Introduction
Social information plays an important role in the distribution of wildlife across the landscape. Wildlife derive information on resource availability from the occurrence of individuals (Danchin et al. 2004), and the performance of conspecifics and heterospecifics, wherein habitat patches conferring improved fitness attract more individuals (Doligez et al. 2002, Campomizzi et al. 2008). Congregation of individuals within resource patches is often driven by conspecific attraction (Stamps 1988). As such, clustering of species during the reproductive period has shown positive fitness benefits via information transfer on resource availability, predation risk, and mate availability (Alexander 1974, Forbes and Kaiser 1994, Danchin et al. 1998, Strong et al. 2018). Thus, social information is a known determinant of reproductive decisions and underlies the coordination of the timing of reproduction (Brandl et al. 2019).
Coordination in timing of reproduction is driven by resource availability for a wide array of species (Lack 1968, Perrins 1970) as optimization of reproductive success hinges on matching reproductive activities with environmental conditions (Ims 1990). As such, temporal clustering of reproductively-active individuals is typically driven by climatic seasonality (Ims 1990), especially when breeding seasons are restricted to shorter temporal periods (Emlen and Demong 1975, Findlay and Cooke 1982). The availability of social information, which underlies spatial clustering, can influence temporal clustering (Helm et al. 2006) and certain life history events (migration, reproduction) are inherently clustered temporally (Lack 1968, Gochfeld 1980). Monogamous species regularly demonstrate a high degree of reproductive synchrony (Emlen and Oring 1977, Gochfeld 1980) as male investment in courtship limits extra-pair reproductive activities (Grant and Kramer 1992) with the consequence being synchronized reproductive activities (Knowlton 1979). Colonial birds consistently demonstrate high degrees of clustered nesting, (Darling 1938, Lack 1968, Gochfeld 1980), as individuals synchronize reproduction to simultaneously reproduce (Gochfeld 1980), resulting in higher rates of nest success (Di Maggio et al. 2013) by reducing offspring mortality (Darling 1938). However, in non-monogamous systems, social rank may dictate breeding access of individuals within a local population (Robel and Ballard 1974, Foster 1981). Typically, higher ranked males copulate with more females (Robel 1970, Buchholz 1997, Krakauer 2008), creating a pronounced reproductive skew (Emlen 1976, Mackenzie et al. 1995). When high-ranking males can more effectively monopolize access to females, asynchronous breeding is predicted to occur (Post 1992, Webster 1994). Thus, asynchronous breeding may disproportionately affect fitness amongst individuals, potentially increasing fitness of higher ranking individuals and decreasing fitness of lower ranking individuals.
The eastern wild turkey (Meleagris gallopavo silvestris ; hereafter, wild turkey) has a complex social structure, wherein flocks exhibit social hierarchies where the highest ranking individual dominates others and the lowest ranking individual dominates none (Watts and Stokes 1971, Eaton 1992, Healy 1992). The establishment of dominance hierarchies occurs through agonistic interactions within social groups and rank seldom changes as long as the dominant bird survives (Watts and Stokes 1971, Healy 1992). Male and female wild turkeys maintain separate social hierarchies within and between flocks and dominance is influenced by age (Watts and Stokes 1971) and various morphological and behavioral attributes (Buchholz 1995, 1997, Badyaev et al. 1998). Wild turkeys use a male dominance polygynous mating system comparable to exploded lekking, wherein males communicate with females via elaborate courtship displays and vocalizations (Krakauer 2005, Chamberlain et al. 2018, Wakefield et al. 2020). The establishment of dominance hierarchies determines access to mates for both sexes (Emlen and Oring 1977, Williams and Austin 1988). In species that maintain social hierarchies, higher-ranking females may prevent subordinate females from gaining access to dominant males (Bro-Jørgensen 2002), and in some birds, higher ranking females may realize fitness advantages associated with early nesting (Robel 1970, Robel and Ballard 1974). In fact, social status can influence the onset of laying activity and lower ranked females may delay nesting attempts, causing asynchronous reproduction within social groups of females during a single breeding season (Cristol 1995).
We evaluated reproductive synchrony within and between presumed social groups of GPS-tagged female Eastern wild turkeys by inferring female social rank based on timing of nest initiation (Watts and Stokes 1971, Schmutz and Braun 1989, Healy 1992, Cristol 1995). We hypothesized that the social rank of dominant females, inferred from the onset of nest initiation, would influence the timing of reproduction in subordinate females. We predicted that dominant females would nest first, and when their initial nest failed, would rejoin their previous social group and reinsert themselves in the reproductive hierarchy over remaining subordinate females presumably attempting to mate. Therefore, we predicted that dominant females who nested first would be more likely to have subsequent renest attempts before subordinate females attempted their first nest. We also predicted that dominant females would travel shorter distances within their reproductive ranges prior to onset of nest initiation.