Effects of livestock grazing on flocks of seed-eating birds inthe central Monte desert, Argentina

A ZARCO; CUETO VR; SAGARIO MC; L MARONE

CANADIAN JOURNAL OF ZOOLOGY

NATL RESEARCH COUNCIL CANADA-N R C RESEARCH PRESS

Lugar: Otawa; Año: 2019 vol. 97 p. 606 - 611

0008-4301

Despite itsimportance in bird conservation, flocks´ response to human disturbance ispoorly understood. In central Monte desert, Argentina, seed-eating birds formflocks during winter. The main economic activity in the region is cattlegrazing, which reduced availability of grass seeds. Since flocking increasesforaging efficiency, it is to be expected that a reduction in food availabilitywill cause changes in flock structure. To investigate this effect, we studieddifferent flock properties in grazed and ungrazed desert woodland. In grazedwoodland, flocks were smaller and less rich, and birds showed a lower flockingpropensity. However, we found a greater number of flocks per individual ingrazed woodland. The pattern observed can be explained by three non-exclusivehypotheses. Grazing, by means of food reduction, (i) produces a numericaldecrease of seed eating birds, and concomitantly generates smaller flocks; (ii)reduces the density of nuclear species of mixed-species flocks, and decreasesthe group cohesion in large flocks and/or (iii) makes large flocks lesseffective by increasing in competence for food. Our results provide evidencethat cattle grazing affect seed-eating birds? interactions by reducing foodabundance, and suggest the importance of understanding their flocking behaviorin order to bring about management action.