Why Do Canada Geese Fly at Night?

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Why do Canadian geese fly at night?

Stefan Pociask:

There are actually very good reasons that these geese fly at night, and I will go over them with you. But first ... I must point out that any goose you see that is carrying a valid passport from the great country of Canada, may be called a Canadian Goose. All others should be referred to by their actual name, which is Canada Goose, or Branta canadensis, if you prefer.

I can’t count how many nights at 10 p.m., at midnight, at 3 a.m., and any and all other hours of the night, I have had that all too familiar “Honk! honk-honk-honk HONKhonk HONK HONKhonkhonkhonk HONK honk HOOOONK!” cacophony pass right outside my bedroom window, as the familiar flying-V formations of Canada geese fly over my home.

Those V formations are quite extraordinary. You can’t tell from the ground, but the lead goose is the lowest of the bunch. Each goose behind is slightly higher than the one in front of it, all the way to the last goose, which is flying the highest. They do this because of the aerodynamics of their wings. The only goose that is using all its wing power is the lead goose—point-man, so to speak. When that goose flaps its wings, it causes a certain turbulence of the air that’s following the wing. The next goose in line benefits from this swirling air, and doesn’t need to apply 100 percent of its wingpower. The next goose again benefits from that one, and so on down the line. Flying in formation this way adds 71 percent more distance that they can fly, than when flying alone.

So who gets chosen to be point-man? You’d think the one with the map! Or ... the leader? Or the new guy? No. None of these. They actually take turns. When one gets tired, he will drop back so he can rest a bit and benefit from another goose’s turbulence. When migrating ... in good weather ... with favorable winds, a strong tail wind ... these guys can make up to 1500 miles in a single day ... Hard to imagine, but it’s been done. They are migration masters.

So … the flying at night thing … I’ve already touched upon one of the reasons they prefer the night. It has to do with that turbulence I just mentioned.

You see ... many other large birds (and these are large birds) use thermals to gain altitude and to soar on. Raptors do this. Hawks, eagles, etc. During the day, the landscape is riddled with all kinds of thermals rising from the ground, all depending on what the surface looks like below; how much heat was absorbed and stored from the sun; if it’s dark or light … or even water. These thermals are great for raptors—lots of vertical air movement, all over. But geese don’t soar, and they don’t have need to fly in circles. They have somewhere to go. And all those daytime thermals are a pain in the butt; doesn’t make for smooth sailing. Plus, they interfere with the aforementioned wing turbulence that they use to keep from tiring. At night, several hours after sunset, the Earth cools and those pesky vertical thermals disperse.

So that’s one reason they like the night. Another reason for night flight is to prevent overheating (makes sense, right?). Nights are cooler, so birds that expend a lot of energy with constant flapping (as opposed to soaring) take advantage of the cool of the night.

A third reason is also something I’ve already mentioned. Hawks! And eagles! And falcons! All those guys are diurnal hunters, meaning they hunt during the day. Which goose in its right mind would want to share the not-so-friendly skies with something called a raptor? Now, if you’ve ever seen flocks of geese on the ground and tried to get amongst them or feed them or something … you may already know how mean and nasty they can get. People have used geese instead of watchdogs. They are tough! Especially on the ground. But falcons, hawks, and eagles, hitting them from the air often spells doom. In other words ... their goose is cooked. During the day, they often rest and feed and rejuvenate in the water, where they are safe from raptor attack. As long as they stay in the water.

So given the choice, they take the red-eye.

Otherwise, this can happen ... (WARNING: Extremely dramatic footage follows of a falcon/goose battle. Also extremely exciting! Who will win?!)

You’ll certainly see Canada geese fly during the day. But the smart goose prefers the night.

All migratory birds are split up into three classes, regarding migration habits. Nocturnal Migrants, are the first classification, [and they fly] at night. This would include most of the seed-eating songbirds, such as sparrows and thrushes. They will fly all night, then rest up, top off the tank with food, and try to stay out of sight of raptors during the day.

The second group is the Diurnal Migrants, who migrate during the day. These are often the insect-eaters; jays, swifts, swallows, larks, etc. They benefit greatly from the daytime thermals during their journey—not for reasons of soaring, like raptors use thermals, but rather because these warm updrafts send up clouds of insects from the fields, right into the paths of the migrating birds, like a food delivery service. Most insects are so light that a gust of wind or a thermal current can lift them high into the air—and unwittingly into the beak of a hungry swallow.

And the third class of [migratory birds] are those that have a preference, but actually migrate day and/or night, depending on the circumstances. Canada geese, and many waterfowl, fit into this last category.

This post originally appeared on Quora. Click here to view.

How Is a Sunscreen's SPF Calculated?

Rawpixel/iStock via Getty Images
Rawpixel/iStock via Getty Images

I’m a pale person. A very pale person. Which means that during these hot summer months, I carry sunscreen with me at all times, and apply it liberally. But I’ve never really understood what those SPF numbers meant, so I asked some sun care to break it down for me—and to tell me how to best apply the stuff so that I can make it through the summer without looking like a lobster.

Soaking up the sun ... safely

SPF stands for Sun Protection Factor, and it indicates a sunscreen’s ability to block UVB rays. The concept was pioneered at the Coppertone Solar Research Center in 1972; in 1978, the FDA published an SPF method based on Coppertone’s system, according to Dr. David Leffell, chief of Dermatologic Surgery and Cutaneous Oncology at Yale.

The numbers themselves stand for the approximate measure of time a person who has applied the sunscreen can stay out in the sun without getting burned. Say you get burned after 20 minutes in the sun without sunscreen; if properly applied (and reapplied), SPF 30 will allow you to stay in the sun 30 times longer without burning than if you were wearing no protection at all. So, theoretically, you should have approximately 600 minutes, or 10 hours, in the sun. But it’s not an exact science because the amount of UV light that reaches us depends on a number of factors, including cloud cover, the time of day, and the reflection of UV rays off the ground, so it’s generally recommended that you reapply sunscreen every two hours (or even sooner).

What gives a sunscreen a higher SPF comes down to the product’s formulation. “It’s possible that an SPF 50 might contain slightly more of one or more sunscreen active ingredients to achieve that higher SPF,” Dr. Patricia Agin, president of Agin Suncare Consulting, says. “But it’s also possible that the SPF 50 might contain an additional active ingredient to help boost the SPF performance to SPF 50.”

No matter what SPF your sunscreen is, you’ll still get a burn if it’s not properly applied. So let’s go over how to do that.

How to apply sunscreen

First, make sure you have a water-resistant, broad spectrum sunscreen—which means that it protects against both UVB and UVA radiation—with an SPF of at least 30. “Typically, you don’t have to buy sunscreen that has an SPF higher than that unless you have very sun sensitive skin,” Leffell says. “That’s a very small percentage of the population.” (Redheads, people with light eyes, and those who turn pink after just a few minutes in the sun—you’ll want to load up on SPF above 30.)

Twenty minutes before you go out to the beach or the pool, begin to apply your sunscreen in an even coat. “Don’t apply it like icing on a cake,” Leffell says. “I see these patients and they’ve got the tops of their ears covered with thick, unevenly applied sunscreen, and that’s not a good sign.” Sunscreen sprays will easily give you that even coat you need.

Whether you’re using lotion or a spray, when it comes time to apply, Leffell recommends starting with your scalp and face, even if you plan on wearing a hat. “Make sure you’ve covered the ears and nose and under the eyes,” Leffell says. “Then, I would move down to the shoulders, and make sure that someone can apply the sunscreen on your back beyond the reach of your hands.”

Other areas that are important that you may forget to cover, but shouldn’t, are the tops of your feet, the backs of your hands, and your chest. “We see it all the time now—the v of the chest in women has become a socially and aesthetically huge issue when they are 50 and beyond. Because even though they can treat their faces with all sorts of cosmetics and procedures, the chest is much harder, and they are stuck with the face of a 40-year-old and the chest of a 60-year-old. You want to avoid that using sunscreen.”

Another important thing to keep in mind: Water-resistant doesn’t mean waterproof. “I always tell patients to reapply every couple of hours while you’re active outdoors," Leffell says, "and always reapply when you come out of the water or if you’ve been sweating a lot, regardless of whether the label says water resistant."

Determining whether or not you’ve succeeded in properly applying your sunscreen is easy: “You know you’re applying your sunscreen properly if, after the first time you’ve used it, you haven’t gotten a burn,” Leffell says.

Agin has a caveat, though: "It’s not a good idea to think of sunscreens only as a way to extend your time in the sun," she says. "One must also understand that even before becoming sunburned, your skin is receiving UV exposure that causes other damage to the skin. At the end of the 600 minutes, you will have accrued enough UV to cause a sunburn—one Minimal Erythema Dose or MED—but there is pre-MED damage done to skin cells’ DNA and to the skin’s supporting structure of collagen and elastin that is not visible and happens even before you sunburn. These types of damage can occur without sunburning. So you can’t measure all the damage done to your skin by only being concerned about sunburn."

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us atbigquestions@mentalfloss.com.

An earlier version of this post ran in 2014.

What's the Difference Between Ice Cream and Gelato?

iStock/Getty Images/zoff-photo
iStock/Getty Images/zoff-photo

'Tis the season for beach reads, tan lines, and ice-cold desserts. You know it's summer when going to the local ice cream or gelato shop becomes part of your daily routine. But, what exactly is the difference between these two frozen treats?

One of the key differences between the two is butterfat. While ice cream's main ingredients include milk, cream, sugar, and egg yolks, the secret to making gelato is to use much less cream and sometimes little to no egg yolk. This leads to a much smaller percentage of butterfat in gelato. The FDA rules say that ice cream cannot contain less than 10 percent milkfat (though it can go as high as 25 percent) while gelato, much like soft serve, stays in the 4- to 9-percent range.

The churning method for both also differs, which affects the treat's density. Ice cream is churned at a much faster pace, leading to more air being whipped into the mixture. Ice cream's higher butterfat content comes into play here—due to all of that milkfat, the mix absorbs the air more readily. Gelato, on the other hand, is churned at a slower pace and absorbs far less air, creating a much denser dessert.

You also might have noticed that the serving style for the two treats aren't the same, either. In order to get those perfectly stacked ice cream scoops on a cone, buckets of ice cream must be stored at around 0°F to maintain its consistency, while the softer gelato is stored at a warmer 10°F to 22°F. Ice cream is then scooped into fairly uniform balls with the round ice cream scooper, whereas a spade or paddle is best for molding gelato into mound in a cup or a cone.

You can't really go wrong with either gelato or ice cream on a sweltering summer day, but there is one more difference to keep in mind while you debate which to get: taste. If you want a bolder flavor, you'll want to go with gelato. Because of the density of the cream and because there's less butterfat to coat your taste buds, gelato can seem to have more intensity to its flavors.

Have you got a Big Question you'd like us to answer? If so, send it to bigquestions@mentalfloss.com.

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