title: Barn owl feathers as biomonitors of mercury: sources of variation in sampling procedures.
abstract: Given their central role in mercury (Hg) excretion and suitability as reservoirs, bird feathers are useful Hg biomonitors. Nevertheless, the interpretation of Hg concentrations is still questioned as a result of a poor knowledge of feather physiology and mechanisms affecting Hg deposition. Given the constraints of feather availability to ecotoxicological studies, we tested the effect of intra-individual differences in Hg concentrations according to feather type (body vs. flight feathers), position in the wing and size (mass and length) in order to understand how these factors could affect Hg estimates. We measured Hg concentration of 154 feathers from 28 un-moulted barn owls (Tyto alba), collected dead on roadsides. Median Hg concentration was 0.45 (0.076-4.5) mg kg(-1) in body feathers, 0.44 (0.040-4.9) mg kg(-1) in primary and 0.60 (0.042-4.7) mg kg(-1) in secondary feathers, and we found a poor effect of feather type on intra-individual Hg levels. We also found a negative effect of wing feather mass on Hg concentration but not of feather length and of its position in the wing. We hypothesize that differences in feather growth rate may be the main driver of between-feather differences in Hg concentrations, which can have implications in the interpretation of Hg concentrations in feathers. Finally, we recommend that, whenever possible, several feathers from the same individual should be analysed. The five innermost primaries have lowest mean deviations to both between-feather and intra-individual mean Hg concentration and thus should be selected under restrictive sampling scenarios.
authors.affiliation: LabOr - Laboratório de Ornitologia, ICAAM - Instituto de Ciências Agrárias e Ambientais Mediterrânicas, Universidade de Évora, Núcleo da Mitra, Ap. 94, 7002-554, Évora, Portugal. iroque@uevora.pt.
authors.forename: Inês
authors.initials: I
authors.lastname: Roque
authors.affiliation: LabOr - Laboratório de Ornitologia, ICAAM - Instituto de Ciências Agrárias e Ambientais Mediterrânicas, Universidade de Évora, Núcleo da Mitra, Ap. 94, 7002-554, Évora, Portugal.
authors.forename: Rui
authors.initials: R
authors.lastname: Lourenço
authors.affiliation: LabOr - Laboratório de Ornitologia, ICAAM - Instituto de Ciências Agrárias e Ambientais Mediterrânicas, Universidade de Évora, Núcleo da Mitra, Ap. 94, 7002-554, Évora, Portugal.
authors.forename: Ana
authors.initials: A
authors.lastname: Marques
authors.affiliation: CESAM (Centre for Environmental and Marine Studies), Department of Chemistry, University of Aveiro, 3810-193, Aveiro, Portugal.
authors.forename: João Pedro
authors.initials: JP
authors.lastname: Coelho
authors.affiliation: CESAM (Centre for Environmental and Marine Studies), Department of Chemistry, University of Aveiro, 3810-193, Aveiro, Portugal.
authors.forename: Cláudia
authors.initials: C
authors.lastname: Coelho
authors.affiliation: CESAM (Centre for Environmental and Marine Studies), Department of Chemistry, University of Aveiro, 3810-193, Aveiro, Portugal.
authors.forename: Eduarda
authors.initials: E
authors.lastname: Pereira
authors.affiliation: LabOr - Laboratório de Ornitologia, ICAAM - Instituto de Ciências Agrárias e Ambientais Mediterrânicas, Universidade de Évora, Núcleo da Mitra, Ap. 94, 7002-554, Évora, Portugal.|Department of Biology, University of Évora, Ap. 94, 7002-554, Évora, Portugal.
authors.forename: João E
authors.initials: JE
authors.lastname: Rabaça
authors.affiliation: Department of Ecology and Evolution, University of Lausanne, Building Biophore, 1015, Lausanne, Switzerland.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Roulin
mesh_terms: D000818:Animals; D004784:Environmental Monitoring / Q000379:methods*; D004785:Environmental Pollutants / Q000378:metabolism*; D005241:Feathers / Q000378:metabolism*; D008628:Mercury / Q000378:metabolism*; D018978:Molting; D020305:Strigiformes / Q000378:metabolism*
chemical_list: D004785:Environmental Pollutants; D008628:Mercury
keywords: Barn Owl; Biomonitor; Feathers; Intra-individual variations; Mercury