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Barn Owl Nestboxes: Gopher Control or Just Another Gimmick by Mike Taber in Sept-Oct WCT Magazine.

 

Barn Owl Nest Boxes, Gopher Control or Just Another Gimmick??

I recently read an article in a well respected vineyard and winery publication that featured barn owl nest boxes.  In the article the author speculated that not only will a healthy population of barn owls eliminate a gopher problem but they’ll also greatly reduce the need for pesticide use in the vineyard.  By pesticides, the author was actually inferring rodenticides, not insecticides or fungicides-although it was a pretty broad statement.

I refuted this claim by writing a letter to the editor and got an interesting response from an individual in Pennsylvania who is much more well versed in population dynamics than I am.  This response, combined with the empirical data we’ve collected dealing with growers over the years leads me to ask the question, are barn owl nest boxes really that effective for gopher control or are they just another gimmick.

Rex Marsh asserted years ago that promoting barn owls to control rodents was a mistake. (Sept. 1998 The Probe) In fact, the title of the article was “Promoting Barn Owls to Control Rodents is Deception”.  Rex’s point was that not only will barn owls not control rodents, but the growers belief that they may is detrimental overall to the cause of rodent control because the individual will let the rodent population explode, while vainly hoping for a biological solution, and eventually have to use significantly more rodenticides to bring the problem into balance than if proper measures had just been used initially.

Rex is a pretty well respected guy-I mean he knows more than, well, anyone, in most people’s opinion, when it comes to rodent control.  Few people have made a career of teaching other people how to kill gophers.  Rex has-and is one of the most respected people in the vertebrate control world.

So, there’s a point in the gimmick corner.

The problem as I see it here is that Barn Owls eat gophers.  We all know that-and if you don’t just go check out the base of an owl box in the spring.  You’ll find hundreds of gopher bones-along with other rodent parts-but gopher skulls, legs, ribs-heck you could probably build a gopher skeleton, something every wildlife control professional needs, out of what you find at the base of an owl roosting point or nest box.  So we know they do eat gophers.

The assertion in the article I read a couple months ago was basically what I like to call the “Field of Dreams Theory”.  If you build it, they will come.  So, if theoretically you had an area with a high population density of gophers or other pest rodents and you had barn owls in that part of the country (Barn Owls are in most parts of the country) then the more boxes you built-the more would get used because you are creating good nesting habitat-Barn Owls are cavity nesters-and there is an abundant food source with the aforementioned gopher population-so see, if you build it they will come!

Now we have our field of dream….uh, gophers, and we have a great gopher predator, and what will happen is the barn owls will thrive, to the point that they eat thousands of gophers per year.  So many gophers that there is no way that the hapless little rodents can keep up from a breeding standpoint and you’ve attained control.  Right?? Well, could be.

Let’s look at a couple things.  We know species adapt-so a percentage of these gophers are going to get wise to the “death from above” threat and adapt their habits to be less vulnerable.  We also know that predators will move away from an area that provides a decreasing prey base, due to competition from other predators, territorial disputes and so on.  So we have some changing variables here that are going to affect the outcome in our field.  I think this is the point at which the goal, effectively managing a rodent problem, gets lost sight of in the discussion.  If the owls have reduced the gophers to acceptable levels-then, we have a winner don’t we?  I’m not aware of anything, short of extinction, that controls a single pest species until the end of time, so for a moment in time, the owl nest box deal worked.  So, a point for the owls then.

Ultimately, there are a couple larger questions at work here.  The first is the predator/prey relationship.  So I ask you.  Does a large prey base control/attract the predator population, by supporting a high number of predators?  Or do predators control the prey population by keeping fluctuating numbers of prey at a steady predictable/declining level?

In my conversations with the gentleman in Pennsylvania he brought up his support for the reintroduction of wolves to the eastern seaboard in an effort to help control the white tailed deer population explosion that we all are so familiar with.  I couldn’t help but think of a gentleman by the name of Frank Glaser.  Frank was a government trapper and hunter from the mid 1920’s through the early 50’s in Alaska.  Frank was charged with tracking the migrating caribou populations and recording the effect of wolves on caribou and moose.

In his autobiography, Alaska’s Wolf Man, the Real Life Adventures of Frank Glaser (Jim Reardon) Glaser, who is refreshingly not in any way shape or form, politically correct (it was 1950 after all) blows away any notion that wolves only kill what they need and then only the sick, old or orphaned animals.  In fact, Glaser often shot them out of disgust or more correctly distain, after watching them kill caribou and moose strictly for sport-or for a display of territorial dominance.  Young caribou were routinely killed out of frustration, when the adults were too fast, and then left, untouched, by sulking wolves looking for an apparent “good or worthy kill”.

And the moose-they nearly wiped them out in parts of Alaska.  Wolves won’t take on moose in the summer or fall, they wait until the winter or early spring, when the prime adult males are exhausted from the rut and mating and can’t move around much in the deeper snow.  Then the wolves simply run them down, feed on their hindquarters while their still alive and then leave.  The moose dies in a couple days from the injuries, but the wolves won’t feed on a dead moose or even finish one off and feed on the hundreds of pounds of meat available-they just want a couple prime chunks out of the hindquarters, while it’s still warm…

So it would seem that our hope, that a predator, like a wolf or a barn owl, could be focused on a certain pest species is a little more hope and a little less biologically founded than we might be willing to admit.  Now, for perspective here, no one is worried about a declining gopher population due to “owl abuse”.  So the comparison kind of runs out of steam at this point, but I wasn’t the one who brought it up-the zoological expert from PA. made the comparison, so I’m just passing it along here for thought.

The next, much more difficult thing in my opinion to look at is the subjective nature of the term control.  What is control?  First of all, as wildlife damage professionals we all have an idea of what we think control is-but in most cases it’s the customers idea of control that matters the most.  Problem is few people spend as much time defining control as we do, so we’re all left with this interpretation variance to deal with.

I know in my experience with people with gopher problems, control is seeing dead gophers.  They (the customer) haven’t taken time to quantify the problem, they just see dirt mounds, or holes, or plant damage and want it to stop.  So if I install a Barn Owl nest box and they see owls-well then it must be working.  Notice I didn’t say anything about dead gophers.  If they see owls actually eating a gopher, I should be nominated for some sort of award.  If they see owls eating gophers and fewer mounds (cause I kicked them all down) and no more plant damage, I am some sort of animal control God.

Since I’m a God now, I’m filled with the wisdom and knowledge that I actually may have only started to scratch the surface of their problem.  Or that I could have used a rodenticide or traps and achieved the same results more quickly and consistently at a lower cost.  Or it could be that their problem was never really that large in the first place because I know that one pocket gopher makes several mounds and if you have 3-5 gophers in an area it looks like you have 100.

I guess the bottom line here is that Barn Owl boxes do work for gopher control, for some people, in some situations.  In other areas, it’s a feel good gimmick, because either the owls don’t exist in large enough numbers to offer any measure of control or the problem is simply to vast and varied for one type of control.  At the end of the day, that’s why you need a professional on site, to give you honest and informed feedback about what tools and options are available and how and why they should be used.

I guess the answer here is that before we label something either a sure thing, or a gimmick, we need to spend some time assessing the problem, the options and the goal.  Then we’ll know for sure whether or not what we’re getting ready to use is the best tool for the job. 

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