Bird Deterrence in the vineyard: netting and other options
Birds. Will they come and happily destroy this year’s yield? Or are the costs of using netting more than the price of going without it? Managing netting is a game of calculating risk, and flipping the bird coin.
Introduction
Like any vineyard management strategy, the context of whether the problem exists and how severe it is, is an important consideration. How prevalent are birds in the area? What neighboring sources of food (post harvested fields, etc.) could lead them to your vineyard (know what attracts birds!)? What predatory birds exist in the area to ward them off?
If you find yourself in a place of very little bird pressure, you may want to consider taking less extreme precautions to prevent bird damage. Of course, you’re always welcome to overprotect your grapes too, which of course comes with its own cost. Keep reading below to learn more about visual, auditory, and physical types of bird deterrents, and what factors weigh into their working ease, time consumed implementing (putting up and taking down), and effectiveness in deterring birds.
Visual and Auditory Deterrents
Old CD’s, holographic reflective ribbons streamed to end posts, fake owls with metallic eyes- these are all examples of reflective objects meant to frighten birds and keep them away from the grapevine rows. Fake predators and shiny objects can work to frighten birds with sound and visuals, and it is important to consider birds can become acclimated to these tactics and stop caring, meaning they essentially stop working.
Depending on how large your vineyard is, you may need to construct dozens of dowels tied with reflective ribbons or create structure holding CDs to effectively implement this strategy. So plan time for making and installing the objects. Most reflective tape is relatively inexpensive (e.g., $10/150ft) and old CDs are widely available, which is a big plus.
Predatory bird noise machines also exist and similarly may work for a while to keep birds away. They tend to cost somewhere between $150-600. Keep in mind that anything electronic out in the vineyard will need a power source. Machines also vary in the area they cover, with cheaper ones usually covering less area.
One vineyard where I have worked was fortunate to have predatory birds that regularly visited and scared away smaller birds. Nesting boxes can be put in place for sheltering predatory birds if present in the region. Because of the protection at the vineyard I mentioned, we were able to net fewer rows- at a 50% rate-and possibly could have done even less because our bird pressure was so low.
bird-exclusion Netting
All netting materials and styles are not made equal. For starters, they are crafted from different materials. Extruded netting is made out of black polypropylene and is less flexible and weaker than other types, such as knitted and knotted style nettings. The way extruded and other nets are applied and stored is also very different, which influences their cost and effectiveness.
The size of the netting holes will change their deterrence level. Some bird netting with very small hole and flexible material can actually cause a hazard for birds that get caught in it. It’s not uncommon to find a dead bird dangling from some fine knit netting at some point.
A third and very important consideration is the overall height of your net and whether each row will have one overhead net or two single sided nets. From my previous experience, I highly recommend overhead netting for vineyards that are accessible to equipment such as a tractor as it takes far less time to put on, secure, and take down again.
Finally, netting is not a one person job. Overhead netting tends to require three people for efficient application and, while one person can hang single side nets, it usually takes two people to take them down and reel them up.
Extruded Netting (Black Polypropylene)
Extruded netting can come as single sided pieces that are stitched together at the top and bottom, or single, wider pieces that can hang over the top of each row and only secured at the bottom. The stiff quality of extruded netting allows for it to spool well for storage. For the purposes of being compatible with the width of our fork lifts, the netting in this photo (right) is wound upon a 4” industrial PVC tube. Each tube has two bands on either end and the initial net is connected with a bread clip to both bands . The wheel that is used to crank up the netting is constructed of a PVC insert piece attached to a large wooden wheel with a crank (see video below for more details).
Net Installation
If you are stitching together to single sided pieces (not recommended for larger properties due to the long time it takes to reel the netting back up), you can run a net the length of the row and pin it loosely to the top wire and then run the other side and connect the second side to the bread clips. How thoroughly you choose to secure your netting will depend on how windy it is- poorly secured netting can blow off and tangle into neighboring rows. Be cautious hanging netting on other inner row structures, such post holes to prevent any unnecessary tearing in the net.
Taking Down Netting
Taking down and reeling up extruded netting does take more time than bunching up knit netting (described below), which is a huge downside to using it as a method. After a net has been unclipped and laid to the ground, it is attached the PVC tube on the fork and wound up by hand.
Knit Netting
What I’m about to share in regards to knit netting may be applicable to knotted netting and other types that are more flexible and overhanging in nature. These types of nets differ in the thickness (and strength) of the ropes that compose their webbing, as well as the size of their holes, and their total width. Some nets are so wide as to go overtop and then be pinned onto the ground with stakes, while others are shorter and bread clipped together at the bottom.
Unless the netting your working with has a reputation for knotting together when bunched (nightmare!), this style of netting can be mindlessly stuffed and pulled out of a storage sack.
It takes two to three people to apply the netting: 1 to drive the tractor and 1 or 2 to guide the net onto the rows and clip it secure. And then it takes three people to take the netting down: 1 person to drive the tractor, 1 to pull the netting back into the stuff sack, and 1 to guide the net off of the vineyard row. Watch the two videos below that show how it is put up and taken down. The other issue to avoid when taking down this netting are any bands, agrities, aglock, and other training devices that could snag the net. This similarly goes for trellis hardware, open loops, etc.