Athene noctualittle owl

Geographic Range

Commonly known as little owls, Athene noctua is found within 84 countries of the Palearctic region and the northeastern portion of the Ethiopian region. The range of Athene noctua extends north to the 56th parallel and south to the southern border of the Palearctic region in Asia. The southern extent includes the Middle East to southern Ethiopia and south of western Europe to northern Niger. The eastern limit of the range borders the Sea of Okhotsk and the western limit is found along the Atlantic Ocean. (Johnson, et al., 2009; Van Nieuwenhuyse, et al., 2008)

Habitat

Athene noctua inhabits a range that encompasses a wide variety of landscapes. This species is adapted to mostly dry climates as rain decreases hunting success. Habitable landscapes also vary in altitude as Athene noctua has been observed at elevations ranging from sea-level to 2600 m. Athene noctua is a cavity nesting species and may reside in tree and rock cavities, crevices in cliffs and man-made structures, and even the nests, holes, and burrows of other animals. It prefers habitats with open hunting grounds, many small prey, areas to perch, cavities for nesting, and a stable climate. These habitat preferences of Athene noctua can be met by many landscapes and thus this species is found in a wide variety of habitats, both natural and man-made. It resides in many natural, temperate regions including: open fields, grasslands, open woodlands, steppes, semi-deserts, deserts, cliffs, non-wooded mountains, and ravines, gorges, and gullies. Athene noctua also strongly associates with anthropogenic habitats including agricultural landscapes (farmlands, meadows, pastures, orchards) and urban and suburban habitats (villages and urban buildings). (Grzywaczewski, 2009; Hardouin, et al., 2008; Johnson, et al., 2009; Le Gouar, et al., 2010; Thorup, et al., 2010; Tomé, et al., 2008; Van Nieuwenhuyse, et al., 2008; Żmihorski, et al., 2009)

  • Range elevation
    Sea-level (0) to 2600 m
    to 8530.18 ft

Physical Description

At hatching Athene noctua has pink skin, cere, and toes and a light white or gray bill and claws. The first down is called neoptile and is short and white. After one week the second down, the mesoptile, begins to grow and young little owls appear a mottled gray color. The mesoptile resembles feathers but is shorter and softer. On the tenth day, the eyes open and the iris is a light yellow color. For three or four weeks the neoptile is still attached to the mesoptile. Overall the young little owls are grayer and show less contrast in their coloring than adults. Even first year adults have differences in feather shape and texture than older adults. (Van Nieuwenhuyse, et al., 2008)

Little owl adults are mostly a dark brown color with cream markings over the entire body. The cream markings include streaks on the forehead and crown, rings around the eyes, a cream chin, spots and streaks on the breast and abdomen, round spots on the back and tail, and a distinct V-shape mark on the back of the head. The males and females share a similar appearance with males tending to have a lighter face. The bill and iris of A. noctua are bright yellow and the eyelids are dark. The cere, a part of the bill, is grayish to black in color. The legs are gray with a possible yellow tint. The toes are a darker gray to brown or black color and the claws are dark brown to black. Some coloring anomalies have been reported including partial albinism, leucistic coloration, or a russet color. (Van Nieuwenhuyse, et al., 2008)

The wing length of A. noctua has a reported maximum of 174 mm and minimum of 158 mm but normally ranges between 151 mm and 178 mm. The wingspan of male little owls is 557.67 mm (plus or minus 11.90 mm) and for females the wingspan was recorded as 565.64 mm (plus or minus 13.15 mm). Females are generally larger than males and on average have a wing length that is 3 to 5 mm longer than males. Also, one year old little owls have a wing length that is, on average, 3 mm shorter than older adults. The subspecies of A. noctua do differ in sizes with the largest little owls from Tibet and Kashmir mountains and the smallest little owls from northeast Africa. (Van Nieuwenhuyse, et al., 2008)

As the common name suggests, little owls are small with an average weight of 164 g. Male little owls are 9 to 10% lighter than females. The minimum recorded weight of an A. noctua is 98 g, the wild maximum is 270 to 280 g, and the maximum recorded in captivity is 300 to 350 g. (Johnson, et al., 2009; MØLLER, 2006; Van Nieuwenhuyse, et al., 2008)

  • Sexual Dimorphism
  • female larger
  • Range mass
    98 to 350 g
    3.45 to 12.33 oz
  • Average mass
    164.0 g
    5.78 oz
  • Average wingspan
    557.67 (males) and 565.64 (females) mm
    in

Reproduction

The courtship period of A. noctua begins with the male defending his territory. He patrols the borders of his territory and calls. The call serves as both a territorial defense to fend off other males and to attract a mate. Once a potential mate makes contact, pair bonding begins. This includes the little owls flying in pairs and sitting in the same tree. The female begins to make a "begging" call to her partner and this prompts the male to feed her prey he has captured. This feeding habit is important because it indicates that there is enough food to reproduce and feed young and also to supply the female with more food so she can gain weight for egg formation and incubation. The vocalization between partners increases as pair bonding strengthens and the couple begins nest visiting and/or copulation. The male selects potential nests within his territory and, around the time of copulation, he shows the female the nest sites until she selects one. Upon successful copulation, the female will remain in the nest and continue to "beg" her mate for food at an increasing rate. After the young have fledged the bond between the pair decreases and aggression increases. Often the partners are willing to separate at this point but not all do. The little owls show a high rate of mate fidelity. The partners will often fly together and hunt near each other. They also share body contact while sleeping and preen and scratch each other. Scratching and copulation outside of the breeding season has been reported and is believed to reduce aggression between mates when not reproducing. Although A. noctua is monogamous, when little owl densities are high and prey is plentiful, sometimes extra-pair copulations occur. (Hardouin, et al., 2008; Johnson, et al., 2009; Van Nieuwenhuyse, et al., 2008)

Athene noctua is iteroparous (produces a clutch every year). The mating season of A. noctua begins in early February and ends as late as May depending on the region. The time of egg-laying also varies with the location but can begin as early as March and end as late as August when taking into account replacement clutches. The clutch size is normally between 1 and 7, averaging 3.3, but as many as 12 has been recorded. If the first clutch is lost for some reason, a pair can lay a replacement clutch, usually of a smaller size. As soon as the eggs are laid, the incubation period begins. The incubation period is from 18 to 35 days, usually reported as 28 days. Overall hatching occurs approximately one month after laying and owlets are dependent upon the parents for two months. The average weight of newly hatched owlets is 10 to 12 g. The female remains with the nestlings for 16 days. The owlets begin to catch their own prey at 28 days and kill prey at 34 days. The offspring become fledglings as early as 28 days and as late as 35 days. The owlets become juveniles and no longer need parental care between August and the beginning of November. The juveniles settle an average of 2700 m away from their first nest. The little owls reach reproductive age at 1 year.

Hatching success of little owls is as low as 49.3%. Fledging success has been reported as low as 46.6%. These losses can be due to infertility, adults losing or abandoning the nest, predation, low prey availability, and other nest complications. The most important trait linked to the production of young is food availability. The success of young is effected by the distance of the nest to the hunting grounds and by weather during the preceding winter, the breeding season, and after hatching. Supplementing nests with food has been shown to greatly increase the production of young. The number of young fledged per breeding pair ranges from 0.6 to 2.8 fledglings per pair. (Grzywaczewski, 2009; Holsegård-Rasmussen, et al., 2009; Johnson, et al., 2009; Le Gouar, et al., 2010; MØLLER, 2006; Thorup, et al., 2010; Tomé, et al., 2008; Van Nieuwenhuyse, et al., 2008)

  • Breeding interval
    Athene noctua breeds once per year
  • Breeding season
    The breeding season of little owls begins at the earliest in February and continues until May at the latest
  • Range eggs per season
    1 to 12
  • Average eggs per season
    3.3
  • Range time to hatching
    18 to 35 days
  • Average time to hatching
    28 days
  • Range fledging age
    28 to 35 days
  • Average time to independence
    12 to 16 weeks
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    1 years

Before copulation occurs, little owls must strengthen pair bonding. Part of this pair bonding includes the male defending his territory and providing food to the female. The female must develop fat reserves to help her produce eggs before the nest site is selected. Before the female lays eggs, she remains in the nest and the male brings prey to her. As soon as the eggs have been laid, the female begins incubating the eggs to keep them warm. Pre-hatching parental investment also includes the male bringing the female food as she incubates the eggs. The eggs hatch after about 28 days and the pre-fledging parental care begins. The male still catches prey and brings it back to the nest for the nestlings and female. The female defends, warms, and feeds her young. After 16 days the female also leaves the nest and begins bringing prey back for the nestlings. The offspring become fledglings as early as 28 days and as late as 35 days. Pre-independence parental care includes the parents still feeding and protecting the owlets one month after they reach fledgling age. Parental care ceases at the beginning of September to the beginning of November. In general, there is a two month post-hatching dependency period in which the parents are very active and energetically stressed. As the brood ages, the activity rates of the parents increase. The males are more active than the females during this period and are the main food provider, possibly linked to their lighter weight allowing them to move further and faster. Also the heavier weight of the females may help them care for and defend the nest. Although the roles of the A. noctua parents are different, both provide provisioning and protection throughout the development of the young. (Holsegård-Rasmussen, et al., 2009; Thorup, et al., 2010; Van Nieuwenhuyse, et al., 2008)

  • Parental Investment
  • altricial
  • male parental care
  • female parental care
  • pre-fertilization
    • provisioning
    • protecting
      • male
      • female
  • pre-hatching/birth
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-weaning/fledging
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • male
      • female
    • protecting
      • male
      • female

Lifespan/Longevity

The longest lifespan of A. noctua in the wild is 15 years and 7 months old, however the median lifespan of A. noctua is 4 years. The mortality rate of adult little owls is between 24.2% and 39% per year. The mortality rate of juveniles is much higher, reported to be between 69% and 94%. The lifespan of little owls is limited mostly by prey and nest availability, but predation, parasites, weather, and human influences (habitat destruction, traffic, chemicals, electrocution, etc.) also effect longevity. Information on A. noctua lifespan is not well documented in both the wild and captivity. (Le Gouar, et al., 2010; MØLLER, 2006; Thorup, et al., 2010; Van Nieuwenhuyse, et al., 2008)

  • Range lifespan
    Status: wild
    15.583 (high) years
  • Typical lifespan
    Status: wild
    4 (low) years

Behavior

Athene noctua is a sedentary species and remains close to its birthplace for life. Little owls have been seen flying 20 to 30 m and even higher, but they usually fly low to the ground. Their feathers are greased every two to three days. Little owls also take dust or sand baths regularly and have even been spotted bathing in smoke rising from chimneys. When A. noctua sleeps, it is able to position itself in a way that hides all light feathers and camouflages itself extremely well in its habitat. Also, to close their eyes to sleep, little owls raise their lower eyelids. Athene noctua preens often and thoroughly. Mutual preening has also been noted between mates and even fledgling siblings. Athene noctua is crepuscular; it has been seen at daytime and nighttime hunting and calling, however, the height of activity is at dusk and dawn. (Le Gouar, et al., 2010; Van Nieuwenhuyse, et al., 2008)

  • Range territory size
    .018 to .95 km^2
  • Average territory size
    .151 km^2

Home Range

The home ranges of little owls vary in size throughout the year from 1.8 to 95.0 ha (.018 to .95 km^2). The average home range is 15.1 ha (.151 km^2). Through the winter little owls must scavenge for scarce food. This contributes to the larger sizes of home ranges and increases overlaps of territories among individuals. Home ranges decrease and do not overlap during the breeding season. The decrease in home range is influenced by an increase in energy expenditure during courtship, laying, hatching, and raising of owlets. Little owls require more energy to defend and hunt a larger territory. Also, the parents must hunt closer to the nest to reduce the amount of energy spent on travel. The smallest home ranges were seen during the laying period, with an increase during incubation and nestling periods. There is another decrease in home range during the fledgling period of offspring. The second smallest home ranges were observed as juveniles reached independence. It is believed parents decrease and defend their home range to scare independent juveniles out of their natal territory. Owls that have lost clutches or were unsuccessful in breeding will increase their home ranges and often forage in the same areas as other owls. Although, A. noctua is territorial, there has been little or no aggression found between little owls near each other. The average distance between little owl nests is 560 m. (Grzywaczewski, 2009; Van Nieuwenhuyse, et al., 2008; Zuberogoitia, et al., 2007)

Communication and Perception

Athene noctua is a very vocal bird with a repertoire of between 22 and 40 different calls. These calls are are used to contact or attract mates, defend territories against enemies and other little owls, alarm, and communicate. The vocalizations occur on average 1.87 times per hour and there is an average of 415 total seconds of calling in an hour. The vocal activity varies with time of year and day. There is usually a peak in calling before and during courtship and is lowest in the winter and summer. Also, there is an increase in call duration at dusk, called a dusk chorus phenomenon and a less pronounced increase at dawn with a lull through the night. There are more song vocalizations than calls at night. Also, little owls have been known to vocalize during daylight. The female call is generally shorter and higher pitched than the male call. The male calls are also louder and clearer than the female calls. When a predator is detected, A. noctua quiets and waits until the threat is presumably gone before resuming vocal activity. It has also been demonstrated that little owls learn to recognize the calls of neighboring little owls versus unknown little owls to reduce energy expenditure during territory defense.

Sight and hearing also allow little owls to perceive their environment. Little owls have retinal cells more similar to diurnal birds and have the poorest visual acuity compared to other birds of prey. Athene noctua can see yellow, green, blue, and (to a lesser extent) red. Little owls can also distinguish between different shades of gray, increasing the ability to see at night. Little owls can also hear sound frequencies of 3 to 4 kilocycles per second (kc/s). This ability to hear allows A. noctua to locate rodents extremely accurately. Little owl pairs often preen and scratch each other and sleep in contact with each other. These tactile cues are used to increase pair bonding between mates. Mutual preening has also been seen amongst fledgling siblings. (Hardouin, et al., 2008; Johnson, et al., 2009; Van Nieuwenhuyse, et al., 2008; Zuberogoitia, et al., 2007; Zuberogoitia, et al., 2008)

Food Habits

Little owls hunt in various ways, even mixing the styles of hunting to suit their prey. They can be found perching and watching the ground or the air. To catch prey items on the ground, A. noctua will run and hop along the ground. They can also catch prey on the ground while flying low. Athene noctua can catch prey out of the air while flying as well. Athene noctua carries its prey with either its beak or claws. Males and females hunt and carry prey similarly, but females seem to prefer to carry prey by the neck, whereas males carry prey more often by the head. Little owls are known to catch prey as heavy as themselves. Little owls also create holes to hold surplus food. Hunting occurs mostly at night or dusk, but they have been seen hunting in daytime. Athene noctua is an opportunistic carnivore that is known to feed on a wide variety of prey including mammals, birds, reptiles, amphibians, fish, insects, molluscs, crustaceans, and other invertebrate species. The diet mainly consists of small rodents and large invertebrates (earthworms and insects). In the palearctic region, A. noctua is recorded to prey on 544 different species. The portions of the prey that little owls cannot digest are compacted internally and regurgitated as a pellet. (Hardouin, et al., 2008; Holsegård-Rasmussen, et al., 2009; Johnson, et al., 2009; Le Gouar, et al., 2010; Thorup, et al., 2010; Tomé, et al., 2008; Van Nieuwenhuyse, et al., 2008; Zuberogoitia, et al., 2008)

  • Primary Diet
  • carnivore
    • eats terrestrial vertebrates
  • Animal Foods
  • birds
  • mammals
  • amphibians
  • reptiles
  • fish
  • insects
  • terrestrial non-insect arthropods
  • mollusks
  • terrestrial worms
  • aquatic crustaceans

Predation

Little owls have many anti-predator adaptations. Athene noctua is known to call in response to predators as an alarm and defense. When other little owls hear the defense call they will hide. When A. noctua sleeps, the white markings are hidden which allows the owl to camouflage. Also, the V-shaped marking on the back of the head mimics eyes to prevent predation from behind. Further, it has been noted that in the presence of barn owls (Tyto alba), little owls will hide or become silent until the threat is perceived to be gone. Although not a normal predator of A. noctua, sometimes intraguild predation occurs between little owls and Tyto alba. The predators of little owls are larger birds including tawny owls, eagle owls, long-eared owls, peregrine falcons, common buzzards, goshawks, sparrowhawks, red kites, tawny eagles, rough-legged buzzards, booted eagles, lanners, marsh harriers, black kites, imperial eagles, and long-legged buzzards. Other predators include pine martens, feral cats, fox, domestic dogs, and corvids. The main predators of the nests are mammals, including stone martens and common genets. The eggs and chicks of little owls are predated upon by stoats, hedgehogs, brown rats, corvids, and magpies. (Hardouin, et al., 2008; Tomé, et al., 2008; Van Nieuwenhuyse, et al., 2008; Zuberogoitia, et al., 2008; Żmihorski, et al., 2009)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Little owls feed mainly on insects and small mammals and can keep these populations under control. Also, A. noctua serves as the prey for other species. Although A. noctua interacts with many species, there are no mutualistic relationships documented. Two commensal species of little owls are Trichophagata petzella and Monopis laevigell. There are at least 67 parasite species of little owls. The main types of parasites are from the groups Protozoa, Sporozoa, Metazoa, Nemathelminthes, Arachnida, and Insecta. The blood parasite Leucocytozoon ziemanni and the ectoparasite dipteran Carnus hemapterus have been reported to use little owls as hosts. It could be stated that A. noctua is a commensal species of humans. The little owls use agricultural landscapes and urban and suburban areas as habitats. Also, little owls have been seen following farming equipment that stirs up insects and taking "smoke" baths in the rising smoke of chimneys. (Van Nieuwenhuyse, et al., 2008)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Little owls eat many insects and small mammals, controlling populations that are pests to humans. There has been a dramatic decline in some owl populations throughout Europe, including A. noctua. Athene noctua is perfect for studying owl declines in rural habitats because the species is well known to the public, present in significant numbers, easy to research, and quickly reacts to conservation actions. The presence of A. noctua attracts predators that were once desirable to humans. Due to this, little owls used to be traded and carried on staffs to attract and catch their predators. Little owls were also once traded as pets. (Van Nieuwenhuyse, et al., 2008)

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

Athene noctua can be found nesting in and on the faces of buildings. This is considered unattractive and measures have been taken in some places to avoid this (including nets hung over signs). Other than this superficial damage, Athene noctua has no known adverse affects on humans. (Van Nieuwenhuyse, et al., 2008)

Conservation Status

Athene noctua is listed by the International Union for Conservation of Nature and Natural Resources (IUCN) Red List as least concern. However, there is a documented decline seen throughout Europe of not only little owls, but also other owls. It is important to research little owls to gather information about the general decline of owls. The main contributors to population decline are prey and nest availability and human habitat destruction. The development of nest boxes appropriate for little owls has boosted numbers, while current conservation efforts focus on increasing food availability during the breeding season and gathering more information about the causes of decline. (Grzywaczewski, 2009; Le Gouar, et al., 2010; Thorup, et al., 2010; Tomé, et al., 2008; Van Nieuwenhuyse, et al., 2008; Zuberogoitia, et al., 2007; Żmihorski, et al., 2009)

Other Comments

Little owls have been associated with humanity for centuries. Athene noctua is seen as an omen of death, a sign of wisdom, and even a symbol of creators across time and civilizations. Little owls can be found on coins, medallions, in literature, and other works of art dating as far back as 8000 to 7500 BCE. The little owls were traded to hunt small birds and even used as domesticated pets. Athene noctua was the bird of Athena, the Greek Goddess of Wisdom, and the origin of the genus name Athene. Little owls can still be found in modern art today. Currently there are 12 recognized subspecies of Athene noctua: A. n. noctua, A. n. vidalii, A. n. indigena, A. n. glaux, A. n. saharae, A. n. lilith, A. n. bactriana, A. n. ludlowi, A. n. orientalis, A. n. plumipes, A. n. impasta, and A. n. spilogastra. (Van Nieuwenhuyse, et al., 2008)

Contributors

Kevin Hunt (author), Indiana University-Purdue University Fort Wayne, Mark Jordan (editor), Indiana University-Purdue University Fort Wayne, Rachelle Sterling (editor), Special Projects.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

chemical

uses smells or other chemicals to communicate

choruses

to jointly display, usually with sounds, at the same time as two or more other individuals of the same or different species

crepuscular

active at dawn and dusk

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

male parental care

parental care is carried out by males

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"

suburban

living in residential areas on the outskirts of large cities or towns.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5? N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

visual

uses sight to communicate

References

Grzywaczewski, G. 2009. Home range size and habitat use of the little owl Athene noctua in east Poland. Ardea, 97/4: 541-545.

Hardouin, L., D. Robert, V. Bretagnolle. 2008. A dusk chorus effect in a nocturnal bird: support for mate and rival assessment functions. Behavioral Ecology and Sociobiology, 62: 1909-1918.

Holsegård-Rasmussen, M., P. Sunde, K. Thorup, L. Jacobsen, N. Ottesen, S. Svenne, C. Rahbek. 2009. Variation in working effort in Danish little owls Athene noctua. Ardea, 97: 547-554.

Johnson, D., D. Van Nieuwenhuyse, J. Génot. 2009. Survey protocol for the little owl Athene noctua. Ardea, 97/4: 403-412.

Le Gouar, P., H. Schekkerman, H. van der Jeugd, A. Boele, R. van Harxen, P. Fuchs, P. Stroeken, A. van Noordwijk. 2010. Long-term trends in survival of a declining population: the case of the little owl (Athene noctua) in the Netherlands. Oecologia, 166(2): 369-379.

MØLLER, A. 2006. Sociality, age at first reproduction and senscence: comparative analyses of birds. Jornal of Evolutionary Biology, 19: 682-689.

Thorup, K., P. Sunde, L. Jacobsen, C. Rahbek. 2010. Breeding season food limitation drives population decline of the little owl Athene noctua in Denmark. Ibis: The International Journal of Avian Science, 152(4): 803-814.

Tomé, R., P. Catry, C. Bloise, E. Korpimäki. 2008. Breeding density and success, and diet composition of little owls Athene noctua in steppe-like habitats in Portugal. Ornis Fennica, 85: 22-32.

Van Nieuwenhuyse, D., J. Genot, D. Johnson. 2008. The Little Owl: Conservation, Ecology and Behavior of Athene noctua. Cambridge, New York: Cambridge University Press.

Zuberogoitia, I., J. Martínez, J. Zabala, J. Martínez, A. Azkona, I. Castillo, S. Hidalgo. 2008. Social interactions between two owl species sometimes associated with intraguild predation. Ardea, 96: 109-113.

Zuberogoitia, I., J. Zabala, J. Martínez, S. Hidalgo, J. Martínez, A. Azkona, I. Castillo. 2007. Seasonal dynamics in social behaviour and spacing patterns of the little owl Athene noctua. Ornis Fennica, 84: 173-180.

Żmihorski, M., J. Romanowski, G. Osojca. 2009. Habitat preferences of a declining population of the little owl, Athene noctua in Central Poland. Folia Zoologica, 58: 207-215.