A male Montagu's harrier identified as AU has become the primary driver for the recovery of the UK's rarest bird of prey. By successfully breeding with multiple females in secret locations, AU has helped revive a species that recorded no breeding pairs between 2020 and 2023.
How AU produced 16 chicks since 2018
The male bird known as AU has demonstrated an extraordinary capacity for reproduction, fathering at least 16 chicks since 2018. According to the report, AU's most recent success includes six juveniles hatched this year across two separate nests. This achievement is attributed to his mastery of "skydancing," a complex courtship ritual involving high-altitude dives,loops, and rhythmic undulations accompanied by cackling vocalizations.
The Royal Society for the Protection of Birds (RSPB) has monitored AU since he was first tagged as a chick in 2016. Mark Thomas, a spokesperson for the RSPB, noted that the organization had no way of knowing a decade ago that this specific bird would eventually prop up the entire species within Britain. AU's ability to maintain multiple nests simultaneously highlights a level of resilience and adaptability that has become the cornerstone of the Montagu's harrier's current survival.
From 30 pairs in the 1950s to a total collapse by 1974
The current struggle of the Montagu's harrier is part of a long-term decline that reflects the fragility of British raptor populations. As the report states , the species once had a breeding population of approximately 30 pairs in the mid-1950s, but that number plummeted to zero by 1974. While a brief resurgence occurred in the late 2000s with up to 13 breeding pairs, the species remained on the verge of local extinction until AU's recent successes .
This pattern of collapse and fragile recovery is common among migratory birds of prey, which face threats both in their European breeding grounds and during their arduous journeys to Africa. The Montagu's harrier, often called the "aristocrats of the bird world," is particularly sensitive to human disturbance, making the recovery of the population dependent on highly specific environmental conditions and extreme discretion.
What satellite tags on July juveniles will reveal about African migration
In July, RSPB fieldworkers equipped one chick from each of AU's two nests with satellite tracking tags. This marks the first time in the United Kingdom that juvenile Montagu's harriers have been fitted with such technology . The goal is to gather data on the precise migration routes these birds take from the UK to their wintering grounds in Africa and their subsequent return.
Despite this technological leap, several critical questions remain. It is currently unknown what the exact survival rate is for these juveniles during their first migration, or if other males are breeding in undiscovered secret locations. Furthermore, because the report focuses heavily on AU's success, it remains unclear if the genetic diversity of the current population is sufficient to sustain the species without a wider influx of migratory males from mainland Europe.
The role of barley patches and farmer secrecy
The survival of AU's offspring has depended as much on human cooperation as on the bird's own instincts. One of the nests discovered this year was located within a patch of barley that a local farmer intentionally left untouched to provide a safe habitat. This collaboration between the RSPB and private landowners has been essential,as the birds are easily disturbed by human presence.
To protect these vulnerable sites, the RSPB is keeping the exact locations of the nests a closely guarded secret. This strategy prevents birdwatchers and intruders from disrupting the nesting process and protects the privacy of the farmers providing the land. The success of the 2024 and 2025 breeding seasons serves as a model for how community-led conservation and targeted habitat preservation can prevent a species from vanishing entirely.
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