Pel's fishing owl
Pel's fishing owl is a large species of owl in the family Strigidae. The species is found in Africa and lives near rivers and lakes. It feeds nocturnally on fish and frogs snatched from the surface of lakes and rivers. The species prefers slow moving rivers with large overhanging trees to roost and forage from. It nests in hollows and the forks of large trees. Though as many as two eggs are laid, often only one chick is raised.
Taxonomy
The species' common and specific name honours Hendrik Severinus Pel, who was governor of the Dutch Gold Coast from 1840 till 1850.Description
Pel's fishing owl is one of the largest owl species in the world. Among the world's owls, it ranks as the fifth heaviest on average, the seventh longest in length and measured wing chord and fourth longest in mean wingspan, although not all large species have had measured wingspans. It measures in length, spans around across the wings and weighs up to at least. One male was found to weigh and four females averaged, it may outrival the snowy owl as the fifth or sixth heaviest living owl on average. Under current classification, it is the heaviest extant owl outside of the genus Bubo, although some authors may also include the fishing owls in Bubo. Among standard measurements, the wing chord is and the tail is long. They are well adapted to their aquatic lifestyle. Unlike most owls, they have minimal feathering on the toes and the tarsus, thus minimizing the amount of plumage that gets wet while fishing. Like diurnal raptors that specialize in fish, they have spiky scales on the bottoms of their feet that help them grip slippery fish. Since hearing and auditory stealth is not important to its hunting techniques, this owl does not have strong hearing and does not have the soft edges to its flight feathers that most owls share, which makes them almost impossible to hear in flight.Adults are colored a rich ginger-rufous with dense dark bars to the upperparts and scaling to the underparts. The feathers around the head are loose and long, giving the head a shaggy appearance. The tarsi and toes are unfeathered and straw-colored. The white throat is often largely obscured but can be puffed up in displaying birds during courtship. The flight and tail feathers are barred with lighter and darker feathers. The eyes are distinctly dark, often blackish in color. The two adult sexes are similar looking but females are generally less rufous in color and have a more indistinct facial disc. There is considerable variation in coloration and barring in adult birds, with some birds having extensive pale feathers with others having several blackish markings. Juveniles are more uniform buff than adults. Unlike the eagle-owls, the ear tufts of the Pel's fishing owl are barely visible, giving it a very round-headed appearance. The two related fishing owls are smaller and lack the dark barring and scaling.
The song of the male Pel's fishing owl is a deep, sonorous, horn-like boom, first a single and then a higher pitched huhuhu. The male also utters a ringed hoot, much higher pitched than those of most eagle-owls, followed by a deep, soft grunt: whoommmm-wot or hooomm-hut. The calls of the male are repeated every 10 to 20 seconds and can be heard from up to away. While singing, the male's throat and breast are often highly inflated. The female's songs are similar but are higher pitched and even in a double-note, i.e. hoot-oot. Females and young at the nest wail a shrill wheeoouu while anticipating food.
Distribution and habitat
It is found throughout a large part of sub-Saharan Africa, but it is generally rather local, uncommon and absent from drier regions. It is patchily distributed in Nigeria, Senegal, the Gambia, Guinea, Sierra Leone and in central Africa from the coast to eastern Zaire and discontinuously to South Sudan, Somalia, Kenya and Tanzania and southwards to Zimbabwe, Botswana and eastern South Africa.The Pel's fishing owl is found in forests along rivers and lakes. They can found in swamps and estuaries at sea level up to an elevation of around. Their favorite habitat is riverine forests with large trees, although large numbers are also found on islands with large, old trees within larger rivers, swamps or lakes, so long as the islands are not too far from the bank. The species is largely residential and has no seasonal movement, although young, non-breeding birds may wander somewhat before claiming their own territories. Pel's fishing owl may move outside of their own range in pursuit of prey.
Behaviour
In general, this species is nocturnal and is most vocally active on moonlit nights, especially near dawn. However, they are sometimes seen to be active during the day, especially when prey is scarce. During the daytime, they usually roost on a large tree branch. Often, the male and female roost together. At dusk, they leave the roost and instead perch on stumps, branches and other objects that extend over the water.Diet and feeding
The main prey of Pel's fishing owl is fish. They can take fish weighing as much as but the majority of fish caught are much smaller, usually weighing. They are not picky eaters among fish species and any fish that is in a reasonable size range and found close to the water's surface is readily caught and consumed. Compared with the fish owls in the genus Bubo, the three fishing owls are more completely piscivorous and rarely vary their prey selection from fish. However, seldom, they will also take other aquatic animals such as frogs, crabs, mussels and large insects. In one case, a Pel's fishing owl was observed to predate a baby Nile crocodile. While perched over the water, these owls detect the movement of fish from ripples in the water and swoop down to seize their prey with their powerful talons and then swoop back to their perch for consumption. Unlike many other fish-eating birds, Pel's fishing owl rarely submerge themselves or get particularly wet while hunting. More uncommonly, this species will forage by wading into shallow water along sandbanks.Breeding
Pel's fishing owls nest during the dry season, which has the benefit of lower, clearer water and thus more easily detectable fish. They are monogamous and territorial, claiming a stretch of river or lakeshore for themselves. All life history activity in the species occurs within striking distance of water. Territories are claimed by hooting at the start of the breeding season. When prey selection is good, populations can be quite dense. At such bountiful times, territories are often quite small with the central activity of breeding pairs sometimes occurring within of each other. In Botswana, 23 territories were found along 60 km of river and, in Kruger National Park, up to 8 pairs can be found in an 18 km stretch of the Levubu River.The nest is a natural hollow or cavity in an old shady tree close to the water, quite often around where thick branches emerge from the trunk. The clutch size is typically one or two eggs, which average in length and weigh around. The female lays the eggs when water's at its peak or starting to fall, so that brood feeding coincides with low water and concentrated prey. The female does all incubation for around 32 days, while the male feeds her. If there is more than one egg, hatching occurs at 5-day intervals. The second chick often disappears, probably due to starvation. At hatching, the chick weighs, with their eyes opening 7 days later. Within 20 days, their weight increases to around and then balloons to around by the time they are 68 to 70 days old. The young remain in their parent's territory for 6 to 9 months after fledging and resemble the adult by around 10 months of age. At the first sight of danger to their offspring, both parents may engage in distraction displays. These consists of behaving as if injured, to draw the attention of potential predators, and penetrating screeches. Pel's fishing owls may attack African fish eagles which come too close to their nests. The fish eagles and Verreaux's eagle-owls are perhaps the only predatory threat to this species, though encounters between the two large owls are likely very rare due to significantly different habitat preferences. Due to the relatively late stage at which the young become fully independent, Pel's fishing owls usually only breed in alternate years.