15 November 2017
Massive Eggs and Wings
The egg of Argentavis is estimated to weigh approximately 1 kg and it has been hypothesized that they were laid once every two years. At 1 kg the egg is only a little smaller than that of the Common Ostrich, but Argentavis' egg laying cycles were similar to gulls and albatrosses rather than animals that reproduce annually. It has been hypothesized that the incubation cycle of these eggs was such that the birds were forced to incubate over winter. Chicks were thought to have lived with the parents for approximately 16 months before permanently leaving the nest. By contrast, the Wandering Albatross is the longest fledging extant bird, with the young bird remaining in the nest for 278 days. As with many extant gulls and other seabirds, Argentavis is thought to have then had a sexually dormant period, not achieving maturity until approximately 12 years old; Royal and Wandering Albatrosses reach maturity between 6 and 10 years. The fact that Argentavis was so large means that most predation and death probably occurred either in the nest or by from accidents and old age. How old Argentavis lived to be naturally is up for debate, but we know that a lot of extant birds, large and small, live extremely long lives today. The Kakapo of New Zealand is thought to live well over 100 years; with so few in the wild and their histories not being cataloged until recently, however, the oldest known member was approximately 80 at his death. Other parrots have been known to live into their 80's in captivity and individual Royal Albatrosses have been documented at 58 years old in the wild. The largest flying birds, Great Bustards, live to approximately 10 years, whereas the oldest eagles have been recorded at between 30 and 40 years old (depending on the species). All of these numbers make pinpointing the ages of large birds, especially those that can fly, difficult. Argentavis could have lived a lifespan like that of a large eagle, meaning that it could have lived up to 40 years. That means that an adult pair, laying one egg every two years, could have possibly reared 14 young during their lifespan. Not only a large bird, Argentavis may have had a rather sizeable population at one time or another because of their long lives, large size, and dedication to a single offspring.