|Mom: Sigh, I'll feed you if you beg the loudest.|
Source credit: Britannia
This brings in another important question: if parents give more food to chicks that beg more, why don't well-fed chicks beg as often as they could? After all, consuming more food is always good for a growing baby. There shouldn't be any physiological reason why wed-fed nestlings couldn't make as much noise as hungry ones. This puzzle can be resolved when we realise that begging also has a cost.
Begging not only costs energy but may also attracts predators. The same amount of noise made by two chicks, one hungry and one well-fed, would presumably be equally harmful in attracting predators. But the benefits of the begging would be greater to the hungry chick resulting in its louder and more insistent calls. In contrast, a more well-fed chick doesn't need more food and doesn't wish to make noises that would attract predators (which would eat them up); so, they keep quiet.
Paradoxically, it is the costs of making the signal that can keep begging an honest signal of need. Here's one question to consider: if begging had no cost, would chicks beg continuously? How would parents respond then?
Separate studies have shown that step-siblings tend to beg for food louder and more frequently. Most birds - 90% of them - have extra-pair copulation; they play around with other birds that aren't their social partners; they're promiscuous individuals who sleep around.
As such, their children are genetically less related. They care less about the survival of their step-siblings. They make louder noises when hungry even though such noises may attract crows that'd have them for lunch.
|"I'll beg louder since you ain't my brother!"|
Source credit: Indiana State University
The more genetically related we are, the more we tend to care for one another. Perhaps this may account for why we can't ignore the cries of our blood relatives for help.
In life, there're trade-offs. We often measure what is costly or beneficial to us relative to the people around us. Perhaps that's why we're always comparing, always so competitive?
If everything comes without a price, without a cost, if everything comes without checks and balances, then our society may just devolve into a morass of vices.
In these big-mouthed, wide-eyed, somewhat ugly nestlings, we see humanity; we see ourselves.
Reference: APS209 Animal Behavior, notes on Evolution of Communication, University of Sheffield