Effect of drought and megafire in Iberá National Park, Corrientes, on the reproduction of the Iberá seedeater (Sporophila iberaensis)

CATAUDELA, J. F.; BROWNE, M.; DI BITETTI, M. S.; DI GIACOMO, A. G.

Gramado

Congreso; II Ornithologicail Congress of the Americas; 2023

The Iberá Seedeater [Sporophila iberaensis ], is a migratory bird, categorized as Endangered by the IUCN, endemic to South American flooded grasslands and with a restricted distribution. Its only reported breeding site is found within the Iberá wetlands. It nests in isolated stands associated with shallow lagoons.As a result of the intense and prolonged drought of the last three years, there has been an 87 reduction in the number of existing lagoons and in average rainfall. In February 2022 a series of megafires occurred in Iberá National Park (PNI), affecting 47 of its surface area. In particular, the San Nicolás Portal, our study area was one of the most affected. The intensification of drought and the loss of ponds in the PNI may be increasing the accessibility of terrestrial predators to Iberá seedeater nests, which could be negatively affecting the survival of this threatened species.The objective of this work was to evaluate whether extreme climatic conditions such as drought and megafires, impacted the reproduction of S. iberaensis. Bird nests were searched to determine their survival. They were visited every two or three days to record their success or failure. Camera traps were installed in active nests to identify the main predators. Nest associated vegetation measurements were taken. We compared the success of 73 nests during breeding seasons 2022(dry and post fire, N=35) and 2018 (wet and no recent fire, N=38). The grasses most frequently used as nest support were Paspalum durifolium (50%) and Rhynchospora corymbosa (14%). We found no significant differences in the basic reproductive parameters (clutch size and hatching success). Predation rate was significantly lower during the 2022 season (56%) than during the 2018 season (79%, Fisher's exact test, p=0.047). The main cause of nest failure was predation (55%) and stormsthat caused nest falling (12%). Our results suggest that Iberá seedeater reproduction was positively affected in the 2022 season in drought and post fire conditions, where it presented lower predation rates. Possible explanations include: 1) changes in the assemblage of nestling and egg predators such as snakes and foxes affected by the drought and fires, and 2) increased food availability as a result of post fire the regrowth of grasslands.