Wild New Jersey - Human Nature by Lynda Hester D'Orio.
Nature provides for many species to survive by having multiple offspring.
It is not unusual that some will die due to natural causes, but this does not seem to be the case. Their numbers are declining. Birds are the indicators of the health of the planet, they are easy to study and provide a wealth of information on environmental health, so when a species like the osprey is at the top of the food chain, their population and health become an area of concern. The rate of chicks' survival is now estimated to be .88, down from 1.5 earlier in the 90's. New Jersey now has about 250 nesting pairs of osprey in New Jersey and in order to grow the population, the success ratio of raising their young must go up over 1.0.