The impact of annual cumulative rainfall on the breeding performance of the Black-winged Stilt Himantopus himantopus in a lagoon complex at Essaouira (west central Morocco)

In arid and semi-arid regions, interannual variability in rainfall strongly influences wetland hydrology and can critically affect the breeding performance of wader species. Here we study the breeding biology of the Black-winged Stilt during three consecutive seasons (2017–2019) in a peri-urban lagoon complex near Essaouira city on the Atlantic coast of Morocco. At this site, water level is primarily linked to cumulative annual precipitation and disturbances by humans are frequent. Mean pond percent area full was lower in 2018 (59%) than other years (76–79%), reflecting drier conditions in that year. Analysis of individual clutches revealed that most were laid in late April, with an average of 3.25 ± 1.08 SD eggs per nest. The incubation period lasted 24.03 ± 0.91 days. Hatching success over the entire study period was 69.7% of all laid eggs and mean productivity was 2.32 hatched chicks per successful nest. Unsuccessful nesting attempts were mainly attributed to nest and egg destruction due to human disturbance (39%) and weather conditions (20%). The length of the laying period differed significantly between 2017 and 2018 (56 vs. 30 days), although that recorded in 2019 (48 days) was not significantly different from either year. The shorter laying period observed in the dry year of 2018 likely reflects that only higher-quality individuals were able to breed under the less-favorable conditions (low cumulative annual precipitation, lower percent pond area full), which was associated with a reduced availability of suitable nesting sites. Overall, our results highlight the combined influence of rainfall-driven hydrological variability and human disturbance on breeding performance, emphasizing the vulnerability of peri-urban wader breeding populations in temporary wetlands.