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Wednesday, October 13, 2010

Birds of prey - owls - maxi - Belgium



There are some 220 to 225 extant species of owls, in two families: typical owls (Strigidae) and barn-owls (Tytonidae). Some entirely extinct families have also been erected based on fossil remains; these differ much from modern owls in being less specialized or specialized in a very different way Berruornis and Ogygoptynx show that owls were already present as a distinct lineage some 60 - 57 mya (million years ago), and, hence, possibly also some 5 million years earlier, at the extinction of the non-avian dinosaurs. This makes them one of the oldest known groups of non-Galloanserae landbirds. The supposed "Cretaceous owls" Bradycneme and Heptasteornis are apparently non-avialan maniraptors.

Owls have large forward-facing eyes and ear-holes, a hawk-like beak, a flat face, and usually a conspicuous circle of feathers, a facial disc, around each eye. Most birds of prey sport eyes on the sides of their heads, but the stereoscopic nature of the owl's forward-facing eyes permits a greater sense of depth perception necessary for low-light hunting. Although owls have binocular vision, their large eyes are fixed in their sockets, as with other birds, and they must turn their entire head to change views. Owls can rotate their heads and necks as much as 270 degrees in either direction. Owls are farsighted and are unable to see anything clearly within a few centimeters of their eyes. Caught prey can be felt by owls with the use of filoplumes, which are small hair-like feathers on the beak and feet that act as "feelers". Their far vision, particularly in low light, is exceptionally good.

The smallest owl is the Elf Owl (Micrathene whitneyi), at as little as 31 g (1.1 oz) and 13.5 cm (5.3 inches). Some of the pygmy owls are scarcely larger. The largest owls are two of the eagle owls; the Eurasian Eagle Owl (Bubo bubo) and Blakiston's Fish Owl (Bubo blakistoni)—which may reach a size of 60 – 71 cm (28.4 in) long, have a wingspan of almost 2 m (6.6 ft), and an average weight of nearly 4.5 kg (10 lb).

Different species of owls make different sounds; the wide range of calls aids owls in finding mates or announcing their presence to potential competitors, and also aids ornithologists and birders in locating these birds and recognizing species. The facial disc helps to funnel the sound of prey to their ears. In many species, these are placed asymmetrically, for better directional location.[4][verification needed]

The plumage of owls is generally cryptic, but many species have facial and head markings, including face masks, ear tufts and brightly coloured irises. These markings are generally more common in species inhabiting open habitats, and are thought to be used in signalling with other owls in low light conditions.

I am posting here under a maxi card set of Belgium. The stamps are cancelled on 20-2-1999 at Ransart post office. The stamp portion with post mark is cut of and shown below for better view. First set of maxi card is shown below.  Second set follows.

My thanks to Wikipidea and other web authors. The information given above are, as appeared in different web sites.


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