Birds breeding on roadside borders of the Argentine Pampas: assessing predation risk through the monitoring of artificial and real nests

MERMOZ, MYRIAM E; DEPALMA, DANIELA M

Cape May

Congreso; 2019 joint meeting of the Association of Field Ornithologists and the Wilson Ornithological Society; 2019

Association of Field Ornithologists -Wilson Ornithological Society

Pampas grasslands have been continuously modified by grazing and agriculture, leading to habitat loss for birds. Although roadside borders provide nesting sites, it is essential to assess the predation risk that they involve in order to evaluate their suitability. Our objectives were to identify nest predators and environmental factors affecting nest success. Regarding the latter objective, we hypothesized that nest detectability and the amount of habitat available for predators in the landscape reduce nest success. To identify predators, we monitored 60 artificial nests containing two quail eggs (one natural egg and the other filled with paraffin). To study real nest survival we searched and monitored 114 nests belonging to 18 species, until predation occurred or one fledging was produced. Real nests were found on substrates such as clumps of grass, thistles, wetlands and trees. We evaluated the effects of environmental variables on nest success with a logistic exposure model. Paraffin eggs of artificial nests exhibited marks from small mammals and, to a lesser extent, from medium mammals, birds and ophidians. Daily survival rate of real nests was 0.937, and 86.6% of failures were due to predation. According to the logistic exposure model, nest height was the most important variable increasing nest success. The positive effect of nest height suggests that mammals may be an important source of predation. Enhancing vegetation height and the presence of tall native grasses (Pampas grass Cortaderia selloana) might help to preserve the bird community nesting on these roadside borders.