|Back to Back Issues Page|
What are Cotyledons & Bird Vision
March 19, 2012
This is yet another newsy or lengthy letter.
Take your time reading it and absorb some of the information you may not be aware of.
You may even discover a bit of trivia.
(A couple pictures of daffodils in early bloom and one of Karen's geranium moved outside for now.)
Spring officially arrives on Tuesday, yet the weather is more like late May right now.
With some thunderstorms to wash away the winter grime and the warmth, everything is greening up way to fast.
Here in Southwest Michigan, the weather can be very fickle, and I still have concerns for a stretch of cold weather that will kill off many flowering buds, especially on fruit trees.
Tornadoes ravaged parts of Eastern Michigan this past week, Thank you Lord that there were no fatalities.
On the warm evenings, I can here the Peeper frogs singing.
American woodcocks can be heard as well as they fly around at night with mating calls from both wings and vocally.
Sandhill cranes continue to make the voyage north (picture was on a cloudy day)
A few Turkey vultures have arrived.
Along with crows and ravens, they arrive in time to clean up the roadkill.
The female robins are arriving (always about 2 weeks after the males).
Now that the ladies are here, the males are busy impressing the girls as the skirmishes and jocking for dominance is in full swing.
Feeder birds are in less numbers as many of them have headed off to breeding grounds.
Killdeer and Tree swallows have successfully made the trip north as well as the wretched Brown headed cowbirds.
Mallard ducks and Canada geese are very frisky as well.
Geese mate for life, while the ducks .............
It's every duck for himself.
Often you will see several males ganging up on a hapless female, sometimes resulting in her death.
Sometimes you may see a male duck hanging out with a female.
He isn't being the season long mate or protective male as it may appear.
He is simply trying to keep other males away from his action.
When her head is turned or she is nesting, he will be out there doing his thing as well, leaving her to all the nesting and parenting duties.
Looks can be deceiving.
You know for sure that spring is in the air, when you see rabbits in pairs or multiples.
Again, no loyalty amongst rabbits.
Here is a reminder of some of you and very important information for all new to gardening.
As the weather has warmed up and some spots in the yard and gardens are workable, (I have made time to do a little weeding and transplanting).
I have decades of experience and hopefully I know what I am doing .
Pay attention now.
If your soil is still too damp to work, stay off it as you do more harm (compacting the ground) than you do good by walking and working it.
The ideal test is to take a hand full of dirt and squeeze it into a ball.
Does the ball ooze or stay in form?
Can you crumble it with ease.
A crumbling dirt ball make for good working conditions.
Remember, plants breathe oxygen through their roots and compacted soil chokes off the breathing, which make for a weak and dieing plant.
If you haven't been collecting your eggshells and banana peels, start now.
Crushed and ground eggshells are a great source of calcium for your plants (especially tomatoes).
Banana peels offer Potassium and Phosphorous, both are required for strong blooms and roots (great for roses).
There is also something special about bananas and peels that deter
Start tossing banana peels now for the young growth to take in.
Banana peels dry and dissolve rather quickly and I never have issues with critters feeding on them.
Toss your citrus peels and products around any and all acid loving plants.
First Signs of Growth:
I place bagged seed trays on the cable boxes, they make a great heat mat and are visible for me to check daily.
I no longer mass plant, so the boxes work well for me as I plant in waves.
Once your seedlings begin poking through the soil, they will start to straighten up and unfurl.
Your seedlings will need between 12-18 hours of light each day.
This may seem extreme, but artificial light and even the low rays of the winter sun are not as intense as full summer sun.
Those first leaves you see, aren't really leaves at all.
They are cotyledons, part of the embryo of the seed.
Cotyledons contain the remainder of the stored food reserves of the seed and keep the seed fed until the true leaves sprout and the plant can begin photosynthesis.
Much like a yolk sack helps to feed egg laying reptiles until they can find enough food on their own.
Birds also have a yolk sack to help nourish.
Often the cotyledons disappear shortly after the true leaves appear.
Because potting mixes offer very little nourishment, you begin fertilizing your seedlings once it has developed true leaves.
Seedlings tend to need a fertilizer high in phosphorous, like a 1-2-1, N-P-K ratio.
Instead of purchasing special food for seedlings, you can dilute your regular food to meet the baby plants needs.
The number of cotyledons present is one characteristic used to classify the flowering plants (angiosperms).
Species with one cotyledon (like grass), are called monocotyledonous or, "monocots".
Plants with two embryonic leaves are termed dicotyledonous or dicots.
Last week I touched on the importance of birds having excellent hearing all the way around.
Today, I attempt to touch on the all important requirement that all birds must have.
The ability to see and how God has given them all special eyes.
Yes, Bird Vision.
Birds, with their mastery of the air, have always held a fascination for me.
While science has been able to approximate their soaring journeys with our airplanes, our understanding of their keen vision and related behaviors is still in its infancy.
As with all animals, studying vision and color perception in birds is challenging.
While most birds lack a keen sense
Last week I touched on the keen hearing birds have.
This week I will attempt to make it clear on the superior vision or eyesight that God also gave our feathered friends.
I can't begin to tell you what some of the fancy names and terms are all about.
And yes, bird eyes have retinas, corneas, and so on, but i wont get into that.
I do know this, when it comes to vision or eyesight, birds are superior hands down.
Vision is the most important sense for birds, since good eyesight is essential for safe flight, and finding food.
Indeed, a pigeon has been described as "two eyes with wings"
Here are a few Fun Facts.
The main structures of the bird eye are similar to those of other vertebrates, but most similarities end there.
Because a bird's eyes are large in comparison, most birds cannot move their eyes, although there are exceptions, such as the Great Cormorant.
Birds with eyes on the sides of their heads have a wide visual field, useful for detecting predators (monocular vision).
Those with eyes on the front of their heads, such as owls,and most birds of prey have binocular vision and can estimate distances when hunting.
The American Woodcock probably has the largest visual field of any bird, 360° in the horizontal plane, and 180° in the vertical plane.
The eyelids of a bird are not used in blinking.
Instead the eye is lubricated by the nictitating membrane, a third concealed eyelid that sweeps horizontally across the eye like a windscreen wiper
The eye of a bird is larger compared to the size of the animal than for any other group of animals, although much of it is concealed in its skull.
The Ostrich has the largest eye of any land vertebrate, with an axial length of 50 mm (2 in), twice that of the human eye.
Bird eye size is broadly related to body mass.
Birds of prey have relatively large eyes for their body mass.
Studies even show that many avian species focus on distant objects preferentially with their lateral and monocular ﬁeld of vision, and birds will orient themselves sideways to maximize visual resolution.
For a pigeon, resolution is twice as good with sideways monocular vision than forward binocular vision, whereas for humans the converse is true.
There are two sorts of light receptors in a bird’s eye, rods and cones.
Rods, which contain the visual pigment rhodopsinare better for night vision because they are sensitive to small quantities of light.
Cones detect specific colours (or wavelengths) of light, so they are more important to colour-oriented animals such as birds.
The density of the photoreceptors is critical in determining the maximum attainable visual acuity.
You and I have about 200,000 receptors per mm, while the average backyard bird has about 400,000 and vultures have up to 1,000,000.
The photoreceptors are not all individually connected to the optic nerve, and the ratio of nerve ganglia to receptors is important in determining resolution.
Like mammals, birds have a small blind spot without photo receptors at the optic disc, under which the optic nerve and blood vessels join the eye.
I'm not going to bore you to tears with anymore scientific babble that most of us don't understand anyway.
So let's get to some bare bone interesting information.
Birds not only see better than we do, they have a larger color scale.
Studies show that birds need color to mate, find food, such as colored fruits, to recognize predators and so on.
Not to mention ultraviolet light.
The Common Kestrel can detect the ultraviolet trail of its vole prey.Some birds can see ultraviolet light, which is involved in courtship and in hunting for some species.
Many birds show plumage patterns in ultraviolet that are invisible to the human eye; some birds whose sexes
Species where male and female look alike to us, show vivid color patterns in ultraviolet.
A UV receptor may give an animal an advantage in foraging for food.
The surfaces of many fruits and berries reﬂect UV light that might advertise their presence.
Kestrels are able to locate the trails of voles visually as the small rodents lay scent trails of urine and faeces that reﬂect UV light, making them visible to the kestrels, particularly in the spring before the scent marks are covered by vegetation.
(Bald Eagle credit to the National Zoo in D.C.)
Owls have very large eyes for their size, 2.2 times greater than the average for birds of the same weight, and positioned at the front of the head.
The eyes have a field overlap of 50–70%, giving better binocular vision than for diurnal birds of prey (overlap 30–50%).
Large eyes bring in more light.
With sharp night vision and ears that triangulate sound, Owls can swoop down on prey in pitch darkness with astounding success.
The vision or eyesight of eagles and hawks is legendary.
The eyesight of birds is 3-4 times sharper than ours.
Eagles with their eyes positioned in the front of their head and binocular vision can spot prey from several miles away while hawks often scan the earth from a height of 10-15,000 feet looking for a meal.
And when they spot one, these birds can dive (stoop) at over 100mph and still keep their target in complete focus.
So extreme is their eyesight, it is believed that these birds can read a news paper from a 1/4 away (if they could read).
Again, colored vision comes into play as they recognize not only shapes of prey, but color as well.
Birds that fish for a living, not only spot fish from great distances, but often gage the depths and compensate for light reflection and water distortion.
Bird that dive into the water for food, have special protective coverings that allow for sight, yet protect from damaging stuff floating in the water.
So important is vision, lives depend on it.
Not only is vision and color receptors needed for courting and mating, but think of this.
Birds flit through your yards and flowerbeds grabbing insects by the mouth full.
Birds can notice the slightest movement, even a tiny insect walking across the leaf of a Zinna on the other side of your yard.
A green bug on a green leaf and it is nailed.
Swallows so impress me.
Not only with their acrobatic flight, but simply to watch them feed on the fly.
Watch as they swerve and dip on a micro-second.
Snatching and grabbing insects that also are flying in who knows what direction, I can't see the insects, but the birds can.
That not only is superior eyesight, but to have accuracy to pick off moving targets when you yourself are moving is a special skill.
Color comes into play as birds learn to stay away from certain insects that taste nasty (Monarch butterflies).
How is a bird to know if your strawberries and raspberries are ripe or not if they can't see the bright red?
Color is a main attractant to the female of most species.
Color often dictates a hierarchy in a territory such is the case with Northern cardinals.
Brighter color cardinals get the prime real estate.
Brighter colored breasts on robins and meadowlarks attract more females.
See now how vision and color are so important for birds.
Have you ever taken the time to watch your birds at work and play?
Jays will often find a shinny or some other object and make a game out of it.
Some birds like crows will collect all sorts of shinny and pretty objects and keep them in a cache.
Why, some birds are attracted by the color, or like what they see.
Personalities play a roll too.
Another one of those 'Wonders of Nature".
You'll like this one.
Here is a little something I learned about a couple of years ago and only now can work it in to a newsletter.
Thirsty trees make noise.
Bioacoustician Bernie Krause has recorded the amazingly rhythmic vascular systems of thirsty trees:
He discovered that the cells in the xylem and phloem of the tree fill with air to try to maintain proper pressure that's usually produced by the sucking of water up through the roots.
At a certain point, cells begin to pop.
When trees begin to pop, certain insects expect sap and arrive in droves expecting a feeding frenzy.
(We can't hear the sucking sound, but insects can.)
Now I don't know if birds can hear the trees popping too, but they sure can see and hear the hoards of insects as they arrive.
And there becomes a feeding frenzy.
Once again, one of 'Nature's' own insect controls hard at work.
Here is another interesting tidbit.
Not So Keen Eyesight.
The largest cause of bird fatalities is due to collisions with tall man-made objects like telephone poles and lines. Now, researchers understand why. Birds simply can’t see them.
"From a human perspective it appears very odd that birds so often collide with large objects as if they don't see them. It is widely held that flight in birds is primarily controlled by vision, an idea captured by the phrase 'a bird is a wing guided by an eye," said Professor Graham Martin from Birmingham University, author of a recent study in IBIS. "However birds live in a different visual world to humans."
According to the study, birds have different fields of vision. Their frontal vision is tuned to movement, rather than spatial details. When looking down, birds may miss what’s directly in front of them. And, if flying at a high rate of speed, it may be difficult for them to take in all the visual clues around them, particularly if their visibility is challenged by rain, mist or low level lights.
Researchers suggest sounds or signals attached to large objects to distract or divert birds from a possible deadly flight path.
Read more on this in the Science Daily.
Well, it is time to fly for now.
Before I go, here is your positive thought for the week.
The beauty of friendship is that it’s a celebration, not of what we do, but of who we are and how we share our humanity with another soul.
Harvey L. Rich, M.D.
Take your friendship to the next level.
“This is my commandment, that you love one another as I have loved you. Greater love has no one than this, that someone lay down his life for his friends. You are my friends if you do what I command you.
No longer do I call you servants, for the servant does not know what his master is doing; but I have called you friends, for all that I have heard from my Father I have made known to you.
"Treat the earth well:
It was not given to you by your parents,
It was loaned to you by your children.
We do not inherit the Earth from our
Ancestors, we borrow it from our Children."
Ancient Indian Proverb
Your friend indeed,
Better yet, have them sign up so they can receive their own letters.
|Back to Back Issues Page|