Animal Even sparrows get grumpy in old age
Even sparrows can apparently become grumpier in old age. In old age, the number of social contacts decreases, reports a research team in the journal "Philosophical Transactions B" of the British Royal Society.
02.11.2024, 06:30
SDA
The researchers hypothesize that while birds need to be friendlier to succeed in life when they are young, they can grumble to their heart's content in old age.
In sparrows, young birds can hardly be distinguished from older ones, as the birds do not develop gray feathers or wrinkles. The researchers benefited from a special research project: on the tiny island of Lundy in the UK, the life of every house sparrow (Passer domesticus) has been recorded from egg to death since 2000.
Data on hundreds of island sparrows
From 2013 to 2017, detailed social data was also collected based on interactions between the birds at video-monitored feeders. In total, more than 1600 observations of 615 sparrows up to seven years old were analyzed for the study.
According to the results, the average number of friends per bird - defined as conspecifics with whom a particular bird was frequently observed - decreased with advancing age. This was partly due to the fact that conspecifics of the same age died off over time. But old birds not only lost contact with old friends, they also formed fewer new social relationships.
Friendliness only decisive at a young age
Making friends gives young birds an evolutionary advantage, explained study leader Julia Schroeder from Imperial College London. Previous analyses had shown that friendliness in sparrows - especially towards the opposite sex - contributes to breeding success.
"But once they have reproduced, it seems that unfriendliness has no evolutionary 'cost' - there is no downside," Schroeder said. "This evolutionary mechanism could also come into play in humans - it could be that older people are less inclined to make new friends as they get older," the scientist explained. "Combined with a smaller number of potential friends of the same age, this could be a factor in the loneliness crisis in older people."
Friendships under greater scrutiny
Studies have shown that people become more selective about who they spend their time with as they get older. As social interactions require time and commitment, people may increasingly opt for quality over quantity, according to the London team's study. "In fact, there is evidence in humans that social networks peak in early adulthood, followed by a decline in later life."
House sparrows have spread across almost the entire globe and are one of the most widespread bird species in the world. However, populations have been declining sharply in many places for decades, including in the EU. The small birds feed mainly on seeds and their young are initially fed almost exclusively on insects and their caterpillars.
The house sparrow is very sociable and always moves around in flocks or smaller groups together with conspecifics - which is hard to miss thanks to their loud chirping. Sparrows usually have a lifelong permanent marriage. However, their lives are not particularly long, often only lasting around two years. Under optimal conditions, more than ten years are possible.
