Causes and consequences of avian within-season dispersal decisions in a dynamic grassland environment

Breeding dispersal in a resident boreal passerine can lead to short‐ and long‐term fitness benefits

“…Of course, for breeding dispersal to be a factor at the population level, the improvement in individual reproductive success would have to be strong enough to affect population growth rates. This could be the case in some declining populations of other species where breeding dispersal has been shown to be beneficial at the individual level (Palestis andHines 2015, Williams andBoyle 2019), but it is probably unlikely in Canada jays given their relatively low annual reproductive output (Sutton et al 2021b). Breeding dispersal acting as a mechanism for negative density-dependence would also rest on the assumption that most dispersal at low densities would occur within the population (i.e., short distances).…”

“…Individuals can also be prone to high rates of mortality when in transience or settlement stages of dispersal (Jack and Fedigan 2004, Stamps et al 2005, Palestis and Hines 2015. In contrast, breeding dispersal can be beneficial when it leads to the acquisition of a higher-quality territory or mate or improved breeding position; upgrades that can lead to improvements in reproductive performance and probability of survival (P€ art and Gustafsson 1989, Payne and Payne 1993, Forero et al 1999, Jack and Fedigan 2004, Rosenfield et al 2016, Weitzman et al 2017, Williams and Boyle 2019. For example, adult grasshopper sparrows (Ammodramus savannarum) that exhibit within-year breeding dispersal have higher nest survival than site-faithful breeders (Williams and Boyle 2019).…”

“…In contrast, breeding dispersal can be beneficial when it leads to the acquisition of a higher-quality territory or mate or improved breeding position; upgrades that can lead to improvements in reproductive performance and probability of survival (P€ art and Gustafsson 1989, Payne and Payne 1993, Forero et al 1999, Jack and Fedigan 2004, Rosenfield et al 2016, Weitzman et al 2017, Williams and Boyle 2019. For example, adult grasshopper sparrows (Ammodramus savannarum) that exhibit within-year breeding dispersal have higher nest survival than site-faithful breeders (Williams and Boyle 2019). Additionally, adult male whitefaced capuchins (Cebus capucinus) that disperse display longer tenure as a dominant breeder and, thus, a greater number of reproductive opportunities compared to site-faithful counterparts (Jack and Fedigan 2004).…”

“…Even though the immediate consequences of breeding dispersal can be either positive or negative for individual performance, much less is known about the lifetime consequences of dispersal (Berteaux and Boutin 2000). Part of the reason for this is that most breeding dispersal studies are primarily restricted to cost-benefit analyses over short time frames (Payne and Payne 1993, Pasinelli et al 2007, Valcu and Kempenaers 2008, € Ost et al 2011, Palestis and Hines 2015, Weitzman et al 2017, Williams and Boyle 2019. Typically, such studies compare performance the year before and year after dispersal (e.g., Payne and Payne 1993, Pasinelli et al 2007, Valcu and Kempenaers 2008, € Ost et al 2011) and face challenges with tracking individuals over large spatial scales or throughout an individual's lifetime.…”

The effects of management practices on grassland birds—Grasshopper Sparrow (<i>Ammodramus savannarum</i>)

“…On reclaimed surface mines in Pennsylvania, the earliest nest initiation for Grasshopper Sparrows was May 12 and the latest known fledging date was August 11; 20 percent of nest initiations occurred after July 1 (Stauffer and others, 2011). Throughout most of their range, Grasshopper Sparrows can produce two broods, one in late May and a second in early July (George, 1952;Smith, 1968;Williams and Boyle, 2019;Vickery, 2020). However, in the northern part of its range, one brood is probably more common (Jones and others, 2010).…”