Functional Equivalency between Rice Fields and Seminatural Wetland Habitats

Abstract

Evaluating the potential for anthropogenic habitats to act as surrogates for the natural habitats they replace is a key issue in conservation biology. In California, flooded rice fields are used by numerous aquatic birds during winter. If this habitat functions similarly to more natural wetlands, increased flooding may help replace the extensive wetlands that occurred in the region prior to agricultural development. I tested whether food abundance, perceived predation threat, foraging performance, and the way in which birds allocate their time to different behaviors differed between flooded rice fields and seminatural wetlands for several species of aquatic bird. When appropriate, I also compared flooded and unflooded fields. Invertebrate densities did not differ among habitats. Seminatural wetlands had less rice grain but more seeds from other plants than the two rice habitats. The frequency with which predators passed over a feeding area was lower in flooded fields than in unflooded fields or seminatural wetlands. Most differences in feeding performance and time allocation among habitats were small and statistically insignificant. For some species, feeding efficiency was greater in seminatural wetlands than in flooded fields. Increasing attack rates and the amount of time spent feeding when in flooded fields, however, may allow birds to compensate for reduced efficiency. Multivariate analyses showed that group size, predation threat, time of day, date, and water depth often were associated with behaviors, but that these variables rarely accounted for habitat differences. Flooded fields apparently provide equivalent foraging habitat to seminatural wetlands and, because of reduced predation threat, may be a safer habitat for waterbirds. Thus, if managed appropriately, one of the world's dominant forms of agriculture can provide valuable waterbird habitat. Equivalencia Funcional entre Hábitats de Arrozales y Humedales SeminaturalesResumen: La evaluación del potencial en hábitats antropogénicos para actuar como substitutos de los hábitats naturales que remplazaron es un tema clave en la biologíá de la conservación. En California, tierras inundadas para cultivo de arroz son utilizadas por numerosas aves acuáticas durante el invierno. Si estos hábitats funcionan en forma similar a humedales más naturales, el incremento de inundaciones podría ayudar a reemplazar los extensos humedales que existieron en la región antes del desarrollo agricultural. Analizé si la abundancia de alimento, la percepción del peligro de depredación, el rendimiento en forrajeo y la forma en que las aves distribuyen su tiempo hacia diferentes conductas difieren entre arrozales inundados y humedales seminaturales para diferentes especies de aves acuáticas. Cuando fue posible, también comparé arrozales inundados contra no inundados. Las densidades de invertebrados no difirieron entre hábitats. Los humedales seminaturales tuvieron menos grano de arróz, pero más semillas de otras plantas que los dos tipos de hábitats de arrozal. La frecuencia con l...

Breeding waterbirds in relation to artificial pond attributes: implications for the design of irrigation facilities

“…Nevertheless artificial habitats as well as other semi-natural wetlands such as traditional salines and ricefields have been found to provide valuable habitat if they are properly managed (Ferrer 1986;Elphick 2000;Mu´rias et al 2002;Masero 2003). Besides, ponds may be favouring connectivity among wetlands within the study area (Amezaga et al 2002).…”

Three decades of Landsat-derived spring surface water dynamics in an agricultural wetland mosaic; Implications for migratory shorebirds

“…More than 90% of the historically occurring wetlands have been lost in the Central Valley (Frayer et al, 1989). The Sacramento Valley hosts 96% of California's flood-irrigated rice (~20% of U.S production, Central Valley Joint Venture, 2006; Strum et al, 2013), which serves as important surrogate habitat for shorebirds in areas with high wetland loss (Barbaree et al, 2015;Elphick, 2000Elphick, , 2010. Despite extensive historical wetland loss, the Sacramento Valley is recognized by the Western Hemisphere Shorebird Reserve Network as a site of international importance (Western Hemisphere Shorebird Reserve Network, 2009).…”

Patterns of Waterbirds Abundance and Habitat Use in Rice Fields

“…이 부각되고 있으며 (Benton et al, 2003;Bengtsson et al, 2005;Butler et al, 2009;Gabriel et al, 2010;Winqvist et al, 2011), 그 중 자연습지의 대체서식지로 논습지(rice fields) 에 대한 관심이 커지고 있다 (Elphick and Oring, 1998;Elphick, 2000;Tourenq et al, 2001;Ma et al, 2004).…”

“…이 외에도 논습지는 다양한 형태의 먹이 자원을 수조류에게 제공한다 (Stafford et al, 2010). 따라서 점차 줄어드는 자연습지의 대체 기능을 하는 논습지는 수조 류 서식지로서 가치가 더욱 높다 (Fasola and Ruíz, 1996;Elphick, 2000;Maeda, 2001;Czech and Parsons, 2002;Sánchez-Guzmán et al, 2007;Toral and Figuerola, 2010).…”