Loss of tall grass reduces nest survival in Argentinian grasslands

Abstract

Breeding success in grassland birds is influenced by various environmental factors, with vegetation structure- particularly the cover of tall grasses- playing a vital role in providing shelter from predators and harsh weather. This study evaluated nest survival of the Spectacled Tyrant (Hymenops perspicillatus) and the Grassland Yellow-Finch (Sicalis luteola) in grazed and ungrazed tall grasslands in the Pampas region of Argentina over three breeding seasons. Using daily survival rates (DSR), we found significantly higher nest survival in ungrazed areas, where tall grass cover was more abundant. Additionally, for the Grassland Yellow-Finch, vegetation height positively influenced nest survival, while nests placed higher above the ground and those initiated later in the season had lower survival probabilities. Our results highlight the critical role of tall grass patches in supporting the reproductive success of grassland birds. Promoting sustainable management, such as moderate stocking rates and rotational grazing systems, can effectively balance livestock production with the conservation of these key grassland species.