Does feather type matter to evaluate concentrations of essential and nonessential elements in a pantropical seabird?

Feathers are widely used as a matrix for monitoring environmental quality. However, most studies quantify the concentrations of trace metals using only a single feather type, often disregarding the variability among feathers from different regions of the bird's body. This variability, combined with a lack of standardization, can lead to underestimation of elemental concentrations and hinder comparisons across studies. In this study, we showed that the concentrations of trace elements differ significantly among feather type. The total concentrations of essential elements (Cu, Zn) and non-essential elements (Cd and As were analyzed in the ventral, dorsal, wing (S1) and tail (R7) feathers of adults (males and females) and juveniles of brown boobies (Sula leucogaster). The feathers were collected from breeding individuals in the Santana Archipelago (Brazil) between 2023 and 2024. All analyzed elements showed significant differences among feather's type. Feather from tail, generally, presented the highest concentrations among the elements. Zinc concentrations differed between adults and juveniles and between sexes. The differences in concentrations in feather types may be primarily related to the kind of element, the feather growth sequence, the molting strategy and environmental exposures during feather development. This finding highlights the importance of carefully selecting the feather type for studies involving trace elements, as distinct feather may yield different results. Further studies on other seabird species are needed to elements in different feather types. Such research is essential for better understanding the variations in element concentrations among feather types and their implications for environmental quality monitoring.