In order to determine the causes of the trend (progress or decline) of a population, it is important to clearly map the breeding success. To make the collection of breeding success data of various bird species easier, the AviNest App has been developed. This App allows the input of breeding success data in the field in a simple way. You can keep a good overview of your own imported nests in different areas. The App can automatically calculate when the chicks will come out of the egg, around which date you could ring the boy and the expected date that the youngsters are flying. You can see this per litter and area in a clear overview. The data can be easily uploaded to the Sovon database Nest Map, which allows the data to be used by the organization for large-scale research.