Amazing stuff! The longer you observe, the more you discover!
"... The only complex "friend-like" relationship seen in vertebrates is known as cooperative breeding, in which two individuals assist in raising the young. Yet, for African starlings, the bonds they form go far beyond mere parenting duties. ...
Now, a new study with 20-years of field data, published in the journal Nature, has discovered that the African superb starling (Lamprotornis superbus) forms mixed-kin groups with anywhere from 7 to 60 members, living similarly to how we humans do. ...
After surveying for over 40 consecutive breeding seasons, researchers were able to decipher the relationship between breeders and helpers.
They found each breeding pair was aided by up to 16 non-breeders, i.e., helpers. This aid even included foraging for the hatchlings and defending the nest from predators. In return, this helped in group augmentation, increasing group size. The adult survival rate of larger starling groups was seen to be higher than that in smaller groups. ..."
From the abstract:
"Identifying the mechanisms that underlie cooperation is fundamental to biology. The most complex form of cooperation in vertebrates occurs in cooperative breeders, in which helpers forego reproduction and assist in raising the young of others, typically relatives. Not all cooperative societies, however, are kin-based—nearly half of all avian and mammalian cooperative breeders form mixed-kin societies, much like those of humans. Kin selection in mixed-kin societies occurs when individuals gain indirect fitness from the preferential helping of relatives, but helpers also frequently assist non-kin, highlighting a potential role for direct fitness in stabilizing cooperative societies.
Here, using a 20-year study of superb starlings (Lamprotornis superbus), we examined how direct and indirect fitness jointly influence helping behaviour. Although we detected kin-biased helping (demonstrating kin selection), non-kin helping was common despite opportunities to aid kin. Unexpectedly, specific pairs maintained long-term reciprocal helping relationships by swapping social roles across their lifetimes—a subtle pattern of reciprocity requiring decades of observation to detect.
Given the frequency of non-kin helping and the occurrence of reciprocal helping among both kin and non-kin, helping behaviour in superb starlings seems to be greatly influenced by direct fitness. However, the relative importance of direct and indirect fitness varied with helpers’ sex and dispersal history. By uncovering a cryptic yet crucial role of long-term reciprocal helping, we suggest that reciprocity may be an underappreciated mechanism promoting the stability of cooperatively breeding societies."
Extended Data Fig. 1: Superb starlings are obligate cooperative breeders, with every breeding pair assisted by up to 16 nonbreeding helpers.
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