Breeding and Life Cycle
The Southern Ground Hornbill is an obligate cooperative breeder, with each breeding pair always assisted by at least two other birds. It is known via experiments in captivity that birds without six years experience as helpers at the nest are unable to breed successfully if they do become breeders. This suggests that unaided pairs cannot rear young and that helping skill as a juvenile is essential for rearing young as an adult.
In captivity, a maximum lifespan of 70 years is recorded, and it is generally believed that the life expectancy of a bird that survives long enough to fledge is as high as thirty years or more, which is comparable to more famously long-lived birds like the Wandering Albatross.
Ground hornbills are believed to reach maturity at six to seven years, but very few breed at this age. Nests are almost always deep hollows in very old trees, though there exist reports ground hornbills have on occasions nested on rock faces. One to three eggs are laid at the beginning of the wet season but siblicide ensures that only one nestling is ever fledged. The eggs measure 73 millimetres (2.87 in) by 56 millimetres (2.20 in) and are pure white in colour but very rough in texture.
The period of parental dependence following a 40 to 45-day incubation period and an 85-day fledging period is between one and two years depending on climatic conditions before young are independent of parents and helpers, which is the longest of any bird. This means that ground hornbills can normally breed successfully only every third year. Triennial breeding is extremely rare in birds: probably the only other bird which breeds on a triennial basis is the Ornate Hawk-Eagle of Neotropical rainforests.
Read more about this topic: Southern Ground Hornbill
Famous quotes containing the words breeding, life and/or cycle:
“The surest route to breeding jealousy is to compare. Since jealousy comes from feeling “less than” another, comparisons only fan the fires.”
—Dorothy Corkville Briggs (20th century)
“In this lucid and flexible pattern only one thing remained always stationary, but this fallacy went unnoticed by Martha. The blind spot was the victim. The victim showed no signs of life before being deprived of it. If anything, the corpse which had to be moved and handled before burial seemed more active than its biological predecessor.”
—Vladimir Nabokov (1899–1977)
“The cycle of the machine is now coming to an end. Man has learned much in the hard discipline and the shrewd, unflinching grasp of practical possibilities that the machine has provided in the last three centuries: but we can no more continue to live in the world of the machine than we could live successfully on the barren surface of the moon.”
—Lewis Mumford (1895–1990)