Europe’s highest densities of breeding Mallards (Anas platyrhynchos) are found in the Netherlands, but the breeding population there has declined by ~30% since the 1990s. The exact cause of this decline has remained unclear. Here, we used an integrated population model to jointly analyze Mallard population survey, nest survey, duckling survival and band-recovery data. We used this approach to holistically estimate all relevant vital rates, including duckling survival rates for years for which no explicit data were available. Mean vital rate estimates were high for nest success (0.38 ±0.01) and egg hatch rate (0.96 ±0.001), but relatively low for clutch size (8.2 ±0.05) compared to populations in other regions. Estimates for duckling survival rate for the three years for which explicit data were available were low (0.16-0.27) compared to historical observations, but were comparable to rates reported for other regions with declining populations. Finally, mean survival rate was low for ducklings (0.18 ±0.02), ... : We built an Integrated Population Model (IPM) and fitted parameters with four datasets: (1) population survey data, (2) nest survey data, (3) duckling survival data, and (4) annual band-recovery data. Our study area covers the entire country of the Netherlands, as all data were collected as part of national monitoring programs or citizen science projects. We limited our analyses to the years 2003-2020 due to a limited sampling effort in the years before 2003 for most datasets. Population survey data. Breeding bird populations have been monitored in the Netherlands as part of a national Breeding bird Monitoring Program (BMP) starting in 1984 (Boele et al. 2014). BMP is based on intensive territory mapping in fixed study plots carried out by well-trained volunteers and professionals who follow a standardized protocol. Territory mapping is based on a large, and annually constant, number of field visits (5-10 between March and July depending on species) in which all birds with territorial behavior (e.g., pair ...