Common tawny owl Strix aluco sitting on a mossy branch of an old oak in a Polish deciduous forest, dark motionless eyes, rounded head without ears, soft twilight light — PLATE Nº 01 *Strix aluco*

SPECIES PROFILE · Birds of prey

Owl tawny owl

Strix aluco · Linnaeus, 1758

Common tawny owl — the voice of the Polish night, the most common owl of our forests and parks, master of noiseless flight and three-dimensional hearing.

The tawny owl is not just a bird — it is the voice of the Polish night. Its hooting 'hoo-hoo-hooo' is known by everyone who has listened to the winter forest or an old park after dusk. The most common Polish owl, an inhabitant of hollow oaks and urban avenues, a master of noiseless flight and three-dimensional hearing, hunting from ambush for voles, field mice, and everything that can be caught in the dark. This profile is dedicated to the tawny owl as a representative of Polish owls — with references to the long-eared owl, little owl, and barn owl.

37–43 cm: body length
81–96 cm: wingspan
350–650 g: mass (females larger)
4–7 years: life in the wild (up to 19 in captivity)
5–80 ha: pair territory
2–5 eggs: per clutch
28–30 days: incubation
80–120 thousand pairs: Polish breeding population

LC Least Concern Strict protection in Poland — species listed as strictly protected (Regulation of the Minister of Environment of 16.XII.2016, Annex 1); EU Annex I of the Birds Directive; protection of nesting habitats — hollow trees Stable or slightly increasing — PL population approx. 80–120 thousand breeding pairs; increasing trend in urban areas (parks, old gardens, cemeteries)

Kingdom	Animalia
Phylum	Chordata
Class	Aves
Order	Strigiformes
Family	Strigidae
Genus	Strix
Species	S. aluco

Appearance, anatomy, and diagnosis from other owls

A stocky medium-sized owl with a rounded head without 'ears' — and with black, not yellow eyes. Key diagnostics in the Polish terrain.

The tawny owl is a medium-sized owl with a stocky, compact build — significantly smaller than the eagle owl, but larger than the little owl or boreal owl. Rounded silhouette, large spherical head, without distinct feather 'ears' — this is one of the two key diagnostic features in the field.

The body length of an adult individual is 37–43 cm, wingspan 81–96 cm, mass 350–650 g. Sexual dimorphism is reversed — females are 20–25% heavier than males. This is typical for owls, falcons, and hawks, where the female incubates eggs and defends the nest, and the male — faster and more agile — provides food. The short, thick tail and short, rounded wings are an adaptation for flight in dense forest — the tawny owl maneuvers between trunks with a precision that even a larger goshawk might envy.

The second diagnostic feature — and decisive in the field — is the eye color. The tawny owl has black eyes (deeply dark, almost without an iris), unlike the yellow-orange eyes of the long-eared owl, little owl, boreal owl, or eagle owl. Black eyes indicate that the species evolved to hunt in dense forest under the canopy, where eye color has no camouflage importance, and a larger pupil provides an advantage in low light. Among Polish owls, only the barn owl (Tyto alba) also has black eyes — but its white, heart-shaped facial disc is so characteristic that a mistake is practically impossible.

Coloration occurs in two basic forms — color morphism: reddish-brown (most common in Poland, approx. 70% of the population) and grey (rarer, more common in Northern Europe and older boreal climates). The reddish-brown form camouflages better in forests with oaks and beeches; the grey form in spruce and pine stands. The underside of the body is light cream with dark vertical streaks and dashes, characteristic 'lettering' in the chest area. The facial disc is clearly marked with a dark border in a heart or circle shape — it directs sounds toward the ears like a parabola.

Black eyes — key diagnostic feature from other Polish owls (except the barn owl)
No feather 'ears' — rounded head, unlike the long-eared owl (Asio otus) with distinct plumes
Stocky, compact silhouette — short thick tail, short rounded forest wings
Heart-shaped facial disc — directs sounds to asymmetric ears like a parabolic antenna
Color morphism — reddish-brown form (70% PL) or grey (30%)
Reversed sexual dimorphism — female 20–25% heavier than male
Feathers with frayed edges — adaptation for silent flight (see Diet section)

Tawny owl vs Eagle owl — scale difference

Although both species belong to the same owl order, the eagle owl (Bubo bubo) is about four times heavier than the tawny owl — the eagle owl's mass is 1500–4000 g (females up to 4 kg!), with a wingspan of 160–190 cm. The eagle owl also has distinct 'ear' plumes, large orange-red eyes, and a much deeper voice — a low 'uhuuu' carrying through valleys for 2–3 km. The tawny owl and eagle owl do not compete for the same niche — the eagle owl hunts hares, deer, foxes, and larger birds; the tawny owl limits itself to rodents and thrush-sized birds. A separate species profile is dedicated to the eagle owl.

Anatomy of the common tawny owl — silhouette with described features: black eyes, no ears, facial disc, frayed feathers — Fig. 01Tawny owl in diagnostic view — black eyes, lack of feather ears, and a heart-shaped facial disc are three features that distinguish it from other Polish owls.

Feature	Tawny Owl	Long-eared Owl	Little Owl	Barn Owl
Body length	37–43 cm	35–37 cm	21–23 cm (smallest)	33–39 cm
Eyes	black	orange-yellow	light yellow	black
Feather ears	none	long, distinct	none	none
Facial disc	round, dark brown	rusty, distinct	small, faint	white heart
Environment	deciduous forests, parks	coniferous forests, orchards, crow nests	open areas, village outskirts	churches, barns, attics
Polish population	80–120k pairs	30–60k pairs	1–3k pairs	1–2k pairs

Environment and range in Poland

Deciduous forests, urban parks, and old gardens — wherever there are hollow trees.

The tawny owl is a forest species, but extraordinarily adaptable. It only needs old trees with hollows and night-time open spaces for hunting — it fills in the rest itself. It inhabits all of Poland except the highest parts of the Tatra Mountains and the exceptionally open agricultural landscapes of Greater Poland.

Optimal habitat is deciduous or mixed forest over 100 years old, with oaks, beeches, lindens, or hornbeams having natural hollows. Pine and spruce stands are inhabited less frequently — mainly where they neighbor deciduous enclaves or old nests of ravens, goshawks, and buzzards (the tawny owl readily uses others' nests). Population density in optimal riparian and oak-hornbeam forests of the Polish lowlands reaches 2–4 pairs/km², falling to 0.2–0.5 pairs/km² in coniferous forests.

Synanthropization is one of the most interesting phenomena concerning the tawny owl in the last half-century. The species has colonized large cities — in Warsaw, Kraków, Wrocław, Poznań, and Gdańsk, the tawny owl nests in old urban parks (Royal Łazienki, Jordan Park, Szczytnicki Park), in cemeteries (Powązki, Rakowicki), and in monastery gardens. Density in Łazienki exceeds 1 pair/10 ha — one of the highest rates in Europe. The tawny owl supplements its park diet with brown rats and urban rats, making it a useful neighbor to humans.

Other Polish owls have distinctly different habitat preferences: the long-eared owl (Asio otus) chooses coniferous forests, orchards, and mosaic landscapes; the little owl (Athene noctua) — open agricultural areas, village outskirts, and orchards (it is extremely endangered in Poland, already extinct in many regions); the barn owl (Tyto alba) — churches, barns, attics of farm buildings (threatened by the decline of insect breeding in attics and renovations of old roofs). The boreal owl (Aegolius funereus) is a mountain species — Carpathians, Sudetes. The tawny owl is the only one that connects the forest with the city.

Deciduous and mixed forests >100 years old — optimal habitat (2–4 pairs/km²)
Urban parks and cemeteries — clear synanthropic expansion since the 1970s
Old gardens and monastery orchards — with hollow fruit trees
Mid-field thickets — rows of oaks, linden avenues
Absent in extremely open landscapes and above the tree line
Habitat key: nesting hollows = old trees = protection of old-growth forest

Old urban park as tawny owl habitat — oak avenue with 200-year-old trees, hollows visible on trunks — Fig. 02Old urban park with hollow oaks — typical habitat for the urban tawny owl population. In Warsaw's parks, density exceeds 1 pair per 10 hectares.

Diet and hunting technique

Rodents at 70%, ambush hunting, and silent flight — the three pillars of the tawny owl's hunting effectiveness.

The tawny owl is an opportunistic predator with a wide food spectrum, but with a clear rodent dominance. Its hunting strategy relies on three pillars: ambushing from an observation point, silent approach flight, and precise localization of prey by sound.

Diet composition in Polish forests (pellet analyses from IBL and PTOP studies): small rodents 60–75% (wood mice, field mice, bank and field voles, birch mice, shrews), small birds 10–20% (thrushes, tits, robins, sparrows), insects 5–10% (cockchafers, bush-crickets), frogs and toads 2–5%, occasionally fish from shallow streams and bats. In cities, the share of brown rats and house mice increases to 30–40%, and birds reach 25%.

Hunting technique is spectacular and called perch-and-pounce hunting. The tawny owl sits on a branch 2–10 m above the ground, in complete stillness and silence, sometimes for 20–40 minutes. Once it localizes prey by hearing, it performs a silent gliding flight with a descending trajectory and grabs the animal with its talons. Silent flight is a unique adaptation of owls — feathers on the wing edges have comb-like serrations that disperse air turbulence, and the underside of the wings is covered with velvety, sound-absorbing down. As a result, the prey does not hear the approaching predator until the last second.

The tawny owl's hearing is so precise that the species hunts effectively even in zero visibility — in the full darkness of a moonless night or in fog. The key is asymmetric ear placement: the left ear (actually the ear opening hidden under feathers) is located higher than the right one, which creates a microscopic delay in sound arrival. The tawny owl's brain analyzes this delay in three dimensions (horizontal, vertical, distance) and localizes a vole with an accuracy of 1–2 degrees. The tawny owl can detect a vole under a 30-centimeter layer of snow — frozen snow acts as an acoustic filter but does not block all frequencies.

Pellets — how to read the tawny owl's diet

Pellets are compact bundles of indigestible remains — bones, fur, feathers, and chitin — coughed up by the owl 1–2 times a day. In the tawny owl, they measure 3–7 cm in length and 1.5–2.5 cm in diameter, are grey-brown, cylindrical, and show no signs of strong digestion (bones remain intact, unlike hawk pellets where bones are fragmented). Under the nest or at a regular roost site, multi-year layers form. Pellet analysis is the basic method for studying owl diets — under a microscope, the rodent species is identified by skull and tooth remains. Polish forestry and ornithology schools often conduct such analyses with children.

Diet component	Forest (% biomass)	Urban park (% biomass)
Small forest rodents	60–75%	20–30%
Rats and house mice	0–5%	30–40%
Small birds	10–20%	20–30%
Insects	5–10%	5–10%
Frogs, toads, fish	2–5%	1–3%
Anthropogenic remains	<1%	5–10%

Reproduction — the earliest clutch in Poland

First eggs in January, lifelong monogamy, nesting in hollows — tawny owl breeding biology.

The tawny owl lays eggs the earliest of all Polish birds — first clutches are recorded as early as January, regularly in February. This is an adaptive strategy: young hatch when rodent-prey activity increases after winter, and the chick-rearing season falls in May–July, the period of maximum food availability.

A pair of tawny owls is monogamous for life — they maintain a multi-year territory of 5–80 ha, depending on habitat quality. The mating phase starts in autumn (October–November) and intensifies in winter — this is when characteristic calling duets are heard: the male's hooting 'hoo-hoo-hooo' (long, carrying) and the female's short, sharp 'kewick' response. The pair sings alternately, sometimes for several hours on freezing, windless nights — it is one of the most beautiful sounds of Polish nature.

The nest is most often placed in a natural hollow of an old deciduous tree (oak, beech, linden, hornbeam) — a black woodpecker hollow is preferred. The tawny owl also uses abandoned nests of ravens, goshawks, and buzzards, and increasingly — type A or D nesting boxes hung by amateur ornithologists and forest districts. The site is chosen by the female; the male accompanies her. The clutch consists of 2–5 eggs (average 3–4), white, almost spherical, laid every 2–3 days. Only the female incubates for 28–30 days; the male delivers food to her at the nest.

Chicks hatch asynchronously — the oldest and youngest can differ by 7–10 days. This is a brood reduction strategy: in poor food years, the youngest chick starves, while the older ones survive. In good years, the whole clutch fledges. Chicks leave the nest on day 32–37 while still flightless — this is the 'brancher' stage, when owls walk on branches and the ground, and parents continue to feed them. They achieve full flight capability on day 45–50, but parents care for them until September — a long period for learning to hunt.

Do not pick up 'abandoned' chicks!

Tawny owl chicks that have left the nest but cannot yet fly are NOT abandoned — this is a normal phase of development when the 'brancher' sits on the ground or a low branch, while parents observe from hiding and feed them. If you take such a chick, you risk its death in captivity (hand-rearing is very difficult) and deprive the parents of a chance for breeding success. What to do: if the chick is on a path, road, or within reach of dogs/cats, gently move it 1–3 meters to a safe place on a low branch. Parents will find it by its voice. Owls do not reject chicks with human scent — that is a myth. Only an obviously injured chick (bleeding, broken wing) requires intervention from a bird of prey rehabilitation center.

Three tawny owl chicks at 5 weeks old in a natural hollow of an old oak — white-down plumage, black eyes barely open — Fig. 03Tawny owl chicks at 5 weeks old leave the hollow — still in down, flightless, but already with characteristic black eyes and facial disc outlines.

Signs of presence and field identification

Pellets, feathers, droppings, and voice — four ways to confirm the tawny owl's presence in a forest or park.

The tawny owl is easier to hear than to see — active at night, camouflaged perfectly by day, rarely seen by casual walkers. However, its presence is confirmed by numerous indirect signs that are easy to learn to recognize.

Pellets — as described in the diet section — are the surest sign of an owl's presence. In the tawny owl, they have characteristic dimensions of 3–7 cm in length and 1.5–2.5 cm in diameter, are grey-brown or blackish (when fresh), with a compact and fibrous texture. They concentrate under a regular roost site — most often on a thick branch close to the trunk, 4–10 m above the ground. Under such a tree, a layer of a dozen pellets from different months can sometimes be found, and the surroundings are stained with white droppings.

The tawny owl's feathers are characteristic — short, soft, with distinct comb-like fraying on the edges (primary flight feathers), with reddish-brown or grey coloring and a wavy pattern. They are most often found under a plucking site (small feathers of young prey birds mixed with owl feathers) or during the molting period (June–August). Down feathers are light cream, soft, with frayed tips.

Voice is, however, the surest identification method. The tawny owl's vocal repertoire includes: (a) male hooting — a long 'hoo-hoo-hooo' with three syllables (short, short, long tremolo), repeated at 20–40 second intervals, carrying 0.5–1 km on a windless night; (b) female contact 'kewick' — a short, sharp, two-syllable 'ki-wick'; (c) mating duets in February–March, when partners respond to each other alternately; (d) alarm barking near the nest (short raspy 'kuk-kuk-kuk'). Most common vocalization period: October–March, with a winter peak.

Pellets 3–7 cm — under a regular roost, compact, grey-brown
White dropping stains on the bark under a roosting branch
Feathers with frayed edges — impossible to confuse with other birds
Prey remains — bones, fur, small feathers near the nest
'Hoo-hoo-hooo' voice of the male at night from October–March — certain diagnosis
Contact 'kewick' of the female — twice as short, sharp
Field apps (e.g., Merlin Bird ID, BirdNET) recognize the voice automatically

Fresh tawny owl pellets under an old oak — grey-brown cylindrical bundles on leaves with white dropping stains on bark — Fig. 04Fresh tawny owl pellets under a regular roost — under the layer may lie a diet archive from the whole season, a source of invaluable data for ornithologists.

Ethology — territory, monogamy, mating duets

Multi-year territories, lifelong partnership, and voice as a tool for protecting the range.

The tawny owl is strongly territorial and monogamous — a pair occupies a territory for many years, sometimes for the entire lives of both birds. Voice is the primary tool for intra-pair communication and territorial defense against neighbors.

The territory has an area of 5–80 ha (average 15–30 ha in Polish lowland forests, smaller in optimal riparian habitats, larger in coniferous forests). Boundaries are diligently patrolled vocally — the male hoots from various points on the edge of the range in the evening and at dawn. Neighboring pairs overlap territories partially — border zones are dynamic, and winter is the time of the strongest vocal confrontation. Physical fights are rare and usually limited to demonstrations (spreading wings, snapping the beak).

Mating duets — the alternating calling of the pair in February and March — are not only about strengthening the bond but also a public declaration of territorial occupancy. A pair hooting together in the middle of the night informs neighbors: 'territory occupied, breeding in progress'. Ornithologists use playback (playing a hooting recording) to count breeding pairs — territorial males respond to the recording in 80–95% of cases, enabling precise inventory.

Nest defense is aggressive — the female tawny owl does not hesitate to attack humans, foxes, martens, and even goshawks near a hollow with chicks. Attacks on humans are regularly recorded in Polish urban parks (Łazienki, Wrocław Szczytnicki Park) — the owl dives at a passerby's head in silent flight, inflicting talon wounds to the scalp. The most famous case is the tawny owl attack on photographer Eric Hosking in 1937, as a result of which he lost an eye. A woman in Warsaw in 2017 suffered 12 talon wounds from an attack on a path in Łazienki Park. During May–July, it is worth avoiding previously noticed nesting hollows.

How to listen for the tawny owl — field practice

Best time: October–March, hours 18:00–24:00 on windless, freezing, or foggy nights. Best places: old urban parks (Łazienki, Skaryszewski Park in Warsaw; Jordan Park in Kraków), cemeteries (Powązki, Rakowicki), riparian forests along the Vistula and Bug rivers, Białowieża and Kampinos Forests. Technique: arrive an hour after dusk, stop in a quiet place, listen in 5-minute blocks with pauses for movement. Do not use playback — it stresses the birds and disturbs their mating behavior (in the breeding season, it is even illegal in protected areas). The Merlin Bird ID app with Sound ID mode will identify the species with 95% certainty.

Protection, threats, and what you can do

Strict legal protection, but real threats: rodenticides, loss of hollows, collisions. Practical ways to help.

The tawny owl is a strictly protected species in Poland, its population stable or slightly growing. Nevertheless, there are a set of real threats, the scale of which can be significant locally — from rodenticide poisoning to cutting down hollow trees.

Legal status: strict protection in Poland under the Regulation of the Minister of Environment of December 16, 2016, on species protection of animals (Annex 1). Prohibitions include: killing, capturing, disturbing during the breeding season, destroying nests, possessing (except for rehabilitation centers with RDOŚ permission). EU: Annex I of the Birds Directive 2009/147/EC — a species requiring habitat protection. IUCN Category: LC (Least Concern) globally; locally in Poland — not threatened, but requiring monitoring in selected regions.

Real threats: (1) II generation rodenticide poisoning — anticoagulants (brodifacoum, bromadiolone) used to control rats accumulate in the bodies of rodent-prey; a tawny owl eating 3–5 poisoned mice dies of internal bleeding within a few days. This is one of the most serious threats in cities. (2) Loss of nesting hollows — cutting down old trees in urban parks and commercial forests under the pretext of 'safety' eliminates nesting habitat. (3) Car collisions — the tawny owl hunts on roadsides; young individuals are especially victimized. (4) Collisions with power lines and glass buildings. (5) Disturbance during the breeding season — photographers and observers approaching too close to the hollow.

II generation rodenticides — accumulating anticoagulants; the main urban threat
Loss of hollow trees — 'sanitary' felling of old-growth
Road collisions — especially young individuals on roadsides
Power lines and glass facades — fatal collisions
Disturbance during breeding — photographers and playback
Competition for hollows with jackdaws, rooks, squirrels

What you can do for the tawny owl

1. Hang a type D nesting box — internal dimensions 25×25×60 cm, entrance hole 14×14 cm, hung at a height of 5–8 m on the trunk of an old deciduous tree, at least 100 m from the next box. Best in an old park, garden with oaks, cemetery avenue, or on the forest edge. Box plans are available on the PTOP and OTOP websites. 2. Do not use II generation rodenticides in the home and garden — control rats and mice with live traps or mechanical traps. 3. Leave old hollow trees — in the garden, park, forest. 4. Report dead owls from roadsides to the nearest bird of prey rehabilitation center — they can be tested for poisoning. 5. Do not use playback during breeding season (February–July). 6. Support OTOP, PTOP, and rehabilitation centers financially or as a volunteer.

Myths and facts about owls

Common misunderstandings about owls — from 'blindness during the day' to 'head spinning 360 degrees'.

Owls are a group of birds surrounded by the largest number of myths and superstitions in Polish folk culture. Their nocturnal activity, uncanny voice, and the motionless black eyes of the tawny owl led people to see them as omens of death, sages, or witches. Biological truth is less dramatic, but no less fascinating.

MYTH Owls are blind during the day.

FACT Untrue. Owls see perfectly during the day, in full color and with high resolution. However, their eyes are adapted primarily for low light — with large pupils, high density of rods (cells responsible for night vision), and a facial disc that directs sound. In bright daylight, the owl constricts its pupils and may squint, but sees normally. Nocturnal activity does not result from day blindness — it results from the fact that their prey (small rodents) are active at night. A tawny owl seen during the day is most often an individual being mobbed by crows or jays.
MYTH Owls can rotate their heads 360 degrees.

FACT Untrue. The maximum range of an owl's head rotation is 270 degrees in one direction (135° left and 135° right from the starting position). This is still significantly more than a human (approx. 80°) and is possible thanks to 14 cervical vertebrae (humans have 7) and special vascular adaptations protecting the brain from ischemia during extreme rotation. An owl needs such flexibility because its eyes do not move in their sockets — they are almost immobile, shaped like cylinders built into the skull. To change the direction of gaze, it must turn its whole head.
MYTH The hooting of an owl portends death in the house.

FACT A folk superstition without basis. The tawny owl calls from late summer throughout winter, especially on windless, freezing nights — this is a time of increased mating activity and territorial defense. In old Poland, hooting was associated with death because, before electricity, people spent evenings in silence, and the owl's voice was one of the loudest sounds of the night — often associated with the sick and dying (people actually died more often at night). Today, the superstition has no diagnostic value. Hooting under a window only means one thing: there is an old park or forest with a tawny owl population nearby.
MYTH Every owl has feather 'ears'.

FACT Untrue. Only some owl species have 'ears' — in Polish avifauna, distinct plumes are possessed by the long-eared owl (Asio otus), short-eared owl (Asio flammeus), and eagle owl (Bubo bubo). The tawny owl, barn owl, little owl, boreal owl, and pygmy owl have rounded heads without ears. Feather ears are decorative — they serve communication and camouflage functions (mimicking a 'stump with branches') and have nothing to do with real ears. A sowa's real ears are two auditory openings hidden under the feathers of the facial disc, asymmetrically placed (one higher, one lower) — the most effective hearing apparatus in the bird world.
MYTH Owls are wise.

FACT A cultural symbol, not a biological fact. Owls owe their reputation for wisdom to the ancient Greeks — the goddess Athena (wisdom) had an owl as an attribute, hence the famous 'Owl of Athena'. Biologically, however, an owl's brain is relatively small compared to its skull — most of the head's volume is taken up by huge eyes (weighing as much as the whole brain!) and a specialized hearing apparatus. Owl intelligence, measured by learning and problem-solving tests, is significantly lower than that of corvids (Corvidae), parrots, or even great tits. Owls are supreme specialists — but narrow ones: they hunt perfectly at night by hearing, but do not handle innovative tasks very well.
MYTH Owls only eat mice.

FACT Mostly true, but not exclusively. In the tawny owl, small rodents make up 60–75% of the diet's biomass in forests, which drops to 50% in cities. The remaining 25–50% consists of small birds (up to twice their own body weight — a tawny owl can catch a jackdaw, pigeon, or thrush), insects (cockchafers, bush-crickets — an important protein source in summer), frogs and toads, and occasionally fish from shallow streams (the tawny owl is not a fish specialist like the fish owl, but it can catch them). Other Polish owls have varied menus: the little owl — mainly insects and small mammals; the barn owl — almost exclusively rodents; the long-eared owl — rodents with an emphasis on the common vole; the eagle owl — from mice to deer.