Empty nesters can't let go
Caring birds ensure their youngsters don't go hungry
After some adult birds stop feeding their young, they ensure the inexperienced fledglings don't go hungry by calling them to the best foraging sites, researchers at the University of Cambridge have discovered.
The researchers, funded in part by the Biotechnology and Biological Sciences Research Council (BBSRC), believe that parents probably benefit from this seemingly altruistic behaviour by increasing the survival chances of their offspring.
It is well known that the young of some bird species, such as ducks, are capable of feeding themselves immediately after hatching. In other bird species, the young are initially dependent on their parents for food and are often fed for several weeks or months, even after leaving the nest. In many cases, the young disperse when they are no longer fed, marking the end of parental care.
Interestingly, researchers have discovered that African pied babbler adults continue to care for the young after they have stopped feeding them directly, by calling the fledglings to the best foraging spots.
Dr Andy Radford, BBSRC David Phillips Fellow at the Department of Zoology, University of Cambridge, said, "This form of extended offspring care may well be widespread, as the young of many bird species continue to associate closely with their parents even after they are no longer fed directly."
Studying birds once they have fledged is usually very difficult because they tend to fly off whenever an observer approaches. However, by acclimatising the birds to their presence, researchers in Africa's Kalahari Desert were able to monitor closely the behaviour of the pied babblers, discovering the novel form of extended parental care.
By walking within a few feet of the birds, the researchers discovered that parents and helpers (adult birds without offspring) would call the inexperienced fledglings to an area that contained a large amount of readily divisible food. For example, the call was not given when an adult caught a scorpion, a large item that would be difficult to share, but was commonly made when an adult found a termite nest, as it contained many individual prey items.
The fledglings that responded to the calls increased their foraging success rate because they spent less time searching for food. If an adult bird answered the call, they were aggressively chased away.
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