Adverse winter conditions reduce adult survival of the Endangered Dupont’s Lark Chersophilus duponti

Summary Survival is a key life history trait influenced by climate variability and resource availability in many bird species. Understanding the factors affecting survival in threatened species is critical for effective conservation management. However, we lack knowledge regarding survival rates and their annual variations for most threatened species. In this study, we use mark-recapture data collected in eastern Spain between 2011 and 2019 to estimate the annual adult survival of the Endangered Dupont’s Lark Chersophilus duponti , a steppe specialist passerine. We also aim to assess whether survival rates are linked to plant productivity, as a surrogate of resources available, and climate variability during the post-breeding (autumn) and winter periods. A total of 113 adults (89 males and 24 females) were ringed, which yielded 43 recaptures. The average adult survival rate over the nine-year period was slightly higher than previous estimates for Dupont’s Lark and other related species. Nonetheless, we observed substantial annual fluctuations in survival (ranging from 0.34 to 0.80), largely driven by winter climate conditions. Survival rates decreased during winters with a higher number of frost days (below 0ºC) and increased accumulated rainfall. These findings provide new insights into the population dynamics of the species and suggest that factors other than adult annual survival may be contributing to its declining status. Among those factors, a critical area for further research is to study and characterise the dispersal patterns and survival of juvenile birds, which remain largely unknown for this species.