Ornithologists have presented the first evidence of young Gyr Falcons being predated by another raptor.
The northernmost diurnal raptor in the world and the largest of all falcons, Gyrs have few natural enemies and evidence of predation upon them is rare. In Sweden, a Pine Marten was once documented taking a brood of three young, while in Russia, Peregrine Falcons were observed killing a near-adult Gyr.
The size of adults and the scarcity of other predators in the falcon's Arctic and subarctic breeding grounds explains the paucity of observations involving Gyrs becoming prey. However, further evidence suggests that young might be taken now and then, with remains of chicks found in Raven nests on two occasions and a corpse in a Norwegian Golden Eagle nest.
But, for the first time, evidence has been published of the predation of young Gyr Falcons by another raptor.
Just one of a brood of four Gyr Falcons survived the visit from a young female Eurasian Goshawk (Jacob W Frank via Wikimedia Commons).
Camera trap captures attacks
A camera trap forming part of a programme monitoring 11 Gyr Falcon nests in Lierne, central Norway, captured images of a one year-old female Eurasian Goshawk killing three of the four Gyr chicks in the nest and partially eating some of the victims. The hawk paid at least two visits around 2.15 am on 5 June 2021, which was around 30 minutes before sunrise.
The oldest chick killed was judged to be around 23 days old. The female Gyr returned to the nest with prey almost four hours later and proceeded to feed the surviving chick, which had already fed on one of its siblings immediately after the attack. This bird fledged on 29 June.
Goshawks have a long list of documented prey items, including a wide variety of mammals and birds, including owls and raptors such as European Honey Buzzard.
Central Norway is relatively unique in having boreal forest and mountainous areas bordering each other, making an event such as this more likely.
No goshawk territory was known in the area, though the nest was located only 800 m from Norway Spruce woodland, so the predator may have been an unpaired female.
Previous research has shown that Eurasian Goshawks can have a negative effect on the breeding success of other raptors, with Common Buzzard and European Honey Buzzard known to suffer heavier losses when nesting close to the Accipiter.
Reference
Moen, B C, Kroglund, R T, Østnes, J E, Nilsen, E B, & Nygård, T. 2023. Wildlife Camera Monitoring Revealed the Northern Goshawk as a Predator on Gyrfalcon Nestlings. Journal of Raptor Research 57 (4): 671-675. DOI: https://doi.org/10.3356/JRR-23-00007
