Relationship between altmetric and bibliometric indicators across academic social sites: The case of CSIC's members

•Usage and social indicators depend on their own social sites.•Bibliometric indices are independent and therefore more stable across services.•Correlations between social and usage metrics regarding bibliometric ones are poor.•Altmetrics could not be a proxy for research evaluation, but for social impact of science.

This study explores the connections between social and usage metrics (altmetrics) and bibliometric indicators at the author level. It studies to what extent these indicators, gained from academic sites, can provide a proxy for research impact. Close to 10,000 author profiles belonging to the Spanish National Research Council were extracted from the principal scholarly social sites: ResearchGate, Academia.edu and Mendeley and academic search engines: Microsoft Academic Search and Google Scholar Citations. Results describe little overlapping between sites because most of the researchers only manage one profile (72%). Correlations point out that there is scant relationship between altmetric and bibliometric indicators at author level. This is due to the almetric ones are site-dependent, while the bibliometric ones are more stable across web sites. It is concluded that altmetrics could reflect an alternative dimension of the research performance, close, perhaps, to science popularization and networking abilities, but far from citation impact.