Young birds less honest when competing against siblings

November 07, 2016

Chicks that are competing with siblings or whose parents are likely to die or switch partners tend to be less honest when begging for food, research into sibling rivalry in birds by Oxford University scientists has found.

That's because these events introduce conflict into the family group.

Analysis of more than 100 studies across 60 species of bird also found that chicks are more likely to exaggerate their need for food if their parents are likely to breed again in the future - backing up existing evolutionary theory about natural selection.

The results are published in the journal PNAS.

Co-author Shana Caro, a doctoral candidate in Oxford's Department of Zoology, said: 'We hypothesised that you could explain the relative levels of honesty among chicks across species based on how much conflict exists. A chick that has the nest to itself is always going to get the worm, but if you add other chicks then there is going to be conflict over food resources.

'We wanted to see whether dishonesty increases as the number of siblings sharing a nest increases.'

The researchers mathematically analysed 108 scientific studies featuring information relating to the begging behaviour of chicks across 60 species. They took into account factors such as birds' condition, number of siblings, and relatedness to siblings.

Shana Caro said: 'We found that offspring are less honest about their need for food when they face competition from current siblings, when their parents are likely to breed again, and when parental divorce or death means any future siblings can only be half, not full, siblings. In short, anything that brings in conflict is detrimental to honesty. Over millions of years, natural selection has caused species with higher levels of conflict to evolve chicks that beg for food even when they don't need it.'

She added: 'If parents die or switch partners, all future siblings can only be half siblings. Chicks do not "benefit" from an evolutionary point of view when their parents feed unrelated chicks, and they only benefit half as much if their parents feed half siblings. However, they could benefit a lot if their parents feed their full siblings, because those siblings could give them nieces and nephews, helping to continue the bloodline.

'While dishonesty when competing against existing siblings for food might be expected, what's interesting is that these results show that unborn birds - which may or may not ever exist - have an effect on the behaviour of chicks. This may be because if parents are saving resources for future breeding attempts, they could be less responsive to their current brood's begging. It's therefore in chicks' interests to exaggerate their begging to make sure they get enough food and aren't disadvantaged by their parents' attempts to save energy.'

Begging for food can take the form of chicks calling out, flapping their wings, or opening their mouths as wide as possible. The most honest species, according to the meta-analysis, tend to be long-lived, single-mate seabirds such as the shearwater or albatross, while dishonesty is most prevalent among species such as blackbirds or great tits, which produce larger broods and tend to breed with different mates.

University of Oxford

Related Siblings Articles from Brightsurf:

Stars and planets grow up together as siblings
ALMA shows rings around the still-growing proto-star IRS 63

Study of siblings finds moderate cannabis use impacts cognitive functioning
A new study led by researchers from the University of Colorado School of Medicine compares adolescent siblings to determine the impact of early and frequent use of marijuana on cognitive function.

Child disability can reduce educational outcomes for older siblings
A recent paper published in The Economic Journal indicates that, in families with disabled children, the second born child is more adversely affected cognitively than the first-born child.

Siblings of children with intellectual disabilities score high on empathy and closeness
A new Tel Aviv University and University of Haifa study finds that relationships between children and their siblings with intellectual disabilities are more positive than those between typically developing siblings.

Genome testing for siblings of kids with autism may detect ASD before symptoms appear
One of the key priorities of interventions for autism spectrum disorder (ASD) is starting early, with some evidence showing infants as young as seven months old could benefit.

New study debunks myth that only children are more narcissistic than kids with siblings
The stereotype that only children are selfish, or more self-centered than those with siblings is sometimes used as an argument for having more than one child, but researchers from Germany find there's no evidence for the claim that only children are more narcissistic than children with sibling.

Children bullied by friends and siblings are more likely to think about suicide in their early 20s
Depression, self-harm and suicidal ideation are more prominent in adults in their early twenties if they were bullied at home and at school, a study by researchers at the University of Warwick have found.

UBC study finds siblings of problem gamblers also impulsive, prone to risk-taking
Biological siblings of people with gambling disorder also display markers of increased impulsivity and risk-taking, according to a new UBC psychology study.

Québec siblings with rare orphan disease lead to discovery of rare genetic diseases
Mutations in a gene involved in brain development have led to the discovery of two new neurodevelopmental diseases by an international team led by researchers at McGill University and CHU Sainte-Justine Research Center.

The more the merrier? Children with multiple siblings more susceptible to bullying
A child with more than one brother or sister is more likely to be the victim of sibling bullying than those with only one sibling, and firstborn children and older brothers tend to be the perpetrators, according to research published by the American Psychological Association.

Read More: Siblings News and Siblings Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to