Montane species worldwide are shifting upslope in response to recent temperature increases. These upslope shifts are predicted to lead to mountaintop extinctions of species that live only near mountain summits, but empirical examples of populations that have disappeared are sparse. We show that recent warming constitutes an “escalator to extinction” for birds on a remote Peruvian mountain—high-elevation species have declined in both range size and abundance, and several previously common mountaintop residents have disappeared from the local community. Our findings support projections that warming will likely drive widespread extirpations and extinctions of high-elevation taxa in the tropical Andes. Such climate change-driven mountaintop extirpations may be more likely in the tropics, where temperature seems to exert a stronger control on species’ range limits than in the temperate zone. In contrast, we show that lowland bird species at our study site are expanding in range size as they shift their upper limits upslope and may thus benefit from climate change.

Tropical birds are purported to be longer lived than their temperate counterparts, but it has not been shown whether avian survival rates covary with latitude worldwide. Here, we perform a global-scale meta-analysis of 949 estimates from 204 studies of avian survival and demonstrate that a latitudinal survival gradient exists in the northern hemisphere, is dampened or absent for southern hemisphere species, and that differences between passerines and nonpasserines largely drive these trends. We also show that while extrinsic factors related to climate were poor predictors of apparent survival compared to latitude alone, the relationship between apparent survival and latitude is strongly mediated by intrinsic traitslarge-bodied species and species with smaller clutch size had the highest apparent survival. Our findings reveal that differences among intrinsic traits and whether species were passerines or nonpasserines surpass latitude and its underlying climatic factors in explaining global patterns of apparent avian survival.

The "biotic interactions" hypothesis proposes that strong species interactions in the tropics drive faster divergence in the tropics. However, support for the idea that interactions are stronger in the tropics is mixed. Here we propose an explanation for why observed interaction strengths might often be similar across latitudes. We suggest populations might adapt to latitudinal differences in species interaction regimes, which can have the effect of flattening observed latitudinal gradients in interaction rates. To investigate this idea, we examine a canonical example of a strong tropical biotic interaction-nest predation rates in land birds. Surprisingly, we find that daily rates of nest predation vary minimally with latitude. We then consider the possibility that evolved life history differences across latitudes contribute to the flat gradient. We focus on the duration of the nesting period, which is longer in the tropics than in the temperate zone and thought to represent a component of adaptation to tropical nest predators. Greater nesting period duration is known to be associated with lower daily predation rates. When we statistically control for nesting period duration, we recover a pattern where daily rates of nest predation are highest in the tropics. The implication of this analysis is that the evolution of longer nesting periods in tropical species (and shorter nesting periods in the temperate zone) has helped to flatten a "baseline" latitudinal gradient in daily rates of nest predation. More generally, we propose that adaptation to latitudinal differences in biotic interactions can flatten latitudinal gradients in interaction strength.

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Life‐history theory postulates that physiological traits, such as energy metabolism, can be understood in terms of allocation trade‐offs between self‐maintenance and reproduction over an organism's life span, and data show that metabolic intensity and survival vary inversely with latitude, with tropical birds exhibiting a “slow” pace of life relative to temperature species. However, tropical regions harbour strong environmental gradients of their own, and it remains to be shown whether similar life‐history trade‐offs between metabolism and longevity are reflected among tropical birds of the same latitude. We estimated apparent annual survival in 37 species of tropical passerine birds along an elevational gradient (400–3,000 m) in Peru to test whether variation in survival was influenced by basal metabolic rate (BMR; estimated at the same sites), elevation or both factors. We used path analysis to test our prediction that survival would decline as BMR increased, while accounting for the potential direct effects of elevation on survival due to differences in predation pressure or environmental conditions as well as potential indirect effects of elevation on BMR via temperature and the costs of thermoregulation. Higher BMR in tropical passerine birds predicted lower apparent survival, regardless of the elevation at which species occurred. In addition, elevation had a direct negative effect on apparent survival, perhaps due to harsher abiotic conditions, low site fidelity or both at high elevations. We provide evidence of a link between metabolic rate and longevity previously undescribed in populations of free‐living birds. Our results illustrate that tropical montane species may be characterized by a unique suite of traits in their pace of life, in which BMR does not differ from lowland birds, but survival does. A plain language summary is available for this article.

24Tropical birds are purported to be longer lived than temperate species of similar size, but it has 25 not been shown whether avian survival rates covary with a latitudinal gradient worldwide. Here, 26we perform a global-scale meta-analysis to investigate the extent of the latitudinal survival 27 gradient. We modeled survival as a function of latitude for the separate northern and southern 28 hemispheres, and considered phylogenetic relationships and extrinsic (climate) and intrinsic (life 29 history) predictors hypothesized to moderate these effects. Using a database of 1,004 estimates 30 from 246 studies of avian survival, we demonstrate that in general a latitudinal survival gradient 31 exists in the northern hemisphere, is dampened or absent for southern hemisphere species, and 32 that survival rates of passerine birds largely account for these trends. We found no indication that 33 the extrinsic climate factors were better predictors of survival than latitude alone, but including 34 species' intrinsic traits improved model predictions. Notably, species with smaller clutch size 35 and larger body mass showed higher survival. Our results illustrate that while some tropical birds 36 may be longer lived than their temperate counterparts, the shape of the latitude-survival gradient 37 differs by geographic region and is strongly influenced by species' intrinsic traits. 38 39 40 41 42 43 44 48 and behaviors, and also show considerable variation in their lifespan and annual survival. For 49 example, in large-bodied landbirds, such as some raptors and parrots, annual survival is often 50 high (Newton et al. 2016; Maestri et al. 2017) and individuals are long lived, but for small-51 bodied species like warblers and kinglets, rates of annual survival can be low (DeSante et al. 52 2015; Johnston et al. 2016). While differences in body mass account for some of this variation 53 larger species tend to live longer than smaller ones (Lindstedt

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