Ecophysical Limits to Northern Breeding Distributions of Arctic Sandpipers

9423522里克尔夫北极高地的环境对许多形式的生命的存在施加了两个关键的限制。一是环境的极端物理条件：寒冷的温度、高风速和低降雨量。另一个是生长季节的短暂。这种环境对琵琶(蜈蚣科)来说尤其严格，它们在北极的繁殖地只呆了两个月，它们的幼崽是最小的温血动物之一。这项研究项目将利用对蜈蚣酸雏鸟的生长发育、能量、热环境、食物供应和父母照顾的详细测量来发现这些鸟类如何如此成功地利用北极环境。寒冷的温度要求产生新陈代谢热量的能力很高；短的繁殖季节需要快速生长。因此，低温和短季的综合压力似乎会将北极高海拔地区的小型恒温动物推向极限。解决生长速度和产热之间相互冲突的功能之间的妥协问题，是理解生物体的设计如何与其环境设置相关的一个极好的模型。田间和实验室的测量将被用来确定关系的形式，并量化脊柱酸雏鸟的数学模型中的系数。该模型的基本要素包括雏鸡的内部组织以及雏鸡与其环境的关系。该模型随着雏鸡的生长而不断变化，并通过将生长率与组织功能容量和功能容量与成年鸡所达到的比例联系起来的表达式来模拟生长。实验室和野外工作将提供数据来评估蜈蚣酸雏鸡模型。实验室调查将集中在能量收支的组成部分，雏鸟对冷应激产生热量的能力，来自机体的热量损失，包括呼吸表面蒸发造成的热量损失，以及对身体降温的耐受性。在自然家庭群体中观察自由放养的雏鸟，在可行的情况下使用无线电标记的个体，将有助于验证圈养鸟类的结果。将持续监测热环境条件和食品供应情况，以提供有关这些因素的范围和时间变化的数据。

9423522 Ricklefs The environment of the high arctic imposes two critical limits to the existence of many forms of life. One includes the extreme physical conditions of the environment: cold temperatures, high wind velocities, and low precipitation. The other is the briefness of the growing season. This environment is especially stringent for sandpipers (Scolopacidae), which occupy their arctic breeding grounds for as little as two months, and whose chicks are among the smallest of warm-blooded animals. This research project will utilize detailed measurements of the growth and development, energetics, thermal environment, food supply, and parental care of scolopacid chicks to discover how these birds exploit the arctic environment so successfully. Cold temperatures require a high capacity for generating metabolic heat; short breeding seasons require rapid growth. Therefore, the combined stresses of low temperature and short season would seem to push small homeotherms to the limit in the high arctic. The problem of resolving compromises between the conflicting functions of growth rate and heat generation is an excellent model for understanding how the design of the organism relates to its environmental setting. Field and laboratory measurements will be used to determine the forms of relationships and quantify the coefficients in a mathematical model of the scolopacid chick. The essential elements of the model encompass the internal organization of the chick and the relationship of the chick to its environment. The model changes continuously as the chick grows, and growth is simulated by expressions relating growth rate to functional capacity of tissues and functional capacity to the proportion of adult size achieved. Laboratory and field work will provide data to evaluate the scolopacid chick model. Laboratory investigation will focus on components of energy budgets, capacity of chicks to generate heat in response to cold stress, loss of heat from the b ody, including that caused by evaporation from the respiratory surfaces, and tolerance of body cooling. Observations of free-ranging chicks in natural family groups, using radio-tagged individuals where practical, will help to validate the results from penned birds. Conditions of the thermal environment and the availability of food items will be monitored continuously to provide data on the range and temporal variability of these factors.