Question: What happens as peregrines age? Does it affect how many eggs the female lays or how many of them hatch? How long do they live?
Answer: This year (March 2010) the female peregrine at the Gulf Tower (Tasha) was 14 years old, possibly older.
According to Birds of North America‘s peregrine falcon article: “Female age has a significant effect on all measures of reproductive success: clutch size, fertility, hatchability, brood size, nestling survivability, and number of fledglings. In all but nestling survival, the data best fit a quadradic model, reflecting initial increase in performance followed by decrease with age.”
In other words, a 14 year old female peregrine will not lay as many eggs as she used to. Some of her eggs won’t be fertile, some of the fertile eggs won’t hatch, and she won’t produce as many fledglings as she used to. In 2008, Tasha laid 4 eggs but only 2 hatched. In 2009 she laid 5 eggs but only 2 hatched.
Weakness in an aging peregrine will eventually become evident to other peregrines. If the bird has a prime nesting location, a younger peregrine will try to take its territory and will eventually do so. In the spring, the challenge is often a fight. At other times of the year, the older peregrine may disappear (die) before the new one arrives.
The maximum life span of peregrines in the wild is 16-20 years. For comparison, the maximum life span of humans is 105-122 years. The majority of individuals in both species die before reaching maximum age.
Peregrines are highly territorial and will not easily abandon their long held territories. When an aging peregrine disappears from its territory is likely to have died.
(photo of Tasha at the Gulf Tower from the National Aviary webcam, March 2010)