“…Birds have been successfully used as sentinel species to monitor the levels and effects of POPs in the environment because they are widespread, sensitive to environmental changes, and often high on the food chain (Dauwe et al, 2006;Van den Steen et al, 2010a,2010bCuster et al, 2012;Sun et al, 2012;Eng et al, 2014). Predatory birds have been widely used as biomonitoring species for POPs (Chen et al, 2009b;Chen and Hale, 2010;Eulaers et al, 2011;Gómez-Ramírez et al, 2014), but most of these birds are less suitable to reflect the local contamination status because they are migratory and live in an extended area with low population densities (Dauwe et al, 2006(Dauwe et al, , 2009. Thus, resident passerine bird species have been successfully used as biomonitoring tools to determine POPs contamination (Dauwe et al, 2009;Van den Steen et al, 2010b;Eens et al, 2013;Morrissey et al, 2013;Eng et al, 2014).…”