Archive for December 30th, 2009

New Year’s Eve blue moon

by Katie Bowell, Curator of Cultural Interpretation

For those readers lucky enough to live in the Eastern Hemisphere (Europe, Africa, Australia and Asia), you’ll have a treat on December 31st – the last lunar eclipse of the year. Lunar eclipses occur when the Moon passes through the Earth’s shadow. The more central the moon in the shadow, the more total the eclipse. This eclipse, known as a minor partial eclipse, won’t be too spectacular – just a tiny sliver of the Moon (~7.6%) will go dark as it passes through the Earth’s shadow. However, no matter where you live, we’re all in for another treat this New Year’s Eve, something that only happens once in a blue moon. What’s that? A Blue Moon.

Full Moon from Air & Space Museum

Today, the expression “blue moon” has two meanings: (1) something rare and (2) two full Moons occurring in one month. However, those meanings have changed over time (the last 400-ish years, to be exact).

The earliest recorded use of the phrase “blue moon” happened in 1528, in a pamphlet criticizing the English clergy. The line, “Yf they say the mone is belewe/We must believe that it is true” (If they say the moon is blue, we must believe that it is true), was used to describe an impossible event. By the 18th century, the phrase “until a blue moon” was used to mean “never.” So why, today, do we used the expression “once in a blue moon” to mean something that happens every now and then, or rarely? Well, it turns out the moon can appear blue.

When the Indonesian volcanic island Krakatoa erupted in 1883, the particles of ash it shot into the atmosphere were around 1 micron wide, the right size to scatter red light while letting other colors pass through.  Sunsets looked green and the Moon looked blue all around the world for almost two years. Blue Moons could happen. A similar phenomenon happened in 1927 when an extra-long dry season created enough dust in the air for a blue Moon in India, and in 1951, smoke from forest fires in Canada turned the Moon blue over North America.

So when I say that we’ll see a blue Moon this Thursday, am I psychically predicting a forest fire or volcanic eruption? Happily, no. Besides, if I had psychic powers, I’d want to know lotto numbers, not the color of the Moon.

Here’s where the story continues: In North America, the expression “blue moon” also came to mean the third of four full Moons in a season. Traditionally, almanacs (the handy publications that tell you things like when the Moon was going to be full) worked on the tropical year, which goes from Winter Solstice to Winter Solstice, instead of from January 1st to December 31st. Most tropical years have 12 Moons, three per season (winter, spring, summer, and fall). But every once in a while, a tropical year will have 13 Moons – giving one season four Moons instead of three. The third of those four Moons was the one that didn’t belong, and came to be called the “Blue Moon.”

1853 Maine Farmers' Almanac from Old Farmer Almanacs

The switch in definition from “Blue Moon” meaning the third of four full Moons per season to meaning the second full Moon in a calendar month happened in 1946, when a writer for Sky & Telescope Magazine misinterpreted the Maine Farmers’ Almanac’s listing of a “Blue Moon.” The new definition caught on, which is why on Thursday the second full Moon of December will be a “Blue Moon.”

So, why are there two full Moons this month? We usually only have one full Moon per month because there are 29.53 days between each moon. However, get a month that’s long enough (31 days) with a full moon happening early enough (this month the first one happened December 2nd), and you can have two full Moons in one month. The definition of a “Blue Moon” as something rare still holds up, too, since these double Moons only occur once every 2.7 years.

Happy New Year and, as always, “Good seeing.”

Science at home: Who did I see?

by Treloar Bower, Curator of Education

I rarely see or even hear one of my favorite animals, and, no, that’s not because I love elephants and can only see them in a zoo or on safari (which is a highly unlikely trip for me anyway). No, this critter is a native of Colorado but it’s a nocturnal carnivore with such specialized adaptations that even sensitive-eared prey animals like mice don’t hear it coming. So imagine my surprise when on an evening a couple of weeks ago, sitting in my car at a stoplight west of Windsor on 392, with the temperature hovering at 0º F, my favorite animal, an owl, emerged from the blackness of the night, flying slightly above the intersection right over my car! Just enough light was emitted from my headlights and the street lamps to cause its light-colored belly feathers and under-wings to faintly glow in the night. It was beautiful!

My mom, another bird-lover, was with me. We’ve been debating about what species of owl we saw. It was a large owl but I’ve certainly seen larger. I’d guess it had a wing span of 3 feet. Great Horned Owls (Bubo virginianus) have a wing span range of 3 to 5 feet, and a wide range of color variation, but a white belly is one possibility. Barn Owls (Tyto alba) all have white bellies, with a wing span of 3 to 3.5 feet. We could have seen a small Great Horned Owl or an average-sized Barn Owl. In flight, the feathers on its head that give the Great Horned its “horned” appearance, are folded against the head, so that diagnostic feature was not visible to us (if it was a Great Horned). Barn Owls have distinctive heart-shaped faces, long legs and a squared tail but in all honesty, this sighting occurred so fast and in such dim light I didn’t really catch anything of those features.

Great Horned Owl. Photo from Wikimedia Commons

That said, I’m leaning towards Barn Owl simply because the owl, including its face, looked so white to me. Barn Owls are often called “ghost owls” because they are so eerily silent in flight and their faces and underbellies are so pale. I’m hoping we might see this owl again sometime. Owls are creatures of habit: they have roosts and hunting grounds they return to over and over again. You can spot these locations not by spotting the owl (my goodness, owls are hard to spot!) but the cough pellets and whitewash they leave behind over many, many visits to the same favored haunt. It’s possible my mom and I crossed the regular evening route of a hunting owl. I’m going to time my trips down 392 and keep my eyes open!

Barn Owl. Photo from Wikimedia Commons

If you ever have a chance to go on an “owl prowl” with a professional ornithologist, I highly encourage it. An owl prowl is a late night walk through an area where owls live. By using their own voices, or sometimes tape recordings or calls, these owl experts can call to owls that will sometimes respond with calls of their own or even a flight in to see what’s up. Owl prowls are not for the impatient, nor are they for cold-weather-averse folks. The best prowls I’ve been on are at 10 pm in freezing weather (less than 30º F) – shout out to Jerry Garden of the Chicago Audubon Society – thank you for all the prowls you lead that I attended while I lived in Chicago!

Be prepared to be amazed and totally surprised by the sight of the feathered hunter who sneaks up on you. I once saw a great raptor naturalist and educator, Ryan DePauw, formerly of Spring Brook Nature Center in Illinois, illustrate the sound a single hawk feather makes when flapped, versus the sound of an entire owl’s wing when flapped. There’s no comparison: the single hawk feather sounds like a herd of elephants tap dancing with the Rockettes, while the owl’s wing didn’t make a sound at all.

One thing I will never, never do is call an owl myself. If you call different species of owls in the wrong order, you will either fail to hear or see any owls, or worse, you may cause the death of a small owl. Great Horned Owls eat smaller species of owls, like saw-whets and screech owls. I would hate to call in a screech owl only to draw the attention of a Great Horned!

The best Fort Collins-area resource for learning about owls is the Rocky Mountain Raptor Program. Their mission is to rehabilitate and return to the wild injured and sick raptors, including owls. Some birds that cannot be released are used for educational programs. Check out their website: www.rmrp.org. See if you can identify the Great Horned Owl and the Barn Owl in the pictures on their homepage!


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