Decreasing scientific outcome in biologging projects
Despite the increasing use of online repositories such as Movebank, the information on publications generated by each biologging project is difficult to track, especially in the case of grey literature. Consequently, it is challenging to analyze to what extent the use of biologgers is really being trivialized. To solve this lack of information, we have conducted an exhaustive search to review all the biologging projects performed on diurnal and nocturnal raptors (hereinafter raptors) in the Iberian Peninsula from 1978 to 2020 (N=462). Raptors are one of the groups of birds in which, historically, more biologgers have been installed because, due to their size, they offer fewer limitations in terms of the type of device to install. Consequently, they have received more attention from researchers compared to other groups of animals. For this reason, they are an excellent study model to examine the evolution of the output of biologging projects. We recorded the number of biologgers used in each project and if they generated scientific papers (i.e. peer review articles), grey literature (i.e. technical reports, popular publications, communications in conferences or congresses, etc.) or if, on the contrary, they were not published in any format. To assess whether there have been any changes in publication trends, we divided our dataset into projects which started before (N=45) and after the year 2000 (N=401). We established this threshold to make the periods more comparable to the period analyzed in Movebank database (See Figure 1). For these analyses, projects with an uncertain starting date were excluded (N=16).
Only 22.3% of the raptor projects analyzed have led to any scientific paper, while 38.1% of the projects contributed to grey literature, and 39.6% have not been published (Figure 1). Based on these results, most of these projects do not generate easily available scientific knowledge. In this regard, it is essential to highlight that although grey literature may have an important applied value (e.g. technical reports for environmental managers), this kind of publications is much more difficult to track than a peer-reviewed journal which keep from extending their application beyond the local scale. Therefore, their impact is more limited. Also, it is noticeable that there has been a drastic increase (χ2= 106.74, df = 2, p < 0.001) in projects that do not generate any publications and a decrease in projects that generate publications, especially scientific publications (Figure 1).
Our results also showed that biologging projects including more devices (i.e. a larger number of tracked animals) are more likely to generate scientific publications (ANOVA, F=10.68, p<0.001; Figure 1). In this sense and considering the average number of biologgers per project in each of the categories of publication output, the threshold of 10 biologgers that we established in our analysis of Movebank’s data (Figure 1) seems to be a good reference to predict if a project will generate publications or not. In addition, this result may be useful in establishing a minimum sample size limit that is both ethically acceptable and scientifically productive (Hebblewhite & Haydon 2010). Based on our findings, we can conclude that the rise in projects with limited sample sizes is not aligned with the primary objective of advancing scientific knowledge and making it available globally. Therefore, results at local scale in our raptors dataset reinforce concerns about the global trend in Movebank data (Figure 1) and evidence the process of trivialization of biologging.