Supplemental frightening devices can enhance the effectiveness of harassment patrols at both farms and roost sites. Automatic exploders have been used effectively to supplement cormorant harassment in more remote night roost sites.
Exploders at production sites should be turned off after sunset to prevent habituation and to avoid harassment of other wildlife.
Where birds are scared easily by the presence of humans or vehicles, a few strategically placed exploders and scarecrows (human shaped and/or old vehicles) can increase the effectiveness of frightening programs on farms.
Automatic pop-up scarecrows may be more effective than conventional types since they have the added factor of motion. In field trials, such passive frightening devices (i.e., ones that do not require a constant human presence to function) have deterred cormorants for a few days to several weeks.
Passive frightening devices are less effective against herons and egrets than cormorants.
Since effectiveness of frightening techniques varies, producers should not rely solely upon them. Rather, they should employ exploders and scarecrows as some of many tools in an aggressive, integrated bird management program.
Scarecrows, exploders, or pop-up scarecrows usually are effective for only short periods, but they can be especially useful at isolated ponds or where access is difficult. Passive frightening devices may also make a subtle but significant difference by preventing birds from landing on a section of the facility between the times when it is monitored by harassment patrols.
The effectiveness of scarecrows and cannons should be monitored closely and these devices should be moved to new locations every few days to reduce habituation by birds. Scarecrows should be replaced periodically with human shooters. Where birds have become habituated, exploders and scarecrows should be removed for several days or weeks while aggressive harassment is continued.
The devices can be tried again later if the birds once again are frightened easily by humans and vehicles. Even the most aggressive harassment program rarely eliminates all bird predation. Herons, egrets, and gulls can be exceedingly difficult to disperse.
Frightening devices can scare away large flocks of cormorants, but groups of less than 10 birds may remain on the farm and move from pond to pond despite continued harassment. In general, producers should expect scaring programs to reduce but not totally eliminate bird predation.
When non-lethal scaring programs are ineffective, producers may have to resort to limited killing of birds to reinforce fear in the remaining birds. Depredation permits are required from the U.S. Fish and Wildlife Service and, in some states, from the state wildlife agency, to kill almost any species of birds.
Contact your nearest USDA Wildlife Services Control office about procedures for obtaining a permit. New federal regulations proposed in 1997 would allow persons engaged in aquaculture production to kill double crested cormorants at their farms without a permit.
At the time of printing for this publication, however, these proposed regulations were still undergoing review. For currently applicable laws, contact your nearest USDA Wildlife Services office, aquaculture specialist, or the U.S. Fish and Wildlife Service.
Costs and benefits of frightening programs:
The costs of employing frightening programs on farms can vary substantially, depending on the mix of techniques used, the species of birds involved, the size and configuration of the farm, and road and levee conditions. Below is an example of daily costs (1997 estimates) for a typical scaring program on a farm of 500 acres or less of contiguous ponds:
- Labor (10 hr @ $8/hr) …………$80.00
- FICA on Labor @ 7.65% …………6.12
- Vehicle expenses (100 mi @ $.30/mi) ………………………………30.00
- Pyrotechnics (average 20 rounds @ $36.50/100 rounds) …………….7.30
Live ammunition for harassment of birds:
- (300 rounds .22 shells @ $1.25/100 rounds) ………………………………….3.75
- (25 rounds 12 gauge small game loads @ $5.25/ 25 rounds) ……..5.25
TOTAL………………………………$132.42
For example, if cormorants were a problem for five months of the year, then scaring costs under this scenario would be almost $20,000 annually. Supplementing the program with exploders and scarecrows would require initial start up costs of an additional $1,000 to $2,000. Many
farmers spend considerably less, while others spend substantially more than these amounts. Employing bird scaring programs on facilities of more than 500 acres or on those facilities with widely separated pond complexes would require additional personnel, vehicles, and ammunition.
These costs usually are justified on facilities with serious cormorant depredation. For instance, constant feeding activity by 100 cormorants (but not necessarily the same individuals) throughout the day would result in fingerling losses of $400 per day, which would easily offset and justify the costs of an aggressive scaring program.
During the winter in the southeastern U.S., several hundred or even thousands of cormorants sometimes visit farms that are close to night roosts. Harassing cormorants at these night roosts can help alleviate this problem, but the costs of roost dispersal programs to individual farms vary with the number of roost sites involved and the number of farms participating in the dispersal program.
The total cost of dispersing birds from 30 to 40 roost sites over the course of two winters in the Mississippi Delta ranged from $16,757 to $32,302. The average cost per farm of the 40 to 50 participating farms ranged from $400 to $640 per year.
Producers also reported average savings of $1,400 to $3,200 per year due to reduced costs of harassing cormorants on their farms.
Authors:
Gary A. Littauer , James F. Glahn , David S. Reinhold and Martin W. Brunson
