In this work, the first results obtained in the study of two mounted birds are presented: a golden eagle, made by José Maria Benedito in 1914, which belongs to the Complutense University (UCM), and a pink flamingo (MNCN-CSIC reference: 7511) dated in 1891, which came from Cuba to Spain and is property of the National Museum of Natural Sciences of Spain (MNCN-CSIC). Although both birds were mounted in close dates, differences may be observed in the methodology and the materials employed in preparing them (preservatives, internal iron armatures, paint and fillings although it has been determined that both birds contain arsenic-based compounds). These can be either due to geographical reasons (taxidermists could have used different techniques in different places), to historical changes in preparing specimens, or simply due to the factor that they were not created by the same professional. In order to make the comparative study of both pieces and to determine the nature of the materials employed, different analytical techniques have been used: X-ray computed tomography (CT) to study the internal configuration of the pieces (metallic structure and distribution of fillers), stratigraphic study with optical microscopy (OM) and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) to identify the materials used for coloring parts of the animal, preservatives and the nature of the internal armatures, and finally OM for the nature of the internal filler. The characterization of the coatings has been done by using SEM/EDS, Fourier transform infrared spectroscopy (FTIR), gas chromatography/mass spectrometry (GC/MS) and/or OM with selective staining.