Philippine Eagle-Owl Ketupa philippensis Scientific name definitions

40–43 cm (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ); no data on body mass. Smallish, rufous eagle-owl with small, outward-slanting ear tufts. Facial disc rufous buff; head , breast and upperparts tawny-rufous with broad dark brown stripes; wings and tail barred dark brown and rufous buff; upper throat unstreaked buff; lower breast to belly buffy white streaked dark brown; tarsi feathered to base of toes; irides bright yellow to golden yellow (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ); cere color similar to bill but darker, bill horn blue at base, paler at tip (2 Kennedy, R. S., P. C. Gonzales, E. C. Dickinson, H. C. Miranda, and T. H. Fisher (2000). A Guide to the Birds of the Philippines. Oxford University Press, Oxford, UK. Close ); toes pale grayish brown (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ). Juvenile undescribed.

Philippine Eagle-Owl has 10 full-length primaries (numbered distally, from innermost p1 to outermost p10), 15-17 secondaries (numbered proximally, from outermost s1 to innermost s14), 3 tertials (numbered distally, t1 to t3), and 12 rectrices (numbered distally, from innermost r1 to to outermost r6 on each side of the tail). Owls are diastataxic (see 3 Bostwick, K. S., and M. J. Brady (2002). Phylogenetic analysis of wing feather taxis in birds: macroevolutionary patterns of genetic drift? Auk 119(4):943–954. Close ) indicating that a secondary has been lost evolutionarily between what we now term s4 and s5. Geographic variation in appearance slight and subspecies differences based primarily on size; see Systematics: Subspecies for subspecific differences. See Molts for molt and plumage terminology. The following applies to both subspecies and is based on descriptions in Kennedy et al. (4 Kennedy, R. S., P. C. Gonzales, E. C. Dickinson, H. C. Miranda, and T. H. Fisher (2000). A Guide to the Birds of the Philippines. Oxford University Press, Oxford, UK and New York, NY, USA. Close ), König and Weick (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ), and Marks et al. (5 Marks, J. S., R. J. Cannings, and H. Mikkola (1999). Family Strigidae (Typical Owls). In Handbook of Birds of the World Volume 5: Barn Owls to Hummingbirds (J. del Hoyo, A. Elliott, J. Sargatal, N. J. Collar, Editors). Lynx Edicions, Barcelona, Spain. pp. 76–151. Close ) along with examination of Macaulay Library images; see Cramp (6 Cramp, S. (1985). The Birds of the Western Palearctic. Volume 4. Oxford University Press, Oxford, United Kingdom. Close ) and Pyle (7 Pyle, P. (1997). Flight-feather molt patterns and age in North American owls. Monographs in Field Ornithology no. 2. American Birding Association, Colorado Springs, CO, USA. Close , 8 Pyle, P. (2022). Identification Guide to North American Birds. Part I, Second Edition. Slate Creek Press, Forest Knolls, CA, USA. Close ) for more details on ageing large owls by molt patterns and flight-feather characteristics. Sexes are similar in all plumages; definitive appearance achieved following the third (or possibly sometimes the fourth) prebasic molt.

Natal Down

Undescribed. Natal down is white in most or all other Ketupa owls.

Juvenile (First Basic) Plumage

Generally resembles later plumages but juvenile body feathers soft and loose, somewhat similar to down in texture; feathers of lower undeparts particularly long and fluffy. Head can be rufous or brown; ear tufts are small or not visible, the outer feathers washed dusky; upperparts resemble later plumages in pattern; underparts are creamy with narrower streaks. Remiges, primary coverts, alula, and rectrices similar to Definitive Basic Plumage but rectrices narrower overall and more tapered at tip than adult rectrices. Juvenile remiges and rectrices may also have relatively distinct dark bars compared to basic feathers, with relatively small distance between adjacent bars; rectrices often have distinct pale buff tips.

Formative Plumage

Formative body feathering and upperwing coverts similar to those of Definitive Basic Plumage. Unlike older birds, all flight-feathers juvenile (as described above), uniform in shape, wear, and color pattern, and often more buff or cinnamon in tone than basic feathers due to fading and wear.

Second Basic Plumage

Similar to Definitive Basic Plumage but likely can be identified by retained juvenile wing and (sometimes) tail feathers mixed with a single generation of basic feathers. One to 4 primaries and 5–12 secondaries may usually be replaced among p5–p8, s1–s2, s5–s7, and s11–s17 (see Molts); 1–6 juvenile outer rectrices (among r4–r6) may also sometimes be retained. Juvenile feathers contrastingly worn, narrow, and with narrower and more distinct dark bars; replaced second basic rectrices can appear more juvenile-like than definitive rectrices.

Third Basic Plumage

Third Basic Plumage similar to Definitive Basic Plumage but in at least some birds it likely can be identified by retained juvenile feathers in wing mixed with two generations of basic feathers (see Molts). One to 6 juvenile primaries (among p2–p4 and p9–p10) and 1–5 juvenile secondaries (among s3–s4 and s7–s10) may be retained, these juvenile feathers contrastingly very worn, narrow, and with more-distinct dark bars. All juvenile remiges can probably be replaced by Third Prebasic Molt in which case Third Basic not separable from Definitive Basic Plumage. Some individuals may also be identified in Fourth Basic Plumage, as in other Ketupa and Bubo owls, by retained juvenile feathers in wing, most typically among p3, p10, s4, and/or s9–s10, mixed with three generations of basic feathers. Study is needed on replacement patterns in Ketupa owls.

Definitive Basic Plumage

Head including prominent ear tufts bright rufous to rufous brown, the crown with indistinct and narrow brown streaks and the facial disks sometimes tinged grayish or brownish; upperparts tawny rufous with narrow to broad brown streaks to brownish with rufous feather edgings, some lateral scapulars with buff outer webs forming two indistinct pale streaks; tail rufous-buff barred brown above, and off-white barred dusky on the underside. Upperwing coverts brown with tawny fringing, the greater coverts tipped buff; remiges brown with buff to rufous, oval-shaped bars to outer webs. Remiges and rectrices are broader and may show less distinct bars and terminal tops than found on juvenile feathers. Throat and sides of neck bright rufous to rufous brown, becoming paler tawny to brownish on upper breast and buff to cream on remaining underparts, distinctly streaked brown, the streaks becoming sparser ventrally and often absent on lower vent, femoral feathers, and undertail coverts; underwing coverts buff with dark tips to the greater coverts forming dark curved bar.

Definitive Basic Plumage is distinguished from other plumages by lack of juvenile remiges, the feathers being a mixture of 2-4 generations of basic feathers (see Molts), wider and darker than juvenile feathers, generally with more diffuse dusky bars, and with less contrast between replaced and retained feathers (see 7 Pyle, P. (1997). Flight-feather molt patterns and age in North American owls. Monographs in Field Ornithology no. 2. American Birding Association, Colorado Springs, CO, USA. Close , 8 Pyle, P. (2022). Identification Guide to North American Birds. Part I, Second Edition. Slate Creek Press, Forest Knolls, CA, USA. Close for more information on ageing by molt patterns in large owls).

Molt and plumage terminology follows Humphrey and Parkes (9 Humphrey, P. S., and K. C. Parkes (1959). An approach to the study of molts and plumages. Auk 76(1):1–31. Close ) as modified by Howell et al. (10 Howell, S. N. G., C. Corben, P. Pyle, and D. I. Rogers (2003). The first basic problem: a review of molt and plumage homologies. Condor 105:635–653. Close ). Under this nomenclature, terminology is based on evolution of molts along ancestral lineages of birds from ecdysis (molts) of reptiles, rather than on molts relative to breeding season, location, or time of the year, the latter generally referred to as “life-cycle” molt terminology (11 Jenni, L., and R. Winkler (2020). Moult and Ageing of European Passerines. Second edition. Bloomsbury, London, UK. Close ; see also 12 Pyle, P. (2022). Defining moults in migratory birds: a sequence-based approach. Journal of Avian Biology 2022(5):e02958. Close ). Humphrey-Parkes (H-P) and life-cycle nomenclatures correspond to some extent but terms are not synonyms due to the differing bases of definition. Prebasic molts often correspond to “post-breeding“ or “post-nuptial“ molts (the Second Prebasic Molt often equating to the "first post-breeding molt," etc.) and preformative molts often correspond to “post-juvenile“ molts. The terms prejuvenile molt and juvenile plumage are preserved under H-P terminology (considered synonyms of first prebasic molt and first basic plumage, respectively) and the former terms do correspond with those in life-cycle terminology.

As in other Ketupa and Bubo owls, Philippine Eagle-Owl exhibits a Complex Basic Strategy (cf. 10 Howell, S. N. G., C. Corben, P. Pyle, and D. I. Rogers (2003). The first basic problem: a review of molt and plumage homologies. Condor 105:635–653. Close 13 Howell, S. N. G. (2010). Molt in North American Birds. Houghton Mifflin Harcourt, Boston, MA and New York, NY, USA. Close ), including incomplete prebasic molts and a partial preformative molt but no prealternate molts (6 Cramp, S. (1985). The Birds of the Western Palearctic. Volume 4. Oxford University Press, Oxford, United Kingdom. Close , 5 Marks, J. S., R. J. Cannings, and H. Mikkola (1999). Family Strigidae (Typical Owls). In Handbook of Birds of the World Volume 5: Barn Owls to Hummingbirds (J. del Hoyo, A. Elliott, J. Sargatal, N. J. Collar, Editors). Lynx Edicions, Barcelona, Spain. pp. 76–151. Close , 7 Pyle, P. (1997). Flight-feather molt patterns and age in North American owls. Monographs in Field Ornithology no. 2. American Birding Association, Colorado Springs, CO, USA. Close , 8 Pyle, P. (2022). Identification Guide to North American Birds. Part I, Second Edition. Slate Creek Press, Forest Knolls, CA, USA. Close ).

Prejuvenile Molt

Complete, at the natal site. There is no information on timing or sequence of feather replacement; study is needed on the Prejuvenile Molt in Ketupa owls. Prejuvenile Molt appears to be completed prior to fledging.

Preformative Molt

The Preformative Molt in Ketupa owls includes all body feathers and upperwing coverts but no remiges, primary coverts, or rectrices (6 Cramp, S. (1985). The Birds of the Western Palearctic. Volume 4. Oxford University Press, Oxford, United Kingdom. Close , 5 Marks, J. S., R. J. Cannings, and H. Mikkola (1999). Family Strigidae (Typical Owls). In Handbook of Birds of the World Volume 5: Barn Owls to Hummingbirds (J. del Hoyo, A. Elliott, J. Sargatal, N. J. Collar, Editors). Lynx Edicions, Barcelona, Spain. pp. 76–151. Close ). Based on Macaulay images this appears to be the case for Philippine Eagle-Owl.

Second Prebasic Molt

Incomplete. Second Prebasic Molt may averages earlier in year than Definitive Prebasic Molt due to lack of constraints related to breeding in most one-year-old individuals. In Ketupa and Bubo owls, the Second Prebasic Molt includes most or all body feathers and upperwing secondary coverts (study needed on extent of secondary covert replacement during prebasic molts), 0–4 primaries (none, p6 or p7 only, p5–p6 or p6-p7, or up to p5–p8) and corresponding primary coverts, 5-12 secondaries (among s1–s2, s5–s7, and s11–s17), and 6 to (usually) all 12 rectrices; retained rectrices, if present, usually among r4–r6 on each side of tail. See Definitive Prebasic Molt (below) for more information on sequence.

Third Prebasic Molt

Incomplete. In other Bubo and Ketupa owls, these molts include most or all body feathers and upperwing secondary coverts, 1–5 primaries and corresponding primary coverts, 4–10 secondaries, and usually all 12 rectrices. During Third Prebasic Molt, replaced primaries and secondaries continue in sequence from positions where arrested during Second Prebasic Molt. Sometimes all juvenile remiges may be replaced by Third Prebasic Molt but more often 1–5 juvenile primaries (among p1–p4 and p10) and corresponding primary coverts, and 1–5 juvenile secondaries (among s3–s4 and s7–s10) retained following this molt. Fourth Prebasic Molt continues in sequence from where the Third Prebasic Molt arrested, and perhaps occasionally in Philippine Eagle-Owl, 1–4 juvenile remiges may be retained following Fourth Prebasic Molt, most often among p2-p3, s4, and/or s9–s10. See Definitive Prebasic Molt (below) for more information on sequence. Study is needed on extents and retention patterns following the Second and Third Prebasic Molts in genus Ketupa including Philippine Eagle-Owl.

Definitive Prebasic Molt

Prebasic molts include complex and bilateral (both distal and proximal) replacement sequence within primaries, as occurs in many owls, with commencement (nodal) position generally occurring more distally in larger genera than in smaller genera (7 Pyle, P. (1997). Flight-feather molt patterns and age in North American owls. Monographs in Field Ornithology no. 2. American Birding Association, Colorado Springs, CO, USA. Close ,8 Pyle, P. (2022). Identification Guide to North American Birds. Part I, Second Edition. Slate Creek Press, Forest Knolls, CA, USA. Close ). In Ketupa and Bubo owls (including Philippine Eagle-Owl) molt appears to commence at p7 (or apparently p6 in some Ketupa owls) and proceeds bilaterally, but also can commence at p1 and proceed distally before the proximal wave reaches p1, resulting in last feather being replaced usually among p2–p4 (6 Cramp, S. (1985). The Birds of the Western Palearctic. Volume 4. Oxford University Press, Oxford, United Kingdom. Close , 14 Pyle, P. (2022). Examination of digital images from Macaulay Library to determine avian molt strategies: a case study on molts and plumages in eight species of North American hummingbirds. Wilson Journal of Ornithology 134:52–65. Close ). Secondaries are replaced proximally from s1 or perhaps sometimes bidirectionally from s2 (15 Solheim, R. (2012). Wing feather moult and age determination of Snowy Owls Bubo scandiacus. Ornis Norvegica 35:48-67. Close ), proximally from s5, and distally from the tertials, often with a node at the middle tertial. The last secondaries replaced in sequence are thus most often among s3–s4 and s7–s10. Rectrices are generally replaced distally from r1 on each side of tail, with the outer rectrix (r6) sometimes replaced before adjacent inner rectrices (r4–r5).

Annual prebasic molts can be variable in extent, often ranging from 0–6 primaries and 4–12 secondaries replaced per molt. New replacement sequence commences before all feathers of previous sequence replaced, similar to birds with Staffelmauser most strategies (16 Stresemann, E. and V. Stresemann (1966b). The molt of birds. Journal of Ornithology 107 (Supplemental):1-448. Close , 8 Pyle, P. (2022). Identification Guide to North American Birds. Part I, Second Edition. Slate Creek Press, Forest Knolls, CA, USA. Close ); thus, last juvenile feathers replaced may not occur until Fourth Prebasic Molt or later. Small variations can occur between wings in extent, leading to lack of symmetry in replacement patterns in older birds following multiple prebasic molts. Rectrices more-often completely replaced each year, up to 6 sometimes be retained.

Bill and Cere

Horn-blue at base, paler at tip; cere similar but darker (4 Kennedy, R. S., P. C. Gonzales, E. C. Dickinson, H. C. Miranda, and T. H. Fisher (2000). A Guide to the Birds of the Philippines. Oxford University Press, Oxford, UK and New York, NY, USA. Close ); tip often greenish in older birds.

Iris

Bright yellow to golden yellow (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ).

Tarsi and Toes

Dark grayish; toes grayish brown (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ), with dark horn to blackish-brown claws. Legs feathered.

Ketupa philippensis was long treated in the genus Bubo, but it has been found that the genus Ketupa is embedded within the traditional Bubo, while Scotopelia either may be embedded with the Ketupa group of species, or perhaps is sister to this clade (17 Salter, J. F., C. H. Oliveros, P. A. Hosner, J. D. Manthey, M. B. Robbins, R. G. Moyle, R. T. Brumfield, and B. C. Faircloth (2020). Extensive paraphyly in the typical owl family (Strigidae). Auk: Ornithological Advances 137:1–15. Close , 18 WInk, M., and H. Sauer-Gürth (2021). Molecular taxonomy and systematics of owls (Strigiformes) - an update. Airo 29:487-500 Close ). Provisionally we recognize three genera: Bubo (Old and New World); Ketupa (tropical Afro-Asian, including some species formerly included in Bubo); and Scotopelia. Note that Ketupa is expanded to include eight species previously classified in Bubo; four of these (Ketupa poensis, Ketupa lactea, Ketupa nipalensis, and Ketupa sumatrana) are confirmed by genetic data as belonging to the Ketupa clade (18 WInk, M., and H. Sauer-Gürth (2021). Molecular taxonomy and systematics of owls (Strigiformes) - an update. Airo 29:487-500 Close ), while the remaining four (Ketupa shelleyi, Ketupa coromanda, Ketupa leucosticta, and Ketupa philippensis) are inferred to belong to Ketupa based on morphological similarities to species of the first group. In the past, Ketupa philippensis was sometimes also placed in monotypic genus Pseudoptynx.

Two subspecies recognized.

Relationships of Ketupa philippensis have not been studied. Its placement within Ketupa is inferred based on morphological similarities to others in the genus.

Northern, eastern, and southeastern Philippines: Luzon, Catanduanes, Samar, Leyte, Bohol, and Mindanao.

Lowland forest , forest edge and lower montane forest, often near rivers or lakes. Also found in coconut plantations and patches of second-growth forest (2 Kennedy, R. S., P. C. Gonzales, E. C. Dickinson, H. C. Miranda, and T. H. Fisher (2000). A Guide to the Birds of the Philippines. Oxford University Press, Oxford, UK. Close ); occurs up to ca. 1,025 m elevation on Luzon, 1,170 m on Mindanao (19 Mallari, N. A. D., M. J. Crosby, and N. J. Collar (2004). Unexplored Philippine forests as revealed by point-locality mapping. Forktail 20:124-128. Close ).

Resident (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ).

No information; large and powerful feet and bill suggest that diet composed of small mammals or birds (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ).

Varied and not well understood. Male reported to give series of low staccato notes at intervals of c. 4 seconds: bububububu bububububu bububububu.... (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ). Also a series of cries, aheeehhh (xeno-canto: XC79257) or eeehhh, repeated every 3 or 4 seconds (2 Kennedy, R. S., P. C. Gonzales, E. C. Dickinson, H. C. Miranda, and T. H. Fisher (2000). A Guide to the Birds of the Philippines. Oxford University Press, Oxford, UK. Close ).

No information from wild birds (2 Kennedy, R. S., P. C. Gonzales, E. C. Dickinson, H. C. Miranda, and T. H. Fisher (2000). A Guide to the Birds of the Philippines. Oxford University Press, Oxford, UK. Close , 1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ). Has nested in captivity multiple times at the NFEFI-Biodiversity Conservation Centre, Negros Occidental, Philippines, but details apparently unpublished (20 Warburton, T. (2009). The Philippine Owl Conservation Programme: why is it needed? Ardea 97(4):429-438. Close ).

VULNERABLE. Previously listed as Endangered. CITES II. Rare; very few recent records, most from Luzon ; unexpected sighting in 1994 on Bohol, where previously unrecorded; found in lower montane forest in Mount Kaluayan–Mount Kinabalian complex, Mindanao, in 1998 (19 Mallari, N. A. D., M. J. Crosby, and N. J. Collar (2004). Unexplored Philippine forests as revealed by point-locality mapping. Forktail 20:124-128. Close ). Global population estimated to be 2,500–10,000 individuals. Rapid population decline due to extensive lowland habitat destruction, and possibly hunting. The presence of more than 10 individuals kept in Manila Zoo in 1994 would seem to indicate that species may be locally less rare than scarcity of records suggests.