Alan Werner, of the USDA Wildlife Services, applies anthraquinone to a plot of rice to study what concentration of the chemical works best to keep birds from feeding on maturing rice.
A study conducted in 2015 by the U.S. Department of Agriculture at the H. Rouse Caffey Rice Research Station could lead to the release of a product that would address the problem of blackbirds feeding on maturing rice.
Scott Werner, research wildlife biologist from the USDA National Wildlife Research Center at Fort Collins, Colorado, chose to conduct the study at the station.
“The National Wildlife Research Center has worked with the Rice Research Station through the years and the blackbird problem has been prominent here, so it’s a natural fit for this kind of study,” Werner said.
This field efficacy study was supported by the manufacturer of AV1011 and AV4044 blackbird repellents, Arkion Life Sciences, of New Castle, Delaware, Werner said.
The study used 30 cages where plots of rice were planted. Just as the rice reached the milk stage of maturity, five red-winged blackbirds were released into each enclosure. A maintenance diet of bird seed was left in all of the cages for the birds to eat, and the food was weighed daily to determine how much of the feed was eaten.
Of the 30 plots, the rice in 10 was untreated. Another 10 plots were sprayed with a low rate of AV4044 per acre, and the last 10 plots were sprayed with a higher rate of AV4044 per acre.
The product AV4044 contains anthraquinone, the same material used in the AV1011 seed treatment used to prevent bird predation after planting. The chemical has no long-lasting effects on birds, but the birds find it unappealing to eat.
Werner said AV4044 also has a component that is activated by ultraviolet rays in sunlight that cannot be detected by the human eye, but birds can see it. They learn to associate the visual cue with rice that has been treated with the unappetizing chemical.
Werner said he has conducted lab experiments with this product to confirm its effectiveness by comparing blackbird consumption of repellent-treated and untreated food.
“With regard to rice yield, we observed greatest rice yield among plots treated with the higher rate, and least rice yield among untreated plots,” Werner said.
The second measure of efficacy was provided by weighing blackbird consumption of a maintenance diet of bird seed provided for the birds in each enclosure.
“As predicted, blackbirds in plots treated with the AV4044 repellent consumed more of the maintenance diet than birds within untreated plots throughout the 22-day field study,” Werner said. “These repellent efficacy data suggest that AV4044 shows promise for the protection of ripening rice from blackbird damage throughout the three weeks prior to harvest.”The blackbird problem is not confined to the southern U.S., Werner said, with the pest also feeding on crops in Asia, South Africa, and Central and South America.
Shelagh DeLiberto of the U.S. Department of Agriculture Wildlife Services releases a blackbird into an enclosure to study the effectiveness of a bird repellent on maturing rice.