Effects of Acacia melanoxylon R. Br. removal on bird assemblages in the Tandilia Hill System, Argentina

Abstract

The grasslands in Argentina's Pampas region have been largely transformed into agricultural fields and grazing areas, leaving the native grasslands fragmented into isolated patches in areas unsuitable for farming. In the Tandilia Hill System, these remnants face threats from invasive species, particularly trees like Acacia melanoxylon, which alter habitat structure, biodiversity, and ecosystem functioning. This study evaluates bird assemblages across different stages of grassland restoration following Acacia removal in a Private Natural Reserve. Four zones were surveyed: a control site dominated by Acacia (AC) and three restored areas representing increasing restoration stages—three years restored area (R3), recently restored (SC), and recently restored with resprouting (SG). Vegetation composition and bird richness, abundance, and assemblages were assessed using vegetation cover sampling and bird point counts.  Bird richness and abundance were significantly higher for grassland specialist species in restored areas compared to AC. The R3 zone harbored the greatest number of species, including Bearded Tachuri (Polystictus pectoralis, NT). Bird assemblages differed among zones, with generalist species dominating AC and grassland specialists characterizing restored areas. This study demonstrates the positive impact of Acacia removal on native grassland restoration as evidenced by increased bird richness of grassland specialists and their abundance.