title: Unravelling trophic subsidies of agroecosystems for biodiversity conservation: food consumption and nutrient recycling by waterbirds in Mediterranean rice fields.
abstract: Waterbirds can reallocate a considerable amount of nutrients within agricultural fields and between agriculture sites and wetlands. However their effects on biogeochemical cycles have rarely been quantified. We estimated bird numbers, diet (from stable isotope analysis), food supply, and the food consumption on rice fields by overwintering waterbirds in one of the most important areas for rice production in southwestern Europe and a key area for various migrating and resident waterbird species. Herein, we modelled the nutrient (N and P) recycling in rice fields, and their transport to reservoirs. The energy consumption by waterbirds (96,605±18,311 individuals) on rice fields during winter averaged at 89.9±39.0 kJ·m(-2), with its majority (89.9%) belonging to foraging on rice seeds. Thus, the birds removed about 26% of rice seeds leftover after harvest (estimated in 932.5±504.7 seeds·m(-2) in early winter) wherein common cranes and dabbling ducks (four species) were the most important consumers. Waterbirds foraging and roosting in the rice fields recycled more than 24.1 (1.0 kg·ha(-1)) of N and an additional 5.0 tons (0.2 kg·ha(-1)) of P in the Extremadura's rice fields during winter. Additionally, we estimated that 2.3 tons of N and 550 kg of P were removed from rice fields and transported to reservoirs. The seasonal foraging of wildlife should result in a direct benefit for rice farmers by improving nutrient recycling through defecation by waterbirds with respect to artificial fertilisation. Additionally, rice fields located in the cranes' core wintering areas can provide sufficient food supply to induce habitat shift from their traditional wintering habitat in 'dehesas' to rice fields, which causes indirect socioeconomic benefit through reduced acorn consumption by cranes. Our modelling approach may thus be especially helpful for management decisions regarding rice agroecosystems in areas which are also important for the conservation of migratory waterbirds.
authors.affiliation: Instituto de Ciencias Marinas y Limnológicas, Universidad Austral de Chile, Facultad de Ciencias, Campus Isla Teja, 5090000 Valdivia, Chile; Conservation Biology Research Group, Universidad de Extremadura, Avda. Elvas s/n, 06002 Badajoz, Spain. Electronic address: jgnavedo@uach.cl.
authors.forename: Juan G
authors.initials: JG
authors.lastname: Navedo
authors.affiliation: Department Bird Migration, Swiss Ornithological Institute, Seerose 1, 6204 Sempach, Switzerland.
authors.forename: Steffen
authors.initials: S
authors.lastname: Hahn
authors.affiliation: Conservation Biology Research Group, Universidad de Extremadura, Avda. Elvas s/n, 06002 Badajoz, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Parejo
authors.affiliation: Conservation Biology Research Group, Universidad de Extremadura, Avda. Elvas s/n, 06002 Badajoz, Spain.
authors.forename: José M
authors.initials: JM
authors.lastname: Abad-Gómez
authors.affiliation: Conservation Biology Research Group, Universidad de Extremadura, Avda. Elvas s/n, 06002 Badajoz, Spain; Department of Marine Ecology, Royal Netherlands Institute for Sea Research (NIOZ), PO Box 59, 1790 AB Den Burg, Texel, The Netherlands.
authors.forename: Jorge S
authors.initials: JS
authors.lastname: Gutiérrez
authors.affiliation: Conservation Biology Research Group, Universidad de Extremadura, Avda. Elvas s/n, 06002 Badajoz, Spain.
authors.forename: Auxiliadora
authors.initials: A
authors.lastname: Villegas
authors.affiliation: Conservation Biology Research Group, Universidad de Extremadura, Avda. Elvas s/n, 06002 Badajoz, Spain.
authors.forename: Juan M
authors.initials: JM
authors.lastname: Sánchez-Guzmán
authors.affiliation: Conservation Biology Research Group, Universidad de Extremadura, Avda. Elvas s/n, 06002 Badajoz, Spain.
authors.forename: José A
authors.initials: JA
authors.lastname: Masero
mesh_terms: D000383:Agriculture; D000818:Animals; D044822:Biodiversity; D001717:Birds / Q000502:physiology*; D003247:Conservation of Natural Resources / Q000379:methods*; D055669:Ecological and Environmental Phenomena; D017753:Ecosystem; D012275:Oryza; D053833:Wetlands
keywords: Cranes; Dabbling ducks; Ecosystem services; Extremadura; Isotopes; Management; Nitrogen; Phosphorous