Meeting Abstract
The growth of nestlings to fledging is an energetically demanding period for songbirds that requires the balancing of several major tradeoffs. Parents must balance investment decisions of feeding and brooding with self-maintenance activities. The rapid rate of development and growth of altricial nestlings is highly susceptible to variation in environmental conditions and parental investment as they have a limited capacity to manage their own energetic requirements. Highly variable environments with short breeding seasons, such as the Arctic, magnify these tradeoffs. Arctic nesting passerines provide a good model system in which to explore variation within and between species in growth rates with regards to environmental conditions. Here we present our findings on the inter-annual and inter-species variation in nestling mass gain for two species of arctic nestling passerines: Gambel’s white-crowned sparrows (Zonotrichia leucophrys gambelii) and Lapland longspurs (Calcarius lapponicus) from 2013 and 2014 breeding seasons on the North Slope of Alaska. Comparisons of environmental variables between years suggest that conditions were more challenging in 2014 as compared to 2013, as birds experienced lower temperatures and increased precipitation during the nestling period. In addition, arthropod biomass was also reduced in shrub tundra in 2014 as compared to 2013. These more challenging abiotic and biotic conditions in 2014 resulted in a reduced rate of nestling mass gain in both species. We suggest that this effect may have been mediated by changes in parental investment patterns in response to sub-optimal environmental conditions as birds were forced to reallocate time budgets for brooding and foraging thus negatively impacting growth rates.
