Light pollution and early maternal investment

The lifecycle of almost all organisms is determined by light. However, the rapidly growing number of artificial light sources increasingly distorts the natural day and night cycles. These developments have dramatic consequences for many organisms. There is growing empirical evidence for surprisingly high costs of light-at-night (ALAN) for the development, health, behavior and physiology of almost all living beings. Especially during the early stages of development, for example during embryonic development or immediately after birth, many organisms are sensitive to stimuli from their immediate environment. One physiological process is particularly interesting: the "early maternal investment" (EMI). EMI is the allocation of certain nutrients or hormones by the mother to the embryo depending on her health, nutritional status or environmental conditions. These processes allow females to adjust the offspring phenotype, beyond their genetic predisposition, to survive in a certain environment. To-date it remains largely unknown how ALAN affects EMI during pregnancy and egg laying. In this project, we aim to investigate the effects of ALAN on the reproductive strategy, especially EMI, and ultimately the reproductive success in house sparrows. Birds are particularly well studied in this regard because EMI is restricted to the period of egg formation and all resources necessary for the embryo must be deposited in the egg prior to laying. In our study, we focus on house sparrows, because they are found in cities worldwide and show remarkably high plasticity in physiology and behavior to survive and reproduce in urban habitats. In a series of experiments, we will first investigate how light pollution alters maternal physiology and consequently EMI and parental behavior. We breed birds in large outdoor aviaries with different light regimes and simulate ALAN as it is found in many cities. We will regularly check the hormonal status of the mother and later determine the hormonal components in egg yolk and egg white. In further experiments, we will test whether there is a sensitive period for ALAN induced changes in nestlings and the role of EMI in mediating these effects. For this purpose, the development (e.g. growth, physiology) and behavior of the juveniles will be monitored until adulthood. Vertebrates are similar in their physiological traits and the results of our study are applicable to other species. Our findings will provide new insights with relevance for both, basic research and nature conservation.