Thomas Johnson, a researcher associated with the Hawk Conservancy Trust and Leeds University, studied the breeding behaviour of White-backed Vultures at two sites near Kimberley in South Africa using camera traps on 10 nesting trees.
Thomas observed an extremely interesting, but very unexpected, solo egg incubation attempt by a White-backed Vulture including the longest uninterrupted nest attendance ever recorded for this species: 3 days 18 hours and 40 minutes. The time-lapse video below shows this unusually long ‘sit’ on the nest by the dedicated solo breeder. This exceptional attendance period is much longer than has been previously reported in other studies, and the vulture spent significantly more time at the nest than would have been required if it was sharing duties with a partner.
African White-backed Vultures are monogamous which means they have one breeding partner, which in most cases they will stay with for their whole life. Both the male and female birds share incubation and feeding responsibilities equally. This type of breeding behaviour is common in birds as it enables one parent to forage whilst the other incubates, so the egg or chick is always attended and less vulnerable to predators.
It is an especially effective strategy for White-backed Vultures as they have such a long breeding period. On average, they will incubate the egg for 56 days, followed by 120-125 days of rearing the chick and an additional 5-6 months where the fledgling chick is still partially dependent on the adults. This amounts to almost a year in total and is challenging for a pair of birds; it would be virtually impossible for a single bird.
After laying the egg, the lone breeder was present for the majority of the time (79%) until it sadly abandoned the egg after 30 days. A second bird did make an appearance at the nest after the first 4 days, seemingly to relieve incubation duties; however, it left again, never to reappear, after just 5 minutes.
It is unknown why the lone bird abandoned the egg at 30 days; it is possible that it was too dehydrated or malnourished to continue without detriment to its own health.