Chestnut-bellied Monarch Monarcha castaneiventris Scientific name definitions

Taxonomic note: This account has source material from a combination of multiple species accounts originally published in HBW Alive. Moving forward we will create a more unified account for this parent taxon. Please consider contributing your expertise to update this account.

The Chestnut-bellied Monarch is widespread across the Solomon Islands. Historically, the taxonomy of the Chestnut-bellied Monarch has been complex, and has included multiple taxa that are not recognized here as species, with variation noted in size, song, plumage, and sexual dimorphism. All of the taxa recognized in this account are all sexually monochromatic, but subspecies vary from glossy black above with chestnut bellies to solidly black. Chestnut-bellied Monarch as treated here includes 4 subspecies divided into 3 groups, the nominate "Chestnut-bellied" group, the "Makira" group, and the "Ugi" group. The "Makira" and "Ugi" groups have recently been considered to be distinct species by some authorities (1 del Hoyo, J., and N. J. Collar (2016). HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 2: Passerines. Lynx Edicions, Barcelona, Spain. Close ) on the basis of vocal and phenotypic differences (2 Uy, J.A.C., Moyle, R.G. and Filardi, C.E. (2009). Plumage and song differences mediate species recognition between incipient flycatcher species of the Solomon Islands. Evolution 63(1): 153–164. Close ).

Chestnut-bellied Monarch (Chestnut-bellied)

17 cm; 22–32 g. Medium-sized, glossy blue-black monarch. Male nominate race has head to centre of breast, sides of neck and upperparts, including flight-feathers and tail, glossy bluish black; rest of underparts and axillaries chestnut; iris dark; bill bluish grey, tip black; legs and feet bluish grey or lead-grey. Female is less glossy above, especially on wings and tail. Juvenile undescribed; immature resembles adult except browner wings and tail. Race obscurior is similar to nominate but darker and has more metallic gloss, blackish below more extensive, reaching further onto breast, and upper flanks and axillaries mostly black.

Chestnut-bellied Monarch (Makira)

c. 17–18 cm; 22–33 g. Medium-sized, largely glossy blue-black monarch. Male has entire head down to centre of breast, neck-sides and upperparts, including flight-feathers and tail, glossy bluish black; rest of underparts , as well as axillaries, chestnut; iris dark; bill bluish grey, tip black; legs blue-grey or lead-grey. Distinguished from <em>M. castaneiventris</em> by larger bill and longer wings and tail (tail up to 10 mm longer). Female is similar to male but less glossy above, especially on wings and tail. Juvenile is apparently undescribed.

Chestnut-bellied Monarch (Ugi)

c. 18 cm; 28–33·5 g. Medium-sized, glossy blue-black monarch. Adult plumage is entirely glossy bluish black , but wings are often browner (presumably when plumage is worn); iris dark; bill pale bluish-grey, tip sometimes black; legs lead-grey. Sexes like. Juvenile apparently identical, but may show some tawny fringes on feathers of lower belly.

Editor's Note: This article requires further editing work to merge existing content into the appropriate Subspecies sections. Please bear with us while this update takes place.

The taxonomy of the Chestnut-bellied Monarch is messy, and has at times consisted of 6 subspecies, with varying levels of plumage differentiation, song differences, and sexual dimorphism. Some groups have already been split out and recognized as distinct species here, including M. c. richardsii, here called the White-capped Monarch (M. richardsii), and M. c. erythrostictus, here called the Bougainville Monarch (M. erythrostictus). While most authorities now recognize the White-capped Monarch as distinct (3 Dickinson, E. C., and L. Christidis, Editors (2014). The Howard and Moore Complete Checklist of the Birds of the World. Fourth Edition. Volume 2. Aves Press, Eastbourne, UK. Close , 4 Clements, J. F., T. S. Schulenberg, M. J. Iliff, S. M. Billerman, T. A. Fredericks, B. L. Sullivan, and C. L. Wood (2019). The eBird/Clements Checklist of Birds of the World: v2019. Cornell Laboratory of Ornithology, Ithaca, New York, USA. Close ), there is less agreement on the other taxa in this complex. For instance, based on genetic data from Uy et al. (2 Uy, J.A.C., Moyle, R.G. and Filardi, C.E. (2009). Plumage and song differences mediate species recognition between incipient flycatcher species of the Solomon Islands. Evolution 63(1): 153–164. Close ), the Bougainville Monarch may not be distinct from Chestnut-bellied Monarch, appearing to be embedded within nominate castaneiventris, and may best be treated as a subspecies, a move some authorities have already taken (3 Dickinson, E. C., and L. Christidis, Editors (2014). The Howard and Moore Complete Checklist of the Birds of the World. Fourth Edition. Volume 2. Aves Press, Eastbourne, UK. Close , 1 del Hoyo, J., and N. J. Collar (2016). HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 2: Passerines. Lynx Edicions, Barcelona, Spain. Close ). The birds from Makira (megarhynchus) and its satellite islands (ugiensis) present a different case. Genetically, these two subspecies form a well-supported group that may not be easily distinguishable from each other (2 Uy, J.A.C., Moyle, R.G. and Filardi, C.E. (2009). Plumage and song differences mediate species recognition between incipient flycatcher species of the Solomon Islands. Evolution 63(1): 153–164. Close ). However, these two subspecies differ substantially in plumage (megarhynchus has a chestnut belly, ugiensis is all black) and song, and experimental evidence suggests that the two are able to differentiate each other on the basis of plumage (5 Uy, J. A. C., R. G. Moyle, C. E. Filardi, and Z. A. Cheviron (2009). Differences in plumage color used in species recognition between incipient species is linked to a single amino acid substitution in the melanocortin-1 receptor. The American Naturalist 174(2):244-254 Close ).

Chestnut-bellied Monarch (Makira)

Chestnut-bellied Monarch (Ugi)

Chestnut-bellied Monarch (Chestnut-bellied)

Primary forest and, less frequently, tall secondary forest, from sea-level to mountains, reaching c. 1450 m (rare above 1100 m).

Chestnut-bellied Monarch (Makira)

Primary forest and tall secondary forest, from sea-level to mountain tops at c. 1040 m.

Chestnut-bellied Monarch (Ugi)

Coastal forest , including beach forest and scrub.

Chestnut-bellied Monarch (Chestnut-bellied)

Resident.

Chestnut-bellied Monarch (Makira)

Resident.

Chestnut-bellied Monarch (Ugi)

Resident.

Chestnut-bellied Monarch (Chestnut-bellied)

Food items not well known; mainly small invertebrates. Solitary or in pairs, but mostly in small parties and mixed-species foraging flocks. Forages actively and methodically among outer foliage of middle levels to upper canopy of forest trees; also pursues insects in flight, and hovers while taking insect prey from outer edges of foliage.

Chestnut-bellied Monarch (Makira)

Few data. Diet mostly small invertebrates. Forages singly or in pairs, often in small parties and with mixed-species flocks, in outer foliage of trees. Behaviour not known to differ significantly from that of M. castaneiventris.

Chestnut-bellied Monarch (Ugi)

Diet and foraging behaviour not recorded; presumably much as for M. megarhynchus and M. castaneiventris.

Chestnut-bellied Monarch (Chestnut-bellied)

Song a rapid series of whistles, “kwee kwee kwee kwee kwee.” Calls mostly a series of harsh buzzing or rasping notes, a harsh “chak” and a quiet “squirk” or “whirr” contact note while foraging; similar to calls of M. richardsii.

Chestnut-bellied Monarch (Makira)

Presumed song is a repeated fluting whistle, lasting c. 0·5 seconds, with a rising part and a falling part, usually one of the two parts is emphasized and has the larger frequency range (quite unlike the rather flat-pitched whistle of M. castaneiventris or the three-note song of M. ugiensis). Calls include a fast series of raspy notes and loosely repeated single grating “krr” notes.

Chestnut-bellied Monarch (Ugi)

Poorly documented. Presumed song consists of three whistles, the middle one by far the longest, “du-wheee-it”. Also emits a fast series of raspy notes , “reh-reh-reh”.

Chestnut-bellied Monarch (Chestnut-bellied)

One observation of an adult feeding a fledged juvenile Brush Cuckoo (Cacomantis variolosus) on Guadalcanal, in Jul, and most males collected on Isabel in Jun/Jul were in breeding condition. No other information available.

Chestnut-bellied Monarch (Makira)

No information.

Chestnut-bellied Monarch (Ugi)

No information available.

Chestnut-bellied Monarch (Chestnut-bellied)

Not globally threatened (Least Concern). Restricted-range species: present in Solomon Group EBA. This species’ global population size has not been quantified, but it appears to be generally common within its rather large range. Common in reasonably undisturbed forest and relatively common in degraded forest. Its total population, however, is suspected to be in decline as a result of rapid rate of logging across lowland forests of Solomon Is.

Chestnut-bellied Monarch (Makira)

Not globally threatened (Least Concern). Restricted-range species: present in Solomon Group EBA. Common to fairly common, and a recent survey found this species to be most abundant in garden habitat, but is also reasonably numerous in secondary forest and mixed cocoa plantations, and is apparently least common in intact forest and cocoa monocultures. Global population size not yet quantified. This species is suspected to be in decline as a result of the continuing rapid logging of lowland forests throughout most of the Solomons including Makira.

Chestnut-bellied Monarch (Ugi)

Not globally threatened (Least Concern). Restricted-range species: present in Solomon Group EBA. The global population size of this species has not been quantified, but it appears to be reasonably common within its very small range. The ongoing rapid logging of lowland forests throughout the Solomon Is suggests, however, that its numbers may be suffering a slow decline.