Birds, like humans help their children raise grandchildren

December 22nd, 2007 - 4:47 pm ICT by admin  

Washington, December 22 (ANI): University of East Anglia researchers have discovered the existence of grandparent helpers in the Seychelles warbler, a small songbird found on four granitic and corraline islands in the Seychelles.

This is the first time that this behaviour, which rarely occurs except in humans, has been observed in birds.

The new finding is based on a research that continued for more than two decades. During the course of study, the researchers observed a population of birds on Cousin Island in the Seychelles.

They found that just like humans, older adults in birds that no longer bred themselves, often helped their children to raise grandchildren.

According to the researchers, the concept is of evolutionary importance because it provides another route to co-operative breeding, where adult individuals act altruistically by helping the dominant pair in the group to rear offspring.

Co-operative breeding is known to take place in birds, mammals and in some fish. However, the helpers are usually offspring from previous years who, due to lack of breeding opportunities elsewhere, stay within the territory and become subordinates who help their parents rear more young.

The researchers say that in the case of the Seychelles warbler, co-operative breeding occurs because the island is full and many birds cannot find suitable habitat in which to breed, and therefore they instead become helpers.

Dr David Richardson from UEAs School of Biological Sciences, who has been studying the Seychelles warbler for more than 10 years, said that the existence of grandparent helpers had been largely overlooked outside humans.

Published in the journal Evolution, the study found that dominant females could be deposed from their breeding position by younger relatives. While some deposed females might then leave to live out a solitary life, a large proportion would stay to help other related females, often daughters to reproduce.

Because the subordinate females are helping to raise offspring they are related to, they are helping to produce more birds and increasing the spread of their genes. For those birds prevented from breeding because of a lack of suitable habitat, this is an effective strategy. They are helping their daughters to raise their grandchildren by helping to protect and provision these offspring. This has never been seen in birds, said Dr. Richardson.

It is important because it provides a case that may reflect what happens in humans and gives us a way of looking at what pressures are creating these grandparent helpers. This gives us a model to look at how this might have evolved. Its a way to compare and contrast what has been observed in humans, he added.

He also revealed that the research team would continue its research on the species to determine, for example, why dominant females are deposed in the first place.

In the long term we want to look at why certain females carry on breeding and why others seem to get deposed and become grandparent helpers. Are they being pushed out or are they moving out to allow their daughters to breed? We dont know whether they are getting pushed out by their male partner or their daughter, said Dr. Richardson. (ANI)

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