Understanding sources of reproductive variation can inform management and conservation decisions, population ecology and life-history theory. Annual reproductive variation can drive population growth rate and can be influenced by factors from across the annual cycle (known as carry-over effects). The majority of studies, however, focus solely on the role of current environmental events. Past events often influence future reproductive decisions and success but can be logistically difficult to collect and quantify, especially in migratory species. Recent work indicates that glucocorticoids may prove good indicators to evaluate carry-over effects across life-history transitions. Here, we evaluated three different measures of glucocorticoid physiology (feathers, faeces and plasma) to evaluate the predictability of future breeding decision in the harlequin duck (Histrionicus histrionicus). We collected tail and back feathers, plasma and faeces for glucocorticoid analysis, and fitted female harlequin ducks with very high-frequency transmitters to track their breeding decisions. Both back feathers (moulted immediately before the current season) and faecal glucocorticoid metabolites were identified as important predictive factors of reproductive decisions; high concentrations of glucocorticoid metabolites in back feathers and faeces predicted a higher likelihood of reproductive deferral for the year. Although back and tail feather corticosterone concentrations were correlated, tail feathers (moulted at the end of the previous breeding season) did not predict breeding decisions. Plasma corticosterone concentrations were collected over too broad a time range after capture to be useful in this study. This study demonstrates the utility of non-invasive corticosterone metrics in predicting breeding decisions and supports the use of feathers to measure carry-over effects in migratory birds. With this technique, we identified the prenuptial moult as an important life-history phase that contributes to reproductive decisions. Identification of critical life-history phases is paramount to efficient management of species.

Organisms continuously face environmental fluctuations, and allocation of metabolic investment to meet changing energetic demands is fundamental to survival and reproductive success. Glucocorticoid (GC) hormones (e.g. corticosterone –CORT) play an important role in energy acquisition and allocation in the face of environmental challenges, partly through mediation of energy metabolism. Although GCs and metabolic rate are expected to covary, surprisingly few empirical studies have demonstrated such relationships, especially in wild animals. Moreover, studies testing for associations between GCs and fitness generally do not account for among-individual differences in energy expenditure or energy allocation. We measured CORT (baseline and stress-induced) and metabolic traits [resting metabolic rate (RMR), cold-induced VO2max (Msum) and aerobic scope (the difference between Msum and RMR)] in female tree swallows (Tachycineta bicolor) during chick-rearing, and tested for their associations with several variables of reproductive performance. We found a positive relationship between RMR and baseline CORT, but no consistent associations between stress-induced CORT and Msum. This suggests that while baseline CORT may be a good indicator of an individuaĺs baseline metabolic investment, stress-induced CORT responses are not associated with aerobic scope or the upper limits of aerobic performance. Furthermore, we found that metabolic traits were associated with reproductive performance: females with higher reproductive output showed higher Msum, and also tended to show higher RMR. Overall, these results suggest that metabolic traits are better predictors of reproductive output in tree swallows than CORT concentrations. They further point to the maximal aerobic capacity being higher in females investing more heavily in a current reproductive event, but whether this association reflects trade-offs between current and future reproductive efforts remains to be tested.

Tending to long-term landscape health and resilience is a highly complex enterprise. To address this complexity, we must imagine and facilitate a community-based response that is just as complex, inclusive, interdependent, informed, deliberative, and adaptive as the challenges we face. Conservation and stewardship partnerships are a now-familiar way to try to tackle this monumental task. However, successful conservation partnerships are not possible without leadership that can explore shared values amidst dissenting views, navigate complex and technical information to bring all parties to a shared understanding of the issues, manage conflict and facilitate difficult conversations, and approach these multi-faceted challenges with humility and empathy. This is both the challenge and the opportunity of collaborative leadership. The series of papers in this issue of Parks Stewardship Forum on "Collaborating Well" explores what makes collaborative leadership work. This introductory piece illustrates why collaborative leadership is so critical to meet our landscape stewardship needs. The article on the Partnership Impact Model goes beyond describing this work and delves into how to measure its impact. Moreover, the article on peer learning provides

No abstract