Young birds of altricial species are highly dependent on one or both parents for their survival. Without fully developed motor control or feathers, hatchlings begin life as sightless and uncoordinated creatures with gaping maws as big as their appetites. With just a few days or weeks before they are fledglings ready to leave the nest, they need to consume plenty of calorie-rich foods to fuel their intense growth and development.
A nestling’s need for energy can take a toll on parents who may sacrifice their own well-being during chick rearing. A recent study of Zebra Finches showed that when food is limited, offspring remain healthy – their growth rates and body mass did not differ from treatment groups – but their parents lose body mass and have elevated levels of stress hormones. To ensure the success of the next generation, these parents divert energy towards their parenting efforts. Thanks to the many moms and dads making daily sacrifices for their offspring!