Can livestock farming prevent the extinction of threatened grassland birds? A study case in South America

MELANIE BROWNE; ALEJANDRO G. DI GIACOMO; ADRIAN S. DI GIACOMO

Virtual

Congreso; VII North American Ornithological Conference; 2020

The Strange-tailed Tyrant (Alectrurus risora) is a threatened grassland birdthat experienced a drastic 90% reduction in Argentina. Remaining populationsoccur in the provinces of Corrientes and Formosa in northeastern Argentinawhere livestock production is the main land-use. We evaluated its breeding biology to use as a study case of the response of endemic threatened grasslandsbirds to differing grazing histories. The study was conducted in a protected areawithout cattle in Formosa, another protected area in Corrientes, and severallivestock ranches in Corrientes. The daily survival rate (DSR) wassignificantly greater in the protected area of Formosa than in Corrientes andin livestock ranches, with a probability of nest success of 0.30, 0.15 and 0.07respectively. Nest density was also significantly higher in protected areasthan in livestock ranches (nest density= 0.74 ± 0.09 nests/ha, and0.09 ± 0.01 nests/ha; respectively). Grazing history could explainthe different DSR observed between the provinces. Cattle was introduced inCorrientes 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 inCorrientes is greater than in Formosa. The lower DSR and nest density oflivestock ranches could be influenced by current livestock practices (i.e. annual-fire,high animal stocking and pesticide use) affecting vegetation structure and foodavailability. These results are alarming considering that most threatened grassland birds? populations are in private lands devoted to livestock grazing.  <!-- /* Font Definitions */ @font-face{font-family:"Cambria Math";panose-1:2 4 5 3 5 4 6 3 2 4;mso-font-charset:0;mso-generic-font-family:roman;mso-font-pitch:variable;mso-font-signature:3 0 0 0 1 0;}@font-face{font-family:Calibri;panose-1:2 15 5 2 2 2 4 3 2 4;mso-font-charset:0;mso-generic-font-family:swiss;mso-font-pitch:variable;mso-font-signature:-469750017 -1073732485 9 0 511 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal{mso-style-unhide:no;mso-style-qformat:yes;mso-style-parent:"";margin-top:0cm;margin-right:0cm;margin-bottom:8.0pt;margin-left:0cm;line-height:107%;mso-pagination:widow-orphan;font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-font-family:Calibri;mso-bidi-font-family:"Times New Roman";mso-ansi-language:ES-AR;}.MsoChpDefault{mso-style-type:export-only;mso-default-props:yes;font-size:10.0pt;mso-ansi-font-size:10.0pt;mso-bidi-font-size:10.0pt;font-family:"Calibri",sans-serif;mso-ascii-font-family:Calibri;mso-fareast-font-family:Calibri;mso-hansi-font-family:Calibri;mso-ansi-language:ES-AR;mso-fareast-language:ES-AR;}size:612.0pt 792.0pt;margin:72.0pt 72.0pt 72.0pt 72.0pt;mso-header-margin:36.0pt;mso-footer-margin:36.0pt;mso-paper-source:0;}div.WordSection1{page:WordSection1;}