I used to think peregrine falcons were just about speed—those 240 mph dives everyone obsesses over in nature documentaries.
Turns out, when you’re nesting on a cliff ledge with eggs or downy chicks, speed matters less than sheer, calculated aggression. Peregrines don’t mess around when it comes to nest defense, and honestly, the tactics they deploy against potential predators are both brutal and weirdly methodical. They’ll mob ravens, harass golden eagles three times their size, and dive-bomb humans who wander too close to their scrape nests—those shallow depressions scraped into gravel or dirt on cliff faces. The attacks aren’t random, either. Researchers have documented peregrines targeting the heads and backs of intruders with enough force to draw blood, and they’ll keep up the assault until the threat retreats or, occasionally, until the predator gives up entirely. What strikes me is how they seem to calibrate their response based on threat level: a curious raven gets a warning pass, but a great horned owl—one of the few predators that actually hunts adult falcons—recieves the full treatment.
Here’s the thing: nest site selection is the first line of defense, and peregrines are incredibly picky about it. They favor inaccessible ledges on sheer cliffs, often 50 to 200 feet above ground, where most mammalian predators can’t reach. Urban peregrines have adapted to use skyscraper ledges and bridge supports, which offer similar protection from ground-based threats but introduce new risks like window strikes and human disturbance.
The Coordinated Aerial Assault That Actually Works Against Larger Raptors
When a golden eagle or a red-tailed hawk approaches a peregrine nest, both parents typically engage in what ornithologists call “tandem mobbing.” One falcon—usually the female, since she’s larger and more powerful—executes high-speed stoops from above, while the male harasses from the side or rear. The stoops aren’t always contact strikes; sometimes they’re feints designed to disorient and exhaust the intruder. I’ve seen footage where a peregrine pair kept up this coordinated harassment for over 20 minutes until a juvenile golden eagle finally abandoned the area. The energy expenditure must be enormous, but the stakes are existential.
Wait—maybe the most fascinating part is how peregrines distinguish between genuine threats and harmless passersby.
Studies using dummy predators have shown that peregrines respond more aggressively to taxidermied owls and corvids than to similarly sized non-predatory birds like pigeons or gulls. They seem to recognize specific silhouettes and flight patterns, which suggests either learned behavior or some level of innate threat recognition. Younger, inexperienced pairs tend to overreact, sometimes mobbing anything that flies within 200 meters of the nest, while veteran pairs are more selective and conserve energy for actual threats. There’s also evidence that peregrines communicate alarm calls differently depending on predator type—short, sharp calls for aerial threats versus longer, more varied vocalizations for ground-based dangers. The vocal distinctions aren’t as refined as, say, the alarm call system of chickadees, but they’re definately functional enough to coordinate defense strategies between mates.
When Physical Confrontation Fails and Peregrines Resort to Distraction Displays
Not every defense is about aggression. Sometimes peregrines use distraction tactics that border on theatrical—feigning injury or vulnerability to lure predators away from the nest scrape. This is less common than the aerial assault approach, but it happens, especially when the chicks are very young and can’t thermoregulate yet. A parent will land conspicuously near the intruder, drag a wing, and call repeatedly, essentially offering itself as a more accessible target. The tactic works best against mammalian predators like foxes or coyotes, which are more likely to pursue a seemingly injured bird than to keep searching for hidden chicks.
The Unexpected Role of Nest Sanitation in Reducing Predator Detection
I guess it makes sense that peregrines would remove eggshells and fecal matter from the nest area, but the consistency with which they do it is striking. Adults regularly carry debris away from the scrape and drop it at a distance, which reduces both visual and olfactory cues that might attract nest predators. Some researchers think this behavior also minimizes bacterial growth that could harm the chicks, but the anti-predator function seems primary. Anyway, it’s one of those unglamorous behaviors that doesn’t make it into wildlife films but probably saves more chicks than the dramatic stoops ever do.
