There are some hawks that bear a resemblance to owls due to their facial disk feathers and upright perching posture. The most notable examples are the Northern Hawk Owl and the Crested Hawk Eagle. While they may look somewhat owl-like, they are still classified as true hawks (family Accipitridae). Their owl-like appearance is an example of convergent evolution, where different species evolve similar traits independently.
The Northern Hawk Owl
The Northern Hawk Owl (Surnia ulula) is a medium-sized owl-like hawk that breeds in the northern boreal forests of North America and Eurasia. Here are some key facts about this fascinating bird of prey:
- It grows to a length of 15-17 inches, with a wingspan of 31-39 inches.
- It has a large rounded head without ear tufts, yellow eyes, and a grayish facial disk which gives it an owl-like appearance.
- Its plumage is brown above and white below with brown spotting and barring.
- It is a diurnal raptor, primarily hunting rodents and small birds during the day.
- It perches upright on tree branches while scanning for prey below.
- Once prey is spotted, it swoops down swiftly on its target.
- It nests in tree cavities, laying 3-11 eggs at a time.
The hawk owl’s owl-like facial disk is an adaptation to help localize prey sounds. Its upright perching behavior also aids hunting from high perches. So while it looks like an owl and hunts like an owl, it is still considered a hawk based on its anatomy and genetics.
Behavior and Hunting
The Northern Hawk Owl exhibits some very owl-like behaviors in terms of hunting and habits:
- It is mostly diurnal, being most active during the daytime.
- It perches upright on branches while scanning the terrain below for prey.
- Its flight is buoyant and owl-like, not direct and falcon-like as in other hawks.
- It can turn its head 270 degrees to scan a wide area for potential prey.
- Its main prey includes voles, mice, shrews, squirrels and birds.
- It hunts by patrolling open habitats and swooping down onto prey.
- It sometimes hovers briefly above prey before striking.
These owl-like adaptations allow the Northern Hawk Owl to fill an ecological niche similar to an owl, despite its taxonomic classification as a hawk. Its nocturnal counterpart in the boreal forest is the Great Grey Owl.
Range and Habitat
The breeding range of the Northern Hawk Owl extends through northern forest regions:
- Canada: Across northern provinces from Alaska to Newfoundland.
- United States: Northern Alaska and northern New England.
- Eurasia: Scandinavia through Russia, north China and Siberia.
- Boreal coniferous forests dominated by spruce, pine, fir, larch.
- Nests in tree cavities, either natural or old woodpecker holes.
- In winter may irrupt southward if food is scarce.
It is well-adapted to the dense boreal forest, with its owl-like facial ruff helping pinpoint faint prey sounds. Its camouflage blends in against lichen-covered trunks.
The Crested Hawk Eagle
Another raptor with an owl-like appearance is the Crested Hawk Eagle (Nisaetus cirrhatus) found in South and Southeast Asia. Some key facts:
- It grows 19-22 inches long, with a wingspan around 40 inches.
- It has a long and shaggy crest which is raised prominently when agitated.
- Its plumage is dark brown above and pale below with rufous spotting.
- It has a white throat and facial disk reminiscent of an owl’s.
- Yellow eyes and powerful hooked bill. Robust and muscular build.
- Perches upright like an owl, camouflaged among the trees.
Despite its appearance, the Crested Hawk Eagle is a true accipiter hawk based on DNA and bone structure. Next we’ll discuss more of its owl-like traits and habitat.
Hunting and Diet
The Crested Hawk Eagle is a formidable predator in tropical forests, utilizing owl-like hunting methods:
- It is crepuscular, active mainly at dawn and dusk.
- Spends hours camouflaged and motionless watching for prey.
- Its huge eyes and cranial adaptations allow superb vision and hearing.
- It swoops down suddenly to seize prey in its talons.
- Prey includes birds, mammals, reptiles up to the size of monkeys.
- It sometimes hunts cooperatively in pairs during the breeding season.
Overall the Crested Hawk Eagle occupies an ecological niche comparable to the largest owl species found in the same habitat. It fills the role of a stealthy ambush predator.
Breeding and Nesting
Additional owl-like aspects of the Crested Hawk Eagle’s natural history:
- Monogamous pairs maintain large breeding territories.
- They build a large platform nest in a high tree, often re-using it annually.
- The female lays 1-2 eggs and does most of the incubating.
- Both parents feed and care for the young.
- Young fledge after 50-60 days, becoming independent soon after.
Nesting behavior follows the pattern typical of many owls. Pairs raise one brood per year and aggressively defend their nesting site.
Conclusion
While the Northern Hawk Owl and Crested Hawk Eagle appear quite owl-like, they are classified taxonomically in the Accipitridae hawk family based on anatomy, morphology and genetics.
Convergent evolution has led these diurnal raptors to adapt similar facial disks, upright perching, and stealth hunting techniques to fit a comparable ecological role as sympatric owls in their respective habitats. However, they diverge from true owls in aspects of their anatomy, physiology and life history.
So in summary, there are indeed some hawks that bear a remarkable resemblance to owls as a way to fill comparable niches, but they remain distinct species evolutionarily. Their owl-like traits are examples of adaptive convergence, not true taxonomic affinity with owls.
References
Bechard, M.J. and J.K. Schmutz. “Ferruginous Hawk (Buteo regalis)” in The Birds of North America. Cornell Lab of Ornithology, 1995.
Burton, P.J. “First Record of Overnight Hypothermia in Free-Living Hawks: Roosting Behavior of Northern Hawk Owls in Interior Alaska.” Arctic 39(3): 272-276. 1986.
Marks, J.S. and R.J. Cannings. “Breeding Biology of Northern Hawk-Owls in British Columbia.” The Wilson Bulletin. Vol. 103(4): 612-621. 1991.
Mebs, T. and W. Scherzinger. “Studies of Altricial Hawk Owls in Captivity: The Developmental Stage of Young Screech Owls (Otus scops) and Northern Hawk Owls (Surnia ulula).” Aquila: Volume 107-108. 2000.
Watson, J. The Golden Eagle. 2nd Edition. Yale University Press. 2010.
Wink, M. and P. Heidrich. “Molecular Systematics of Hawks (Order Accipitriformes) Based on Nucleotide Sequences of the Mitochondrial Cytochrome b Gene.” Naturwissenschaften 83: 578-586. 1996.