Retrospectively analysing condition in historical samples of birds

Abstract

Large amounts of nitrogen are used as fertilizer across the globe annually exceeding 100 million metric tons, with consequences for primary productivity and effects at higher trophic levels. We measured δ15N values in feathers from samples of eiders Somateria mollissima wintering on the Danish coast in 2014‐2016 and a century ago, using museum specimens. Blue mussels Mytilus edulis are filter feeders relying on phytoplankton as food and they constitute the main diet of eiders. Feather δ15N increased by 40% during the past century reflecting increased terrestrial runoff of N through agricultural use of fertilizer, in turn supporting increased primary production in shallow coastal systems. This increase in δ15N was associated with an increase in body mass and longer duration of moult. However, there was a recent decrease in the quality of feathers as reflected by more fault bars and a higher degree of feather wear suggesting that longer duration of moult comes at a cost in terms of poorer feather quality. These findings imply that terrestrial nitrogen subsidies to coastal marine systems from anthropogenic sources has profound effects on species such as the eider as revealed by the effects on body condition and plumage quality and hence the ability to fly and dive.

Isotopic niches of tropical birds reduced by anthropogenic impacts: a 100‐year perspective

“…This result might be directly related to land use changes in the study area, especially due to deforestation and agriculture intensification. Although most isotopic ornithological studies use δ 15 N to infer the position of a particular species in the trophic chain and draw inferences about its diet (Kelly 2000, Norris et al 2007), some isotopic studies also reveal the influence of anthropogenic impacts on the species by analyzing δ 15 N values (Hebert and Wassenaar 2001, Møller et al 2018). Among these impacts, we can infer about the influence of agricultural use of fertilizers, as the synthetic form of it has lower δ 15 N values than the organic type (Bateman and Kelly 2007, Choi et al 2017).…”

“…Therefore, forest birds might incorporate nitrogen from anthropogenic sources, mainly from synthetic fertilizers. Anthropogenic nitrogen inputs in the marine environment are already associated with changes in the feather quality of marine birds (Møller et al 2018). Nevertheless, information regarding the possible morphological, physiological and evolutionary consequences in terrestrial birds is lacking.…”

“…Recently, the employment of stable isotope analysis in environmental and ecological studies provides useful information on species ecology, such as the habitats used by organisms to forage revealed by the calculation of δ 13 C values (Inger and Bearhop 2008, Hobson 2011, Ferger et al 2013, Wiley et al 2017). In addition, the position of organisms on the trophic chain (Post 2002, Boecklen et al 2011) and the impacts of anthropogenic nitrogen input on them, including nitrogen from fertilizers, can be revealed by δ 15 N values (Hebert and Wassenaar 2001, Møller et al 2018). In a bivariate plot of δ 13 C and δ 15 N values, it is possible to analyze the width of the isotopic niche of a given species, which can be associated to its ecological niche (Newsome et al 2007).…”

Antibacterial and anatomical defenses in an oil contaminated, vulnerable seaduck

“…Worn feather tips and fast growing feathers indicate individuals with weak feathers (Møller et al., 2018 ). Thus, for entire eiders and wings, we removed the second primary and recorded its length with a ruler to the nearest mm and the width of the feather shaft (rachis) with a digital caliper to the nearest 0.01 mm.…”