Meeting Abstract
Life history theory describes a slow-fast continuum within and across species. Species and individuals living at higher elevations often have slower life histories than relatives at lower elevations. This pattern mimics the wide-spread and well-studied pattern across latitudes, but hypotheses for latitudinal life history variation do not explain the variation observed across elevations. We first provide data verifying this pattern using two communities of birds at two continuous but disparate field sites (1500m asl and 3200m asl), and second, experimentally test a novel hypothesis for the causes of this pattern. The harsh weather hypothesis states that slow life history traits at high elevations are caused by parental constraints due to cool ambient temperatures exacerbated by wetting from rainfall. This harsh weather requires parents to spend more time warming offspring, resulting in less time available for food provisioning. Reduced provisioning rates may cause delayed post-natal development, a key life history stage. We tested this hypothesis by adding supplemental heat to nests of Mountain Blackeyes (Chlorocharis emiliae) at 3200 m asl on Mt. Kinabalu, Malaysian Borneo. Our results support the harsh weather hypothesis showing that heated nests cause lower adult brooding and increased nestling provisioning rates. Thus, our results explain one mechanism by which life history traits of high elevation birds fall closer to the slow end of the life history continuum than those at lower elevations.
