The Swing of a  Gourd

I've been asked a number of times about the method I use to tie my gourds to my racks and about the excessive amount of swing that can take place because of it.  In most of those questions, I'm asked about whether or not I'm worried about the contents inside the gourds being tossed out.  I've done a good amount of observation of my colony and the gourds used in it and the following is why I tie my gourds and let them swing the way I do.  For those that haven't seen my picture before, I tie my gourds using coated 12 gauge electrical wire.  In my following explanation, I'm going to approach it from an engineering standpoint, since that's my field. And also, I also change my wires out every other year. Fatigue of the wire ‘in any situation’ can result in a gourd coming down and that’s something you don’t want.

And let me also add here: You will get different answers about hanging gourds from just about everyone you talk to on the subject. Each landlord has their own reasons for hanging them the way they do. Some like them rigid. Some, like me, like to let them swing. The following are my reasons.

The swing of a gourd, when hung at the top as shown above, is actually good for a number of reasons.  No, it doesn't prevent any other kind of bird from nesting in them.  That's a myth and someone's wishful thinking.  It also doesn't prevent any kind of predator from attacking the gourds.  Only properly installed predator guards will do that.

The swing of a gourd means that it is 'hinged' so to speak at the top, thus bringing the laws of centrifugal force and momentum into play.  (Not so with hard mounted gourds, which I'll explain).  If a sudden movement or jolt of the mounting structure (T-bar, rack, house or whatever form of housing is used and from this point on, called 'rack') occurs, the top of the gourd follows with it.  However, the bulb of the gourd does not.  One of the laws of physics says that, bodies in motion tend to remain in motion and bodies that are at rest tend to remain at rest until acted upon by another outside force.  But then, everybody knows all that stuff from high school, so back to the swing of the gourd.

Any outside force on the rack causes it to sway back and forth.  This swaying of the rack moves the top of the gourd while the bottom (bulb) only moves slightly, usually only tipping slightly to match the movement of the top.  Normal bumps or wind actions on the rack will set up a rhythm of the rack and if not continued, the rack slowly returns to normal.  The hinge (at the top of the gourd) stays with the rack while the bulb actually stays somewhat in place.  So in reality, the contents of the gourd do not move around as much as most fear.

Note here: I actually have a camera in a gourd and have watched what happens to the contents of the gourd on very windy days and thus, I can make the above statement with a high degree of confidence.

If the motion is continuous and consistent, then the gourd bulb simply sets up a sort of back and forth tipping action and really doesn't move that much.  However, if the motion becomes stronger, such as a high wind can cause, this causes the gourd bulb to begin to swirl and also sets centrifugal force into motion.  This tends to make the contents inside stay put simply because of the nature of the force.  The bowl tends to tip in the direction ‘normal’ to the force and thus, the contents tend to remain in place.  This can only happen with gourds that are allowed to swing in any direction, such as the way I let mine swing.

However, if a gourd is hard mounted, (and this applies for all hard mounted housing), then the contents of the gourd are at the mercy of the mounting structure and the back and forth momentum of that structure causes the contents to bounce and bump around.  A sudden jolt or movement of the house or rack with a hard mounted gourd will mean the nest, which is usually packed into the compartment and is essentially hard mounted itself, will want to move with the house or gourd, but the contents of the nest, being loose, will not.  It's kind of like yanking a tablecloth out from under the place settings.  If the nest is moved drastically out of the way, the nest contents, because of momentum, will want to remain in place and thus, will be forced out of their nest and unfortunately, will be thrashed about the compartment.  The nest cannot tip to accept the force such as with a gourd that is allowed to swing.  Centrifugal force of the nest cannot become a factor in such a case, but momentum of the nest contents, can.  The faster the motion of the mounting structure, the more momentum takes over and the more the contents are bounced.  If a fast back and forth cycle of the house is set in place, the nest will want to stay with it, but the nest contents are not hard mounted and they will move all about thus actually becoming more susceptible to breakage or tossing out.

Now, let’s test our theory!

Hard mount!

Place a cereal bowl on the counter and put a couple of marbles in the bowl and let them settle till they aren’t moving any more. The bowl is duplicating our martin nest and the marbles are our eggs. Now bump the side of the bowl hard enough to make it move a couple of inches. Notice what happens to the marbles. They move and roll all over the place. If this bump were hard enough, the marbles would quickly roll right out of the bowl.

This duplicates the same results you would get from any form of housing that is hard mounted. Yes I agree that the ‘bump’ would have to be a pretty good one, but they do happen and the results are the same.

Swing Mount!

Now take that same bowl of marbles and place it into a ‘hanging plant holder’. Holding the top of the hanger, quickly move your hand to the side by about 3 inches. Notice how momentum initially keeps the bowl in place. Then, it slowly swings to catch up and within a short time, will settle back in place. In fact, swing the top of the hanger in a circle of about 6 inches in diameter and watch what happens. The marbles will stay right in the bottom of the bowl.

This is the same theory that I use and the reason I hang my gourds the way I do.

Now, there are extremes to everything and there is a point at which no type of structure, including this one, will contain the nest contents. Hurricanes and tornadoes or major bangs into the pole are extremes.  But for normal day to day happenings in a martin colony, the above will hold true.

Thus my reason for letting my gourds swing in any direction they wish.  But no twisting or turning...  That is a no-no. Gourd openings should ALWAYS return to the exact same direction they were to begin with.

One more thing...  In all my years of keeping martins, I HAVE NEVER LOST AN EGG OR BABY due to the way I hang my gourds.  As long as they are allowed to swing, they can accept any small sudden jolts that may occur on a daily basis.

Chuck Abare