Barred Owl Expansion Threatening Far More Than Spotted Owls
New DNA study reveals widespread predation on vulnerable wildlife across the Pacific Northwest
A predator with a vast ecological footprint
Researchers analysing the diet of 788 Barred Owls across Washington, Oregon and California have revealed that the invading species is consuming an extraordinary range of prey. Using DNA metabarcoding, the study identified at least 162 species eaten by the owls, including mammals, birds, reptiles, amphibians and invertebrates. Some individuals had taken as many as 17 different species in a single feeding cycle.
The most frequently consumed animals included shrews, voles, woodrats, flying squirrels, salamanders and garter snakes. This breadth of prey indicates that Barred Owls are exerting strong top-down pressure on forest ecosystems, far beyond their well-documented competition with the Spotted Owl Strix occidentalis.
Species already under strain face added pressure
Among the prey list were 29 species classed as threatened, endangered or otherwise of high conservation concern at state or federal level. Amphibians featured prominently, including Northern Leopard Frog, Cascades Frog and Western Toad.
Although these species appeared infrequently in the owl diet, the authors warn that rare prey can still experience population-level impacts, especially where numbers are already low or populations are isolated. Amphibians, many of which are declining because of habitat loss and disease, may be particularly vulnerable to predation by a generalist raptor now occurring at high densities.
Impacts on other predators
The study also highlights risks to native carnivores. Barred Owls share much of their prey base with Fisher, Marten, Western Screech Owl, Northern Harrier and several skunk and squirrel species. DNA evidence of predators such as Ringtail and Western Spotted Skunk in the owls’ diet confirms that intraguild predation is already taking place.
The combination of competition and predation poses significant risks to species with naturally low densities or slow reproductive rates, potentially suppressing native predator communities across the region.
More than “owl versus owl”
Public debate around Barred Owl control has focused heavily on competition with the Spotted Owl. The authors argue that this framing misses the broader picture: Barred Owls behave as an invasive non-native predator in the western United States, having expanded westward through landscapes altered by human activity.
Their high densities, wide diet and continued southward expansion suggest that impacts on native wildlife could grow substantially in the coming decades unless action is taken.
A case for precautionary management
The authors contend that the Precautionary Principle supports continued large-scale removal of Barred Owls to prevent biodiversity loss. Lethal control has already proven effective in stabilising and improving Spotted Owl numbers, and may also benefit dozens of other native species now being taken as prey.
As climate change and land-use alteration drive further range expansions in many species, the Barred Owl story may serve as an early warning: some “native” movements can deliver invasive-level impacts. Evaluating and acting on these impacts early could be critical to conserving biodiversity in rapidly changing ecosystems.
November 2025
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