"Hunting bag statistics to assess the onset of the pre ‑ nuptial migration - The case study of the song thrush in the central Mediterranean" is the title of the article by Andreotti A., Macron S., Imperio S., three ISPRA researchers , published in the scientific journal “European Journal of Wildlife Research”. The illustrated research deals with the pre-nuptial migration of song thrush in Liguria, an element as is known to be fundamental for the definition of sampling times for this species, but it would seem to be vitiated by a not very objective approach. The data presented in the article had already been partially exposed during the two meetings of October 2018 on Key Concepts and in the XX Ornithology Conference of 2019 in Naples, immediately highlighting the methodological shortcomings that make this analysis really weak on the results plan, in particular due to the selection made upstream on the data used.
The authors analyze six hunting seasons, from 2006/07 to 2011/12 and, on the basis of the increase in sampling of song thrushes during the season only in the provinces of Imperia and Savona, conclude that this demonstrates a start of the pre-nuptial migration to beginning of January. As this Office has already highlighted several times, there is a total lack of direct recapture confirming these shifts, but the most surprising fact is that only those six seasons were used, although the subsequent ones up to 2020/21 are also available.
The article was received by the magazine in May 2021, so it is assumed that the authors prepared it in the years 2019 and 2020. There were therefore no less than six to seven more hunting seasons to analyze. The data of the song thrush of the following seasons (see graphs in the attached document), i.e. both the total sampling and the CPUE index in the provinces of Imperia and Savona, have different trends, of decrease, stability or very small increases, even more evident if you look at the CPUE index. This choice would therefore suggest that the authors of the study selected that group of seasons and ignored the others, suggesting that the data were used according to a criterion of convergence based on their own hypotheses.
Had the other seasons been more correctly considered, which would have increased the validity of the results, the authors' conclusions could not have been the same. In addition, even in the seasons analyzed in the study, the increase in withdrawal rates in the provinces of Imperia and Savona actually occurs starting from the second or third decade of December, and in some cases even earlier than the end of November. For this reason, the conclusion that the data suggest the start of migration in the second decade of January appears rather arbitrary.
On the contrary, following the authors' assessments, migration should begin in December or at the end of November, which is obviously impossible, while this early but continuous increase, however limited to a few seasons, suggests erratic movements and not migration. Furthermore, this reference to the decade in which prenuptial migration began in the second of January represents the fourth change of mind of ISPRA researchers in the space of just 5 years. We now ask ourselves if ISPRA will use the same data to show that in Liguria neither the redwing nor the cesena begin the pre-nuptial migration in January, given that in no season there is an increase in withdrawals in this month (Faunistic and Agro-Environmental Studies and Research Office - FIDC).