Waterbirds as Bioindicators of Environmental Conditions

One of the aims of monitoring is to provide information for ecological assessment, which can provide early warning of changes that could negatively affect species or ecosystems (Burger 2006). Since it is impractical to monitor all biological and physical components, a few of them can be used as indicators of wider conditions. Biological components chosen with this aim are called bioindicators (e.g. Matsinos and Wolf 2003). Several aspects of the ecology of waterbirds make them useful as bioindicators. First, waterbirds have been shown to track environmental variations, at short (months) and long (years) temporal scales, and at both species and community levels (e.g. Nudds 1983; Amat et al. 1985; Guinet et al. 1998; Abraham and Sydeman 2004; Almaraz and Amat 2004; Rendón et al. 2008). Second, because many species are top predators and several contaminants often accumulate along the trophic chain, such species may be used as indicators of changes occurring at lower trophic levels (e.g. Matsinos and Wolf 2003; Burger and Eichhorst 2005). And third, either the waterbirds themselves or their prey are exploited by humans (e.g. hunting and fisheries), so that hunting bags of waterbirds may be indicative of productivity in nesting areas (Miller et al. 1988) or breeding parameters of birds may inform on fish stocks (Einoder 2009). In this chapter we give some examples of the usefulness of using waterbirds as bioindicators. We explain why in other cases the use of waterbirds as indicators may be more limited, and we also identify how the design of studies can improve the utility of indicators.