This month I wanted to spend some time discussing bird damage. I had a person ask me why bird damage was an issue for wine grape growers the other day and it occurred to me that there were several different answers to that question.
Bird damage in grapes comes in two basic forms. Starling, robins, cedar waxwings, and assorted orioles and tanagers will take whole grapes off the clusters. Any of these bird species is capable of stripping every grape from a cluster. Starlings, however, are the most damaging species because of their flocking nature. Where a grower may have 25 or 30 robins, the same grower could have several thousand starlings. Obviously, there is strength, or in this case, severe damage, in numbers, and starlings have got that part down.
Cedar waxwings are a distant second to starlings. West Coast growers should be thankful that cedar waxwings are migrating through wine country in February and March rather than September and October. In the East, these birds voraciously consume large quantities of whatever berry they target, and frequently that means grapes. Like starlings, cedar waxwings have a very “streamlined” digestive system. What goes in, goes back out again real fast. This means that these birds can consume an unbelievable amount of your grapes in a very short period of time.
House finches, rosy finches, english sparrows, Eastern and Western bluebirds and that ever growing category, “linnets”- which seems to most people to include any small bird that can’t be easily identified - can’t get a whole grape in their beaks. So, they peck at the grapes on the cluster. This makes your wine grapes look like raisin grapes. It invites insect damage and, in the right climate, mildew. Although none of these birds create the catastrophic damage that starlings do, the cumulative effect of ruined berries, insect damage and disease is close enough to catastrophic. In addition, most of these birds are ground feeders.
Starlings can be seen roosting on power lines or swirling in clouds over the vineyard. This is always a bad sign,but at least it is a sign. You can have a “ton” of finches or robins and never know it. They fly in in small groups, land on the vineyard floor and just seem to multiply. You can walk down one row, jump up 5 or 10 birds which fly 30 feet or so. By the time you get to the next row you think you’re chasing the same bunch of birds around - you’re not, it just seems that way. Then you start to get an idea ofhow manybirdsare in this vineyard.
The “why this is a problem” part seems pretty obvious. But still, most don’t realize the damage that occurs in situations like the ones described above. What starts as a few vines, or maybe “a row or two down by the creek,” is in the process of turning into a reliable food source for a migratory species like starlings. If you’ve noticed an increase in the bird population around your vineyard, or if you have a tasting room on site and you’re
spending a lot more time than you used to cleaning up after birds, you need to stop and think a minute. Am I supporting an ever growing population of birds? Not that this is all bad, birds are beautiful. I wouldn’t be in the occupation I’m in if I didn’t enjoy birds more than almost any thing else. But it gets back to the “why this is a problem” portion of this article. Your vineyard is a major source of food, water and shelter.
An example of this that is non grape related is snow geese. Snow geese in the central flyway - north to Hudson Bay, south to Texas and Mexico- are in a critical stage right now. The state and federal refuge systems in the Dakotas with the assistance of great organizations such as Ducks Unlimited, have worked for years to provide migrating waterfowl with food and habitat along the migratory flyways. They’ve had too much success with snow geese. The combination of the refuge systems, improved farming practices that consistently provide excellent grain food sources, and sound management practices have led to an explosion in the snow goose population.
They’re feeding out their breeding grounds in the north and devastating crops along the migratory path. What will happen? Are these birds so smart that they have learned how to triple their own population? Probably not. Snow geese will most likely be devastated as species in the next ten years because they will destroy their own feeding grounds in the north. They are overgrazing the Canadian tundra during breeding season leaving no available food source for the broods that are hatched. Oh that the same plight would await the starling. Unless Ducks Unlimited and the Canadian and U.S. Federal management organizations can control the population, to avert the impending crash, with sound biological and scientifically proven methods (I can assure you that animal rights groups everywhere will oppose this), snow geese are in big trouble.
Many will tell you that the reason birds are in the vineyard is because they are so smart. They have found a source of food and they come back to it every year and feed on it when the sugar content is the highest to get the most energy to help them on their journey.
Parts of that may be true, but look at it another way. Vineyards are a constantly regulated ecosystem. Vineyard managers spend their time and money controlling everything they can for the sake of consistency, which yields great winegrapes. No drought. Predators are controlled. Cover is provided. Grapes are present, but too acidic to be tolerated by birds until after vorasin.
So, why is bird damage even an issue in the vineyard? Because, we have created the perfect environment for them to feed, breed, live in and migrate to. They are a constant- always will be a constant. This leaves the grower with the task of keeping them out as best he/she can. Next month we’ll tackle that one.