MORTALITY OF GALLINACEOUS BIRDS ASSOCIATED WITH 2-PERCENT ZINC PHOSPHIDE BAITS FOR CONTROL OF VOLES IN ALFALFA

Nontarget hazards to 52 ring-necked pheasants and 51 California quail were studied using 2 . 0% zinc phosphide (Zn3P2) steam-rolled-oat (SRO ) baits to control gray-tailed voles in 12 (0 . 2-ha) enclosures plant ed in alfalfa. Pen raised birds were wing-clipped and 25-26 of each sp ecies were randomly assigned to three Zn3P2 baited or three control ba ited enclosures (eight or nine birds and 23-24 voles in each). Twenty- four birds of each species were also monitored twice daily using radio telemetry. Following acclimation and pre-baiting (7 days), 2 . 0% Zn3P 2 or control (0 . 0% Zn3P2) bait was broadcast by mechanical spreaders , and birds were observed or monitored for 14 days post-baiting. Zinc phosphide deaths, supported by necropsy results, occurred in 69% (18/2 6) of the pheasants, and none (0/26) of the quail. Other bird deaths w ere associated with six predator attacks, four accidents, and three es capes. Eight birds were missing at the completion of the study. These losses were not significantly different between species, baiting group s, and radiocollar status. The occurrence of all but one Zn3P2 death ( 17/18) within 24 h of exposure was highly significant (p < 0 . 00001) vs mortality observed prebaiting and >1 day post-baiting. Sublethal to xic effects of Zn3P2 were observed in two pheasants. Postulated attrib utes of the efficacious bait (> 94% mortality for voles) that may have decreased nontarget exposure and environmental risks (particularly to quail) are discussed Plans for research to assess the potential hazar d of Zn3P2 to wild, free-ranging pheasants following a typical vole co ntrol program in alfalfa are underway.