Seychelles Swiftlet Aerodramus elaphrus Scientific name definitions

Occasionally considered conspecific with the slightly smaller Mascarene Swiftlet (Aerodramus francicus), from which it differs in its proportionately longer and broader-based wings, darker upperparts, deeper loral mask, and browner underparts, this is the only regularly occurring swift species in Seychelles. Nevertheless, the Seychelles Swiftlet is confined as a breeding bird to just three granitic islands in the archipelago, Mahé, Praslin and La Digue, although there are historical records from Felicité and the species has wandered to Aride and some other islands. Considered Vulnerable to extinction by BirdLife International, the population has been estimated at just 2,500‒3,000 mature individuals, based on assessments at know colonies, although the potential for finding additional nest sites, at least on Mahé, is considered to be quite high. The species perhaps breeds year-round, albeit with pronounced peaks in activity, in September‒October, January‒February and April‒May; it nests colonially in caves, building a bracket-shaped nest of grey-green lichen strands bound together with a large quantity of saliva.

Small swiftlet with forked tail; brown upperparts with rump marginally paler, underparts paler mid-brown. In hand has copious white rami of back feathers, and longer wings and larger bill than Mascarene Swiftlet (Aerodramus francicus). Sexes similar but juvenile apparently undescribed (1 Chantler, P., and G. Driessens (2000). Swifts: A Guide to the Swifts and Treeswifts of the World. 2nd edition. Pica Press, Robertsbridge, UK. Close , 2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ). Available information suggests species probably capable of echolocation.

Identification is relatively straightforward, as this is the only regularly occurring swift in Seychelles. Vagrants of Common Swift (Apus apus) and Pacific Swift (A. pacificus) are both much larger, longer-winged and longer-bodied, and the latter also has a white rump. Another vagrant, Little Swift (A. affinis) is also white-rumped, but is closer in size to the present species. Aerodramus francicus (no overlap) has proportionately shorter wings and shorter bill, a narrower wing base (evident in flight) with secondaries clearly shorter than the tertials, and appears less hirundine-like. Also compared to the latter, the present species has a larger eye set within a deeply recessed loral mask, whereas Mascarene Swiftlet has a relatively small eye and shallow loral mask.

Sexes alike; only adult plumage has been described. The following is from Safford and Hawkins (2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ).

Adult

Top of head blackish brown with slight oily green gloss; mantle, scapulars and back grayish brown, with concealed white rami to the feathers; rump and short uppertail-coverts also grayish brown, with white bases to the feathers; longest uppertail-coverts dark gray-brown, with greenish gloss; slightly forked tail (see Measurements) is blackish on upperside with oily green gloss, and brownish gray on the underside; primaries and primary-coverts blackish, secondaries and tertials and remaining upperwing-coverts dark gray-brown, and all upperwing feathers have an oily green gloss, which becomes more purplish in worn plumage; axillaries and underside to median and lesser coverts blackish gray, and underside to greater coverts and flight feathers brownish gray. Lores blackish brown, ear-coverts, cheek, sides of neck and breast gray-brown, behind eye clearly demarcated from darker cap, but otherwise grading gently into pale gray-brown chin, throat and rest of underparts, except darker gray-brown undertail-coverts with pale fringes and faint dusky shaft-streaks, the latter also being evident on the rear flank feathers.

All data from McDonald (3 McDonald, R.A. (1978). The biology of the Seychelles Cave Swiftlet Aerodramus (francicus) elaphrus. Pp. 92–112 in: Racey, P.A. ed. (1978). Aberdeen University Expedition to the Seychelles Report. Unpublished report. Close ) and Safford and Hawkins (2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ), the latter based on unpublished information. Molt of primaries and rectrices is centrifugal and centripetal, respectively, progressing symetrically and slowly, and probably is ongoing throughout much of the year; on Praslin during drier southeast monsoon, 72% of birds examined were in molt during July (n = 29), 75% (n = 20) in August, and 52% (n = 50) in September, and feather replacement has also been observed during wetter northwest monsoon on Mahé, where 50% were molting their primaries, 4% their secondaries, and 9% their rectrices (n = 151) during late February, but only 11% were replacing their primaries by late in the second week of March (n = 120).

Bill

Black (2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ).

Iris

Brown (2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ).

Legs and Feet

Gray (2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ).

Linear Measurements

Overall length 11 cm (4 Chantler, P. and Driessens, G. (2000). Swifts. A Guide to the Swifts and Treeswifts of the World. 2nd edition. Pica Press, Robertsbridge, UK. Close ).

Linear measurements (sexes combined, also including some unsexed individuals, in mm, sample sizes in parentheses):

Mass

10.7 g (5 Cheke, A. S. (1987). An ecological history of the Mascarene Islands, with particular reference to extinctions and introductions of land vertebrates. In Studies of Mascarene Island Birds (A. W. Diamond, Editor), Cambridge University Press, Cambridge, UK. pp. 5-89. Close ).

Sometimes considered conspecific with Mascarene Swiftlet (Aerodramus francicus) (6 Peters, J. L. (1940). Check-list of Birds of the World. Volume 4. Harvard University Press, Cambridge, MA, USA. Close , 7 Gaymer, R., Blackman, R.A.A., Dawson, P.G., Penny, M. and Penny, C.M. (1969). The endemic birds of Seychelles. Ibis 111(2):157–176. Close ).

None reported.

Monotypic.

Thought to be closest to Aerodramus francicus, and they are sometimes considered conspecific (6 Peters, J. L. (1940). Check-list of Birds of the World. Volume 4. Harvard University Press, Cambridge, MA, USA. Close , 7 Gaymer, R., Blackman, R.A.A., Dawson, P.G., Penny, M. and Penny, C.M. (1969). The endemic birds of Seychelles. Ibis 111(2):157–176. Close ), but have been isolated from one another for c. 500,000 years based on 1% divergence in the mitochondrial marker cytochrome b (8 Johnson, K. P. & Clayton, D. H. 1999. Swiftlets on islands: genetics and phylogeny of the Seychelles and Mascarene swiftlets. Phelsuma 7:9–13. Close ).

The species’ scientific name, elaphrus, is a Latinized Greek word meaning nimble or light.

No information.

Breeds on Mahé, Praslin and La Digue, in the granitic Seychelles (2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ). Formerly occurred on Felicité (9 Diamond, A.W. and Feare, C.J. (1980). Past and present biogeography of central Seychelles birds. Pp. 89–98 in: Johnson (1980). Close ).

Occurs over wide variety of habitats, including forest, boulder areas, rocky slopes, residential areas and a variety of wetland types, from sea level to highest mountains (930 m) in range (2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ).

Resident and broadly speaking sedentary. Recorded as a wanderer to Aride, Silhouette and North Island (10 Skerrett, A., I. Bullock, and T. Disley (2001). Birds of Seychelles. Christopher Helm, London, UK. Close ,2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ), and possibly other inner islands within the archipelago.

Flying ants and other Hymenoptera predominated (> 90%) in a study of food brought to young, with the remainder involving Diptera (flies, c. 5%), Hemiptera (< 1%), spiders and beetles (3 McDonald, R.A. (1978). The biology of the Seychelles Cave Swiftlet Aerodramus (francicus) elaphrus. Pp. 92–112 in: Racey, P.A. ed. (1978). Aberdeen University Expedition to the Seychelles Report. Unpublished report. Close ). Species is gregarious, foraging in groups numbering up to a dozen individuals, occasionally single, typically 5–20 m above ground (10 Skerrett, A., I. Bullock, and T. Disley (2001). Birds of Seychelles. Christopher Helm, London, UK. Close ), occasionally higher or lower (latter especially over wetlands), and tends to fly higher during middle of day and lower early morning and evening (7 Gaymer, R., Blackman, R.A.A., Dawson, P.G., Penny, M. and Penny, C.M. (1969). The endemic birds of Seychelles. Ibis 111(2):157–176. Close ,11 Penny, M. (1974). The Birds of Seychelles and the Outlying islands. Collins, London. Close ,12 Evans, P.G.H. (1977). Aberdeen University Expedition to Praslin, Seychelles, 1976: preliminary report. Unpublished report. Close ,3 McDonald, R.A. (1978). The biology of the Seychelles Cave Swiftlet Aerodramus (francicus) elaphrus. Pp. 92–112 in: Racey, P.A. ed. (1978). Aberdeen University Expedition to the Seychelles Report. Unpublished report. Close ,13 Watson, J. (1984). Land birds: endangered species on the granitic Seychelles. Pp. 513–527 in: Stoddart, D.R. ed. (1984). Biogeography and Ecology of the Seychelles Islands. Monographiae Biologicae 55, The Hague. Close ,2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ).

Uses echolocation inside nesting caves, emitting repeated high-bandwidth double clicks, sometimes also outside them (perhaps during mist or at other times when light levels are low (2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ). Echolocating clicks are very similar to those of Mascarene Swiftlet Aerodramus francicus and apparently also to those given by many Asian species of Aerodramus (14 Price, J. J., K. P. Johnson, and D. H. Clayton (2004). The evolution of echolocation in swiftlets. Journal of Avian Biology 35(2):135–143. Close ). The two sub-clicks have minimum and maximum frequencies of 1.91–4.71 kHz, for the first, and 1.78–5.90 kHz, for the second, respectively, with a mean 1.24-second silent interval between them (15 Thomassen, H.A. and Povel, G.D.E. (2006). Comparative and phylogenetic analysis of the echo clicks and social vocalizations of swiftlets (Aves: Apodidae). Biological Journal of the Linnean Society. 88(4):631–643. Close ). It has recently been hypothesized that these clicks serve in social interaction as well as echolocation (15 Thomassen, H.A. and Povel, G.D.E. (2006). Comparative and phylogenetic analysis of the echo clicks and social vocalizations of swiftlets (Aves: Apodidae). Biological Journal of the Linnean Society. 88(4):631–643. Close ). The clicks are sometimes prolonged into a rattle, and have been described as ‘a flat, medium- to high-pitched, rapid clacking ot ticking takakakakakak ... [at rate of] 2–3 notes/second’ (2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ). Also gives twittering calls, interspersed with the echolocating clicks, such as a ‘high-pitched squeaking riiik-riik-riiiiik-rieek moving slightly up and down scale, probably aggressive; or high-pitched, rapid chipping and trilling tiwwiiiwwwit ...; also a slightly lower chowii, each note lasting 0.5–1.0 second, repeated every 1–2 seconds’ (11 Penny, M. (1974). The Birds of Seychelles and the Outlying islands. Collins, London. Close ,16 Medway, Lord, and D. Pye (1977). Echolocation and the systematics of swiftlets. In Evolutionary Ecology (B. Stonehouse, and C. M. Perrins, Editors), Macmillan, London, UK. pp. 225–238. Close ,10 Skerrett, A., I. Bullock, and T. Disley (2001). Birds of Seychelles. Christopher Helm, London, UK. Close ,2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ).

May breed throughout year, and certainly extended as colonies visited early July 1970 contained eggs and young of various ages (17 Procter, J. (1972). The nest and the identity of the Seychelles Swiftlet Collocalia. Ibis 114(2):272–273. Close ); season initially thought to relate to southeast monsoon from June to November, but nest occupancy now known to peak in September–October, January–February, and April–May, which coincides with periods of highest rainfall (18 Rocamora, G. ed. (1997). Rare and Threatened Species, Sites and Habitats Monitoring Programme in Seychelles. Project G1 EMPS. Final Report. Vol. 1. Monitoring methodologies and priority actions. Ministry of Environment, BirdLife International & European Union, Cambridge, UK. Close ,2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ). Apparently monogamous and may pair for life (3 McDonald, R.A. (1978). The biology of the Seychelles Cave Swiftlet Aerodramus (francicus) elaphrus. Pp. 92–112 in: Racey, P.A. ed. (1978). Aberdeen University Expedition to the Seychelles Report. Unpublished report. Close ,2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ). Courtship display presumed to occur in flight, and mating in nest or in air (3 McDonald, R.A. (1978). The biology of the Seychelles Cave Swiftlet Aerodramus (francicus) elaphrus. Pp. 92–112 in: Racey, P.A. ed. (1978). Aberdeen University Expedition to the Seychelles Report. Unpublished report. Close ,2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ). Nests moderately to densely clustered, in caves located in granite boulder fields between 50 m and 250 m (2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ) at one site in a valley where two colonies of 14 and 23 nests in 1970 (17 Procter, J. (1972). The nest and the identity of the Seychelles Swiftlet Collocalia. Ibis 114(2):272–273. Close ). Bracket-shaped, self-supporting, tough and flexible nest of grey-green lichen strands (e.g. Lodoicea maldivica), dead Casuarina needles, or palm fronds, agglutinated with saliva, strong, yet dry and flexible, presumably constructed by both members of pair (17 Procter, J. (1972). The nest and the identity of the Seychelles Swiftlet Collocalia. Ibis 114(2):272–273. Close ,3 McDonald, R.A. (1978). The biology of the Seychelles Cave Swiftlet Aerodramus (francicus) elaphrus. Pp. 92–112 in: Racey, P.A. ed. (1978). Aberdeen University Expedition to the Seychelles Report. Unpublished report. Close ); nest hinge dark brown with large quantity of saliva; one nest on La Digue 55 mm high × 105 mm wide, with depression 35 mm front to back, but others deeper, but two on Praslin measured 60–65 mm (external diameter), 45–50 mm (internal diameter), 45–55 mm (external depth) and 30–35 mm (internal depth) (17 Procter, J. (1972). The nest and the identity of the Seychelles Swiftlet Collocalia. Ibis 114(2):272–273. Close ,3 McDonald, R.A. (1978). The biology of the Seychelles Cave Swiftlet Aerodramus (francicus) elaphrus. Pp. 92–112 in: Racey, P.A. ed. (1978). Aberdeen University Expedition to the Seychelles Report. Unpublished report. Close ,2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ). Clutch is probably always a single dull white egg; records of two eggs probably reflective of two different females laying in same nest (3 McDonald, R.A. (1978). The biology of the Seychelles Cave Swiftlet Aerodramus (francicus) elaphrus. Pp. 92–112 in: Racey, P.A. ed. (1978). Aberdeen University Expedition to the Seychelles Report. Unpublished report. Close ,19 Watson, J. (1979). Clutch sizes of Seychelles’ endemic land birds. Bull. Brit. Orn. Club 99(3):102–105. Close ,18 Rocamora, G. ed. (1997). Rare and Threatened Species, Sites and Habitats Monitoring Programme in Seychelles. Project G1 EMPS. Final Report. Vol. 1. Monitoring methodologies and priority actions. Ministry of Environment, BirdLife International & European Union, Cambridge, UK. Close ,2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ). Replacement clutches and fresh clutches after successful fledging within 14 days; incubation period estimated at 25–30 days (n = 1) and unknown whether both sexes share duties (2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ); fledging period c. 42 days, with both adults provisioning young, which fledge when > 10. 5 g (3 McDonald, R.A. (1978). The biology of the Seychelles Cave Swiftlet Aerodramus (francicus) elaphrus. Pp. 92–112 in: Racey, P.A. ed. (1978). Aberdeen University Expedition to the Seychelles Report. Unpublished report. Close ). Fledging success apparently very high (during a 1977 study on Praslin, no single chick death was observed), but in contrast hatching success is much lower, the latter probably due to human disturbance and eggs being accidentally cemented to the nest cups by adults, while on Praslin there is evidence that spontaneous nest dislodgement, apparently provoked by heavy rainfall, is a common factor in failure (and the same has been observed on La Digue), with sometimes fewer than 10% of nests surviving (3 McDonald, R.A. (1978). The biology of the Seychelles Cave Swiftlet Aerodramus (francicus) elaphrus. Pp. 92–112 in: Racey, P.A. ed. (1978). Aberdeen University Expedition to the Seychelles Report. Unpublished report. Close ,2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ). Re-laying after first clutch fails is apparently common, usually at least 14 days later, with all fresh nests being completed after c. 2–3 months (2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ).

VULNERABLE. Restricted-range species: present in Granitic Seychelles EBA (20 Stattersfield, A. J., M. J. Crosby, A. J. Long, and D. C. Wege (1998). Endemic Bird Areas of the World: Priorities for Biodiversity Conservation. BirdLife Conservation Series 7. BirdLife International, Cambridge, UK. Close ). Only three nesting sites are currently known: above Glacis, on Mahé, which site was discovered in 1992 (2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ); Mont Cabris, on Praslin (3 McDonald, R.A. (1978). The biology of the Seychelles Cave Swiftlet Aerodramus (francicus) elaphrus. Pp. 92–112 in: Racey, P.A. ed. (1978). Aberdeen University Expedition to the Seychelles Report. Unpublished report. Close ); and La Digue (17 Procter, J. (1972). The nest and the identity of the Seychelles Swiftlet Collocalia. Ibis 114(2):272–273. Close ). However, others reported in past, including a cave near Le Niol reservoir, on Mahé, which is now abandoned (13 Watson, J. (1984). Land birds: endangered species on the granitic Seychelles. Pp. 513–527 in: Stoddart, D.R. ed. (1984). Biogeography and Ecology of the Seychelles Islands. Monographiae Biologicae 55, The Hague. Close ); and on Praslin, cave of colony at L’Amitié has been destroyed, and colony believed to be at Fond d’Azore cannot be located (21 Collar, N. J., and S. N. Stuart (1985). Threatened Birds of Africa and Related Islands: the ICBP/IUCN Red Data Book. Part 1. Third edition. International Council for Bird Preservation and International Union for Conservation of Nature, Cambridge, United Kingdom, and Gland, Switzerland. Close ,2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ). Lack of additional suitable sites may limit both population and distribution. Disturbance, quarrying and vandalism have caused concern, and fitting of metal grilles across cave entrances has been recommended (21 Collar, N. J., and S. N. Stuart (1985). Threatened Birds of Africa and Related Islands: the ICBP/IUCN Red Data Book. Part 1. Third edition. International Council for Bird Preservation and International Union for Conservation of Nature, Cambridge, United Kingdom, and Gland, Switzerland. Close ). Vulnerable also to alien predators, especially feral cats and Barn Owls Tyto alba, and these require control, perhaps by fencing-off colonies; also, in past, perhaps pesticide use (21 Collar, N. J., and S. N. Stuart (1985). Threatened Birds of Africa and Related Islands: the ICBP/IUCN Red Data Book. Part 1. Third edition. International Council for Bird Preservation and International Union for Conservation of Nature, Cambridge, United Kingdom, and Gland, Switzerland. Close ,2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ). Overall population believed to number 2,500–3,000 birds and < 1,000 breeding pairs in 1996–1997. Mahé population estimated at 2,263 (± 371) individuals using capture-recapture technique in March 1997, with the La Gogue (Glacis) colony estimated at 500–600 nests in January 1996 (18 Rocamora, G. ed. (1997). Rare and Threatened Species, Sites and Habitats Monitoring Programme in Seychelles. Project G1 EMPS. Final Report. Vol. 1. Monitoring methodologies and priority actions. Ministry of Environment, BirdLife International & European Union, Cambridge, UK. Close ). It is likely, especially in Morne Seychelles National Park, that undiscovered cave colonies exist on Mahé. Numbers, at least on Praslin and La Digue, subject to some fluctuations (2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ), e.g. on latter island from 40 to 80 nests based on occasional counts between 1970 and 2009, and on former between 56 and 80 nests between 1977 and 2001 (3 McDonald, R.A. (1978). The biology of the Seychelles Cave Swiftlet Aerodramus (francicus) elaphrus. Pp. 92–112 in: Racey, P.A. ed. (1978). Aberdeen University Expedition to the Seychelles Report. Unpublished report. Close ,2 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ). Recent increase on La Digue may be due to changed hydrological conditions or immigration from former colony on Felicité. Protected under Seychelles law, and the species’ nesting caves on Praslin and La Digue are regularly monitored by staff from the Department of Conservation and designated as Environmentally Sensitive Areas, with unauthorized visits being prohibited.