Conspecific attraction for conservation and management of terrestrial breeding birds: Current knowledge and future research directions

Conspecific presence can indicate the location or quality of resources, and animals settling near conspecifics often gain fitness benefits. This can result in adaptive conspecific attraction during breeding habitat selection as demonstrated in numerous terrestrial, territorial birds. There is growing interest in using simulated conspecific social cues (e.g., decoys, broadcasted vocalizations) to manage bird distributions, yet it remains unclear when this approach is likely to succeed. We reviewed published studies to evaluate whether the strength of conspecific attraction in terrestrial birds is mediated by characteristics of species (life history traits), simulated cues (e.g., timing and duration), sites (e.g., quality), and how conspecific attraction was measured. We identified 31 experiments that simulated social cues and compared conspecific settlement between treatment and control sites. We then used phylogenetically controlled meta-regression to assess the impacts of 19 moderators on settlement. Nearly all species included in these experiments were migratory passerines, and social cues generally had a strong, positive influence on their settlement decisions, as the odds of site occupancy were 3.12× (95% CI: 0.81–11.69) greater in treatment sites relative to control sites. Within this group, conspecific attraction was evolutionarily conserved with ≥25.5% (95% CI: 5.1%–65.4%) of the variance in treatment effects explained by phylogenetic relatedness. However, we found no evidence that any covariates influenced the response to social cues, and we posit this stems from limited research specifically designed to identify the mechanisms mediating conspecific attraction. We therefore developed a research agenda that provides a framework for testing mechanistic hypotheses regarding how cue characteristics, species traits, and spatial contexts may mediate attraction to conspecifics. Evaluating these hypotheses will greatly advance the field by helping managers understand when, where, and why simulating social cues can be used to enhance populations of species that are of conservation concern.

Nonchalant neighbours: Space use and overlap of the critically endangered elongated tortoise

To prevent population extirpations we need to understand species’ requirements, especially for critically endangered species inhabiting biodiversity hotspots. Studying animal movement provides insights into such requirements and gauges protected area effectiveness. Southeast Asian protected areas are becoming isolated; thus, we must ensure existing areas can sustain populations. We used multi-year radio-telemetry with the critically endangered Elongated Tortoise (Indotestudo elongata) to assess: movements, space-use, and conspecific overlap in a small protected area –Sakaerat Biosphere Reserve, Thailand. Movements were weakly seasonal, increasing in hot and wet seasons compared to the dry season. Individuals annual space-use varied (4.24–55.57 ha), while frequently overlapping with conspecifics. Conspecific comparisons revealed males (n = 5) moved similarly to females (n = 12) but used larger areas. Explorations of temporal avoidance versus attraction reveal more instances of conspecific attraction than avoidance (20:8). Avoidance/attraction behaviour appeared disconnected from carapace length or mass; therefore, that conspecific interaction patterns may potentially be a result of resources (mates or food) rather than competition (i.e., no apparent evidence of smaller individuals avoiding larger individuals). Female-female attraction suggests an absence of resource exclusion tactics at the temporal resolution of our data. Male-female attraction may indicate reproductive movements coinciding with hot season, but we failed to detect significant interactive effects linking conspecific attraction or step length to proximity to breeding activity. Our observations of annual space-use and space overlap present critical components when designing robust population assessments; assessments that will underline any successful I. elongata conservation effort. When considered in the context of previous work connecting space overlap with population viability, our results suggest the biosphere population of I. elongata to be reproductive, with enough resources to be potentially viable; the findings help emphasise the importance of even relatively small protected natural areas.