Preventing Bird Damage
Bird damage in sweet corn is always a problem though it is worse in a dry year, it can be damaging in any year. It is better to take action in advance of the problem, because once birds get in the habit of feeding on your corn, it will be harder to stop them! Redwing blackbirds and other flocking birds can cause serious crop losses in some fields. Unfortunately there is no easy answer and no guarantee that a
particular tactic will work.
Some General Tips on Repelling Birds:
- Birds invade sweet corn fields about three days before picking. Time any control techniques so they are in place BEFORE harvest, and stay until harvest is complete.
- Use multiple tactics that reach more than one sensory mode. For example, combine scareeye balloons with auditory repellents like shellcrackers or distress calls. This is likely to be more effective than using one tactic alone.
- Move devices frequently. Birds can learn and become habituated to any device that is used for a long time in one place.
- Good insect control will reduce the corn’s attraction to birds. Birds eat insects, which is not a bad thing, but they also like succulent grains of sweet corn and apparently can’t tell the difference. And, they cause a lot more damage than most insects do.
- After harvest, scare devices can be removed from one block and concentrated in the next block. Some growers then allow birds to scavenge in the old block. A method that some growers say works is to rotary mow or disc the interior blocks of the previously harvested fields. Birds like to feed on the ground because it is easier than clinging to an ear, but they prefer perching nearby for protection and rest.
Sweet corn topping:
A new technique that has been studied and tested in NYS is to ‘top’ the corn.
Topping is the removal of the top of the corn plant from just above the silk or top of the ear, after pollen
shed and pollination. Growers who use this method report the advantages to be:
- 2 to 3 days early harvesting compared to untopped
- Improved picking ease (and happier pickers)
- Reduced bird damage
- Reduced lodging due to wind.
Other benefits may also include better spray coverage. It is important to use equipment that is designed for this purpose to ensure safety; one source for a topper unit is Haigie.
To test this, and evaluate possible negative effects as well, Chuck Bornt and Ted Blomgren of the Capital District Vegetable Program, Cornell Cooperative Extension, have completed several studies. In 2004, they tested it in early and late plantings, with topping at different corn stages (just after pollination, and after dried silk) and different heights (just above the ear, or with two flag leaves remaining). Topping was completed using a handheld gas powered weed wacker with a blade for different treatments. There were no yield differences except where early corn was topped low, at one site; early corn also showed earlier yields by 23 days. At one location where bird damage pressure was high and no other bird controls were used, bird damage was significantly reduced where topping had occurred compared to untopped plots,
which resulted in higher marketable yields.
Visual Scare Devices:
Eyespot balloons and reflective mylar ribbons are effective and fairly economical for small fields. Many growers are using these silent deterrents and the general feeling is that they are fairly effective, especially when combined with auditory deterrents. Growers report that the following methods make balloons more effective: use at least 8 balloons per acre, place them in the field several days before harvest, and leave the previous block standing, without balloons, to allow birds to feed in older corn.
‘Rejex-it Migrate’ is liquid bird repellent made from a blend of food grade ingredients extracted from common sources such as concord grapes, neroli oil, acacia, gardenia blossoms, etc. It is non-phytotoxic and meets the EPA’s new “reduced risk” criteria and is registered in MA as of 2010. It is labeled for use in sweet corn. Migrate is a contact repellent. It must be eaten before the birds get the repellent effect and learn to avoid treated areas. A small amount of sampling will occur after the initial treatment.
Auditory Scare Devices:
Exploders are gas fired cannons placed in the field and fire with automated discharge timings. These can be quite effective. Cannons are available from some agriculture supply sources. Do check with your farm neighbors and the local police to let them know what you are going to do. Cannons are very loud.
Shellcrackers are 12 gauge shotgun shells in which the lead shot has been replaced with a bulldog firecracker. When fired from a shotgun, this firecracker travels 75 to 150 yards and explodes in the air with a loud report. Use a single shot, inexpensive 12 gauge shotgun as the loads are very corrosive.
Firing a few rounds early and late in the day will unsettle birds. Federal permits are not required. Again, notify local police and neighbors to let them know what you are doing. Check on local town ordinances. This method can be satisfying on a short term basis. The disadvantage is that it requires a person to take time in the field to discharge the shellcrackers. For a more detailed fact sheet on shellcrackers and other
prevention devices, contact USDA Wildlife Services (413) 253-2403.
Here are three sources for shellcrackers:
- ReedJoseph International Co. P.O. Box 894
Greenville, MS 38702 (800) 6475554
- Margo Supplies Ltd. Site 20, Box 11, RR#6
Calgary, Alberta, Canada T2M 4l5 (403) 6521932
- Sutton Ag Ent. 1081 Harkins Rd.
Salinas, CA 93901 (866) 4824240
Recordings of distress calls or the calls of predatory birds, which repeat at regular or random intervals and operate on battery or solarpower, can be quite effective. Because flocking birds are very responsive to the signals from others in their flock, a distress call from one bird is a sign to all the others that an area is unsafe. These have become quite sophisticated, with programmable or random call intervals that help to overcome birds’ ability to get used to regular sound intervals. Make sure you are using a distress call that matches the bird species you need to scare away.
Here are some sources:
- OESCO, www.oescoinc.com, (800) 634- 5557 or (413) 369- 4335
Rte 116, Conway, MA 01341
- BirdGard, Bird Control Products, 888-332-2328
- Birdbusters, 300 Calvert Ave, Alexandria, VA 22301, phone (703) 299- 8855
- BirdX, Inc, 300 Elizatbeth Ave., Chicago, Ill 60607, (800) 860- 0473
- Gemplers’ 100 Countryside Dr., PO box 270, Belleville, WI 53508 (800) 382- 8473
A federal permit is not required to shoot or otherwise control blackbirds, cowbirds, grackles, crows or magpies when they are found committing or are about to commit damage to or “depredation upon” agricultural crops. In Massachusetts, state permits are not needed for controlling starlings. State regulations allow hunting of crows any time of year except during the nesting season. For more details contact the MA Division of Fish and Wildlife Field Office (508) 792- 7270.
R. Hazzard, with information from Laura Henze, US Fish and Wildlife Service; Chuck Bornt and Ted Blomgren, Cornell Cooperative Extension.
Updated July 2006
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