In altricial birds. energy supply during growth is a major predictor of the physical condition and survival prospects of fledglings. A number of experimental studies have shown that nestling body mass and wing length can vary with particular extrinsic factors. but between-year observational data on this topic are scarce. https://www.roneverhart.com/DigiWeigh-Notebook-Digital-Pocket-Scale-1000g-x-0-1g/