The sharp-shinned hawk (Accipiter striatus) is a small bird of prey found throughout North America. As the name suggests, this hawk is known for having slender, pointy wings and relatively thin legs, giving it a overall “sharp” look. But why exactly is this bird referred to as “sharp-shinned”? There are a few key reasons:
Anatomy
The sharp-shinned hawk gets its common name from its distinctive anatomy, specifically its thin, pointed wings and slim legs and feet. Here are some of the anatomical features that contribute to its sharp-shinned appearance:
Wings
– Short, rounded wings that enable swift, agile flight through dense vegetation when hunting small birds and mammals. The short wings allow the hawk to quickly twist and turn.
– Long primary feathers at the end of the wings that taper into sharp points. This gives the wings a narrow, pointed shape.
Legs and Feet
– Relatively slim, elongated yellow legs and feet compared to other hawk species like the red-tailed hawk.
– Long toes and curved talons for grasping and killing prey. The slim feet contribute to the overall narrowness of its body shape.
Tail
– A medium-length, squared-off tail that is narrow compared to broader, fanned tails of hawks like the red-tailed hawk. The narrow tail reinforces its slender silhouette.
Hunting Strategy
In addition to its anatomy, the sharp-shinned hawk’s hunting strategy and diet also play a role in its common name:
– It is an agile, stealthy hunter that maneuvers swiftly through dense vegetation in pursuit of small woodland birds like sparrows, finches and warblers. Its pointed wings and slim profile allow it to move quickly through cramped spaces.
– It relies on surprise aerial ambushes, swiftly flying from a concealed perch toward prey. Its “sharp” features like pointy wings and slim legs likely help it achieve the speed and stealth needed for these ambush attacks.
– It has a varied diet of small birds, mammals and insects – unlike bulkier hawks that take larger prey. Its sharp features help it deftly catch and maneuver small, nimble prey.
So in summary, the sharp-shinned hawk’s distinctive slender, pointed silhouette and agile hunting style are key to how it earned its common name. From narrow pointed wings to a slim profile and lengthy tail, this small accipiter’s overall sharp appearance and actions make “sharp-shinned” an apt description.
Origin and History
To understand why “sharp-shinned” became this bird’s nickname, it helps to look back at the origins and history of its common name:
First Scientific Description
The sharp-shinned hawk was first scientifically described by French naturalist Charles Lucien Bonaparte (a nephew of Napoleon Bonaparte) in 1828. In his description, Bonaparte provided the initial scientific name Falco velox, with “velox” meaning swift in Latin. This early scientific name already emphasized the hawk’s speed and agility as key traits.
Earlier Common Names
Before “sharp-shinned” became the consensus, this bird had some other regional folk names that hinted at its distinct narrow shape, including:
– Pigeon hawk – Likely for its predation on smaller bird species like pigeons and doves
– Bullet hawk – Comparing its narrow bullet-like body shape to the profile of a bullet
– Striker hawk – For its swift surprise aerial attacks on prey
Official Species Description
Naturalist Alexander Wilson first formally described it as the “sharp-shinned hawk” in his early 19th century ornithology book documenting North American birds. The name sharp-shinned hawk stuck and became universally adopted.
Modern Scientific Classification
Today, the sharp-shinned hawk is classified in the Accipiter genus, which includes other short-winged forest-dwelling hawks with long tails and slim bodies built for maneuvering through dense habitat. “Sharp-shinned” aptly describes this shared anatomy across the Accipiter hawks.
Unique Physical Attributes
The sharp-shinned hawk possesses some unique physical attributes and adaptations that contribute to its slender, sharp-edged look:
Size
This is a small hawk, with a total length of just 9 to 14 inches and weight between 3.5-7.3 oz. It is North America’s smallest accipiter. Its petite size enables it to swiftly fly through congested forest and densely branched trees when hunting.
Sexual Dimorphism
There are distinct size differences between sexes, with females (length 10-14 inches; weight 4.6-7.3 oz) averaging 30-50% larger than males (length 9-11 inches; 3.5-5.2 oz). This reversed sexual dimorphism allows the larger female to defend the nesting territory against intruders, while the more agile male can chase down prey.
Plumage Coloration
Its back feathers feature grey barring over a white background. The underparts are light with reddish-orange barring. These markings provide camouflage when perched in trees waiting to ambush prey. Juveniles have brown upperparts with streaking rather than barring.
Vision
It has large eyes positioned more towards the front of its head, giving it excellent binocular vision to pinpoint prey while diving through dense vegetation in pursuit. Its eyes are roughly 1/3 the size of its entire skull.
Beak Size and Shape
This hawk has a small, sharply hooked bill with a curved tip and razor-like cutting edges along the tomium (top mandible). This helps it rapidly tear prey it has captured with its feet.
Hunting and Diet
The sharp-shinned hawk’s unique hunting strategies and food preferences are key to understanding its “sharp” moniker:
Stealth Ambush Hunting
It is an ambush hunter that relies on surprise aerial attacks, using foliage and woodlands to hide and conceal itself:
– It perches discreetly on branches waiting to spot prey while largely motionless and obscured by leaves
– Once potential prey is sighted, it flies out swiftly from concealment on a low, fast, direct flight path to ambush its target
– It uses the element of surprise and its pointed wings to rapidly chase down prey in a blur
Agile Maneuverability
Its short, rounded wings enable incredible agility and maneuvering through dense habitat and between trees and branches. It can swiftly dip, dive and change directions to keep up with evasive prey.
Preferred Prey
It primarily feeds on small birds like sparrows, wrens and warblers plucked from woodland areas. It also takes some small mammals like mice, amphibians and insects.
– Favored avian prey averages from 2 to 8 ounces, less than half the hawk’s own weight
– Prey is often ambushed in flight and then carried back to a perch for dismemberment
Opportunistic Hunting
While it mainly ambushes live prey, it will also opportunistically scavenge already dead animals and prey remains. It may steal prey from smaller raptors. During migration it may hunt at backyard feeders.
Breeding and Nesting
The breeding ecology and nesting habits of the sharp-shinned hawk also relate to its common name:
Nest Sites
It nests in a wide variety of woodland settings from boreal forests to temperate broadleaf forests:
– Nests are typically built 20-50 feet high up in coniferous or deciduous trees in a fork or on a horizontal branch
– Nest sites are usually concealed with dense overhead foliage that provides cover
– The nest itself is a relatively small, flat platform of sticks and twigs, lined with bark strips and evergreen sprigs
Territorial Defense
Like most accipiters, the male initiates breeding by selecting a nesting site and defending a territory around it. He performs dramatic aerial displays to define his territory and attract a female.
Mating and Egg Laying
Once paired, the female lays a clutch of 3 to 8 eggs (most often 4 to 5). The eggs are elliptical and bluish white with reddish-brown blotches. The female does most of the 45 day incubation.
Hatching and Raising Young
Hatchlings emerge after about 30 days. The female broods and feeds the young, with the male providing food to the family. Fledging occurs at 24-27 days, but young remain near the nest for several weeks being fed by the parents.
Migration
The sharp-shinned hawk’s migrations and increased concentrations during travel also relate to its “sharp” reputation:
Northern Populations
Northern breeding populations are migratory, moving south to more temperate areas for the winter:
– They funnel down through migration flyways, concentrating east of the Rocky Mountains and along the Atlantic coast
– During migration they pass through areas with high songbird populations, making easy ambush hunting for them
Stopover Hunting
Being an opportunistic predator, they take advantage of stopover points during migration to hunt concentrated small birds at feeders and vegetation:
– Backyard bird feeders may temporarily attract dozens of sharp-shins during passage as they pick off smaller visitors
– They use orchards and woodlots as convenient hunting spots when traveling to replenish energy
Southern Populations
Southern populations from the Pacific coast, Florida and Mexico are often non-migratory and maintain year-round territories.
Population Status
Despite some declining trends in certain areas, most sharp-shinned hawk populations remain relatively stable, a testament to the species’ adaptability:
| Region | Population Trend |
|---|---|
| Western North America | Declining but still common |
| Eastern North America | Declining until 1990s, now stable |
| Boreal Canada | Stable populations |
| Alaska | Stable populations |
| Coastal and Southern US | Stable year-round populations |
Key reasons for adaptability and continued success:
– Habitat generalist able to occupy diverse forest and woodland types
– Opportunistic hunting of varied prey; not reliant on a single food source
– Wide distribution across the Americas provides buffer against localized declines
– Short generation time allowing rapid breeding population increases
– Has adapted to utilize urban areas and artificial feeders
Conservation Status
The sharp-shinned hawk has a large global population estimated at over 1 million mature individuals. Due to this, it is classified as Least Concern on the IUCN Red List of Threatened Species.
Interactions with Humans
The sharp-shinned hawk has a complex relationship with humans, who both threaten it and aid its success:
Backyard Predator
Its ambush hunting of feeder birds characterizes it as a “feathered terrorist” to some, making it unpopular:
– It lurks in neighborhoods monitoring bird feeders and baths as ambush sites
– Can temporarily frighten away smaller desired songbirds that homeowners want to attract
– Is very hard to deter and prevent once a feeder is discovered
Pest Control
Despite its notorious feeder raids, it also provides free rodent control by preying on mice, rats and other nuisance mammals around homes.
Nesting Adaptability
It has proven able to adapt to nesting in human-altered environments:
– Shows flexibility in nest site placement from natural forests to city parks and residential areas
– Sometimes nests close to buildings on ledges or building cranes
– Tolerant of moderate human disturbances when nesting
Collision Risk
Like many birds of prey, colliding with windows and cars poses a significant hazard:
– Focused intently on prey, it may not see glass windows or vehicles
– Low, swift attack dives put it at risk of crashes
Climate Change Vulnerability
It may be vulnerable to the impacts of climate change in some areas:
– Increased drought could dry up forest wetlands used for nesting and foraging
– Declining populations of prey species could disrupt food supply
– Increased severe weather like hurricanes could damage nest sites
Cultural Significance
The sharp-shinned hawk has permeated human culture in varied symbolic ways:
Native American Culture
It was respected in various Native American mythologies and traditions:
– Seen as a messenger between worlds by the Blackfoot tribe
– Believed to be a reincarnated warrior by the Cherokee
– Portrayed as a scout or sentry watching over sacred lands
Falconry
Their agility and propensity to take bird prey made them favored by falconers centuries ago for the sport of hawk hunting.
Media Portrayals
It has been featured in books, films, sports team logos and academic institutions:
– Auburn University’s pre-game flight of a sharp-shinned hawk named Nova
– Prominently featured in the 1975 book and film My Side of the Mountain
– Mentioned in works by authors from Thoreau to Annie Dillard
Fun Facts
Beyond its appearance and hunting, there are some fun, interesting facts that provide insight into the sharp-shinned hawk:
– During courtship, mating pairs may interlock talons and spiral downwards together from great heights.
– The oldest known wild sharp-shinned hawk was 17 years, 5 months old when recaptured and re-released during banding.
– Nestlings hiss like snakes and may spit regurgitated food when defending the nest from perceived threats.
– Its scientific name “striatus” refers to the streaking pattern on juvenile sharp-shins.
– When migrating, it can fly 100+ miles in a single day propelled by short powerful wing beats.
Conclusion
In summary, the sharp-shinned hawk’s distinct narrow shape, secretive ambush hunting and agility through dense forests all collaborate to give this unique accipiter its famously “sharp” moniker. It is a small but mighty and adaptive predator, with a mix of threatened and thriving populations across North America. While reviled by some, it plays an important role ecologically. And it continues to penetrate human culture in varied symbolic ways. The sharp-shinned hawk remains a quintessential woodland raptor, and one fully deserving of its descriptive, memorable common name.
