Swamp Cooler & Bird Feeders (7/30/08)

As an almost lifetime East Coaster, I had never heard of a swamp cooler until the other evening. I learned about it from Jet Blue. I'm a fairly sophisticated computer user and went ahead and booked two tickets to Maine online. The dates and flight numbers never appeared on any screen after the first page so I did feel a twinge of nerves. That turned into horror when I saw the final screen with the wrong departure date. Hoping not to incur a change fee, I phoned and talked to the most laid back and interesting phone troubleshooter ever. He was in Salt Lake City, runs three businesses, works part-time for Jet Blue answering calls, 90% of which are in Spanish. He does it so as not to lose the Spanish he learned in Chile, where he lived for two years.

We of course talked about the weather and he asked if I had a Swamp Cooler. I thought that was a joke but while he (successfully!) negotiated a ticket exchange for me with no fee, I googled "Swamp Cooler." If you are also ignorant, here's a definition, thanks to Wonderquest.

Q:  What the heck is a swamp cooler and how does it work-Jack W., Washington D.C.

A: A swamp cooler (more formally called an evaporative cooler) is essentially a large box-like frame containing a big fan and walled in by water-wetted pads, usually made of cedar shavings or cellulose. The fan whooshes the hot outside air through the dripping pads (which are continually soaked by a water pump), cooling the air by about 20 ºF as the air evaporates water molecules from the pads. The fan then blows the water-cooled air through the house and out a deliberate vent.

Wet the back of your hand -- then blow on it. Your skin surface feels cooler. That's evaporative cooling.

Folks differ on why it's called a swamp cooler. Some say because it makes the house feel like a muggy swamp-but that's only when the late summer rains come and the cooler is less efficient. On dry days-which is almost every day in a desert-a swamp cooler works fine. In high humidity areas, like Washington D.C., they don't work at all because the water does not evaporate appreciably and thus the air is not cooled.

Swamp coolers are popular in the southwest because they are relatively inexpensive, use a quarter as much electricity as a refrigerated unit, are easy to maintain by the average do-it-yourselfer, and add a comfortable level of humidity to the dry desert air. The smell of fresh cedar pads on the first hot days of summer is delightful.

(Answered by April Holladay, science correspondent, September 19, 2001)

For a more technical explanation, go here.

As a bonus from a school that focuses on communication -- and because we'll be on break next week -- here's something that has nothing to do with Spanish or French or languages at all. We relocated some bird feeders this weekend and our yard has turned into a bird and squirrel preserve. Asking myself "how did all these birds find the feeders" and then, in turn, asking Google, I found the following at another interesting site called The Straight Dope:

Dear Straight Dope:

I recently purchased a new bird feeder, filled it with (what else?) bird food, and hung it in a tree where there had never been a bird feeder before. Within an hour it was crowded with birds munching happily. My question: How did the birds find the bird feeder? Have they evolved to the point where they actually recognize a bird feeder from the air? Can they smell the food? Does one bird find the feeder, then communicate its location to the other birds by some secret tweeting code? Do they hang out at the bird feeder store and follow the bird feeders to their new home? This will forever puzzle me until you uncover the truth. --Kevin Rollins, Aurora, CO
SDSTAFF Colibri replies:

There's nothing particularly mysterious about this. Birds are just very good at finding food. Being small and warm-blooded, they have to consume a relatively large amount of food each day, and need to be efficient.

Small seed-eating birds probably cruise the neighborhood regularly in search of food, both individually and as members of flocks. It's quite likely they recognize a standard bird feeder as a highly concentrated source of food, not because they have evolved to do so, but on the basis of experience with similar feeders in the past, either in your neighborhood or elsewhere.

Most birds have a poor sense of smell, so they find feeders mainly by vision. Upon finding a food source too big for a single individual to consume, some birds will call to mates, or sometimes to flock mates, to alert them to its presence. But not all calls at a food source are altruistic. Once a few birds have gathered, they may fight over access to the food, especially if only a few good perches are available. The threat calls they give may inform other birds in the area that something worth fighting for has turned up, and attract them.

--SDSTAFF Colibri
Straight Dope Science Advisory Board