New study in Seychelles shows value of even elderly warblers raising their young

The Seychelles warbler, also known as Seychelles brush warbler, is a small songbird found on five granitic and coralline islands in Seychelles. (Nature Seychelles)

(Seychelles News Agency) - New research conducted on Seychelles' warblers has shown that the bird's offspring fare better if elderly parents have helped to raise them. 

According to the research paper -- ‘Helpers compensate for age-related declines in parental care and offspring survival in a cooperatively breeding bird’ -- this collaboration within the colony can compensate for a decline in the ability of elderly parents to provide sufficient care and may also promote more social behaviour in family groups with older parents. The research was published in the journal Evolution Letters this month.

Nirmal Shah, the chief executive of Nature Seychelles, a non-government organization, which was part of the study said that the research started with the conservation of the species, which was back then the rarest bird in the world. 

"Subsequently, the research has gone beyond conservation and it is cutting edge. This is why it has been published in one of the best journals in the world," said Shah. 

The study was conducted using data collected over the last 30 years on individual Seychelles warblers studied on Cousin Island. (Serge Marizy Photo License: All Rights Reserved)

Shah said that "the research also studied ageing within the bird population. Because it involves certain anatomical and physiological structures in the bird, it is very relevant to human medicine".

The study was conducted using data collected over the last 30 years on individual Seychelles warblers studied on Cousin Island, which was purchased by BirdLife International in 1968 to save the Warbler, then one of the world's most endangered birds.

The Seychelles warbler, also known as Seychelles brush warbler, is a small songbird found on five granitic and coralline islands in the Seychelles – 115 islands in the western Indian Ocean. 

The study found that female subordinates of the species are more likely to become a helper and provide more help than males. 

The research was also conducted in partnership with researches from the University of Anglia (UEA), the University of Groningen in the Netherlands, and the University of Sheffield. 

The senior author of the research paper, David Richardson, who is from the UEA’s School of Biological Sciences, said that many animal species, offspring from ageing parents do not survive as well as offspring from younger parents. 

The chances of survival of juvenile offspring decline progressively with the age of the mother bird, but these declines are mitigated when helpers are present. (Charli Davies Photo License: All Rights Reserved)

“The cooperative nature of Seychelles warblers means to care for offspring is often shared between the dominant breeding pair and a variable number of adult subordinate helpers that help with various aspects of rearing, including providing food for the offspring," said Richardson.

“The amount of care that dominant breeders provide is reduced when they are assisted by helpers and this lower parental investment can improve the parents own survival and future reproductive output,” added Richardson.

Furthermore, the additional care from helpers reduces offspring mortality, the study found.

"The chances of survival of juvenile offspring decline progressively with the age of the mother bird, but these declines are mitigated when helpers are present," said Richardson.

The findings of the research are further helping to explain why social species, such as humans, often do better if they live in groups and cooperate to raise offspring.