Causes and considerations of the variation in growth strategies among temperate and tropical songbirds
Professor Thomas E Martin from the University of Montana, Missoula, MT, will present the Percy Fitzpatrick seminar with a talk entitled, " Causes and considerations of the variation in growth strategies among temperate and tropical songbirds"
Nestling growth has been measured in hundreds of bird species, and measurements often include multiple traits, but analyses have focused almost solely on mass. Mass is problematic because it reflects both structural and fat components. Yet, the relative contribution of these two components to estimated growth rates is unknown. Moreover, estimates of growth have focused on K, which is a point estimate of maximum growth rate that can be a misleading indicator of overall growth rates, especially among latitudes. More importantly, prioritization of growth of body size versus other traits like wings and legs can vary among species and among latitudes, as a function of variation in parental investment and nest types. Relative size (proportion of adult size) of wings at fledging is influenced by length of the nestling period and the energy available to offspring. Energy available to offspring is influenced by parental investment (food delivery per offspring) and nest structure. Enclosed nests potentially provide thermoregulatory savings, and are used more frequently in tropical and southern hemisphere environments and by small species that are most sensitive to heat loss. Tropical species in enclosed nests produce longer wings at fledging than open-nesters for the same nestling period. Relative size of wings at fledging have strong influences on flight ability at fledging based on high speed videography. An experimental test shows that variation in flight ability strongly influences fledgling survival.