Differences between Scaly-sided Merganser (Mergus squamatus) and Common Merganser (M. merganser) feather microstructure

Abstract

The microstructures of breast feathers, flank feathers, rectrices, and down feathers of both Scaly-sided Merganser (Mergus squamatus) and Common Merganser (M. merganser) were meticulously examined using scanning electron microscope. The observed data were subjected to the Mann-Whitney U test, followed by hierarchical clustering and Fishers discriminant analysis of indicators with significant differences in morphological structure. The findings revealed statistically significant differences between Scaly-sided Merganser and Common Merganser in terms of the length of the base handle from distal barbules in the breast feathers, the length of the base handle, the number of hooked barbules, the number of cilia from distal barbules, and the number of ventral teeth from proximal barbules in rectrices. Additionally, variations in the distance between nodules, the nodular diameter, and the length of the base nodular of the down feathers were noted. Hierarchical clustering successfully categorized Scaly-sided Merganser and Common Merganser into distinct groups, achieving a 100% accuracy rate. Moreover, Fishers discriminant analysis demonstrated a 100% correctness rate when the back-substitution method was used to test the discriminant equation. Consequently, the length of the base handle of distal barbules in breast feathers, along with all selected indicators from rectrices and down feathers, may provide references to identify Scaly-sided Merganser and Common Merganser.