This work was developed in Barrinha de Mira Coastal Lagoon, Portugal. The lagoon belongs to the Natura 2000 network. Its main objectives were to monitor aquatic bird species before, during, and after a desorption intervention on this lagoon. Monitoring of waterfowl was carried out to evaluate the monthly variation of birds in Barrinha, in order to obtain useful information for region's management and planning, as well as for species preservation. In experimental design, it was decided to perform four counts per month in each pond (weekly), to evaluate the effect of increased monitoring effort in relation to previous years. The results revealed that the study area has a significant importance as a wintering zone for water birds. Some species have stable resident populations which, seasonally, see their numbers vary with migratory birds arrival and departure. Another purpose was to verify the influence of desorption intervention on the usual number of individuals by species. The results show that during and after intervention, there was a reduction of birds in the order of 89%, being more visible in the populations of Anas platyrhynchos and Fulica atra.
Keywords: Breeding; Desorption; Habitat; Mallard; Management; Monitoring.