What Animal Kills Birds? Common Predators Explained

Domestic cats are the single deadliest animal threat to birds in the United States, killing an estimated 1.3 to 4.0 billion birds every year. But cats are just one part of a much larger cast of predators. Hawks, snakes, raccoons, crows, rats, and even praying mantises all take birds or their eggs on a regular basis. The full picture of what kills birds is surprisingly broad, and it depends heavily on the bird’s life stage, habitat, and where in the world it lives.

Domestic Cats Top the List

No predator comes close to the sheer number of birds killed by free-ranging domestic cats. A landmark study estimated that cats in the contiguous United States kill between 1.3 and 4.0 billion birds annually, with a median estimate of 2.4 billion. Roughly 69% of that mortality comes from unowned cats, including feral colonies and barn cats, rather than from pet cats that wander outdoors.¹ Those numbers make cats a conservation concern on a continental scale, not just a neighborhood nuisance.

The damage extends well beyond North America. A global review found that free-roaming cats have contributed to at least 63 vertebrate extinctions worldwide, including birds, small mammals, and reptiles.² Beyond direct killing, cats suppress wildlife populations through disease transmission and by creating a landscape of fear that changes how birds behave, where they nest, and how successfully they reproduce.³ If you keep a cat and care about the birds in your yard, the evidence is unambiguous: indoor-only cats eliminate the problem entirely.

Dogs Are a Different Kind of Threat

Dogs rarely catch and eat adult birds the way a cat does, but they are remarkably effective at disrupting nesting. A study of plovers on tourist beaches in Australia found that walkers accompanied by dogs flushed nesting plovers more than 90% of the time when passing through dune habitat, compared with about 48% for walkers alone. Lone dogs roaming the dunes triggered a flushing response 100% of the time.⁴ For ground-nesting shorebirds, repeated flushing means eggs go unincubated and chicks are left exposed to heat, cold, and other predators. Seasonal leash laws on beaches exist largely because of this dynamic.

Hawks, Owls, and Other Raptors

Birds of prey are among the most visible predators of other birds, and they have been doing it for millions of years. In North America, accipiters like Cooper’s hawks and sharp-shinned hawks are built for hunting songbirds. They are agile fliers that exploit cover, ambushing smaller birds at feeders, hedgerows, and woodland edges. Radio-tracking studies have followed these hawks through winter in both rural and urban habitats, documenting how they time their hunting activity to overlap with peaks in prey movement.⁵ Peregrine falcons, the fastest animals on Earth, specialize in mid-air strikes on pigeons, shorebirds, and waterfowl. Great horned owls take birds as large as herons and other raptors. Northern goshawks hunt grouse and woodpeckers in mature forests.

Raptor predation on birds is entirely natural and generally healthy for prey populations, because raptors tend to take weaker, sick, or less vigilant individuals. The presence of a Cooper’s hawk in a neighborhood does not threaten the local songbird population in any meaningful way, even though watching it happen at your feeder can feel dramatic.

Corvids and Other Nest Raiders

Crows, magpies, jays, and ravens are intelligent generalists, and raiding the nests of other birds is a significant part of their diet during breeding season. Corvids take eggs and nestlings rather than adult birds, and they are effective at it because they can remember nest locations and revisit them. A landscape-level study found that hooded crows were the most impactful corvid nest predator in fragmented farmland-forest landscapes, regularly raiding nests in both habitat types. Jays and ravens, by contrast, operated mostly inside larger forest blocks, while magpies and jackdaws concentrated on agricultural land.⁶

The perception that corvids are devastating songbird populations is common but generally overstated. Corvids have always eaten eggs and chicks. The bigger issue is when habitat changes concentrate both corvids and nesting birds into small patches, artificially inflating encounter rates between predator and prey.

Raccoons, Foxes, and Other Wild Mammals

Medium-sized mammalian predators are a leading cause of nest failure for ground-nesting birds. For wild turkey populations across North America, raccoons are the most commonly reported nest predator, and predation is responsible for the majority of nest losses, poult deaths, and hen mortality.⁷ Red foxes, striped skunks, opossums, and weasels round out the usual suspects. These predators are thriving in modern agricultural and suburban landscapes, while many ground-nesting bird species are declining, which has made predator management a persistent issue in game bird conservation.⁸

The challenge is that removing one predator species often just opens space for another. A landscape with fewer foxes may see more raccoons or crows, and the net predation rate on nests changes little. That is why habitat management, rather than predator control alone, tends to produce better outcomes for declining species.

Rats, Mice, and Squirrels

Rodents are easy to overlook as bird predators, but they are surprisingly capable nest raiders. In laboratory trials, white-footed mice attempted to eat eggs more than half the time they encountered them and attacked nestlings roughly 13% of the time. Hungry mice were more likely to attack, and even small mice (averaging around 21 grams) were able to kill nestling pigeons several times their own weight by knocking them from nest branches.⁹ Squirrels showed more individual variation, with some raiding nests opportunistically and others ignoring them entirely.

Invasive rats are an even bigger problem, particularly on islands. On a South Pacific island, researchers documented that rats consumed medium and small eggs placed at any height, while native crows targeted large eggs and ants took only small ones.¹⁰ The combination of rats plus native predators creates a layered threat that leaves few eggs safe regardless of size or nest placement.

Snakes Are the Stealth Predators

Snakes are probably the most underappreciated bird predators. For decades, ornithologists underestimated how often snakes ate eggs and nestlings because snakes leave almost no evidence behind. A nest camera revolution changed that picture dramatically. In six of eight studies that used miniature cameras on New World songbird nests, snakes turned out to be the single most important nest predator.¹¹ Rat snakes, corn snakes, and black racers are common nest raiders in North America. In Asia and the Pacific, cat snakes of the genus Boiga are the dominant egg predators. The invasive brown tree snake on Guam is the most extreme example: it has essentially wiped out the island’s native forest birds.¹²

Before nest cameras became affordable, many snake-caused nest failures were attributed to raccoons, jays, or squirrels simply because those animals were more conspicuous. The lesson is that the true predator community at any nest is more diverse than it looks.

Praying Mantises and Other Invertebrates

It sounds improbable, but praying mantises kill birds. A global review documented 147 incidents of mantises capturing small birds across 13 countries and every continent except Antarctica. More than 70% of the observed events were in the United States, where mantises were seen catching hummingbirds at feeders and nectar-producing plants.¹³ In a broader review of arthropod predation on vertebrates, mantises were the leading invertebrate predators of birds specifically, while spiders accounted for more than half of all arthropod-on-vertebrate predation events when all vertebrate classes were combined.¹⁴

Mantises also raid nests. Female European mantises have been observed eating nestlings of sunbirds and larks, and similar events have been recorded in Taiwan and Brazil with different mantis and bird species.¹⁵ These events are rare enough that they do not meaningfully affect bird populations, but they illustrate how broad the range of bird predators really is.

Cowbirds and the Nest-Destruction Strategy

Brown-headed cowbirds are brood parasites: they lay their eggs in other birds’ nests and let the host raise the cowbird chick. But cowbirds go further than just freeloading. Research has shown that cowbirds behave like a “mafia,” destroying the nests of host birds that eject cowbird eggs. In one experiment, 56% of nests belonging to hosts that rejected cowbird eggs were destroyed, compared with only 6% of nests belonging to hosts that accepted them. No nests were destroyed when cowbirds were denied access, confirming that cowbirds themselves were doing the damage.¹⁶ Hosts that rejected cowbird eggs ended up producing about 60% fewer of their own offspring because of this retaliatory destruction.

Cowbirds may also destroy nests they discover late in the host’s nesting cycle, when the nest is too far along to be useful for parasitism, essentially clearing the way for the host to re-nest and provide a fresh opportunity.¹⁷ This is predation in service of manipulation rather than hunger, and it blurs the line between “predator” and “parasite.”

When Fear Alone Is Enough

A predator does not have to kill a bird to reduce bird populations. The mere presence of predators, or even just the sound of them, causes measurable harm. In a multi-year experiment with free-living song sparrows, researchers played recordings of predator calls near some breeding territories and non-predator calls near others. Parents that heard predators laid fewer eggs, incubated them less attentively, and fed their chicks less often. The net result was about 40% fewer surviving offspring.¹⁸ Over multiple generations, fear of predators reduced the population growth rate significantly, with frightened parents producing 53% fewer recruits to the adult breeding population compared to control groups.¹⁹

This “ecology of fear” effect means that even predators that fail most of their hunting attempts still shape bird populations. A hawk that misses nine out of ten strikes still forces every bird in the area to spend time watching, hiding, and fleeing instead of feeding and breeding.

Habitat Fragmentation Amplifies Predation

Predators do not operate in a vacuum. The landscape itself determines how much predation birds face. In fragmented forests, nests near edges and in small patches are far more vulnerable. A study in the East Usambara Mountains of Tanzania found that nest failure was between about 2 and 197 times more likely in fragmented forest than in continuous forest, depending on the bird species, with nest distance from the forest edge and the total area of the forest fragment being dominant factors.²⁰

A meta-analysis of predator responses to fragmentation found that the pattern is complex and depends on the type of predator and the surrounding landscape. Avian predators like crows and jays showed stronger edge and fragment effects than mammalian predators, and fragmentation effects were most pronounced when the surrounding matrix was agricultural land rather than forest.²¹ The practical takeaway is that preserving large, connected blocks of habitat does more for bird survival than trying to manage individual predator species.

Cities Can Offer a Surprising Refuge

Urban areas are not automatically bad for nesting birds. Shrub-nesting species may actually fare better in cities than in the countryside. A study comparing nest survival across urban, suburban, and rural habitats found that daily survival rates for shrub nests were significantly higher in urban and suburban areas than in rural ones, likely because of lower predation pressure or favorable nesting sites in built-up areas.²² Dense human activity may deter some mammalian predators or push them into different foraging patterns, giving certain bird species a window of safety.

But predation is the primary cause of mortality for both nestling and fledgling birds, and risk peaks in the days just before and after chicks leave the nest, regardless of whether the nest is in a city park or a wilderness area.²³ The urban advantage appears to be strongest for species that nest in shrubs and hedges, not necessarily for ground nesters or open-cup nesters in trees.

Island Birds Face Catastrophic Odds

Island birds evolved without mammalian predators, and when humans introduced cats, rats, stoats, and mongooses, the results were devastating. Across 220 oceanic islands, the probability that a bird species has been wiped out is positively correlated with the number of exotic predatory mammal species established on that island after European colonization, and the effect is stronger for species found only on that island.²⁴ The more types of introduced predators, the higher the extinction toll. On Britain’s overseas territories alone, invasive mammalian predators have caused a catastrophic wave of extinctions and massive reductions in seabird colony sizes.²⁵

The functional diversity of introduced predators matters as much as their number. Different predator species access different nesting habitats, body sizes of prey, and life stages, so each new introduction fills a gap that previous invaders missed.²⁶ Rat eradication programs on islands have produced some of the most dramatic conservation success stories in recent decades, with seabird colonies bouncing back within just a few breeding seasons once the predators are gone.

Backyard Feeders and Unintended Consequences

Bird feeders are one of the most popular ways people interact with wildlife, but they come with a trade-off that few people consider. Feeders that attract more small birds also attract more predators. A study found that birdfeeders drawing larger numbers of songbirds also drew more sparrowhawks and feral cats, regardless of whether the feeders were stocked with food or were empty decoys.²⁷ Predator presence at feeders creates both direct mortality risk and indirect costs as prey birds spend more time scanning for danger instead of eating.

The nesting impact is real too. Magpies, jays, and grey squirrels were frequent visitors to filled feeders, and nest predation rates were significantly higher when nests were close to stocked feeders.²⁸ Another study found that the relative abundance of cowbirds and crows was positively associated with the number of feeders in a neighborhood, and robin nest survival was especially low where both feeders and crows were abundant.²⁹ None of this means you should take your feeders down, but placing them away from known nest sites and keeping the area below clear of cover that hides stalking cats can reduce the risk.

How Birds Fight Back

Birds are not passive victims. Many species mob predators: they approach, harass, and call at hawks, owls, or snakes to drive them away. Siberian jays produce up to 14 different call types during mobbing, with five call types that are specific to predator category. They give distinct calls for hawks versus owls, meaning nearby birds get information not just about the presence of danger but about what kind.³⁰ Jays also gave more calls when kin were present, suggesting they ramp up the warning effort when relatives are at stake.

Some birds take deception further. The brown thornbill, a tiny Australian species, defends its nest against pied currawongs (a much larger nest predator) by giving both its own aerial alarm calls and mimicked alarm calls of other species, creating the illusion of a multi-species alarm chorus. Currawongs hearing these deceptive calls were more likely to flee and waited longer before returning to feed.³¹ A 15-gram bird tricking a 300-gram predator through vocal mimicry is one of the more remarkable arms-race outcomes in nature.

Climate Change Is Reshuffling the Deck

The predator-prey dynamics that have shaped bird populations for millennia are not static. An analysis of nearly 38,200 shorebird nests from 237 populations worldwide found that nest predation rates have increased over the past 70 years. Historically, nest predation was highest in the tropics and lowest near the poles, a pattern that held for decades. Recently, that gradient has flipped in the Northern Hemisphere, with Arctic-nesting shorebirds now facing some of the highest predation rates on the planet.³² The suspected driver is climate-induced shifts in predator communities: warmer conditions allow generalist predators like foxes and gulls to expand into tundra habitats where they were previously rare. For Arctic shorebirds that evolved with relatively few predators, this is an unfamiliar and intensifying threat with no obvious behavioral countermeasure.