Winter Feeding Boosted Finland's White-tailed Eagles - But Only Slightly
New research confirms that decades of supplementary feeding helped more young eagles survive to adulthood, aiding the species’ remarkable recovery
A conservation experiment decades in the making
A new study has finally put numbers to one of Finland’s greatest conservation success stories – the recovery of the White-tailed Eagle. Researchers from the University of Turku have shown that the long-running winter feeding programme, which began in the 1970s to save the species from extinction, increased the number of young birds that went on to breed. Although the population-level effect was modest, the findings confirm that the feeding scheme made a measurable difference during the eagles’ most vulnerable years.
The study, published in Oecologia, combined two decades of data from a feeding site at Yläne in southwest Finland with genetic records from thousands of ringed and feather-sampled birds. It revealed that individuals that visited the feeder more often as subadults were significantly more likely to recruit into the Finnish breeding population later in life. The probability of recruitment rose from 14% in non-visiting birds to 43% in frequent visitors – a striking difference at the individual level.
Feeding Finland’s comeback eagle
In the 1970s, Finland’s White-tailed Eagle population was on the brink of collapse due to persecution and pollutants. WWF Finland responded with a national rescue plan involving nest protection, public education, and – most labour-intensive of all – a winter feeding scheme that supplied eagles with uncontaminated carcasses. The feeding continued for decades, even after the WWF handed the project to local volunteers, and became a cornerstone of the species’ recovery.
By 2024, the Finnish population exceeded 700 pairs and is no longer considered endangered. Yet until now, the long-term benefits of the feeding scheme had never been quantified. Lead author Dr Carina Nebel and colleagues set out to test whether individual feeder use influenced the likelihood of recruitment – the point at which a young bird joins the breeding population – and whether sex or age played a role.
Females fed more, but both sexes benefited
Using tens of thousands of visual sightings and DNA matches between nestlings and adults, the researchers were able to trace the life histories of more than 1,200 birds. They found that females, which are larger than males, spent more time at the feeder during their early years, but this difference did not translate into higher recruitment rates. The benefits of feeding were shared equally between sexes.
Overall, feeding increased the individual probability of recruitment from 13.6% to 43%. But because only a minority of eagles visited the site frequently, the overall population-level benefit was small – about a 1.1% increase in recruitment. “Even such a small improvement can make a big difference for long-lived species,” the authors note, “especially when combined with other conservation measures.”
Why feeding works – and its limits
Winter feeding appears to have given young, inexperienced eagles a critical survival advantage during the harsh months when lakes freeze and natural food sources are scarce. Birds that learned to use feeders may have maintained better body condition and avoided starvation. The researchers found no evidence that feeder use altered settlement behaviour – frequent visitors did not breed closer to the site – suggesting that the effect was genuinely about survival rather than location loyalty.
However, the authors caution that the study period (2003–2012) came long after the species’ lowest ebb. Feeding might have been far more influential during the crisis years of the 1970s and 1980s. They also note that supplementary feeding must be managed carefully to avoid risks such as disease transmission, competition, or dependence on artificial food sources.
Feeding as a modern management tool
Today, Finland’s eagles face new threats from wind farms and lingering toxins, even as the population grows. Understanding which conservation measures contributed most to their recovery is vital for managing other large scavengers across Europe. The study reinforces that feeding can be an effective, if modest, tool for boosting recruitment – particularly when paired with protection and monitoring.
“Our findings show that supplementary feeding has the potential to support population recovery in long-lived scavengers,” says Dr Nebel. “Even small gains in recruitment can have lasting effects for species that breed slowly and invest heavily in each offspring.”
Once a desperate emergency measure, winter feeding may yet have a role in future eagle management – not to save the species from extinction, but to keep it soaring in a changing landscape.
November 2025
Read the full paper here
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