Toxicological Trivia from March 18, 2015: In the mid 1990s the Swainson’s hawk (Buteo swainsoni) became one of the paradigmatic cases of indirect poisoning in Argentina. Spatial aggregation habits, habitat selection and power, combined with environmental conditions that favored population explosions of harmful insects to crops in the region (especially acrididae -locusts and grasshoppers-, with which the grasshopper hawk or locust hawk, feeds), were factors that combined dramatically and concluded in a series of events of poisoning mortality affecting approximately 20,000 individuals of this species, 5% of the estimated total population at that time. The organophosphate insecticide that causing mortality. already retired from Argentine market. and used in control acrididae -locusts and grasshoppers- in the central area of ​​the Pampas was: a) Parathion; b) Chlorpyrifos; c) Monocrotophos.

Correct answer: c. Read more in Spanish page:  "Comentarios sobre adulteraciones tóxicas e intoxicaciones indirectas" y la referencia 5. (SARASOLA, José Hernán; GALMES, Maximiliano Adrián  y  SANTILLAN, Miguel Ángel. Ecología y conservación del Aguilucho Langostero (Buteo swainsoni) en Argentina.Hornero [online]. 2007, vol.22, n.2 [citado  2013-02-23], pp. 173-184 . Ver). Read also in WP: A major cause of Swainson’s hawk population decline was pesticide use in its wintering grounds of Argentina. Farmers there were using pesticides (DDT and monocrotophos) to control grasshopper and locust infestations, and Swainson’s hawks were ingesting these pesticides in several different ways, but mainly by gorging themselves on the insects as they lay dying. The U.S. has worked with Argentine farmers to resolve this problem. (Goldstein, M.I.; Woodbridge, B.; Zaccagnini, M.E.; Canavelli, S.B.; Lanusse, A. (1996). "An assessment of mortality of Swainson’s hawks on wintering grounds in Argentina". Journal of Raptor Research 30 (2): 106–107.)