Showing posts with label animals - birds. Show all posts
Showing posts with label animals - birds. Show all posts

Sunday, April 23, 2017

Apple #743: How Do Birds Sing?

I have to be honest. It isn't just the insanity that has accompanied the new president that has thrown me off my Appling horse, it is also my job.  I have a (relatively) new boss, and he has changed a ton of things about our department, and my workload has tripled.  Where I used to be able to finish all my work ahead of schedule and under budget with great attention to detail, now I am scrambling just to complete all the tasks I'm responsible for.  Most days I leave work late, exhausted, and dissatisfied because I have to leave things incomplete.  I haven't had much time or energy left over for much else.

This past week was an especially grueling one.  I was working on one project that I knew would be complicated.  Most projects of this kind typically take me about 5 hours.  I expected this one to take me a day, maybe day & a half.  It took a week and a half total, the final 3 days of which I spent solely and completely on it with my entire attention for a solid 8 hours, or 9 hours, or 10 hours.

At the end of one of these days, I was staggering out of my building and the sun was going down, but I was pleased because most of the time when I leave work it is dark.  I had that weird floating feeling you get when you've had insufficient sleep for a long time, and as I walked to my car, I was staring at the clouds edged with the peach of sunset and the vivid green of the grass and the potholes in the asphalt as if I had never seen any of them before.



The clouds on that evening looked something like this, though they were smaller than this. As we learned in my Sunsets entry, no two sunsets are alike, from one location to the next, from one day to the next.
(Photo of sunset over Sydney, Australia, from Wikimedia Commons)


When I got to my parking lot, I heard a bird singing.  There is a strip of grass in between two great expanses of asphalt and along this strip of grass is a row of pine trees trying valiantly to keep growing in spite of being surrounded by almost nothing.  I don't know what kind of trees these are, actually.  They look a lot like conifers, but they lose their needles in the fall and the whole concept of deciduous conifers just confuses me.  Because their needles turn brown and fall off, they look sickly most of the time.  Maybe they really are.

But it seems as though they are trying to make some sort of comeback with the spring. They are sprouting some new needles that are that very bright yellow-green of new leaves and they look soft and not stiff & pointy yet.  They are still sparse, though, so you can see the entire shape of the tree like a skeleton.



Maybe the trees in question are European larches -- one of a very few deciduous conifers.
(Photo from Go Botany)


At the very top of one of these trees sat a bird and it was singing and singing and singing.  I couldn't tell what sort of bird it was because the light was behind it so it looked like a dark shape up there.  But its song was complex, liquid, carrying, and beautiful.  It sang a series of songs, like maybe 4 patterns, then paused.  Then it sang another series of 4, but slightly different than the first 4, variations almost, then paused again.  It did this over and over, but each series I heard was different.  No pattern was exactly the same , though some of the sounds were repeated, like the way the letter "y" sounds one way when attached at the end of a word but another way when you put it at the front of a word.

To my exhausted, drained ear, it sounded beautiful and delicious.  It felt physically good to listen to it.  I wondered if I could make it my job to listen to birds' songs all day, recording their patterns.  Probably this is someone's job already, to listen to birdsongs.

I also wondered, how do birds do that?  They are such little things, how do they make a song so complex, that sounds like water bending around a curve?  Tell me more about how birds sing.

Name That Bird

  • I tried to figure out what kind of bird I heard.  The Smithsonian has a wonderful Guide to North American Bird Songs that helps you narrow down the possibilities by choosing among major identifying factors, such as whether the song has one note or two or more than that.
  • I answered several questions and got to a final list of 15 birds it could have been.  Listening to the sample clips of each one, I suppose it could have been any one of them.  It might have been a robin, or some kind of thrush, but I have never heard any robin sing quite like that before.
  • It also might have been an indigo bunting. According to the Cornell Lab of Ornithology, this bird likes to sing in the very tops of trees, and the bird I heard was doing exactly that. It's the males who sing, and they like treetops or shrubs, especially in places where shrubby roadsides meet forests.  They sing to find a mate, defend their territory, or for other reasons unknown.




  • I'm not entirely convinced it was an indigo bunting, though, because the two birds in the video above include some rough almost growly notes, and the bird I heard did not do that.  But maybe the bird I heard was different from its fellows in that way.  Birders say that birds from different parts of the country have slightly different songs, the way people have different accents in different parts of the country.


How Do They Sing Like That?

  • Birds can sing in ways that people can't because their equipment is different.  Where we have a larynx (voice box) at the top of our throats, birds have a syrinx which is situated farther down the windpipe, in their chests.
  • For us, the windpipe below the larynx meets up with the bronchial tubes which branch into two and connect to the lungs.  For birds, the syrinx is closer to the lungs, and where our larynx has one chamber, their syrinx has two.  With two chambers instead of one, naturally birds can make many more sounds than we could and they can do more complex things with the sounds, such as making two happen at once.
  • Here's another way in which the birds have us beat: we use only 2% of the air passing through our larynx to make sound. Birds use 100% of their air going through their syrinx.


A sort of big-picture diagram showing the basics of the two-chambered syrinx and where it is located within a bird
(Diagram from Heather's Site of Birding Basics)



A more zoomed-in view of the syrinx, showing the trachial and bronchial rings which line the trachea and bronchial tubes respectively, and which help create various sounds. The two red blobs on either side of the two tubes, labeled the lateral labia, are bumps of muscle, I think, which constrict the tubes or open them, and that also creates variation in sound. They can regulate volume as well as pitch.
(Diagram from Biology 342 course materials at Reed College, adapted from another source whose page is now defunct)


The Cornell Lab of Ornithology has this wonderful interactive page showing how the syrinx works and what it is doing during the songs of particular birds.  You must investigate this. Watching the interactive pages will give you a much better idea of how the whole mechanism works than any description of mine could.

But let me quote from this rather poetic passage from the British Library which explains how birds sing, and also, well, see for yourself:

As air passes, so an acoustic disturbance is set up, the tympanum vibrates and sound is created. The pitch (frequency) of that sound and the loudness (amplitude) of it can be modulated. So far as the tympanum is concerned, these two effects are usually coupled. The function of the extendable little "bump" is believed to be to change the loudness without having to change the pitch. Bear in mind that the bird may be playing at the same time a second tune on his other half; also that this description is considerably simplified. It will be clear, however that such complexity is necessary to explain the amazing vocal gymnastics certain "higher" songbirds display. "Lower" birds have a syrinx that is of a rather simpler design. In either case the physiology and acoustics of bird vocalisation are unique in the animal kingdom; further, birds produce more complex sounds than any other animal, certainly including man.

One last point: birds do not sing only when inhaling. A grasshopper warbler Locustella naevia may "reel" for over two minutes, a nightjar may chur continuously for eight minutes, and a skylark may "pour forth its full heart" in completely unbroken song for 18 minutes. To replenish their oxygen these birds must breathe in; and must do so while singing. In the case of the night jar, the bird discernibly alternates soft short trills with loud long ones and these short trills are believed to be when the bird inhales. Less continuous singers may also use air travelling in either direction. The white-rumped shama, for example, is believed so to do. (British Library)

What about Owls?

A remark in that British Library passage reminds me that I'm also curious about owls.  On other occasions, in a forest where I like to hike, I have heard barred owls hooting.  But that word "hooting" sounds really tame compared to the sounds I've heard.  The barred owl's call is typically rendered as Who cooks for you? But what I have heard was really frickin' carrying and echoing and loud.  Like you could hear this call from two miles away.  And usually it's more like Who cooks for yooooooooooou?

I have tried to duplicate this call, and every now and then other people walking in the woods have tried to call back to an actual owl. But it doesn't even come close to how full-throated the owl's call is.  Ours sounds like a weak imitation while theirs sounds like it comes from inside a barrel and gets broadcast through a megaphone.

In that British Library passage, I wonder if owls are one of the "lower" birds whose syrinx is less complex than the songbirds'.  Because for all the volume and timbre of the owl's call it is not as complex as a songbird's song.  The barn owl cannot even hoot or call as other owls do; it makes more of a rasping noise.

I couldn't find much information about owl syringes (plural of syrinx; gotta love Latin). Apparently they are not as interesting as the voice boxes of other birds.  But I did find some videos of owl calls.

Here's a video with recordings of barred owl calls.  I don't think you get the sense of volume, but imagine that this recording was made about a mile or two away from where the owl is roosting.





Now here are some calls of several different types of owls. What I love about this and about the barred owl calls above is the variety of voices. Not only do the calls sound different from one species to the next, but they sound different from one individual owl to the next.




Parting Thoughts

Just as no two sunsets are alike, possibly no two birds' songs are alike.  Though birds can sing way better than people can, they are like people in that each bird's voice is unique.

So I may never again hear a bird's song like what I heard the other day.  But I may hear another song some other day that is even more wonderful.




Maybe what I heard was actually a robin. Everybody thinks they're so common, and they are, but I do love them. They remind me of long, good summer days when I was young and spent most of the day playing outside and the sun has gone down and I'm lying in bed, tired in a good way, being lulled to sleep by the soft breeze from the fan, while outside, the robins are singing their good-night songs. No better lullaby.


Sources
Cornell Lab of Ornithology, Indigo Bunting
Audubon, Indigo Bunting
The Guardian, Mystery bird: Indigo bunting, Passerina cyanea
British Library, The language of birds 6. How does a bird sing?
Wingmasters, Who Gives a Hoot -- and Who Doesn't
Frank B. Gill, Ornithology p 223

Tuesday, January 20, 2015

Apple #698: Albatross

I heard someone on the radio say that albatrosses mate for life.  Which, it occurred to me, means that an albatross is saddled with another albatross for life.

Ba-dum ching.

Seriously, folks.  I did want to know more about these not-mythological birds in general, and I also wondered where that idea of an albatross as a terrible thing you're stuck with all your life came from.  Did it originate with old Samuel T., or was it in the lore before he wrote it down in his Rime?

But first, of course, this:





THE POEM


  • Yes, it seems that the idea of an albatross as a burden one can't get rid of originated with the Rime of the Ancient Mariner.
  • Here's the deal.  When the albatross first shows up, following the ship, the crew take it as a good omen.  And good things seem to happen while the albatross is with them.
At length did cross an Albatross,
Thorough the fog it came;
As if it had been a Christian soul,
We hailed it in God's name.

It ate the food it ne'er had eat,
And round and round it flew.
The ice did split with a thunder-fit;
The helmsman steered us through!

And a good south wind sprung up behind;
The Albatross did follow,
And every day, for food or play,
Came to the mariner's hollo!

In mist or cloud, on mast or shroud,
It perched for vespers nine;
Whiles all the night, through fog-smoke white,
Glimmered the white Moon-shine.
  • Then the wedding guest asks the Mariner, well, if that was all so good, why the long face?  And the Mariner says: 
With my cross-bow
I shot the ALBATROSS.


Engraving by The King of Engravings, Gustav Doré
(Image hosted by the University of Adelaide)

  • No good comes of this, of course. The wind drops, the sun gets hotter than blazes, and everyone says it's the Mariner's fault.
And I had done a hellish thing,
And it would work 'em woe:
For all averred, I had killed the bird
That made the breeze to blow.
Ah wretch! said they, the bird to slay,
That made the breeze to blow!
  • Then you get the most famous and best-est lines:
Water, water, every where,
And all the boards did shrink;
Water, water, every where,
Nor any drop to drink.

The very deep did rot: O Christ!
That ever this should be!
Yea, slimy things did crawl with legs
Upon the slimy sea. 
  • It gets even worse.  They have no water to drink so they finally have to bite their arms to moisten their mouths with their own blood.  Then DEATH shows up and the whole crew, one after another, drops dead.  Plunk, plunk, plunk.
Four times fifty living men,
(And I heard nor sigh nor groan)
With heavy thump, a lifeless lump,
They dropped down one by one.
  • The Mariner, however, does not die.  Terrible as it is floating around on this ship full of dead guys, he does not die.
  • But then he sees some water snakes, and he thinks they look beautiful, their colors and how they swim across the water.  Delighted by their beauty, 
A spring of love gushed from my heart,
And I blessed them unaware:
Sure my kind saint took pity on me,
And I blessed them unaware.

The self-same moment I could pray;
And from my neck so free
The Albatross fell off, and sank
Like lead into the sea.
  • Later, he has a vision in which he hears two voices talking about him.  One of them says, basically, "Is this the one?" and the other one says, "Yeah, this is the jerk who shot the 'harmless albatross.'"  They say he's done penance for this deed, but he's got more penance still to do.  More bad things happen on his ship, which winds up sinking, and he asks to be forgiven for his sin of killing the albatross, but basically he's condemned to tell his story for the rest of his life.

OUR CONCEPT TODAY


  • Really, it isn't the albatross itself that is hanging around the Mariner's neck.  It is his sin of killing the bird that haunts him. 
  • But that's not how we remember it.  We think of it as the albatross itself that is the burden one cannot shake.
  • That's very unfair to the bird.  And very much not in keeping with the moral of the poem:
Farewell, farewell! but this I tell
To thee, thou Wedding-Guest!
He prayeth well, who loveth well
Both man and bird and beast.

He prayeth best, who loveth best
All things both great and small;
For the dear God who loveth us,
He made and loveth all. 
  • The Mariner abjures us not to kill or curse beasts but to love them, and to love human kind as well. 
  • So, going around essentially using the name of "albatross" as an insult is not quite in keeping with the spirit of the poem.  Maybe that's why the Mariner has to keep telling his dag-goned tale.  Because we refuse to get it right.  We keep blaming the albatross.

THE BIRD


With the Mariner's injunction in mind, what are some useful things to know about the bird itself?

  • Albatrosses have the longest wingspan of any bird: up to 11 feet.
  • Think about that for a minute.  Their wingspan is as long as two men are tall.

This kind of gives you some idea of the size of an albatross' wingspan.
(Photo from Wallpaper Abyss)

Or this photo might give you an even better indication of the bird's overall size.  They are not small.
(Photo from zoochat)


  • With that huge wingspan, they can glide for hours without moving their wings once.  
  • Since they're gliding, and they don't have to flap their enormous wings, they can glide and glide and glide for hours without landing to take a rest.
  • This type of gliding has a specific name: dynamic soaring.  If you want to know the physics involved, check out this article from IEEE.  Yes, aerospace engineers are studying the albatross.
  • Researchers speculate that they fly while sleeping.  Yes, with their eyes closed.
  • They drink salt water.
  • They can do this because they have a special gland that filters out the extra salt in their blood, and then the salt is excreted through some tubes in the bill. 
  • They also have a powerful sense of smell.  This is what guides them to food sources that can be swimming up ahead for hundreds or thousands of miles.
  • They prefer the ocean and stay at sea for years at a time.  About 5 months after they are hatched, they spend the first five to ten years of their life at sea, without ever coming to land.
  • The main reason they do land is to find a mate, do the deed, lay one egg, and the pair take turns looking after it until it hatches.  Once the chick is old enough to fly, they all take off and don't see land again for maybe as long as a decade.
  • Cornell, which is where all the bird specialists are, hesitate to say that albatrosses mate for life.  They go only as far as to say they "form very long-lasting pair bonds." 

A pair of albatrosses looking after their chick.
(Photo from Wallpaper Abyss)



Albatross in flight
(Photo from RSPB.org.uk, an organization working to conserve the albatross. Check out their site to find out how you can help.)

  • There are actually 22 species of albatross.  All are threatened, some are endangered, some are critically endangered. 
  • Most live in the Southern Hemisphere, around Antarctica, Australia, South America, and South Africa.
  • 3 species live in the North Pacific, around Japan, Hawaii, Alaska, and California.
  • Albatrosses eat squid, crabs, shrimp, krill and fish, but researchers recently discovered they also eat another kind of animal.
  • There are these bizarre-looking gigantic fish called ocean sunfishes.  They get to be over 3 meters long and they weigh one or two tons.  They hang around on the ocean's surface, eating whatever wanders by.


This, by the way, is an ocean sunfish. Weird-looking thing, isn't it?  This one lives in an oceanarium in Denmark.
(Photo from Advanced Aquarist)

  • But unfortunately they get parasites. Crustaceans that latch onto the fish's body and do their icky parasitic thing.
  • A few years ago, a bunch of Japanese researchers observed a school of sunfish all headed in the same direction.  And they figured out they were following the path of an albatross flying above it.  They couldn't figure out what for.  
  • Then the albatross flew down and picked a crustacean off one of the fish.  While the albatross was bobbing in the water, enjoying its crunchy lunch, other fish swam up next to the albatross and sort of showed off its side, as if to say, "Here's another one; eat this one."
  • Researchers hesitate to say that this is a thing lots of albatrosses do on a regular basis -- they haven't seen enough evidence of many albatrosses doing this in many places at many times -- but they are intrigued enough to wonder if this is a habitual thing, and if the albatross might be helping out other fish in similar ways.
  • For these sunfish, having an albatross hanging around seems to be definitely a good thing.
 
If you want to see albatrosses live & in the flesh, Cornell's Lab of Ornithology has an albatross cam.  It's not up at the moment, but they say it will be soon, when the mating season starts.  Check Cornell's page that lists all their bird cams.


I've saved the best for last.  How could anybody shoot anything this fuzzy?
(Photo from Cutest Paw)


Albatross!


Sources

Samuel Taylor Coleridge, The Rime of the Ancient Mariner, (reproduced at Poetry Foundation)
National Geographic, Albatross
Cornell Lab of Ornithology, FAQ: Bird Cams - Laysan Albatross
Darren Nash, Scientific American Blog, Tetrapod Zoology, A symbiotic relationship between sunfishes and . . . albatrosses? Say what? February 1, 2012

Monday, December 1, 2014

Apple #691: Why Duck Feet Don't Freeze

The other day I was walking in a park near my house.  This park has a pond with a fountain to keep the water aerated, which in the cold weather also keeps it from freezing as quickly as it might otherwise.  Ducks love to hang out in & around this pond -- mallards, mostly, but also those larger, darker-feathered ducks, and Canada geese (note: Canada, not Canadian).

It was a super-cold day, probably about 21 degrees.  I was all huddled up in my winter coat & scarf & gloves & hat, and there were the ducks, paddling around in the freezy-cold water, not a single coat or hat or glove on 'em.  Some were standing along the shoreline, a few with one foot tucked up in their feathers, but most of them had both feet on the icy ground.



Ducks standing on the ice, letting the freezing-cold water lap over their toes, paddling in that frigid water -- no problem.  If you're a duck.
(Photo from Eco Habits)


I have seen this for how many winters now?  But this time around, it struck me: those ducks have nothing on their feet.  No feathers, no insulating fat, no socks, no sheepskin-lined boots, no nothing.  And they're paddling their naked orange feet in that freezing cold water like it's no big deal.

How can they do this without those little flappy orange feet freezing?

Answer: Duck feet are marvels of bioengineering, exemplifying the principles of heat exchange.



Duck feet.  Simple genius.
(Photo from io9.com)

  • It's true.  Duck feet have no extra insulation, no waterproofed feathers, no extra layer of fat.  If their bodies worked as ours do, which decrease blood flow to the extremities when it gets cold, ducks would be up a creek in a hurry.
  • Fortunately for them, duck anatomy is not like human anatomy.  Their bodies are equipped with special capabilities that ours are not.
  • First of all, the innards of duck feet are almost entirely tendons.  There's very little musculature, or much of any fleshy stuff at all.  They're pretty much all skin, bone, & tendon.  So there isn't much stuff in there that has to be kept warm.
  • Oh, right, there's something else in their feet: blood vessels.  Arteries & veins.  You will remember from your biology class that arteries carry fresh, warm, oxygenated blood from the heart to all the parts of the body, and veins carry the used, cooler, less oxygenated blood back to the heart for rejuvenation.  Ducks have arteries & veins just like we do, only they have a whole mess of 'em in their feet.

  
The intermeshing of arterial & venous blood vessels is called "retia" which means "wonderful net." The large panel in the third row on the left of this cartoon depicts retia.
(Cartoon from sci-ence.org)

  • Specifically, the arteries & veins in ducks' feet are so closely intermeshed, their many arterial capillaries are cozied up close to their equally multitudinous venous capillaries.  This artery-vein closeness is happening all down their legs & throughout their flappy feet.
  • The reason this is important is because of that engineering phrase I used earlier: heat exchange.
  • The simplest way to describe heat exchange is to say that if you put a warm thing next to a cold thing, the warm thing will heat up the cold thing.
  • For example: your feet are cold, so you put them on the much warmer feet of your spouse/partner/best friend/dog, and though your sig. oth. may shriek at first, eventually, some of the heat from the sig. other's body will transfer to yours, and your feet will warm up.
  • There is a kind of heat exchange particular to fluids, which is called countercurrent exchange.  The same principle of heat exchange applies, in that the warm thing next to the cold thing transfers some of its warm to the cold thing.  The main difference in countercurrent exchange is that it's all about fluids.
  • (I wanted you to have these big science words mainly so you could say to people at parties, "Did you know, ducks keep their feet warm using the principle of countercurrent exchange?")
 
The warm fluid on the left could represent the warmer arterial blood descending down to the duck's toes.  The cooler fluid on the right could be the cooler venous blood going back up the duck feet to the heart.  The proximity of the two results in the arterial blood cooling as it descends while the venous blood is warmed up.
(Diagram from Wikipedia)

  • That intermeshing of multitudinous arterial & venous capillaries means the duck's blood vessels are really making the most of countercurrent exchange, letting it happen as much as possible throughout the duck's legs & feet.
  • While some of the heat from the arterial blood is transferred to the venous blood, the venous blood also cools the arterial blood on its way down.  
  • The result is that while the body of the duck may be around 100+ degrees Fahrenheit, thanks to its layers of fat & downy feathers, their feet will be pretty dang cold: only slightly above freezing.  
  • But that's warm enough, and the ducks are fine with that.


(Photo from CopyPasteRepost) 


P.S. Lots of animals use this principle of countercurrent exchange: most species of waterfowl have it in their feet, whales and sea turtles and other deep sea dwellers use it in their flippers, and cold-dwelling mammals such as arctic foxes and polar bears use this in their feet, too. Fish also use this principle, not to stay warm but to transfer oxygenated water from their gills to their blood.  Desert animals such as kangaroo rats and salt-water-dwellers like seagulls use this principle in their nostrils to conserve fresh water.  We also use this principle in our kidneys to remove water and build up urine, which we then get rid of as necessary.


Sources
Ask a Naturalist, Why Don't Ducks' Feet Freeze?
Beyond Penguins and Polar Bears, How Do Birds Stay Warm?
Bird Watcher's General Store, Duck Feet Do Not Freeze
Dandy Designs, Duck Feet
The Naked Scientists, Why don't ducks get hypothermia?
Encyclopedia of Earth, Counter current exchange

Monday, May 26, 2014

Apple #673: Mallard Ducklings

I hope you all had a lovely Memorial Day weekend.  I just participated in a mallard duckling rescue.



Mallard duckling. The fuzziness of these things is unreal.
(Photo from Postcards from Sussex)


I was walking around the park near my house when I heard all sorts of peeping.  It was getting near twilight, and I caught sight of a little bird in the grass that I thought at first was a sparrow.  But it was moving differently than that, sort of side to side, and then I realized it was a mallard duckling.  A little fuzzy thing, no adult ducks in sight, and it was walking around fast as its tiny little legs could carry it, peeping away like mad, clearly trying to find its parents.

Then it motored its little legs under a parked car.  Which turned out to have a person sitting in it.  She saw me looking under her car, so I told her a baby duckling had just run underneath it.  The woman immediately froze, even though she wasn't driving, didn't even have her car turned on.  She was asking me, "Is it still under there?  Is it still there?"  Every time the little duckling caught sight of me, it would run back under the car and hide next to one of the wheels.



Duckling on the water, where the little one I found probably would prefer to be.  Again, with the fuzziness.  It might be the fuzziness that makes people immediately protective of them.
(Photo by HAZY at RSPB)


Finally, it ran out the other side of the car away from me, across the parking lot, and toward the street.  I pointed out to the woman that the duckling was out from under her car, then followed the duckling to try to keep it from running out into the street.

I kept trying to get on the other side of it, to drive it back away from the street and in the direction of the duck pond.  I don't know if that's where it's parents were, but that's probably where the duckling would stand the best chance of finding them.  But the duckling kept running away from me, still peeping like crazy the entire time.

It ran into the grass, and then along came two dogs followed by their owner.  The dogs were very interested in the fact that I was walking slowly through the grass--clearly stalking something--and it was very hard to see by this time, so I don't think they knew the duckling was there.  The man asked the dogs, "What are you so curious about?"  I told him, "There's a little duckling here.  I'm trying to get it to go to the pond."

Immediately the man understood.  He got on the opposite side of the duckling and tried to close off the duck's exit to catch it.  One of his dogs went forward to get involved, but he pushed the dog out of the way.  The duckling was getting tired, but was still peeping like fire alarm.  The man got his hands on the duck but it wriggled out and ran toward me.  I bent down to scoop it up, and I almost had it.  The duckling was in my hands for not even half a second before it slipped out of my hands and kept running.

Another try, and the man got the duckling in both his hands, the duckling poking its little head out as far as it could to try to get free.  We thanked each other, and he went off toward the pond, carrying the duckling up next to his face, his dogs following, and I went on my way.



You know how you've always imagined that duckling down must feel completely soft?  Well, you've imagined absolutely right.
(Photo from Gower Bird Hospital, sourced from Barbelith)


I've already done a Daily Apple about Mallard Ducks, but I thought I would find out a few things about just the ducklings.

  • A mother duck will not abandon her young if a human touches them.  However, if you come upon a duck family, it's best to keep your distance so you don't scare off the mother.  The ducklings can easily get separated from each other, which may have been what happened in this instance.
  • Usually about 9-13 ducklings, or chicks, are born in one nest.  
  • Predators, accidents, bad weather, and getting separated from the mother usually reduces the number of ducklings that survive by at least half.


This mother duck hatched 14 ducklings.  Eight weeks later, her family was down to 6.
(Photo from Words4It)

  • Ducklings are born with their eyes open.  Ducks have excellent color vision.
  • Ducklings can leave the nest within hours of hatching.  They have a full layer of down to keep them warm, so once they're hatched they do not need to return to the nest to keep warm.  
  • So it is possible for ducklings to survive without their mother, but they stand a much better chance of getting enough food and taking care of themselves if they stay with her for the first 5 weeks or so.


A whole lotta ducklings = a whole lotta fuzziness.
(Photo from Gobirding.eu)

  • They are also born able to swim, but they lack the oil gland called the "preen gland" that produces the oil necessary to waterproof their feathers.  The mother will collect oil from her preen gland and spread it over their down.
  • (By the way, when you see adults ducks standing on the shore going over their feathers with their beaks, they are spreading the waterproofing oil over their feathers, as well as removing any bugs or unfriendlies that might be in there.)


This isn't exactly learning to fly.  It's more like, You can jump and you'll be all right.

  • Ducklings eat mainly seeds and bugs or the larvae of bugs, as well as seaweed and other plants that grow in the water.
  • Ducklings learn to fly at 5-8 weeks old, some say.  Others say the flight lessons don't start until 10-12 weeks.
  • Ducklings look about the same, regardless of sex, for quite a while.  As they leave the fuzzy downiness of ducklinghood, their feathers become the camouflaged brown similar to an adult female's.  It's not until around 14-16 weeks that the males' feathers change and turn into the shiny gray and green.


These ducklings are in the process of trading their fuzzy down for feathers.
(Photo by Derek Stoner at The Nature of Delaware)



Mallard ducklings, about 8 weeks old.  I'd call these teen-agers, or young ducks.  You know, like young bloods.
(Photo from Words4It)

  • One last fact: ducks are never completely asleep.  They often sleep with one eye open, especially if they are on the outer edge of a group and must keep watch.

Sources
Animal Corner, Ducks
Metzer Farms, Mallard Ducks
Mallard Ducks as Pets
Cornell Lab of Ornithology, Mallard
National Geographic's Mallard Ducks
Lakeside Nature Center, Critter Corner--Mallard

Sunday, May 19, 2013

Apple #635: Turkey Vultures

The other day, as I was driving away from a friend's house out in the country, I saw two gigantic black shapes up in a tree.  They were so big, I thought they couldn't be birds, they must be black trash bags caught in the tree or maybe someone had put statues of owls up in the tree to scare away the woodpeckers.  But when I looked again, I realized they were actually birds.  They were so enormous, I knew they had to be turkey vultures.

I stopped, turned around, pulled over to the side of the road, and took pictures using my handy built-in zoom lens. They didn't move, and they looked so bizarre that, even though I was looking at them through my camera, I doubted for a moment that they were real.  They looked like statues, or somebody's bizarre idea of what clown-birds from outer space might look like. Then they moved.  It kind of spooked me.



A pair of turkey vultures (a.k.a. clown-birds from outer space)
(Photo by the Apple Lady)


Basic Facts & Identification

  • Turkey vultures can be anywhere from 25 to 32 inches long, or roughly 2-1/2 feet long.  That's just slightly smaller than a bald eagle.
  • They have a wingspan of 6 feet.  That's right, their wingspan is as wide as a man is tall.
  • For all their size, they only weigh about 6 pounds.  I guess that's part of being a bird and having those special bones that are hollow enough to allow for flight.
  • You most often see turkey vultures flying up in the sky.  They look big enough to be a hawk or an eagle, but you can tell they're turkey vultures by a number of traits:
    • They tend to wobble or teeter as they soar. They're either trying to catch thermals and get a better lift, or trying to catch scents.
    • The undersides of their bodies are black but their tail feathers are white, so if you see a distinct dark vs. light coloring on the underside, it's probably a turkey vulture.
    • Sometimes even though they're up in the sky, you can make out the red head.

 
The light vs. dark coloring on the underside of the turkey vulture might be the most obvious identifier.
(Photo from the Cornell Lab of Ornithology)

Don't They Eat Dead Things? And Isn't that Gross?

  • Turkey vultures eat carrion -- the flesh of dead animals and birds.  A lot of people think they're scavengers that pick off the food that other animals have killed, but most of the time, they are the first to arrive on the scene where an animal has died, whether the animal was hit by a car, or succumbed to disease, or was injured and managed to get away but died later.
  • Turkey vultures are so quick to arrive because they have an extraordinarily powerful sense of smell.  When they're up soaring above the canopy of the trees, they can detect the minutest scent of carrion coming up from the ground through the trees into the sky.
  • Because they eat the flesh of dead animals, most people think vultures are ugly, or undesirable, or a bad omen.  But they are, as Hagrid would say, "dead useful."  Not only do they take care of dead animals -- something most of us wouldn't want to do -- but they have really remarkable immune systems.  Most of us avoid dead animals because the corpses are rife with bacteria and all sorts of other nasty things that would make us very sick.  Not turkey vultures.  They can eat all sorts of stuff and they are not affected by things like botulism, cholera, salmonella, or even anthrax.
  • In fact, even their droppings are disease-free.  So they really help clean up the place. 


Sometimes you see turkey vultures hanging around with their wings open a little, like this.  They're probably letting their feathers dry after a heavy dewfall, or else regulating their body heat.
(Photo from Ask the Birds and They Will Tell You)

  • Tibetan Buddhists regard the vulture in a positive light, as a creature that helps release the human soul from the dead body.  The Latin word for the turkey vulture reflects this view: Cathartes aura means "golden purifier" or "purifying breeze."
  • One of the few things that harm turkey vultures is lead shot.  If a turkey vulture eats an animal that has been shot by a hunter, the vulture will also consume the ammunition, and then eventually it will contract lead poisoning.
  • You don't want to be without vultures (turkey or otherwise).  In some parts of urban India where accidental poisoning killed off so many of the vultures, there aren't enough of the birds to clean up the dead animals.  So now details of people have to go around burying animals so that people don't get sick.
  • So, yes, they eat dead things.  But they're really good at it, and they're doing everyone else a huge favor. 
  • One little note: just because they're circling doesn't necessarily mean they're closing in on something dead down below.  They could just be traveling as a group on the same thermal. 
  • A group of vultures circling is called a kettle.  If they're just hanging out, not flying, then they're called a venue. 


These turkey vultures may look like they're circling over some carrion, but actually, they're just migrating.
(Photo from Cornell Lab of Ornithology's Birdscope)

Turkey Vultures & Wild Turkeys

  • The fact that they eat carrion is why they don't have feathers on their heads -- or at least, that's what we assume.  Vultures can eat and not be affected by all sorts of toxins, but it might be a different thing if they went around with that toxic stuff in their face-feathers.
  • By the way, turkey vultures keep their leg feathers clean by urinating on themselves.  That may sound gross and terrible, but actually the uric acids kill any bacteria they may have picked up, and it's what helps keep themselves healthy.
  • The turkey vulture's bald head is why they're named after turkeys.  Because they look kind of like a wild turkey.



The wild turkey has a bald head like a turkey vulture does, but it also has the wattle under its chin and that knob over the beak which is called a snood.
(Photo by the Apple Lady)

  • But there are several differences between the two types of birds.  Besides the fact that wild turkeys can't fly much higher than low tree branches, as compared to turkey vultures which like to get up there and soar around on the thermals, and the fact that turkey vultures' feathers are more brown while wild turkeys' feathers are more blue-black, there's also a difference in that bald head.  
  • The head of a turkey vulture is red and bald.  A wild turkey's head isn't entirely featherless, and the male's head may be blue, red, or white, depending on the time of year.  It is thought that the color changes are associated with trying to attract a mate, or trying to intimidate other male rivals.  The female wild turkey's head is gray-blue and does not change.
 

Vultures, Buzzards, and . . . What?

  • A lot of Americans use the word "buzzard" to describe vultures, especially out West.  Actually, buzzards are types of hawks that live in Europe (they're related to the red-tailed hawk that we have in the States and look somewhat similar). The misuse probably came about when people from Europe saw vultures and thought they were the same thing as buzzards.  But they're not.
  • Now here's a tidbit that will really tweak your vulture ideas: for a long time, scientists classified vultures with the big birds of prey like hawks and eagles.  But actually, DNA tests show that vultures are not related to raptors (who, for example, have almost zero sense of smell) but rather are more closely related to storks.  Yup, the ones that bring the babies.  Let that float around in your boat for a while.


Wood stork, more closely related to the turkey vulture than the turkey or the hawk.
(Photo from Birds and Gators)


Sources
Cornell Lab of Ornithology, Turkey Vulture (Cathartes aura)
Wisconsin Department of Natural Resources, Environmental Education for Kids, Turkey Vulture
Turkey Vulture Society, Turkey Vulture Facts, Maps, and Statistics
Adirondack Wildlife, Turkey Vultures
National Wild Turkey Federation, What Does a Wild Turkey Look Like?

Monday, November 12, 2012

Apple #610: Carrier and Homing Pigeons

Today is Veterans' Day.  Since we've all been through a pretty rough-and-tumble election with insults being flung literally left and right, I thought it would be nice to talk about a calmer, more soothing topic.  Like pigeons.  And as it turns out, some pigeons are also veterans.



Pigeons can be veterans too. These are homing pigeons in a mobile pigeon loft in Okinawa in 1945.
(Photo from WWII in Color)


What's prompting this Daily Apple is a news story that ran a couple of weeks ago, about a carrier pigeon.  A man in England decided to restore his home's original fireplace and when he had the wall knocked down, he discovered the skeleton of a bird. On closer inspection, he realized it was a pigeon, and it had a little red canister still attached to its leg. Inside the canister, on a piece of paper as thin as a cigarette rolling paper was a series of handwritten letters that were clearly a message in code.



Remains of the carrier pigeon and the red canister it was carrying still attached to its leg.
(Photo from The History Blog)


Based on the style of the canister and the form of the message and various other indicators, it's believed that this pigeon was sent at some point during World War II.  The band on the pigeon's leg says it was born in 1940.  They think that perhaps the pigeon stopped to rest in Surrey, on this man's chimney, but something went wrong and the pigeon died and fell down the chimney.

The message it was carrying was written by a Sergeant W. Stott and it was addressed to "X02," which was England's Bomber Command.  Several pigeons were released on D-Day, meant to carry messages back to England's home command.  So it's possible that this pigeon was sent on D-Day by some British Royal Air Force (RAF) pilot, perhaps requesting a bombing raid.



The coded message that the carrier pigeon was, well, carrying.
(Photo from The History Blog)



Bletchley Park, which was Britain's intelligence and decoding headquarters during the war and is now a museum, has several messages sent by carrier pigeon, but none of them are in code.  Bletchley Park's modern-day decoding counterpart now has the message and they are trying to crack the code.

I wonder if we'll ever learn what it says, or if it will be judged to be too sensitive, even this many years later.

Now for more facts behind the news story.

  • First, a lot of newspaper articles use the phrase "carrier pigeon" pretty indiscriminately.   Usually when they say "carrier pigeon" it turns out it was really a homing pigeon that was also carrying a message.
  • Carrier pigeons and homing pigeons are both of the same species (Columba livia or Rock pigeons), but they're slightly different breeds.  A true carrier pigeon is pretty ugly.  It has a big warty blob on top of its beak and as the bird ages, the warty blob gets bigger and another one grows on the underside of its beak.  It also has a fleshy ring around its eye that gives it a staring, almost vulture-like expression.

 
This image is pretty small, but you can kind of make out the warty blob on top of this carrier pigeon's beak and the fleshy ring around its eye. All the larger pictures I found have copyright insignias all over them. But you might not want to see those images up close, anyway.
(Photo from thelongestlistofthelongeststuff etc.)

  • Today, carrier pigeons are bred primarily as show birds for their fancy and strange facial features and their ornamental plumage.
  • Homing pigeons look more like the regular pigeons you see hanging around city streets and telephone wires. These pigeons have slightly more muscular breasts, but the bigger difference is that they have been bred for centuries and also trained so that, no matter how far they fly, they'll always find home.  Which, to them, means finding their most reliable source of food.
  • Homing pigeons also almost always have an identification band on one leg so that in the rare case when they get lost, the person who finds the bird can contact its owner.
  • (Recently, one homing pigeon named Henry got lost on the way from France to England and wound up in the Bahamas. His owner doesn't believe he actually flew across the entire Atlantic but probably hitched a ride on some cruise ship. His owner has agreed that Henry can stay there rather than risk the flight back. So now the Bahamas are now his new home. I say, smart bird.)

  
Henry the pigeon from Leeds in his new home in the Bahamas.
(Photo from Look at this . . .)


  • I don't know enough about pigeon skeleton anatomy to say for sure whether the skeleton that was found in the man's chimney was a carrier or a homing pigeon, but I have a feeling that it may have been a homing pigeon.
  • The catch with homing pigeons is you can't have them fly off and deliver a message to someone else. They'll just come back home.  You have to take them away from their home base and then release them and they'll fly home.  So, for military intelligence purposes, you have to have a person in the enemy territory who can take the bird into the fray with them and then release it to go back home.
  • During World War II, RAF pilots routinely took pigeons with them on their missions.  (Again, most articles refer to them as carrier pigeons, but I think they were really homing pigeons who were carrying messages.)  If the pilot's plane was shot down and they had no way to communicate their whereabouts, the pigeon would be released to fly back home and "tell" the base where the plane had landed.


A Canadian airman carrying homing pigeons in a box -- WWII's version of the black box.
(Photo from War 44 Forums)


  • This actually happened, and successfully, in one instance. On February 23, 1942, an RAF bomber was pretty much in flames and its crew bailed out into the North Sea.  Yeah, February, in the sea off the coast of Norway, not exactly bathwater.
  • Just before they bailed out, the crew released the pigeon they had on board -- a blue checkered hen named Winkie.  They hoped that Winkie would fly home to her perch in Dundee and thus alert the air base that the plane she'd flown out in had gone down.
  • She flew 120 miles and was discovered "exhausted and covered in oil" by her owner, who then alerted the nearby RAF base.
  • She wasn't carrying any message, but they were able to calculate how far she must have flown, based on their last communications with the plane, and taking into account windspeeds and the fact that her feathers were coated in oil.
  • The rescue mission found the pilot and crew within 15 minutes.
  • A dinner was later given in her honor, and she was awarded the first Dickin Medal, which is an award given to an animal for delivering a message under exceptional difficulties.

  
This is Winkie, the bird who saved the lives of several men on an RAF bomber in World War II.
(Photo from BBC News)

  • One of the reasons the British had all those carrier/homing pigeons was because they'd heard that the Germans had a regular crew of them.  Carrier/homing pigeons were used fairly extensively on all sides during World War I, but after that war, most armies had let their pigeon crews lapse.  Not Germany.
  • (Actually, armies have been using pigeons to carry messages going all the way back to King Cyrus of Persia.) 


A mobile pigeon roost used by the US Army during World War I.
(Photo from Suite 101)

  • When World War II broke out, the Germans had some 50,000 pigeons trained and ready for use. Well, they commandeered the pigeon lofts of civilians and claimed them for the military's use.
  • In fact, the head of the SS, Heinrich Himmler, was in charge of Germany's National Pigeon Society. Which meant he could use the pigeons for intelligence purposes.
  • The French and the British didn't know about the pigeon corps at first, but they began to suspect something was up in 1942, when they noticed lots of pigeons flying around England toward France.
  • The British suspected -- and their suspicions were confirmed by captured German soldiers -- that the pigeons were dropped off by the German troops either by parachute or by boat along the British coastline.  The pigeons carried messages about troop strength, fortifications, gun positions. Sometimes they even carried maps or photos.


German WWII soldier carrying carrier pigeons.
(Photo from the Daily Gun) 


  • The British decided to counteract the German pigeon intelligence in two ways. First, they copied the idea and gathered trained pigeons for their own purposes. Second, they also developed and trained a corps of birds of another kind -- peregrine falcons.  
  • The peregrine falcons were trained to go after the pigeons.  In most cases, they probably simply attacked the pigeons, but they actually brought back two of the German pigeons who became, technically speaking, prisoners of war.


And, what do you know, our military is still using pigeons to this day.
(Photo from The Duffel Blog)

  • After the Department of the Army blew its entire communications budget on a $15 billion-with-a-b radio system that essentially didn't work, they had to find other means of communication. The Army Chief of Staff asked his big thinkers to come up with some other low-cost method that couldn't be hacked or interrupted.  They came up with KITDFOHS (Kinetic Internal Directly Functional Operational Homing Science).
  • Translated, that means carrier pigeons, hand and arm signals, smoke signals, and yelling.
  • Here's what one soldier in Afghanistan has to say about this communications program (please excuse the, um, military language):
“Hand and arm signals, OK. Yelling, OK. But fuck, carrier pigeons and smoke signals? Now on patrol one of my guys has to carry a cage on his back with pigeons in it. Another troop is stuck carrying kindling and flint everywhere we go. Have you ever tried to build a fire while taking fire? It ain’t easy.”

He continued, “These pigeons are the nastiest creatures I’ve ever seen. Not to mention anytime we go through a market all the Afghans ask ‘how much, how much?’”

“While it’s pretty tough to have to carry this stuff, it makes for a good punishment technique. Whoever pisses me off is getting pigeon shit all over their gear by the end of the patrol.”



Who'd have thought that a bunch of pigeons could actually be that important?  In fact it's against the law in New Jersey to delay or detain a homing pigeon.
(Photo from NJ Kegstand)


Sources
David Wilkes, Skeleton of hero World War II carrier pigeon found in chimney with a secret message still attached to its leg, Daily Mail, November 1, 2012
Raven Idiot, Big Sky Birding Column from the Montana Best Times, part 2, The Complex World of Pigeons
Racing vs carrier homer, Pigeon Talk
World of Wings, Military Pigeons, The Birds That Save Lives
Chris Brooke, Not so bird-brained after all! Racing pigeon that went missing en route to Leeds finally turns up 4,500 miles away in the Bahamas, Daily Mail, July 20, 2012
The pigeon that saved a World War II bomber crew, BBC News, February 23, 2012
Rockville man raises, races carrier pigeons, The Washington Post, July 14, 2011
American in WWII, Pigeons of War
Nazis & Their Pigeons
Army Replaces Defective Radios with Carrier Pigeons, Smoke Signals, The Duffel Blog, October 9, 2012

Sunday, June 10, 2012

Apple #589: Blue-Footed Booby

Since my previous entry was on blue-plate specials, I thought I'd continue the blue theme.  I wanted to talk about something unusual as well as blue, and what's more unusual than blue-footed boobies?


Two blue-footed boobies. Looks like they're having a conversation.  "What's up, Deb?" "Not much, Fred."
(Photo from NatureWorks)

  • The blue-footed boobies (Sula nebouxii) have magnificently odd feet -- very large and also blue. The male birds show off their big blue feet to the females with a series of high-stepping struts. The bigger and bluer the feet, the better the ladies like them.
 
The first and most essential part of the mating dance: the male picks up his feet one at a time and shows them off. He returns to this move several times throughout the dance, almost like a refrain.
(Photo from PR Log)


  • The reason the males show off their feet so much is not because foot size corresponds with the size of another male feature, but rather because their feet are important to the survival of their offspring. The blue-footed booby does not sit but rather stands on its eggs. The bigger their feet, the better able they are to keep the eggs warm, and the more viable the hatchling.
  • Granted, it's the female who does most of the standing while the male goes off to collect food. But sometimes the male stands on the eggs too while she's out fishing.  And if she finds a male with big feet, her offspring are more likely to have big feet, which means their eggs will do better, and so on down the line.
  • Males and females look very much alike. The female is slightly larger, and the male has a slightly bigger tail.
  • Their calls are more distinct. The male makes and whispery whishing noise.The female makes a kind of grunting barking sound.
  • Now that you'll be able to tell who's who in the mating videos, here's how the mating dance goes:
  1. The male picks up and puts down his big flue feet, showing them off.
  2. He dips his chest and flares his wings and slows off his feet some more.
  3. Then he presents the female with twigs and other nest materials -- which is a bit strange since they don't actually build nests
  4. The two both participate in a courtship flight (though this doesn't happen in a lot of videos I've seen)
  5. The male shows off his feet again
  6. The female joins in, picking up and putting down her feet too.
  7. They both do the chest dip and wing flare, pointing their beaks skyward. He makes his whispery whishing sound and she makes her louder groaning sound.
  8. Mating happens.
Here's how the mating dance seems to go most of the time: lots of foot-lifting for a long time, and she may finally join in, or she may not.



Below is a link to a sort of art-haus version, showing the dance taking place among several different pairs of boobies and with lots of close-ups. There are also a few shots of the boobies flying, which is very graceful, followed by landings, which are not.  The video ends in the ultimate success for one pair: copulation. Afterward, the male looks very proud of himself.

ARKive video - Blue-footed booby courtship and copulation

  • Boobies are monogamous. Which means that once the female is interested enough to do the full dance with him, the two of them will be dancing like that together until the last disco ball light goes out.
  • They don't have a particular breeding season. One site put it that they are "opportunistic breeders." Which means that when it feels right, they go for it.
  • Other things about the blue-footed booby's nesting habits are kind of disgusting. They don't build a nest but lay their eggs on the bare ground. While the birds are roosting on the nest, they crap all over the place, and the eggs become surrounded by a dried wall of booby excrement.
  • Their big feet may make them ungainly on land -- which is what apparently led Europeans to give them a name which means "stupid" or "clown" or I think this may be the best translation: "goofball" -- but they are anything but in the air.
  • They are sea-going birds, flying out to sea  in search of schools of fish. When they spot some tasty fish, sometimes from as high as 330 feet up, they fold back their wings to become streamlined as an arrow and dive into the water to spear the unsuspecting fish.
   
Blue-footed booby going into a dive. So streamlined and perfectly angular, it almost looks mechanical, doesn't it?
(Photo by Rob Kroenert at Endless Loop)


Photographer Tony Mills put a sequence of photos of a booby diving to create this image, showing the bird's arrow-like entry into the water. 
(You can purchase a signed, limited edition print of this image for £85 from Tony Mills' Action in Nature)

  • They hit the water at speeds up to 60 miles per hour.
  • To the envy of many an Olympic diver, though they plunge from enormous heights, they make almost no splash.
  • They especially like to eat anchovies and flying fish. Sometimes they can snag a flying fish from out of the air.
  • While each booby is so individually gifted, they hunt in flocks. When one booby spots a school of fish, it will call to the others, and they will all swarm over and each go into their stupendous dives, each one spearing a fish.
  • They can also dive down to get fish while bobbing on the water's surface. This is true of only the blue-footeds. Other boobies can't do this.
  • The blue-footeds live along the western coasts of Central and South America.  About half of all blue-footeds live on the GalĂ¡pagos Islands.
 
The range of the blue-footed booby
(Map from National Geographic)



The GalĂ¡pagos Islands is a cluster of about 14 islands off the western-most knob of South America. The islands were once upon a time the haven of pirates, as well as the home of unusual animals like the blue-footed booby.
(Map from worldatlas.com)

  • Every once in a great while they may venture as far north as the coastlines of Texas, Arizona, or California. In California, they are fond of the Salton Sea.
  • The other feature about them that earned them the name "stupid" is that they seem to have no fear of humans. You'd think this would have resulted in their extinction or near-extinction, but the flue-footeds are doing just fine.  Though their colony on the GalĂ¡pagos does have protected status.
  • Actually, the blue-footed booby isn't all that unusual. There are five other species of booby. There is the red-footed (which made an appearance when the Brady Bunch went to Hawaii), the brown, the Peruvian, the Nazca, and the masked. 
  • That last species, the masked, was recently discovered to be the same as the Tasman, which had been thought to be extinct. Well, what did you expect from a bunch of boobies wearing masks, that people would know right off who they were?

Sources
National Geographic.com, Blue-Footed Booby, "Extinct" Booby Exposed -- Found "Masked," Using Alias, August 11, 2009
Cornell Lab of Ornithology, All About Birds, Blue-footed Booby
MarineBio.org, Blue-footed Boobies, Sula nebouxii
FactZoo.com, Blue-footed Booby - Blue Feet, Deep Diver