Saffron-cowled Blackbirds' reduced nest success in Argentina's agricultural land highlights the importance of non-agricultural habitat for its conservation

The Saffron-cowled Blackbird (Xanthopsar flavus) is a globally endangered
icterid endemic to the southern South American grasslands. Temperate
grasslands are among the most threatened ecosystems in South America due
to their high rate of land use change. In northeastern Argentina, over the
last century, the conversion of natural grasslands to livestock farming,
croplands, and afforestation have resulted in significant losses of
breeding habitat for the Saffron-cowled Blackbird. Consequently, it has
suffered severe populational declines, and its remaining populations are
fragmented. In order to understand the impact of agricultural systems on
the Saffron-cowled Blackbird populations, we studied its breeding biology
(clutch size, hatching success, nestling production, and fledgling
success) and the main parameters that influence nest survival rate in five
breeding habitat types. During the breeding seasons of 2015 to 2019 we
located nests and monitored their fate. We found that the cumulative
probability of nest survival over the entire nesting cycle (i.e., laying,
incubation, and chick rearing) was 0.06, and was lower for nests situated
in grazed land covers. Conversely, nest survival was greater in breeding
sites without agricultural use, particularly in marshes. Predation was the
main cause of nest failure (76%), followed by brood parasitism (10%) and
trampling by cattle and agricultural machinery (6%). Brood parasitism
rates were higher in grazed paddocks, contributing together with predation
to the failure of nests in this habitat. Our findings indicate a negative
impact of livestock ranching on Saffron-cowled Blackbird reproduction.
Non-agriculture habitats, like wetlands and flooded areas, are important
as refuges for nesting. Thus, the creation of breeding refuges
(non-productive sites) within agricultural matrices, in association with
biodiversity-friendly agricultural practices, is crucial to ensure the
Saffron-cowled Blackbird's maintenance.