Nontarget bird exposure to DRC-1339 during fall in North Dakota and spring in South Dakota

Abstract

Blackbirds frequently use ripening sunflower ( Heltantbus annuus ) as a food source in the northern Great Plains. In 1999 and 2000, the avicide DRC-1339 (3-chloro-4-methylaniline hydrochloride) was used experimentally on fall-ripening sunflower fields in North Dakota so researchers could evaluate its effectiveness for reducing crop depredations by blackbirds. DRC-1339 was applied to rice and broadcast on the ground in a confined area within ripening sunflower fields. One objective of this study was to determine whether nontarget birds, birds other than blackbirds, were eating rice and were exposed to the DRC-1339. In 1999, 8 of 11 (73%) sparrows collected by shotgun in sunflower fields treated with DRe-1339 had rice in their gastrointestinal (GI) tracts. In 2000, 5 mourning doves ( Zenaida macroura ) and 3 sparrows were collected by shotgun in sunflower fields treated with DRC-1339. Three doves had rice in their GI tracts, 4 doves and all 3 sparrows had measurable DRC1339 concentrations in their GI tracts, and 3 mourning doves and 1 savannah sparrow ( Passerculus sanduncbensis ) exhibited histopathological signs of kidney damage. In April 2002, untreated rice was applied to corn stubble plots in South Dakota to determine which bird species ate rice. In 2002, 3 of 3 song sparrows ( Melospiza melodia ) collected by shotgun had rice in their GI tracts. Our results demonstrate that the use of DRC-1339 to control blackbirds in the northern Great Plains will likely expose nontarget birds to the DRC-1339 bait.