Lyra treated us to some spectacular photos of her fledging phoebes. Of my phoebe's six eggs, only three chicks fledged. Sad, but the way of nature.
If each phoebe pair laid an average of five eggs, twice a season, if all eggs hatched and survived to adulthood, and if all adults lived a maximum phoebe life span (6 years or so), within a few years the air would be chockablock with phoebes. Early death by accident, environmental stress or predation is a necessary part of the phoebe equation.
As it is part of the equation of life.
Three chicks from six eggs is not untypical. As many as 80 percent of fledged phoebes will not survive their first year of life. Evolution takes care to see that the breeding habits of animals insure survival but not overpopulation. Species such as phoebes that care for their young have fewer offspring than species like fish and insects that lay eggs and forget them. Our sympathies quite naturally lie with species that inhabit our end of the care spectrum.
Are we the only species in which the young care for the old?