Poor conditions during early development can initiate trade‐offs that favour current survival at the expense of somatic maintenance and subsequently, future reproduction. However, the mechanisms that link early and late life‐history are largely unknown. Recently it has been suggested that telomeres, the nucleoprotein structures at the terminal end of chromosomes, could link early‐life conditions to lifespan and fitness. In wild purple‐crowned fairy‐wrens, we combined measurements of nestling telomere length (TL) with detailed life‐history data to investigate whether early‐life TL predicts fitness prospects. Our study differs from previous studies in the completeness of our fitness estimates in a highly philopatric population. The association between TL and survival was age‐dependent with early‐life TL having a positive effect on lifespan only among individuals that survived their first year. Early‐life TL was not associated with the probability or age of gaining a breeding position. Interestingly, early‐life TL was positively related to breeding duration, contribution to population growth and lifetime reproductive success because of their association with lifespan. Thus, early‐life TL, which reflects growth, accumulated early‐life stress and inherited TL, predicted fitness in birds that reached adulthood but not noticeably among fledglings. These findings suggest that a lack of investment in somatic maintenance during development particularly affects late life performance. This study demonstrates that factors in early‐life are related to fitness prospects through lifespan, and suggests that the study of telomeres may provide insight into the underlying physiological mechanisms linking early‐ and late‐life performance and trade‐offs across a lifetime.

The widely held assumption that any important scientific information would be available in English underlies the underuse of non-English-language science across disciplines. However, non-English-language science is expected to bring unique and valuable scientific information, especially in disciplines where the evidence is patchy, and for emergent issues where synthesising available evidence is an urgent challenge. Yet such contribution of non-English-language science to scientific communities and the application of science is rarely quantified. Here, we show that non-English-language studies provide crucial evidence for informing global biodiversity conservation. By screening 419,679 peer-reviewed papers in 16 languages, we identified 1,234 non-English-language studies providing evidence on the effectiveness of biodiversity conservation interventions, compared to 4,412 English-language studies identified with the same criteria. Relevant non-English-language studies are being published at an increasing rate in 6 out of the 12 languages where there were a sufficient number of relevant studies. Incorporating non-English-language studies can expand the geographical coverage (i.e., the number of 2° × 2° grid cells with relevant studies) of English-language evidence by 12% to 25%, especially in biodiverse regions, and taxonomic coverage (i.e., the number of species covered by the relevant studies) by 5% to 32%, although they do tend to be based on less robust study designs. Our results show that synthesising non-English-language studies is key to overcoming the widespread lack of local, context-dependent evidence and facilitating evidence-based conservation globally. We urge wider disciplines to rigorously reassess the untapped potential of non-English-language science in informing decisions to address other global challenges. Please see the Supporting information files for Alternative Language Abstracts.

Extra-pair paternity (EPP), where offspring are sired by a male other than the social male, varies enormously both within and among species. Trying to explain this variation has proved difficult because the majority of the interspecific variation is phylogenetically based. Ideally, variation in EPP should be investigated in closely related species, but clades with sufficient variation are rare. We present a comprehensive multifactorial test to explain variation in EPP among individuals in 20 populations of nine species over 89 years from a single bird family (Maluridae). Females had higher EPP in the presence of more helpers, more neighbours or if paired incestuously. Furthermore, higher EPP occurred in years with many incestuous pairs, populations with many helpers and species with high male density or in which males provide less care. Altogether, these variables accounted for 48% of the total and 89% of the interspecific and interpopulation variation in EPP. These findings indicate why consistent patterns in EPP have been so challenging to detect and suggest that a single predictor is unlikely to account for the enormous variation in EPP across levels of analysis. Nevertheless, it also shows that existing hypotheses can explain the variation in EPP well and that the density of males in particular is a good predictor to explain variation in EPP among species when a large part of the confounding effect of phylogeny is excluded.

Divorce can be an important behavioral strategy to improve fitness. This is particularly relevant for species that are territorial yearround with continuous partnerships, where individuals face constraints on partner choice due to limited vacancies and dispersal opportunities. We tested several hypotheses for divorce in such a species, the cooperatively breeding bird Malurus coronatus. Based on 9 years of detailed information on dispersal and survival of 317 breeding pairs, we tested whether divorce is driven by inbreeding avoidance, by a better partner or territory, or by social variables (number of subordinates and fidelity of partners). We found that divorce is important to escape incest: incestuous pairs were substantially more likely to divorce (64%) than non-incestuous pairs (14%). However, incestuous pair bonds lasted up to a year, highlighting constraints on breeder dispersal. Non-incestuous pairs also divorced, but here the only predictor for divorce was the presence of extrapair offspring in a previous brood. Although reproductive failure did not trigger divorce, and reproductive success did not improve in the year following divorce, females that dispersed after divorce obtained higher quality territories, unlike females that dispersed after their partner died. Thus, divorce may be a strategy to improve long-term benefits associated with better territories. Some divorces appeared to be forced evictions by older females, although direct evidence for this is limited. Taken together, our findings demonstrate the complexity of factors that affect the occurrence of divorce when partner choice is constrained.

Changes in climate are shifting the timing of life cycle events in the natural world. Compared to northern temperate areas, these effects are relatively poorly understood in tropical and southern regions, where there is limited information on how timing of breeding and food availability are affected by climatic factors, and where patterns of breeding activity are more unpredictable within and between years. Combining a new statistical modelling approach with 5 years of continuous individual‐based monitoring of a monsoonal tropical insectivorous bird, we quantified (a) the proximate climatic drivers at two trophic levels: timing of breeding and abundance of arthropod prey; (b) the effect of climate variation on reproductive output and (c) the role of individual plasticity. Rainfall was identified as the main determinant of phenology at both trophic levels. Throughout the year, likelihood of egg laying increased very rapidly in response to even small amounts of rain during the preceding 0–3 weeks. Adult body mass and male sperm storage also increased rapidly after rain, suggesting high breeding preparedness. Additionally, females were flexible, since they were more likely to nest whether their previous attempt was longer ago and unsuccessful. Arthropod abundance also increased after rainfall, but more slowly, with a peak around 10 weeks. Therefore, the peak food availability coincided with the presence of dependent fledglings. Fitness benefits of nesting after more rain appeared to be linked to offspring quantity rather than quality: nest attempts following higher rainfall produced larger clutches, but showed no improvement in nestling mass or relative fledging success. The response of clutch size to rainfall was plastic, since repeated sampling showed that individual females laid larger clutches after more rain, possibly mediated by improved body mass. Rapid, individually flexible breeding in response to rainfall and slower increase in arthropod abundance also as a response to rainfall, might buffer insectivorous species living in tropical seasonal environments from climate change‐induced phenological trophic mismatches.