Seabird colonies; Sterna dougallii; Habitat preference; Western Indian Ocean; Canopy cover; Pisonia grandis
Abstract :
[en] We examined the effect of vegetation structure, in particular canopy closure, on colony site occupancy, nesting densities, and reproductive parameters of roseate terns Sterna dougallii breeding in a Pisonia grandis dominated woodland on Aride Island, Seychelles, western Indian Ocean. Long-term observations (1995 to 2006) revealed that areas with high vegetation density and canopy cover (>50%) were abandoned, in favour of nearby more open forest areas, such as clearings. The attractiveness of a forest clearing (0 to 25% canopy cover) to breeding birds was also largely supported by experimental manipulation of vegetation density in 2004. Most birds moved from areas under canopy cover to experimentally cleared plots, where they nested at higher densities and had a higher probability of successfully fledging a chick. However, some individuals remained in their original areas, despite their greater canopy cover, and had a lower fledging success. This site tenacity is presumably explained by an imprinting process leading some birds to breed in successive years in the same, familiar locations, despite their nest-sites having become sub-optimal for fledging success. Roseate terns choosing a nest site in woodland on Aride must trade off the need for some cover, offering
protection from the sun, against the need for easy access through gaps in the canopy to fly to and from their nests. A suitable nest-site should also minimize chick/parent infestation by ticks and mortality caused by contamination of feathers with the sticky fruits of Pisonia grandis. We suggest that, when they are not formed naturally, small artificial forest clearings within the usual breeding area are likely to be attractive for roseate terns and may result in enhanced colony productivity. These findings may be applicable to other seabird colonies (e.g. sooty terns) found under forest cover on oceanic islands throughout the Indo-Pacific region.
Ayrton V (1995) Roseate tern breeding season on Aride Island. Royal Society for Nature Conservation, Lincoln
Battin J (2004) When good animals love bad habitats: ecological traps and the conservation of animal populations. Conserv Biol 18:1482-1491
BirdLife International (2004) Sterna dougallii. In: IUCN 2006 Red List of Threatened Birds. AVdilablt at: www.iucnredlist.org. Accessed: 28 March 2007
Block WM, Brennan,LA (1993) The habitat concept in ornithology: theory and applications. Curr Ornithol 11: 35-91
Blondel J, Dias PC, Maistre M, Perret P (1993) Habitat heterogeneity and life-history variation of Mediterranean blue tits (Parus caeruleus). Auk 110:511-520
Bock CE, Jones ZF (2004) Avian habitat evaluation: should counting birds count? Front Ecol Environ 2:403-410
Burger J, Gochfeld M (1988) Nest-site selection by roseate terns in two tropical colonies on Culebra, Puerto Rico. Condor 90:843-851
Castle GE, Mileto R (1994) Flora of Aride Island, Seychelles. Eco Tech, Shrewsbury
Clark L, Ricklefs RE, Schreiber RW (1983) Nest-site selection by the red-tailed tropicbird. Auk 100:953-959
Cody ML (1985) Habitat selection in birds. Academic Press, London
Collar NJ, Andrew P (1988) Birds to watch. The ICBP checklist of threatened birds. ICBP Tech Publ No. 8. International Council for Bird Preservation (ICBP), Cambridge
de Korte J (1984) Status and conservation of seabird colonies in Indonesia. In: Croxal JP, Evans PGH, Schreiber RW (eds) Status and conservation of the world's seabirds. ICBP Tech Publ No. 2. International Council for Bird Preservation (ICBP), Norwich, p 527-545
Englund SR, O'Brien JJ, Clark DB (2000) Evaluation of digital and film hemispherical photography and spherical densiometry for measuring forest light environments. Can J For Res 30:1999-2005
Feare CJ, Gill EL, Carty P, Carty HE, Ayrton VJ (1997) Habitat use by Seychelles sooty terns Sterna fuscata and implications for colony management. Biol Conserv 81:69-76
Franklin AB, Anderson DR, Gutiérrez RJ, Burnham KP (2000) Climate, habitat quality, and fitness in northern spotted owl populations in northwestern California. Ecol Monogr 70:539-590
Frazer GW, Canham. CD, Lertzman KP (1999) Gap Light Analyser software: users manual and program documentation. Simon Frazer University, Burnaby, British Columbia, and the Institute of Ecosystems Studies, Millbrook, New York
Gochfeld M (1983) World status and distribution of the roseate tern, a threatened species. Biol Conserv 25: 103-125
Gochfeld M, Burger J, Nisbet ICT (1998) Roseate tern (Sterna dougallii). In: Poole A, Gill F (eds) The birds of North America, No. 370. Philadelphia, PA
Johnson M (2007) Measuring habitat quality: a review. Condor 109:489-504
Le Corre M, Cherel Y, Lagarde F, Lormée H, Jouventin P (2003) Seasonal and inter-annual variation in the feeding ecology of a tropical oceanic seabird, the red-tailed tropicbird Phaeton rubricauda. Mar Ecol Prog Ser 255:289-301
Maul AM (1998) Breeding biology and monitoring of 3 seabird species (brown noddy Anous stolidus, lesser noddy A. tenuirostris, roseate tern Sterna dougallii) on Aride Island, Seychelles, with special comments on breeding behaviour and biometrics of the brown noddy. PhD thesis, Karl-Franzens University, Graz
Monticelli D, Ramos JA (2004) The 2004 roseate tern breeding season on Aride. Royal Society for Nature Conservation, Lincoln
Peavey CA, Lane RS (1996) Field and laboratory studies on the timing of oviposition and hatching of the western black-legged tick, Ixodes pacificus (Acari: Ixodidae). Exp Appl Acarol 20:695-711
Ramos JA (1998) Nest-site selection ljy roseate terns breeding on Aride Island, Seychelles. Colon Waterbirds 21:438-443
Ramos JA (2000) Characteristics of foraging habitats and chick food provisioning by tropical roseate terns. Condor 102:795-803
Ramos JA (2001) Seasonal variation in reproddctive measures of tropical roseate terns Sterna dougallii: previously undescribed breeding patterns in a seabird. Ibis 143:83-91.
Ramos JA (2002a) Roseate terns on Aride Island: the contribution of 19 years of monitoring to the conservation of an endangered species. Phelsuma 10:17-27
Ramos JA (2002b) Spatial pattern of breeding parameters in tropical roseate terns differ from temperate seabirds. Waterbirds 25:285-294
Ramos JA (2003) Intraspecific aggression by roseate tern adults on chicks in a tropical colony. Waterbirds 26: 160-165
Ramos JA, del Nevo, A (1995) Nest-site selection by roseate terns and common terns in the Azores. Auk 112:580-589
Ramos JA, Monticelli D (2007) Long-term studies on productivity of roseate terns and lesser noddies on Aride Island, Seychelles. Ostrich 78:443-447
Ramos JA, Bowler J, Davis L, Venis S, Quinn J, Middleton C (2001) Activity patterns and effect of ticks on growth and survival of tropical roseate tern nestlings. Auk 118:709-716
Ramos JA, Maul AM, Ayrton V, Bullock I and others (2002) Influence of local and large-scale weather events and timing of breeding on tropical roseate tern reproductive parameters. Mar Ecol Prog Ser 243:271-279
Rowley I (1983) Re-mating in birds. In: Bateson P (ed) Mate choice. Cambridge University Press, London, p 334-360
Saliva JE, Burger J (1989) Effect of experimental manipulation of vegetation density otr nest-site selection in sooty terns. Condor 91:689-698
Scott-Mills G, Dunning JB, Bates JM (1991) The relationship between breeding bird density and vegetation volume. Wilson Bull 103:468-479
Seddon PJ, Davis LS (1989) Nest-site selection by yellow-eyed penguins. Condor 91:653-659
Sergio F, Newton I (2003) Occupancy as a measure of habitat quality. J Anim Ecol 72:857-865
Shealer DA (1995) Comparative foraging ecology of roseate and sandwich terns in Puerto Rico and its relation to breeding performance. PhD thesis, Rutgers, The State University of New Jersey, New Brunswick, NJ
Stonehouse B (1966) Egg volumes from linear dimensions. Emu 65:227-228
Tree AJ (2005) The known history and movements of the roseate tern Sterna dougallii in South Africa and the western Indian Ocean. Mar Ornithol 33:41-47
Tyzack SM, Volcere O (1986) The roseate tern Sterna dougallii on Aride Island, Seychelles: notes on the 1984 season. Scopus 10:45-47
Warman SR (1979) The roseate tern Sterna dougallii arideensis on Aride Island, Seychelles. Bull Br Ornithol Club 99:124-128
Warman SR, Todd D (1984) A biological survey of Aride Island Nature Reserve, Seychelles. Biol Conserv 28:51-71
Williams B (1983) Some observations on the use of discriminant analysis in ecology. Ecology 64:1283-1291
Zar JH (1999) Biostatistical analysis, 4th edn. Prentice Hall International, Upper Saddle River, NJ
