Vermiculated Fishing-Owl Scotopelia bouvieri Scientific name definitions

46–51 cm; female 637 g (n = 1) (1 Mikkola, H. (2014). Owls of the World. A Photographic Guide. 2nd edition. Firefly Books, Buffalo, NY, USA. Close ). Head buffy-rufous with black streaks on forehead, no ear tufts, inconspicuous light rufous facial disc  ; upperparts  variable, from pale rufous to darker brown or greyish (2 Turk, A. (2000). Fishing owls at Agenebode, Nigeria. Bulletin of the African Bird Club. 7(2): 107-108. Close ), with fine dark brown vermiculations, scapulars with variable whitish on outer webs; flight feathers and tail rufous with dark bars; underparts variably creamy to light rufous, with heavy dark brown streaks, undertail unmarked whitish; tarsi and toes unfeathered; irides dark brown; bill pale yellow  . Juvenile cinnamon-washed white on body and head, streaked above, finer streaking below, fligh feathers more rufous. Allopatric S. ussheri similar in size and general appearance but plain rufous-tawny above, less heavily streaked below and has bluish-grey to blackish-grey bill (3 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second edition. Christopher Helm, London, UK. Close , 4 Monticelli, D., Koroma, A.P. and Bannah, D. (2015). Observations of Rufous Fishing Owl Scotopelia ussheri in Sierra Leone. Bulletin of the African Bird Club. 22(2): 183–189. Close ).

Congo Basin in S Cameroon, Gabon, Central African Republic, Congo, DR Congo, and extreme NW Angola; also in S Nigeria and S Benin (2 Turk, A. (2000). Fishing owls at Agenebode, Nigeria. Bulletin of the African Bird Club. 7(2): 107-108. Close , 5 Dowsett, R. J., and F. Dowsett-Lemaire (2011). The avifauna of Benin: additions and corrections. Bulletin of the African Bird Club 18(2):148–167. Close ).

Gallery forest fringing large rivers, within primary forest; in some areas prefers rivers 10 m or more in width; also smaller rivers, and shallow, still pools in swamp-forest or temporarily flooded forest (6 Dowsett-Lemaire, F. (1996). A comment on the voice and status of Vermiculated Fishing-Owl Scotopelia bouvieri and a correction to Dowsett-Lemaire (1992) on the Maned Owl Jubula lettii. Bulletin of the African Bird Club. 3(2): 134-135. Close ); occasionally found well away from water (3 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second edition. Christopher Helm, London, UK. Close ).

Probably resident (3 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second edition. Christopher Helm, London, UK. Close ); may make similar movements to S. peli during periods of drought.

Small fish (especially Clarias catfish in Nigeria (2 Turk, A. (2000). Fishing owls at Agenebode, Nigeria. Bulletin of the African Bird Club. 7(2): 107-108. Close ) ), frogs, crustaceans, fiddler crabs, and small birds and mammals; appears to eat more crabs and crustaceans than other fishing-owls. Nocturnal. Hunts from perch 1–2 m above water.

The voice of Vermiculated Fishing-Owl long remained unknown, and auditive observations of its voice in the field were initially assigned to the little known Maned Owl (7 Dowsett-Lemaire, F. (1992). On the vocal behaviour and habitat of the Maned Owl Jubula lettii in south-western Congo. Bulletin of the British Ornithologists' Club 112(4): 213-218. Close ,6 Dowsett-Lemaire, F. (1996). A comment on the voice and status of Vermiculated Fishing-Owl Scotopelia bouvieri and a correction to Dowsett-Lemaire (1992) on the Maned Owl Jubula lettii. Bulletin of the African Bird Club. 3(2): 134-135. Close ).

Vocal Development

It is speculated that the Wail vocalization (see below) is uttered by large fledged young (in analogy with Pel's Fishing-Owl (Scotopelia peli)) (6 Dowsett-Lemaire, F. (1996). A comment on the voice and status of Vermiculated Fishing-Owl Scotopelia bouvieri and a correction to Dowsett-Lemaire (1992) on the Maned Owl Jubula lettii. Bulletin of the African Bird Club. 3(2): 134-135. Close ) as a begging call.

Vocal Array

Full song. Full song is a rhythmic phrase that consists of three parts: an initial series of well-spaced low-pitched hoots, followed by a bouncing accelerating series of some 5‒7 shorter hoots and ending with typically once or twice a double hoot: huuu.....huuu.....huuu.....huu-huu-huu-hu-hu-hu....huu-hu....huu-hu. Initial single hoots have a duration of 0.3‒0.4s and are rather flat-pitched with a maximum frequency ranging from 300‒450Hz, bouncing hoots are more overslurred and may shorten to just 0.1s (at same pitch as previous) and finishing double hoots again at same pitch, with first one slightly longer than second one.

Simple song. A simpler song form consists of only the first part of the full song: a long series of well-spaced identical single hoots. Such hooting may go on for minutes, with long pauses of some 5‒15s between hoots.

Duet. Simple song of one individual may be answered with single hoots from a second individual, presumably the mate. Usually there is a slight difference in pitch between the hoots of both birds. Alternatively, two birds can be heard uttering both the Full song at different pitch .

Wail. Recordings of a captive bird document a loud descending wail, repeated several times at intervals (8 Chappuis, C. (2000). African Bird Sounds. Volume 2. West and Central Africa. Société Ornithologique de France & British Library National Sound Archive, Paris & London. Close ). The Wailing note has a duration of about 1.75s and fundamental frequency starts around 600Hz, descends to about 400Hz with a further steep drop at the very end. Harmonics are strongly present, and start of note has a more raucous tonal quality. This vocalization has not yet been observed with certainty from birds in the wild, but a seemingly domesticated young bird in Gabon also uttered such long wailing notes, and after being fed would utter a slightly more excited hoarse rattled wail .

Geographic Variation

Little information. Only recently more recordings from different locations have become available. Full song has the same rhythmic structure everywhere and provides a simple way to identify this species in the field based on voice.

Phenology

Can be heard calling all year round, but peak of vocal activity said to be in May–October (9 König, C., and F. Weick (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ). There may be regional differences however, depending on breeding cycle.

Daily Pattern of Vocalizing

Vocalizing typically starts well after dark. Birds may sing intermittently throughout the night, and may continue until the early dawn chorus gradually takes over.

Places of Vocalizing

Typically sings while perched on a thick bare branch, rather well-exposed at middle levels in the canopy.

Sex Differences

LIttle information. It is assumed that both sexes utter Simple and Full song, with the female hooting at slightly higher pitch. This requires confirmation, however.

Social Context and Presumed Functions of Vocalizations

Male and female duet during courtship (9 König, C., and F. Weick (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ). In areas where populations are rather dense, several singing pairs may be heard from the same place, and thus evidently song has also a territorial function. There is no further information on breeding biology (9 König, C., and F. Weick (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ).

None documented.

Very little information. Lays May–Oct; in DR Congo probably as late as Nov–Dec (3 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second edition. Christopher Helm, London, UK. Close ). Uses old stick nest of large bird; recorded laying in nest of Spot-breasted Ibis (Bostrychia rara). Clutch size 1–2 eggs, usually only 1 nestling surviving (3 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second edition. Christopher Helm, London, UK. Close ); incubation and fledging periods unrecorded. Longevity more than 27 years in captivity.

Not globally threatened (Least Concern). CITES II. Little is known about its biology; this may be because of its secretive lifestyle and remote habitat preferences or because it exists in small numbers. However, may be relatively common on large rivers in the Congo Basin. No information on global population size or population trends, but numbers are thought to be stable in the absence of information on “substantial threats". Further study is necessary to quantify its status.