Species differ strongly in their life histories, including the probability of survival. Annual adult survival was investigated extensively in the past, whereas juvenile survival, and especially survival to independence, received much less attention. Yet, they are critical for our understanding of population demography and life-history evolution. We investigated post-fledging survival to independence (i.e. survival upon leaving the nest until nutritional independence) in 74 species of passerine birds worldwide based on 100 population level estimates extracted from published literature. Our comparative analyses revealed that survival to independence increased with the length of nestling period and relative fledging mass (ratio of fledging mass to adult body mass). At the same time, species with higher nest predation rates had shorter nestling periods and lower relative fledging mass. Thus, we identify an important trade-off in life history strategies: staying longer in the nest may improve post-fledging survival due to enhanced flight ability and sensory functions, but at the cost of a longer exposure to nest predators and increased mortality due to nest predation. Additionally, post-fledging survival to independence did not differ between species from the northern temperate zone vs species from the tropics and southern hemisphere. However, analyses of post-fledging survival curves suggest that 1) daily survival rates are not constant and improve quickly upon leaving the nest, and 2) species in the tropics and southern hemisphere have higher daily post-fledging survival rates than northern temperate species. Nevertheless, due to the accumulation of mortality risk during their much longer periods of post-fledging care, overall survival until independence is comparable across latitudes. Obtaining high-quality demographic data across latitudes to evaluate the generality of these findings and mechanisms underlying them should be a research priority.

Parental care provided by males occurs in a diverse array of animals and there are large differences among species in its extent compared to female care. However, social and ecological factors responsible for interspecific differences in male’s share of parental duties remain unclear. Genetic fidelity of females has been long considered important. Theory predicts that females should receive more help from their mates in raising the offspring in species with high genetic fidelity. Using avian incubation behavior as a model system, we confirmed this prediction. The extent of male’s help during incubation increased with decreasing rate of extra-pair paternity across species (22 species of socially monogamous songbirds from 13 families; male’s share of incubation ranged from 6% to 58%), even after accounting for covariates, biases in species selection and intraspecific variability. Moreover, this result was not sensitive to two different phylogenies and branch length estimates. We suggest that our findings support the notion, backed by theory, that genetic fidelity is an important factor in the evolution of male parental care. We offer several behavioral scenarios for the coevolution between male’s share of parental duties and the genetic mating system.

Juvenile mortality is one of crucial drivers of life-history evolution, and predation is the main cause of nest loss in birds. Thus, understanding how nest predation and failure vary in nature is important for understanding life history evolution and, moreover, for effective conservation. We used published data and unpublished records to study factors influencing nest predation and total failure in 138 populations of 90 species of Australian songbirds. Daily predation (average 2.0% d^−1) and failure rates (2.9%) increased from temperate regions to the tropics, over the last four decades, and were lowest in temperate south-western Australia. Predation and failure were higher in smaller species, and failure rates were lower in species with closed nests than in species with open nests. There was no effect of nest height or nest site (ground, shrub, canopy) or social organization on nest predation or failure rates. Nest predation caused on average 72% of total nest failure, similar to other tropical, subtropical, and temperate areas. Our study spanning from the tropics to temperate regions and using > 10 000 nests confirmed that tropical birds faced higher nest failure rates. We identified an increase in nest depredation rates in the last four decades in Australia, suggesting that a large-scale ecological phenomenon must be responsible. It may include increases in predator abundances and/or ranges, possibly connected with human-caused habitat change. A global comparison of nest failure rates confirmed that predation is the main source of nest mortality in songbirds worldwide. We discuss implications of our results for the evolution of reproductive strategies and for the conservation of Australian birds.

Predation is a major factor in ecology, evolution and conservation and thus its understanding is essential for insights into ecological processes and management of endangered populations of prey. Here we conducted a spatially (main island through to offshore islets) and temporally (1938-2005) extensive meta-analysis of published nest predation rates in New Zealand songbirds. We obtained information on nest predation rates from 79 populations (n = 4838 nests) of 26 species of songbirds belonging to 17 families. Nest predation rates increased from southwest to northeast and also across the last 60 years (by 15-25 percentage points in both cases). We identified a major impact of exotic mammalian predators. Nest predation was lowest in areas where no exotic predators were present (12.8), higher in areas with ongoing predator control (33.9%), and highest in areas without control that had the full set of exotic and native nest predators (47.5). Surprisingly, nest predation rates were higher in introduced as compared to native species. Our analyses demonstrated that human-caused factors (introduced predators and prey) overrode factors such as nest type and habitat identified as important in predicting nest predation in North America and Europe previously.