Consequentially, the impacts of habitat characteristics on birds are frequently assumed to be at least partially due to changes in predator abundance (Thompson et al., 2002; Davis, 2005; Barding and Nelson, 2008; Hirsch-Jacobson et al., 2012) or prey availability in the form of arthropod biomass (McIntyre and Thompson, 2003; Shochat et al., 2005; Hamer et al., 2006; Hickman et al., 2006; Loss and Blair, 2011; Londe et al., 2021). Predation is the leading cause of avian nest failure (Ricklefs, 1969; Martin, 1993), and birds face selective pressure to establish nest sites in areas that minimize predation risk.

Bird communities via changes in the activity or abundance of these predator guilds. For instance, Klug et al. (2010) found that shrub cover in grasslands indirectly decreases avian nest Spain phone number list success by increasing snake abundance, and the negative impact of wooded edges on many grassland birds is understood to be at least partially caused by an increase in the activity of generalist nest predators (Johnson and Temple, 1990; Winter et al., 2000; Galligan et al., 2006) and brown-headed cowbirds.

Similarly, one of the mechanisms through which habitat fragmentation negatively affects grassland bird populations may be an increase in nest predator density in smaller, more fragmented patches compared to large contiguous grasslands (Chalfoun et al., 2002; Ribic et al., 2009). Predation risk is not necessarily determined solely by predator abundance, rather it can be influenced by multiple factors. For instance, alternative prey availability can affect predator behavior by determining the extent to which they target bird nests as a food source (Ackerman, 2002; Schmidt et al., 2008; Nordberg and Schwarzkopf, 2019), as predators may change prey preference according to relative abundance or availability of different prey.