page_title: Eurasian eagle-owl
section_title: Standard measurements and physiology
hierarchical_section_title: Eurasian eagle-owl / Description / Standard measurements and physiology
caption_attribution_description: Bubo bubo English: An Eurasian Eagle-owl at British Wildlife Centre, Surrey, England.
context_page_description: The Eurasian eagle-owl is a species of eagle-owl that resides in much of Eurasia. It is also called the European eagle-owl and in Europe, it is occasionally abbreviated to just the eagle-owl. It is one of the largest species of owl, and females can grow to a total length of 75 cm, with a wingspan of 188 cm, males being slightly smaller. This bird has distinctive ear tufts, with upper parts that are mottled with darker blackish colouring and tawny. The wings and tail are barred. The underparts are a variably hued buff, streaked with darker colour. The facial disc is not very visible and the orange eyes are distinctive.
  The Eurasian eagle-owl is one of the largest living species of owl as well as one of the most widely distributed. The Eurasian eagle-owl is found in many habitats but is mostly a bird of mountain regions, coniferous forests, steppes and other relatively remote places, and have occasionally been found near farmland and in park-like settings within European cities; in 2020, a brood of three chicks were raised by their mother on a large, well-foliaged planter on an apartment window in the city centre of Geel, Belgium.
context_section_description: Among standard measurements for the Eurasian eagle-owl, the wing chord measures 378 to 518 mm (14.9 to 20.4 in), the tail measures 229–310 mm (9.0–12.2 in) long, the tarsus measures 64.5–112 mm (2.54–4.41 in) and the total length of the bill is 38.9–59 mm (1.53–2.32 in). The wings are reportedly the smallest in proportion to the body weight of any European owl, when measured by the grams per square cm of wing size, was found to be 0.72. Thus they have quite high wing loading. The great horned owl has even smaller wings (0.8 grams per square cm) relative to its body size. The golden eagle has slightly lower wing loading proportionately (0.65 grams per square cm), so the aerial abilities of the two species (beyond the eagle’s spectacular ability to stoop) may not be as disparate as expected. Some other owls, such as barn owls, short-eared owls (Asio flammeus) and even the related snowy owls have lower wing loading relative to their size and so are presumably able to fly faster, with more agility and for more extended periods than the Eurasian eagle-owl. In the relatively small race B. b. hispanus, the middle claw, the largest talon, (as opposed to rear hallux-claw which is the largest in accipitrids) was found to measure from 21.6 to 40.1 mm (0.85 to 1.58 in) in length. A 3.82 kg (8.4 lb) female examined in Britain (origins unspecified) had a middle claw measuring 57.9 mm (2.28 in), on par in length with a large female golden eagle hallux-claw. Generally, owls do not have talons as proportionately large as those of accipitrids but have stronger, more robust feet relative to their size. Accipitrids use their talons to inflict organ damage and blood loss, whereas typical owls use their feet to constrict their prey to death, the talons serving only to hold the prey in place or provide incidental damage. The talons of the Eurasian eagle-owl are very large and not often exceeded in size by diurnal raptors. Unlike the great horned owls, the overall foot size and strength of the Eurasian eagle-owl is not known to have been tested, but the considerably smaller horned owl has one of the strongest grips ever measured in a bird.
  The feathers of the ear tufts in Spanish birds (when not damaged) were found to measure from 63.3 to 86.6 mm (2.49 to 3.41 in). The ear openings (covered in feathers as in all birds) are relatively uncomplicated but are also large, being larger on the right than on the left as in most owls, and proportionately larger than those of the great horned owl. In the female, the ear opening averages 31.7 mm (1.25 in) on the right and 27.4 mm (1.08 in) on the left and, in males, averages 26.8 mm (1.06 in) on the right and 24.4 mm (0.96 in) on the left. The depth of the facial disc and the size and complexity of the ear opening are directly correlated to the importance of sound in an owl’s hunting behaviour. Examples of owls with more complicated ear structures and deeper facial disc are barn owls, long-eared owls (Asio otus) and boreal owls (Aegolius funereus). Given the uncomplicated structure of their ear openings and relatively shallow, undefined facial disc, hunting by ear is secondary to hunting by sight in the eagle-owl, this seems to be true for Bubo in general. It is likely that more sound-based hunters such as the aforementioned species focus their hunting activity in more complete darkness. Also owls with white throat patches such as the Eurasian eagle-owl are more likely to be active in low light conditions in the hours before and after sunrise and sunset rather than the darkest times in the middle of the night. The boreal and barn owls, to extend these examples, lack obvious visual cues such as white throat patches (puffed up in displaying eagle-owls), again indicative of primary activity being in darker periods.
caption: The wings have a wide spread
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