MERLIN
I didn’t catch sight of the bird speeding low over the shore until it was passing me. It was slender and very fast, and for a second I wondered “Mourning Dove?” but then in a flash of pleasant recognition realized the bird was a Merlin in “fast contour-hugging” flight (Bildstein 2017) along Goose Lake near Vernon, hunting the shore at maybe 40 km/hr for shorebirds, pipits, longspurs, and sparrows that had strayed too far from the sheltering grasses.
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| Merlin - a female or immature atop a power pole between Vernon and Armstrong. Photo by Chris Siddle. |
If I had to name one favourite bird out of the 10,000 + species of the world, the Merlin might be my top choice, It’s a minimalist’s dream of a raptor, a compact, graceful little killer. What it lacks in bright colour it makes up for in speed. Merlin literature, and there’s a fair bit of it since the bird is found across the Northern Hemisphere, often uses the words “compact” and “dash” to introduce this fast species. Compact it is, one of the world’s smaller falcons, weighing in at 160-170 g for males and 220-240 g for females (compare to America Kestrel 80-143 g males, 86-165g females), making the Merlin about the same size as a kestrel but significantly heavier. I like to think the extra weight translates into strength needed to subdue its mainly avian prey. The American Kestrel has a wider range of prey from insects, rodents, and small birds. The Merlin focuses much more upon small birds, even those as heavy as a Rock Pigeon.
Another common attack pattern involves the Merlin “jumping” a single bird by surprise. This may involve using the landscape as cover, or fast contour-flying, such as I described at the beginning of this piece or spotting the prey while the Merlin is perched or flying
Although I have seen Merlins chasing prey a few dozen times, one memory stands out. On a late September day in the early 1980s an estimated 10,000 Lapland Longspurs were feeding in the farm fields at the tiny farm community of Nig Creek 100 kilometres north of Fort St. John. Among the clouds of longspurs three Merlins coursed, creating panic among the already restless birds. The little falcons worked the edges of the fields, often engaged in tail flights, chasing a longspur from behind. Although dramatic, these chases are often unsuccessful for the Merlins. Flocking is an effective anti-predation strategy used by many species in addition to longspurs.
Principal prey of breeding Merlins varies across its range. The figures I found in the BNA account were for the north and west of its North American range. In urban Saskatoon principal prey was House Sparrows; in Alaska it is American Tree Sparrows, Dark-eyed Juncos, and Lapland Longspurs, in rural Alberta Horned Larks, and Chestnut-collared Longspurs, in Montana Horned Larks, Lark Buntings, Vesper Sparrows. This selection for prey is clearly does not take into account Merlins breeding along the coasts where shorebirds become significant prey. It also doesn’t address the diet of Merlins that overwinter in the interior of North America, where, in the northwest at least, Bohemian Waxwings in their fruit-eating hordes,are commonly preyed upon by Merlins.
At what speeds does a Merlin attack?
In straight migratory flight Merlins have had their air speed clocked at an average of 39 km/hr. A captive Merlin in straight flight flew at 35 km/hr. But during a shallow stoop, this same captive increased its air speed to 70 km/hr. (Sale 2015), certainly fast enough for its impact to stun or kill small prey.
An interesting study of Merlins attacking European Skylarks in winter was carried out by W. Cresswell on the Tyninghame estuary in East Lothian, Scotland. When attacked, besides flying for its life, a skylark may remain mute, sing poorly, or sing well. The Merlin attacking had no way of knowing what its potential prey would do. Skylarks that sang well when being pursued by a Merlin escaped at least twice as often as skylarks that sang poorly and four times more often than larks that didn’t sing at all! Also a Merlin pursuing a full singing bird, did so for the shortest distance before giving up the chase. Cresswell’s data show clearly that Merlins called off the chase of full singing skylarks early. Cresswell hypothesized that larks in good condition with enough energy both to fly well and sing a full song were advertising their fitness, and that the Merlin, in giving up early, was receiving their message and not wasting too much time chasing them.
Some observers have reported Merlins hunting co-operatively in pairs. Sometimes, as in Saskatoon, the attack involved one bird flying along a tree line, flushing waxwings, while the second Merlin followed behind, attacking disturbed singles. When another raptor, like a Northern Harrier, disturbs previously hidden songbirds, Merlins can take advantage of the situation and pursue the prey. Is this true co-ordination, or just the Merlin using the situation to its own advantage?
Besides flushing and chasing a small bird, I have seen a Merlin use a slightly different tactic. BX Dog Park is a field at the foot of a steep wooded hill on its south and southeastern sides. While walking my dog there in late summer I noticed for several evenings, up to 100 Red-winged Blackbirds gather in the tallest Ponderosa Pines to sing before flocking away to the cattail beds of Swan Lake to roost for the night. One evening a Merlin left its customary perch atop a pine snag and flew straight and level for about 150 m over the field at tree top height and straight through the crown of the pine where blackbirds had gathered. There seemed to be no delay as it passed through the crown; it must have had less than a second to attempt a grab at a blackbird. The Merlin emerged from the crown still headed in the same direction, as the blackbirds exploded from their perches to head for their roost early. This unsuccessful attack reminded me more of a Cooper’s or Sharp-shinned hawk’s perch and wait attack than that of a Merlin’s but it does illustrate that as far as tactics go, the Merlin is quite adaptable.
Juvenile Merlins are said to often sally from perches to catch late summer dragonflies. I have seen Merlins doing this, but so far because the juvenile and the adult female so closely resemble each other, I cannot swear that the birds catching dragonflies are all juveniles.
Merlins have benefitted from the European settlement of central and western North America. Townspeople planted ornamental shrubs and trees that bear fruit like Mountain Ash berries. The annual crop attracts swarms of Bohemian Waxwings which, along with House Sparrows, become prey for Merlins that have moved into towns. American Crows and Black-billed Magpies, also favouring parkland within urban boundaries, build nests that Merlins usurp for their own nesting. With plenty of prey throughout the year, some Merlins have ceased migrating south for the winter, or move into town for the winter from the countryside.
Urban hunting is not without its problems. Merlins and their prey collide with plate glass. Also, buildings can sometimes provide desperate prey with refuge. This didn’t stop a Whitehorse Merlin mentioned in Birds of the Yukon that chased his prey into the bay of a downtown garage, killed the pigeon and consumed it in front of interested human spectators.
After a Merlin has killed a bird, his problems may have just begun. I encountered a Merlin trying to walk its very dead Rock Pigeon prize along the inner edge of a sidewalk in Salmon Arm. It reminded me of a Warner Brothers cartoon of a baby hawk trying to persuade the rooster, Fog Horn Leg Horn, that he has been captured and should allow himself to be taken away by the tiny predator. The Merlin was searching for a secure at which to pluck its prey, prior to eating it. Plucking takes from 5-15 minutes. Because Merlins often select utility poles and street lamps as plucking posts, it’s not unusual for a trickle of feathers, including hundreds of tiny contour feathers, to shift down from the Merlin’s plucking.
Several times in downtown Vernon I have seen human pedestrians pass through a shower of feathers coming from the top of a power pole where a Merlin is plucking its prey. Concentrating on their cell phones or just preoccupied with other matters, many a person has become an oblivious temporary resting place for a few feathers. I have fantasized about becoming Sherlock Holmes to amaze people with my observational and deductive powers:
“You have within the past hour walked by the intersection of Main Street and 30th Avenue,” I observe to a friend visiting me.
“Yes! But how could you possibly know that, Mr. Holmes/Siddle?”
“Simple observation and deduction, sir. I noticed as soon as you came into the room your worn but highly polished shoes. From this and from the general appearance of your clothes, though not the newest, but well cared for, I deduced that you take care to appear neat and tidy. However, you have a sparse dusting of down on your shoulders, not something you would tolerate if you had noticed it. The feathers cannot have been on your jacket very long.”
“But where did these wretched feathers come from?”
“There’s a lamp post above the traffic light at Main and 30th. While you stood waiting for the light to change, a Merlin that has made the post a favourite perch, plucked the feathered prey he has just captured.” I reach out and take a feather from my friend’s shoulder to examine it. “House Sparrow,” I would say. “Looks like the unworn greater covert of a juvenile, if I’m not mistaken.”
“Astonishing, Holmes-Siddle!” replies my suitably impressed friend.
When not dusting people with stray feathers, Merlins commonly cache food in breeding season and in winter. So do their distant relatives, American Kestrels. Food may be hidden in a conifer or on the ground. Cached resources may be retrieved by Merlins to see them through periods of bad weather when hunting is poor, and sometimes as a meal eaten just before roosting for the night.
Breeding
Like all falcons, the Merlin has no song, but as Gary Davidson of Nakusp can tell you, come spring the Merlin announces his presence with an insistent, noisy, slightly shrill “kee-kee-kee-kee” that fades and rises on the air over Nakusp’s municipal campground where a grove of pines has provided Merlins with nesting sites for at least 35+ years. The female has a similar call but slightly lower pitched. Courtship involves aerial displays by the male including “power flying” where the male in strongly flapping flight rolls from side to side alternately showing his back and his belly. Males and females are known to power fly together. Less intense with no flapping is the “rocking glide”. One of the most common male displays typically performed around the nest site is the “flutter flight” following a circular or figure eight path. Both sexes soar near the nest in territorial displays (BNA).
In Vernon I live about half a km from nesting Merlins. Another pair or two nests among the tall Douglas-firs, Ponderosa Pines and spruces of Vernon’s East Hill. Call me shy, but prolonged periods of hanging around an elementary school or standing around back alleys of residential neighbourhoods increases my self-consciousness to an excruciating level, preventing me from keeping long watches near nests. Since it is known that Merlins have moved into towns across western North America during the last half century to take advantage of resident populations of House Sparrows and wintering Bohemian Waxwings, where the little falcons have happily taken to nesting in old crow and magpie nests, I will just have to keep looking for a Merlin nest on public property where I can watch the birds in solitude.
When the stick nests of corvids are not available for nesting, Merlins will nest on a ledge on a cliff, a tree cavity or even make a shallow scrape on the ground. The female lays 1-7 eggs (usually 4-5) which are incubated about 30 days since the laying of the last or penultimate egg. The male shares in a mostly minor way with the incubating, with his main role that of provisioning the female. Most of the time the male plucks the prey, usually removing head and wings, at a favoured plucking post often within 150-200 m from the nest, but sometimes he delivers the prey unprepared.
The chicks require brooding by the female for about the first seven days to maintain their body temperatures. Contour feathers first appear in sheaths between 9- 11 days; tail feathers break from their sheaths between 15-17 days. The chicks fledge at about 29 days after hatching and are dependent upon their parents for another 1 – 4 weeks, remaining neat the nest site (BNA 44, 1sted.).
Once old enough to forage on its own, the juvenal Merlin looks very much like an adult female, and under normal field condition, is difficult or impossible to separate. The adult female has a slate brown rump and upper tail coverts that contrast with the dark brown of its back. The rumps of immatures are the same colour as their backs (Temple 1972). This is difficult to see since Merlins typically perch in a high place, their rumps out of sight. There are also differences between immature sexes in the shade of the pale tail bands but nothing really helpful to the birder. Unable to differentiate the ages, I have resorted to writing “female-type” or “female-like” in my field book for brown backed birds.
Rural hunting Merlins fly up to 15 kms into urban areas to roost for the night, selecting the leeward side of conifers, warmer and safer from the Merlin’s nocturnal nemesis, the larger owls such as Great Horned Owl known to predate Merlins.
References: Richard Sale’s monograph The Merlin (2015) was invaluable, as was Keith Bildstein’s Raptors, The Curious Nature of Diurnal Birds of Prey (2017), the Birds of North America Merlin account 44 (1stand 2 versions). Brian Wheeler’s recent field guide, Birds of Prey of the West (2018); Cramp’s Handbook of Birds of the Birds of Europe, the Middle East and North Africa, Vol. 2 (1980); Palmer’s Handbook of North American Birds – Vol. 5 (1988) and S. Temple’s paper on sexing and aging Merlins (1972) were very useful. Regional works consulted include Campbell et al’s The Birds of British Columbia, Vol. 2 (1990); Frank Beebe’s Field Studies of the Falconiformes of British Columbia (1974); Sinclair et al’s Birds of the Yukon Territory (2003) and The Atlas of Breeding Birds of British Columbia 2008-2012 online.
