Whether you’re out bird watching, driving your car, or even looking out of the window into a city garden, it’s not uncommon to see a raptor swooping in at high speed in front of you, and a flurry of startled birds, panicked by the intruder.
So which bird did you see? Sometimes it can be difficult to tell, and we need to compare species more thoroughly. That’s why we’ve created this detailed comparison between merlins and peregrines.
Introducing The Merlin
The merlin (Falco columbarius) is a small, athletic falcon species that inhabits much of the Northern Hemisphere, including North America, Europe, Asia, and even northern parts of South America.
The ‘pigeon hawk’ as they are sometimes known, has an interesting geographical distribution in the US in that it is only a winter resident of three distinct districts: the entire Pacific coast, the entirety of the great prairies (including southern Canada), and most of the Atlantic coastline.
During winter, merlins are rarely seen anywhere in between these three regions, and in the spring these raptors migrate to the breed in Canada, Alaska, and the very northern fringes of the northern United States too.
As one of America’s smallest raptors, males have a wingspan of just 21-23 inches, while females are slightly larger. Their small size makes them agile hunters – perfect for the boreal forests where they breed.
Introducing The Peregrine Falcon
Peregrine falcons (Falco peregrinus) are famous for being the fastest bird in the world. Diving at astonishing speeds of over 240 mph, they are also the fastest member of the entire animal kingdom on our planet!
With a broad geographical range spanning every continent except the Antarctic, peregrines seem equally happy inhabiting equatorial savannahs as they are breeding in the arctic circle, and are the most widespread of any raptor on earth.
It just goes to show how adaptable they must be!
In the US, they are mostly a winter resident or passing migrant, except for a constant population throughout the year on the pacific coast and some states in the southwest and northeast of the country.
With a wingspan of 29–47 inches, their size can vary considerably, with females typically around 30% larger than males. This makes them one of the larger falcons, and, believe it or not, peregrines can take down prey as large as cranes and geese!
Peregrine falcons are also one of the most coveted falconry birds, and have been used by humans to hunt game for more than 3000 years!
Now there’s a raptor with some impressive credentials!
Comparing Merlins With Peregrine Falcons
If you’ve been out bird-watching or seen a flurry of feathers from a falcon attack, you may be wondering whether you saw a peregrine or merlin.
Or maybe you’re simply curious about the differences between these two impressive birds. Let’s take a closer look.
As you may have learned from the introductions, peregrines are one of the largest falcons, whereas merlins are one of the smallest.
While female peregrines can reach wingspans of 47 inches, female merlins, being a more compact falcon, only grow up to 29 inches.
Nevertheless, individual variation as well as the huge size difference between the sexes of both species means that you could still get them mixed up.
The smallest male peregrines can have a body length of 13 inches and can measure 29 inches from wing tip to wing tip, which happens to be exactly the same dimensions as the very largest female merlins!
Now that’s an interesting discovery for me too.
Since we can’t reliably distinguish these two species just in terms of size, how does the rest of their appearance differ?
The first thing you’d notice if you saw these two birds side by side is that mature peregrines have a much darker head and back that is deep bluish-gray in color.
Male merlins have a lighter, blue head and back, which gives them a more gentle, less imposing appearance. Females look even less like a peregrine, with a brownish-gray head and back.
As well as the darker head, peregrines have a dark and noticeable mustache stripe fringing white cheeks and neck.
The facial markings of both male and female merlins are much less pronounced, with only a faint, pale mustache stripe and a speckled face without white cheeks.
If you had time to observe the undersides of these birds, you’d also notice that peregrines have incredibly elegant, uniform thin black bars against a white or cream chest. Merlins, in contrast, have a light brown chest speckled with black flecks.
Another possible way to tell if you saw a merlin or a peregrine is which region you saw it in.
Whereas merlins breed exclusively in Alaska, Canada, and the very northern fringes of the United States, peregrines breed along the pacific coastline, from Mexico to Alaska, in some southwestern states, and along the Atlantic coast from Maine to Virginia.
Unlike merlins, they don’t favor nesting in the boreal forests, but some pairs do migrate to the northernmost parts of Canada and Alaska to breed.
In winter, peregrines can be found across the entire country, whereas merlins can only be found along the Atlantic and Pacific coastlines and most of the Great Prairies. If you see a bird in other parts of the US during winter, it is almost certainly a peregrine.
When we spot raptors out in the field it’s often when they’re hunting. So how do the hunting habits of peregrines differ from merlins?
Merlin Hunting Behavior
Merlins usually hunt by flying fast and low over the ground to flush out small birds, which they then use their incredible aerial agility to chase and catch.
Sometimes flying just a few feet off the ground, merlins have even been known to work in pairs with one bird startling flocks of prey birds to fly out into the open and into the talons of their mate!
Typical prey items tend to be birds that weigh less than 1.5 oz, such as larks, finches, sparrows, and pipits, but merlins will sometimes go after birds that match them for weight including small ducks, pigeons, and ptarmigan.
Flying insects are also very much on the menu for this tiny raptor.
Peregrine Hunting Behavior
Unlike merlins, peregrines prefer to hunt medium-large birds in the open sky, using their sheer speed and power to strike unsuspecting targets from a great height.
Stooping at terrifying speed, peregrines use a clenched talon to stun their prey, then double back to capture it.
When hunting larger birds such as ducks and gulls, the peregrine may tumble down with the bird before finishing the kill on the ground.
Part of the worldwide success of peregrines, however, is their adaptability. When their typical prey birds are scarce, they have been known to hunt bats at night, or even terrestrial mammals such as rats, lemmings, rabbits, mice, and squirrels.
Peregrines vs Merlins In Falconry
Both merlins are peregrine and are highly prized in falconry.
Peregrines are probably the most famous falconry bird in the world, not only because of their hunting prowess but also because they’re so eager to hunt and easy to train.
For thousands of years, peregrines have been used to hunt all manner of game birds including ducks, pheasants, and grouse.
These days peregrines are also sometimes used in modern settings such as airports and landfill sites to eliminate birds such as pigeons and gulls that can be a hazard to site operation.
Merlins were especially popular in falconry during medieval times and are still used by falconry enthusiasts today for their dizzying aerial displays and their specialized skill in catching small birds such as starlings, snipes, doves, quail, and sparrows.
Peregrines and Merlins In Cities
Both peregrines and merlins have become notably adapted to living in urban environments, and the substantial increase in both bird species since the 1980s may be partly due to this increasing adaptation.
The high density of prey birds such as pigeons, ducks, and songbirds in urban settings means that these birds can flourish, and sometimes even choose to remain in cities all year round instead of migrating!
Peregrines have been observed nesting on cathedrals, skyscraper window ledges, tower blocks, and the towers of suspension bridges.
Merlins, preferring instead to nest in trees, will often take over crow nests in conifers planted in residential areas, parks, and cemeteries.
Peregrine and Merlin’s Life Expectancy
If you’re curious to know which one of these birds lives longer, you’ll probably guess it’s the peregrine.
Wild peregrines have a typical lifespan of around 12-15 years, although a few specimens have been known to live longer.
Merlins are shorter-lived. In the wild, they will rarely live to more than 7-9 years, and sadly, many birds die younger due to collisions with motor vehicles, trains, etc. as well as those hunted by larger birds of prey.
Thankfully both peregrine and merlin populations have been increasing in most areas since the all-time lows in the 1970s, thanks to the ban on DDT pesticides, stronger protective measures, and reintroduction campaigns.
Merlins and peregrines are both glorious and powerful falcons that you may have the good fortune to spot whether you’re out in the open country, forest, or even in a city.
While peregrines tend to be much larger than merlins, the huge variation within both species means that the largest merlin could just match the smallest peregrine falcon for size.
Other than size, you can tell these two birds apart by their plumage, geographical range, and hunting behavior.
If you’re still not sure if the bird you saw was either of these two species, you could try our comparison of American kestrels and hawks, here.