Organisms living at high elevations generally grow and develop slower than those at lower elevations. Slow montane ontogeny is thought to be an evolved adaptation to harsh environments that improve juvenile quality via physiological tradeoffs. However, slower montane ontogeny may also reflect proximate influences of harsh weather on parental care and offspring development. We experimentally heated and protected nests from rain to ameliorate harsh montane weather conditions for Mountain Blackeyes (Chlorocharis emiliae), a montane songbird living at ca. 3200 m asl in Malaysian Borneo. This experiment was designed to test if cold and wet montane conditions contribute to parental care and post-natal growth and development rates at high elevations. We found that parents increased provisioning and reduced time spent warming offspring, which grew faster and departed the nest earlier compared to unmanipulated nests. Earlier departure reduces time-dependent predation risk, benefitting parents and offspring. These plastic responses highlight the importance of proximate weather contributions to broad patterns of montane ontogeny and parental care.

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