Breeding biology and nest survival of Hellmayr?s Pipit (Anthus hellmayri) in natural grasslands in Buenos Aires province, Argentina.

COLOMBO, MARTÍN A.; SEGURA, LUCIANO N.

San Juan, Puerto Rico

Congreso; VII North American Ornithological Conference; 2020

Grasslands in central-east Argentina are among the most altered ecosystems in the world, and the biology of many native bird species remains poorly studied while the landscape keeps changing. Information on breeding biology of birds is important to understand their population trends. We present the first study on the breeding biology of Hellmayr?s Pipit Anthus hellmayri, a poorly known ground nesting passerine, and we analyze the effects of habitat characteristics on its nest daily survival rate (DSR). We searched for nests during three breeding seasons (2017 to 2019) in a natural grassland area in Buenos Aires province, Argentina. For each nest we measured habitat features to assess their effects on DSR. The breeding season lasted from September to February, clutch size was 3-5 eggs, incubation lasted 13-14 days and nestling period lasted 10-14 days. DSR was 0.91, which results in a 7% probability of surviving the whole breeding cycle. Predation was the main cause of nest failure, followed by abandonment caused by weather. DSR was negatively associated with visual obstruction and was higher in nests with lateral entrances than in those with vertical entrances. Less visual obstruction could be advantageous by allowing a greater field of view from the nest, and a lateral entrance could offer better protection from rain and aerial predators. Estimated success was very low compared to other grassland bird species, and may indicate that this Pipit population is declining. We emphasize the importance of preserving these habitats and monitoring populations of grassland birds.