Exposure to food insecurity increases energy storage and reduces somatic maintenance in European starlings

Preprint: Exposure to food insecurity increases energy storage and reduces somatic maintenance in European starlings

Abstract

Birds exposed to food insecurity—defined as temporally variable access to food—respond adaptively by storing more energy. In order to do this, they may reduce energy allocation to other functions such as somatic maintenance and repair. To investigate this trade-off, we exposed juvenile European starlings (Sturnus vulgaris, n = 69) to 19 weeks of either uninterrupted food availability, or a regime where food was unpredictably unavailable for five hours on five days each week. Our measures of energy storage were repeated measurements of mass, and fat score at the end of the treatment. Our measures of somatic maintenance were growth rate of a repeatedly plucked tail feather, and erythrocyte telomere length, which we measured five times by analysis of the terminal restriction fragment. The insecure birds were heavier at all measurement points, but by an amount that varied across time points. They also had higher fat scores. We found no evidence that they consumed any more food overall, though our food consumption data was incomplete. Plucked tail feathers regrew more slowly in the insecure birds. Telomere length was reduced in the insecure birds, specifically, in the longer percentiles of the within-individual telomere length distribution. We conclude that increased energy storage in response to food insecurity is achieved at the expense of investment in somatic maintenance and repair.