Biologists have explained why weaver bird chicks assist their parents in varying degrees.

Ornithologists have long been studying weaver finches that inhabit the central and northern regions of Southern Africa. These birds live in family groups consisting of a breeding pair and several fledgling chicks. Previous research has shown that they assist in feeding new siblings that appear in the nest, with a greater contribution from female helpers rather than males.

While scientists were aware of this sexual division in Plocepasser mahali, the reasons behind its emergence remained unclear. An international team of specialists in ecology, conservation, biology, and zoology from the UK, Netherlands, Ireland, and South Africa set out to answer this question. Their study was recently published in the journal PLOS Biology.

It was previously thought that females, who stay in their family groups longer than males, were more actively involved in raising the next generation of chicks, as this could ensure reciprocal help from relatives. However, the results of recent observations, conducted over more than 10 years and employing advanced tracking technologies for weaver finches, led scientists to a different explanation.

It turns out that males, unlike females, spend significantly more time seeking opportunities for living and breeding in other potentially suitable habitats. In other words, the sons of weaver finches lack the time to assist their parents with "family duties."

Researchers believe that the proposed hypothesis may explain similar sexual differences observed in other social species. This division, likely arising through evolution, allows animals to find a balance between the necessity of raising offspring in established areas and expanding their habitat range.

In a previous study, it was found that female drongos (Dicrurus adsimilis), another member of the passerine order from Africa, have learned to "sign" their eggs to combat cuckoos. The unique pattern on the eggshell enabled them to identify impostors and dispose of foreign eggs more than 90 percent of the time.