Raptors and Their Role in the Vineyard

Last month, I provided an overview of gopher control in the vineyard.  This month I would like to focus on biological control, and specifically on the role of raptors in gopher control.

The most frequently recognized raptors in the vineyard are hawks, owls, the occasional golden eagle and kestrels.  Kestrels, members of the falcon family, are commonly called sparrow hawks or pigeon hawks.  Of all the raptors I get asked questions about, Barn Owls seem to generate the most interest.  Over the last two to three years, several authorities have written articles discussing the use of Barn Owls to control rodents.  This is especially interesting because a nesting pair of owls captures up to six  gophers per day to feed their young.  The question is, how does a grower attract a nesting pair of Barn Owls.   Owls are cavity-nesting birds that search out any opening for a possible nest.   Nothing works better than owl nest boxes.  If  Barn Owls cruise anywhere around your vineyard there is a high probability they will find and use the nest boxes prior to the nesting season.  Owl nest boxes are simple wood boxes mounted at the top of 12 to 18 foot tall poles, on a roof top, or any other high structure.  Owls provide their own nesting material - you need not pack the box for them.  See the diagram below for construction details.

Once you have established a nesting pair of owls you will get them back the following year and have the surviving young as well.  This of course depends on habitat and prey population, which brings us to the next part of this month's column. 

What if you don’t have Barn Owls in your part of the country?  Raptor perches are your next best bet.  Kestrels, Red Tailed Hawks, Coopers Hawks, Harriers and Kites will all use perches.  A raptor perch consists of an elevated vantage point that is easily approached near any perimeter of the vineyard.  Look around your vineyard at telephone or power poles and you’ll usually see a hawk or two perched and looking back at you.  You have several options with perches.  Simple 12 to 14 foot high poles may work. The best bet is to install a post that is a “T” at the top.  This will make it extremely “user friendly” for passing hawks.

There are several species of raptors to be found in the vineyard.  The type of bird and their food source is dependent on what part of the country you are in.   Owls receive the most attention because they hunt primarily at night and early morning, the same time most gophers venture above ground.  Smaller species of raptors feed on insects, small birds and reptiles as well as small rodents.  By encouraging raptors to make your vineyard their home you’ll see everything from gopher snakes to cotton tailed rabbits become a food source.

Biological control also involves weed control and different irrigation methods.  Sprinkler irrigation works in a gopher’s favor - flood or furrow irrigation destroys many burrow systems.  As I mentioned last month, if you reduce the quality of the habitat, you reduce the inhabitants.   Gophers feed on roots of plants and will come above ground to occasionally feed on the soft top growth of some grasses or legumes.  The management of unwanted vegitation in vineyards assists in gopher control.  Deep cultivation also destroys some gophers and some burrow systems.

Biological control can be a reality for the vineyard manager.  It is important to maintain a proper perspective on what type of control you are choosing if you are usingonlybiological methods.  You will not find a technique that completely eliminates anything.  The mindset that needs to be adopted is one of management.  The grower will be managing his control methods as well as his target species.  Although not as effective as some trapping methods or chemical controls, it is a practical alternate approach with good PR value.

Gopher control, like bird control or any other type of pest control, is dependent on your ability to take in the big picture.  Before you begin a program, determine why you have a problem.   Are you providing a predator-free environment with an unlimited food source?  Is your neighbor providing the same?  It’s a step by step process and the key is to take the best steps available to solve the problem for the longest period of time.  That is the value of establishing owl nest boxes and raptor perches.

Next month we’ll take an in-depth look at chemical control and trapping of gophers before moving on to another pest species.  I’ll talk with you then.