Phenology of migrating game birds in Italy based on citizen science data: mean maps and grid maps for 23 species

Studying the timing of the seasonal movements of migratory birds, known as migration phenology, is crucial for managing and conserving migratory bird populations. To effectively protect these species during these critical periods, it is vital to employ reliable methods for assessing their migration phenology. Citizen science, which involves the participation of skilled volunteers in scientific data gathering, is a valuable resource for migration studies. It allows the collection of large amounts of data across extensive geographic areas, overcoming some limitations of other datasets and analytical methods. In this study we analysed pre- and post-breeding migration phenology of 23 game bird species in Italy, using citizen science data from the www.Ornitho.it portal. These findings highlight the value of citizen science data in obtaining migration timing and the importance of employing multiple methods to estimate it. This approach is particularly valuable for species subject to hunting, ..., We retrieved the data available on the Ornitho.it databank for 23 species. 
The method is based on the approach first proposed by Ambrosini et al. (2014) and refined to fit partial migratory species and citizen science data by Ambrosini et al. (2023).
The study area (the Italian peninsula and Sardinia, Sicily and the minor Italian islands) was first divided into cells of 0.5° by 0.5° degrees (latitude – longitude). Cells containing fewer than 20 records collected in fewer than 10 different days in a year (the minimum required sample size) were merged with adjacent cells (full details are reported in the Supporting information). This procedure, identical to the one used in Ambrosini et al. (2023), ultimately generated cells of different sizes, inversely proportional to data density. These cells are represented in the grid maps. Data that were spatially isolated were also identified and discarded to avoid the generation of unreasonably large cells. The number of records per day was t..., # Data from: Phenology of migrating game birds in Italy based on citizen science data: mean maps and grid maps for 23 species

Dataset DOI: [10.5061/dryad.fxpnvx14z](10.5061/dryad.fxpnvx14z)

## Description of the data and file structure

The mean_maps folder contains 10 maps for each of the 23 game species included in our analyses. For every species, five maps represent the progression of pre-breeding migration and five represent post-breeding migration across Italy, derived from citizen-science observations submitted to [www.Ornitho.it](http://www.Ornitho.it). Each set of maps corresponds to a different proportion of observations (0%, 1%, 5%, 10%, and 50%), representing the onset of migration for pre-breeding and the end of migration for post-breeding.

In addition, the dataset includes all grid maps generated during the intermediate analytical steps (in the grid_maps folder). These grid maps result from the procedure described in Ambrosini et al. (2023), which creates spatial cells o...,