Retrospectively analysing condition in historical samples of birds
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 N-15 values in feathers from samples of eiders Somateria mollissima wintering on the Danish coast...
| Published in: | Journal of Zoology |
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| Main Authors: | , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
2018
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| Subjects: | |
| Online Access: | https://pure.au.dk/portal/en/publications/28f5baea-4074-45f0-838a-461dbd3f1bc7 https://doi.org/10.1111/jzo.12551 |
| Summary: | 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 N-15 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 N-15 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 N-15 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. |
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