Can Livestock Farming Prevent the Extinction of Threatened Grassland Birds? a Study Case in South America.

BROWNE, MELANIE; DI GIACOMO, ALEJANDRO G.; DI GIACOMO, ADRIÁN S.

DC

Congreso; VII North American Ornithological Conference; 2020

NAOC

The Strange-tailed Tyrant (Alectrurus risora) is a threatened grassland bird that experienced a drastic 90% reduction in Argentina. Remaining populations occur inthe provinces of Corrientes and Formosa in northeastern Argentina where livestock production is the main land-use. We evaluated its breeding biology to use as astudy case of the response of endemic threatened grasslands birds to differing grazing histories. The study was conducted in a protected area without cattle in Formosa, another protected area in Corrientes, and several livestock ranches in Corrientes. The daily survival rate (DSR) was significantly greater in the protected area of Formosa than in Corrientes and in livestock ranches, with a probability of nest success of 0.30, 0.15 and 0.07 respectively. Nest density was also significantly higher in protected areas than in livestock ranches (nest density= 0.74 0.09 nests/ha, and 0.09 0.01 nests/ha; respectively). Grazing history could explain the different DSR observed between the provinces. Cattle was introduced in Corrientes in the 18th century, while it was introduced in Formosa in the 1930s. Early persecution by farmers drove top predators to extinction in Corrientes, while in Formosa they are extant. Thus, nests? mesopredator abundance in Corrientes is greater than in Formosa. The lower DSR and nest density of livestock ranches could be influenced by current livestock practices (i.e. annual-fire, high animal stocking and pesticide use) affecting vegetation structure and food availability. These results are alarming considering that most threatened grassland birds? populations are in private lands devoted to livestock grazing.