Survival and Productivity
Nests: a loose construction of twigs lined with smaller sticks, grass or straw.
Eggs: very pale blue, weigh on average 50.1g.
Clutch size: averages around three but regularly varies between one and five.
Incubation: 24-28 days, both parents incubate and feed the chicks.
Fledging period: 40-50 days.
Independence: the time to full independence varies between individuals, but is usually about two months.
Maturity: three years (in captivity), but apparently, in some cases, even longer in the wild (Hirsch 1979).
Breeding Age: if with an older partner reproduction can start at 2 years old, but many start between 3 and 5 years. The peak breeding age is 8-15 years for both sexes, but is possible up to 28 years old.
Lifespan: 20-25 years in captivity.
Circumstances, such as time spent away from the nest when the chicks are young, may have the biggest influence in the reproductive success, which is largely influenced by the proximity of feeding areas and recent climatic conditions (especially rainfall), affecting food availability, particularly the abundance of invertebrates. (Bowden et al. 2003, Smith et al. 2009).
If a clutch fails early in the season eggs can be relayed. Chick survival is then much more variable and apparently mainly related to climatic conditions and resulting food availability. It was demonstrated that chick survival can be significantly improved by provision of a regular nearby water source (Smith et al. 2009).
Morocco: 9.1% of clutches at the two colonies were lost during incubation and these were attributed to nest destruction by other ibis individuals and Common Ravens (Corvus corax) although there was also evidence of nocturnal predation, possibly by Pharaoh Eagle Owl (Bubo ascalaphus) and for the majority of such clutches, they simply went missing with no known cause (Bowden et al. 2008). Between 1994 and 2004, the reproduction rate per breeding pair has varied from 0.6 to 1.6 fledged chicks in Morocco (El Bekkay et al. 2003).
Syria: limited information shows similar trends and causes (Serra et al. 2009a & 2011). Intensive round-the-clock protection was certainly a factor in the production in Syria during the period 2002-2004, which was 1.75 chick per nest (Serra et al. 2009). Wardening of the sites in Morocco and Syria have prevented a number of potentially serious disturbances and predation events. Before the use of wardens was introduced these would have also been major factors in the loss of nests (Bowden et al. 2008, Serra et al. 2009a & b).