Nest survival of black-backed water tyrant Fluvicola albiventer in relation to nest morphometry and nest site features

Abstract

Understanding the relationship between nest site features and the breeding biology of wetland birds is crucial, as these ecosystems are significantly threatened. Particularly, studies assessing neotropical bird breeding success are sparse. During three consecutive breeding seasons (2016 - 2019), we monitored 66 nests of the Black-backed Water Tyrant Fluvicola albiventer in central Argentina. We described basic nesting parameters and analyzed the relationship between breeding parameters (nest survival, clutch, and brood size), nest site features, and nest morphometry. Breeding season lasted from early September to the end of January, with a peak in October and November. Nests were placed 136.81 ± 60.44 cm above the ground or water. Clutch size was 2.70 ± 0.47 eggs (n = 30 nests), and brood size was 2.11 ± 0.60 chicks (n = 10 nests). We found a positive relationship between external nest width and both clutch and brood size. Conversely, there was a negative relationship between nest concealment and brood size. Daily nest survival rate (DSR) was 0.92, and the cumulative probability of nest survival in a 28-day nesting cycle was 9 %. We found a positive influence of external nest width on DSR. We also found a negative relationship between nest concealment and DSR. The low success probability found in this species raises uncertainties about the future of its populations. Moreover, the availability of suitable nesting sites may be affected by wetland degradation. This study could provide valuable insights into the consequences of wetland loss and design strategies for their conservation.