The mutants of key west
The wild flocks of rock pigeons on key west might look like any other at first sight. however, I was able to find 4 unique mutations among the flock I studied that could be found no where else in my study area.
The rate of physical anomaly was very high in this population. Out of 31 birds studied, 3 had some sort of visible odd mutation. this gives us a rate of mutation of 9%. in a typical situation, the rate of random mutation should be around 1%.
Compare this with a study done on a certain population of barn swallows, where around 8% of adults had some sort of non- albinism related anomaly. This was remarked to be high, but this study is special.
why?
Because these barn swallows where living in the highly-radioactive Chernobyl exclusion zone.
The feral pigeons of key west have vituraly the same non-albinism related mutation rate as birds living in Chernobyl .
let that sink in for a second.
If we are counting albinism related anomalies, the birds I caught in key west only had an albinism rate of 12%, while the Chernobyl swallows had one of 17%. However, New York city pigeons have a rate of albinism rate at 46%, but release of selectively bred birds might also be at play here, so the comparison is not quite fair.
So what do these Key West mutants look like?
why don't you come and meet them!
SIC: KWP3
mutation type: crest
We did not catch KWP3, but even at a distance, it was clear this bird had a mutation. although not much of a crest, the small ruff on the back of this bird's neck is considered a "crest" and unlike many other pigeon mutation, is well understood.
Unlike many other traits, "crest" is caused by a mutation of a single gene. Even within this gene, the mutation is extremely simple, called a missence mutation, the base pair Guanine-Cytosine in the-non crested allele is replaced by the base pair Adenine-Tymine is the crested one.
when translated into a protein, the crested allele produces the amino acid cystine where the non-crested allele creates Argnine.
This change in one amino acid creates a different protein. Because of this, the protein-receptor that is supposed to pick up the no-crest protein (EPHB2) can not, an the signal for "no crest" is never transmitted. because of this, the feathers of an embryonic pigeon with this mutation begin to grow "backwards" instead of having tips pointing towards the pigeon's tail like the rest of the bird's head feathers, these feathers have tips that point towards the head, creating the crest.
This mutation is not just found in rock pigeons, in captivity, similar crests are seen on African ringneck doves. It is believed that a similar genetic pathway to crests exists in pigeons and doves. However, at my tapping site, I found a Eurasian collared dove with such a feature. I have never heard of Eurasian collared doves having crests, and this may be the first recorded case of such a bird.
SIC: KW11
mutation type: eye color
Eye color in pigeons is not as well understood as crests. what we do know is pigeons have three main iris colors: orange (color ranges from red to yellow) pearl, (color ranges from pink to white) and bull (dark gray to black).
We know that orange and pearl are different versions of the same allele, with orange being dominant and pearl being recessive.
the gene for bull eye is linked to the gene for white plumage, but that's all we know about it.
Other colors do exist, but are rare, so you can imagine my surprise when I pulled a bird with orange and green eyes from the net.
Green eyes are rare, so much so that many professional pigeon racers admit to have never seen a living bird with green eyes.
When green eyed birds are produced in captivity, the parentage is often noted. In one case, a breeder hatched a clutch of 75% green eyed birds from a yellow-orange eyed mother and and a true orange eyed father.
The breeder then took one of these chicks and bred it with a pearl eye. It produced all green-eye offspring. When two orange eyed chicks from a clutch of birds with one orange, one green parent where bred, they produced all green eyed chicks.
Green eyes are weird, and may not be understood for a while.
SIC: KW28
mutation type: eye color
This bird's eyes might look normal at first. however, on closer examination, this bird had dark spots on its iris. Because this bird REFUSED to look at the camera durning it's documentation, I made a quick drawing of what its eye looks like from straight on.
My best guess as to what caused these black spots is another eye color mutation, this one called "split eye".
Like green eyes, split eyes are not well understood. Some people guess that split eye is caused by a mutation that hinders normal embryonic migration of eye pigment cells, but this has not been proven. Like other rare pigeon eye colors, split remains enigmatic.
SIC: KW16 "sir soggybottom"
mutation type: uropygial gland failure
If you read my last lab note, you may be familiar with KW16, or "sir soggybottom". If not, or you just need a reminder, KW16 was found sitting on a rock during a heavy rainstorm. When other pigeon flew away, KW16 still sat on his rock until I was able to catch him, unable to fly, with a handheld net. After a wile of holding (about an hour) KW16 was released and able to fly short distances again. The next day KW16 was seen flying like any other pigeon.
What I believe KW16 from flying while wet was an absence or malfunction of an interesting part of bird physiology called the uropygial, or preen oil, gland.
In a normal bird, outer feathers are nearly 90% waterproof. This is because of the structure of feathers that prevents water entry, and a special oil that is put on feathers during preening. This oil is produced by the uropygial gland, near the base of the tail, and is why a preening bird may appear to peck it's own tail. birds need dry feathers to fly, otherwise they are far too heavy to get off of the ground. Their wing and tail shape is also modified by being soaked, because of this they are not able to produce enough lift to fly when wet.
Although this oil is often considered essential to how birds live (keeping feathers waterproof to prevent heat loss), entire species may not have it. For instance, woodpeckers use a powder to keep their feathers dry, while many flightless birds with simple, fur-like feathers (ex, emus) have no need of such an oil.
Most rock pigeons do have this gland, however, it is known to be absent in some domestic breeds. Among pigeon keepers, it is believed that any bird with 14 or more tail feathers has no oil gland, but birds with fewer tail feathers may also lack the gland. I did not do a tail feather count on site, but looking at the photo, KW16 may have 14+ tail feathers.
Because KW16 was clearly non-waterproof and may have 14+ tail feathers, he most likely is one of the birds missing its oil gland.
Like the wild rollers of Boston, a pigeon without an oil gland living in the wild should have a hard time surviving. However, KW16 was a perfectly healthy bird other than his flight issues, and was see bonded to another bird of more normal waterproofing capabilities.
Pigeons are able to do a lot of things they aren't technically supposed to. If pigeons did not exist, and someone where to tell me that a middle eastern cliff-specialist bird would someday colonize tropical islands in the new world, I would have been a bit suspicious. in spite of all odds, pigeons have seemed to do the impossible......
I can't find a line to end this lab not without being cheesy or cliche, so i'm just going to leave it like this.
here are the sources I used if you are interested:
barn swallow study: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1994720/
the Shapiro lab: https://learn.genetics.utah.edu/content/pigeons/
account of breeding green eyed pigeons: http://media.genetikaholubu.cz/newsletter/email_pigeon_genetics_newsletter_2016_11.pdf
extra genetic info: http://mumtazticloft.com/default.asp
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