UMass Extension Vegetable Program

Preventing Bird Damage to Sweet Corn

Bird damage in sweet corn is always a problem.  Although it is worse in a dry year, it can be damaging in any year.  Start now to prevent damage! It is best 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.

The redwing blackbirds nests in hayfields, marshes and ditches and congregate at large nighttime roosts near their nesting sites. Large flocks feed in fields and bottomlands, and the worst damage to sweet corn is reported by growers near rivers and marshes. Insects are the dominant food in the nesting season (May through July), then the diet shifts to grain and weed seeds in late summer.  This, along with the expanding acreage of ripening sweet corn in mid July, may explain the ‘sudden’ appearance of flocks in sweet corn at this time. Grains that are affected by redwing blackbirds include sweet corn, ripening grain corn, sunflower, sorghum, and oats.

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 scare-eye 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.

-Leave old corn for birds to to eat. After harvest, scare devices can be removed from one block and concentrated in the next block. Try to keep the birds foraging in the old block while delaying their move to the one that’s ready for harvest. Some growers allow birds to scavenge in the old block before disking it in.  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.  It also helps if you plant succession blocks at opposite sides of the field, not right next door.

-Good insect control will reduce the corn’s attraction to birds.  Birds that are attracted to ears by the presence of caterpillars will cause damage to non-infested ears in the block as well.  They cause a lot more damage than most insects do.

Visual Scare Devices:

Eye-spot balloons and reflective mylar ribbons are effective and fairly economical for small to medium sized 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. 

Chemical Deterrents:

Rejex-it Migrate is liquid bird repellent whose active ingredient is Methyl Anthranilate (MA), extracted from Concord grapes. It is not phytotoxic, is safe to use, and is labeled for use in sweet corn up to the day of harvest. Migrate is a contact repellent that makes the crop unpalatable to birds.  After the birds taste it, they learn to avoid treated areas. Begin applications when birds begin feeding or crop begins to ripen, get good coverage of the plant, and use repeat applications or higher rates if populations are high. Apply in the evening rather than the heat of the day. Repellents are likely to be most effective if combined with other tactics.

Auditory Scare Devices:

Exploders are gas-fired cannons placed in the field that fire automated, timed discharges.  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. Neighbors may complain.

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:

   -Reed-Joseph International Co.,  Greenville, MS 38702  (800) 647-5554

   -Margo Supplies Ltd.,  Calgary, Alberta, Canada  T2M 4l5  (403) 652-1932

   -Sutton Ag Ent.,  Salinas, CA 93901, (866) 482-4240

Distress Calls and raptor calls.

    Recordings of distress calls or the calls of predatory birds, which repeat at regular or random intervals and operate on battery or solar-power, 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. Conway, MA

   -Bird Guard Bird Control Products, 800-331-2973, email info@birdguard.com, Erie PA

    -Birdbusters, Alexandria, VA phone (703) 299 8855

   -Bird-X, Inc, Chicago, Ill, (800) 860-0473

   -Gemplers,  Belleville, WI (800) 382-8473

Hire a falconer. Even better than recorder raptor calls is the real thing! There are falconer clubs in many areas. Hire a falconer to fly his bird over your field. Nothing will clear out a flock of blackbirds faster than a falcon swooping over the field! 

Sweet corn topping.  A technique that has been studied and tested in NYS and CT 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.   The advantages may include 1) 2 to 3 days early harvesting compared to un-topped, 2) improved picking ease 3) reduced bird damage, 4) easier to monitor bird activity in the block 5) spray coverage and 6) reduced lodging due to wind. One significant risk is that cut stems are sharp and pointed and can cause eye injury to pickers; it’s a good idea for pickers to wear goggles in topped fields. It is important to use equipment that is designed for this purpose to ensure safety; one source for a topper unit is Haigie.  As with other methods, topping should be done early, several days before harvest, so the birds are not already feeding in the block.

Fly model airplanes. This novel method was reported by a grower who says he invites model airplane enthusiasts to his farm. Model planes flying over the fields can scare birds away.

Shooting birds. 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 your MA Division of Fish and Wildlife District Office (western district (413) 684-1646; CT Valley (413) 323-7632; central district (508) 835-3607; northeast (978) 772-2145; southeast (508) 759-3406).  From now through the rest of the corn harvest season, no permit should be required to hunt crows.  While hunting can reduce numbers over the long term, it may not be effective against flocks of invading birds.  It is not illegal to display dead birds in the field, but it is not clear that this is an effective deterrent. For regulations on geese, consult the US Fish and Wildlife service at 413-253-8200.

    --R. Hazzard, with information from Laura Henze, US Fish and Wildlife Service; Chuck Bornt and Ted Blomgren, Cornell Cooperative Extension; Richard Dolbeer, USDA-APHIS-ADC

The information in this article is for educational purposes and is based on the best available information at the time of printing. Always read and follow the label; is this information does not agree with current labeling, follow the label instructions. State regulations may vary. Reference to commercial brand names or products is for informational purposes and no endorsement or approval is intended.