterone levels, and males are more likely to dominate or steal food from shorter snooded (just made up that word) males than long snooded (there it is again) ones.

I haven’t found any documentation that the turkey

snood is named after the hair snood, but it makes sense.

The snood as a garment makes a comeback every 100

years or so, now they are all the rage in McDonalds and

abattoirs (slaughterhouse) –turkeys with snoods are

processed by workers wearing snoods!

But turkeys are rarely served with the head intact, and eating them is what we are most interested in at Thanksgiving. Like chickens, turkeys have both dark and white meat. The difference in color is due to the makeup of the muscles and how they store and use energy.

The red meat of mammals and the dark meat of birds are similar in that they contain high amounts of myoglobin. The muscles that have myoglobin are for prolonged use; muscles used most of the time require lots of oxygen to make lots of ATP. Myoglobin is to muscles cells what hemoglobin is to red blood cells; it is a molecule that binds and holds oxygen. In the muscle cell, the myoglobin will release the oxygen as needed to allow the muscle to make more ATP and then use that ATP for contraction.

Myoglobin is highly pigmented, so the muscles look darker (redder). When denatured by temperature, the myoglobin turns a tan to dark brown color, giving the cooked meat its look.

Myoglobin is structurally similar to hemoglobin, in that it

looks like one of hemoglobin’s subunits. Each subunit in

hemoglobin can carry one oxygen molecule, but act in

cooperative behavior; the first one is hard to bind, the

second is easier and so on. Myoglobin stores oxygen within

the muscle cell. The more you exercise that muscle, the

more myoglobin it will produce.

White meat, on the other hand, has much less myoglobin. Why? The muscles with white meat (like flight muscles) need energy in short bursts, perhaps to evade predation. To do this, they need less oxygen most of the time, but need lots of glucose some of the time. Therefore, they have less myoglobin but more glycogen (a storage form of glucose) so they can react quickly, rather than waiting for the blood to bring more glucose. The glycogen makes the cooked meat look white and glossy.

So, we have a big bird (did you know that Big Bird’s costume is made of turkey feathers painted yellow?) providing us with a big meal on a big holiday. Next week, we look at three stories of fungus-like protists. Can you believe that they are responsible for Irish priests in America and video game theory, and that they can be ranchers with hired cowhands?

Baratti, M., Ammannati, M., Magnelli, C., Massolo, A., & Dessì-Fulgheri, F. (2010). Are large wattles related to particular MHC genotypes in the male pheasant? Genetica, 138 (6), 657-665 DOI: 10.1007/s10709-010-9440-5

Thornton, E., Emery, K., Steadman, D., Speller, C., Matheny, R., & Yang, D. (2012). Earliest Mexican Turkeys (Meleagris gallopavo) in the Maya Region: Implications for Pre-Hispanic Animal Trade and the Timing of Turkey Domestication PLoS ONE, 7 (8) DOI: 10.1371/journal.pone.0042630

For more information or classroom activities, see:

Sexual dimorphism –

www.bio.indiana.edu/community/faculty/ICE.../Selection-All.pdf

http://www.enotes.com/sexual-dimorphism-reference/sexual-dimorphism

http://www2.nau.edu/~bio372-c/class/behavior/lesson1-1-1.htm

http://scienceblogs.com/tetrapodzoology/2008/07/17/bird-bills-sexual-dimorphism/

http://www.bbc.co.uk/nature/adaptations/Sexual_dimorphism

http://animals.about.com/od/zoology12/f/sexualdimorphis.htm

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&ved=0CEwQFjAH&url=http%3A%2F%2Ffall2009bsc307.wikispaces.com%2Ffile%2Fview%2F11th%2BGrade%2BLesson%2BPlan-Martinelli.doc&ei=mfqXUMi2Bc-30AHR24GoCA&usg=AFQjCNE0O1piSijdgE-k9_YJaQR7_SzFTg

http://www.ck12.org/book/Biology-I---Honors-%2528CA-DTI3%2529/r2/section/25.1/Reproductive-System-and-Human-Development-%253A%253Arev%253A%253A-1-%253A%253Aof%253A%253A-Biology-I---Honors-%2528CA-DTI3%2529/

http://www.bioedonline.org/slides/slide01.cfm?tk=60&dpg=5

http://www.agfc.com/education/justForEducators/Pages/lessonPlanDetails.aspx?show=114