Estimating the contribution of carnivorous waterbirds to nutrient loading in freshwater habitats

Hahn, Steffen, Bauer, Silke and Klaassen, Marcel 2007, Estimating the contribution of carnivorous waterbirds to nutrient loading in freshwater habitats, Freshwater biology, vol. 52, no. 12, pp. 2421-2433, doi: 10.1111/j.1365-2427.2007.01838.x.

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Title Estimating the contribution of carnivorous waterbirds to nutrient loading in freshwater habitats
Author(s) Hahn, Steffen
Bauer, Silke
Klaassen, MarcelORCID iD for Klaassen, Marcel
Journal name Freshwater biology
Volume number 52
Issue number 12
Start page 2421
End page 2433
Publisher Wiley-Blackwell
Place of publication Oxford, England
Publication date 2007-12
ISSN 0046-5070
Keyword(s) eutrophication
Summary 1. We estimated nitrogen (N) and phosphorus (P) loading into wetlands by carnivorous waterbirds with alternative physiological models using a food-intake and an excreta-production approach. The models were applied for non-breeding and breeding Dutch inland carnivorous waterbird populations to quantify their contribution to nutrient loading on a landscape scale.

2. Model predictions based on food intake exceeded those based on excretion by 59–62% for N and by 2–36% for P, depending on dietary assumptions. Uncertainty analysis indicated that the intake model was most affected by errors in energy requirement, while the excretion model was dependent on faecal nutrient composition.

3. Per capita loading rate of non-breeders increased with body mass from 0.3–0.8 g N day−1 and 0.15 g P day−1 in little gulls Larus minutus to 4.5–11.5 g N day−1 and 2.1–3.2 g P day−1 in great cormorants Phalacrocorax carbo. For breeding birds, the estimated nutrient loading by a family unit over the entire breeding period ranged between 17.6–443.0 g N and 8.6 g P for little tern Sterna albifrons to 619.6–1755.6 g N and 316.2–498.1 g P for great cormorants.

4. We distinguished between external (i.e. importing) and internal (i.e. recycling) nutrient loading by carnivorous waterbirds. For the Netherlands, average external-loading estimates ranged between 38.1–91.5 tonnes N and 16.7–18.2 tonnes P per year, whilst internal-loading estimates ranged between 53.1–140.5 tonnes N and 25.2–39.2 tonnes P and per year. The average contribution of breeding birds was estimated to be 17% and 32% for external and internal loading respectively. Most important species were black-headed gull Larus ridibundus and mew gull Larus canus for external loading, and great cormorant and grey heron Ardea cinerea for internal loading.

5. On a landscape scale, loading by carnivorous waterbirds was of minor importance for freshwater habitats in the Netherlands with 0.26–0.65 kg N ha−1 a−1 and 0.12–0.16 kg P ha−1 a−1. However, on a local scale, breeding colonies may be responsible for significant P loading.
Language eng
DOI 10.1111/j.1365-2427.2007.01838.x
Field of Research 060202 Community Ecology (excl Invasive Species Ecology)
Socio Economic Objective 970106 Expanding Knowledge in the Biological Sciences
HERDC Research category C1.1 Refereed article in a scholarly journal
Copyright notice ©2007, The Authors
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