Settling Decisions and Heterospecific Social Information Use in Shrikes

Abstract

Animals often settle near competitors, a behavior known as social attraction, which belies standard habitat selection theory. Two hypotheses account for these observations: individuals obtain Allee benefits mediated by the physical presence of a competitor, or they use successfully settled individual as a source of information indicating the location of high quality habitat. We evaluated these hypotheses experimentally in two species of shrikes. These passerine birds with a raptor-like mode of life impale prey to create larders that serve as an indicator of male/habitat quality. Thus, two forms of indirect information are available in our system: a successfully settled shrike and its larder. Typically these two cues are associated with each other, however, our experimental treatment created an unnatural situation by disassociating them. We manipulated the presence of larders of great grey shrikes and examined the settling decisions of red-backed shrikes within and outside the great grey shrike territories. Male red-backed shrikes did not settle sooner on plots with great grey shrikes compared to plots that only contained artificial larders indicating that red-backed shrikes do not use the physical presence of a great grey shrike when making settling decisions which is inconsistent with the Allee effect hypothesis. In contrast, for all plots without great grey shrikes, red-backed shrikes settled, paired and laid clutches sooner on plots with larders compared to plots without larders. We conclude that red-backed shrikes use larders of great grey shrikes as a cue to rapidly assess habitat quality.

Testing the heterospecific attraction hypothesis with time-series data on species co-occurrence

“…Third, the presence of residents can be a signal of low risk of predation, as the residents may already have been predated in patches with a higher predation risk. Heterospecifics can also act as indicators of habitat quality, especially for migrant species arriving to breeding sites (Thomson et al 2003;Forsman & Thomson 2008;Hromada et al 2008;Forsman et al 2009). Migrants need to make fast but reliable decisions about where to breed, whereas residents have had much more time to evaluate patch quality.…”

Experimental identification of social learning in wild animals

“…For example, mate-choice copying (a form of social information use) was demonstrated in wild sailfin mollies (Poecilia latipinna), but the design did not incorporate a subsequent phase without demonstrators to test whether any learning had taken place (Witte & Ryan, 2002). Similarly, Hromada, Antczak, Valone, and Tryjanowski (2008) demonstrated that male red-backed shrikes (Lanius collurio ( ( ) used the social information provided by food caches (impaled prey, artifacts of successful foraging) in making settlement decisions, but the authors did not observe behavior in the absence of the caches. We suspect that learning is likely in such cases, but it was not formally demonstrated.…”

Traditional versus non-traditional nest-site choice: alternative decision strategies for nest-site selection

“…Thus, tradition-defined as the transfer of any kind of information between individuals and species (Avital and Jablonka 2001;Danchin et al 2004;Fragaszy and Perry 2003;Hromada et al 2008)-may play a major role in habitat and (particularly) nest-site choice of many species, and appears to be an underrated mechanism. In line with this, the main route for information transfer is from parents to offspring, so habitat imprinting would be a suitable mechanism for nest-site selection in birds (Glück 1984;Teuschl et al 1998).…”