In addition to the species studied in the regular long-term monitoring programmes, there are several species that merit continuous but non-regular investigation. Due to time restrictions and resource limitations programme priorities are established. However recognizing the importance of other species to Aldabra, efforts are made to record observations whenever possible.
Whenever SIF staff or visiting scientists are in the field they are required to record all unusual, rare, or scientifically interesting phenomena. Staff and visitors are also encouraged to note and report anything of interest to the Island Management, who can fill in an appropriate record card or computer record for the Aldabra Data Base.
Newer monitoring programs include regular land bird point counts and shorebird counts
In April 1995 a pair of greater flamingos (Phoenicopterus ruber) with a grey chick of the season was sighted at an unnamed bassin in the Takamaka region of East Grande Terre. This was the first known record of flamingo breeding on Aldabra and the chick was observed several months later at Bassin Flamant with the flock. It is still unknown whether breeding is sporadic or annual, but this breeding discovery gives Aldabra the unique distinction of being the only coral atoll in the world where this species breeds.
Flamingos have been observed in flocks of up to 500 birds according to Skerrett (see Amin, Willetts and Skerrett 1995), although recent censuses show a maximum of 37 birds in one flock (Research Officer Report 2005). If this small population is resident on the atoll, rather than migratory, information is needed on its adaptations to Aldabra, its demographics and basic ecology. As there is increasing pressure to view and film this species on Aldabra, such information can be invaluable for management purposes.
Caspian terns (Sterna caspia) are annual resident breeders on Aldabra, which makes the atoll the only oceanic site in the world where they breed. However, as a result of the nature and location of their very exposed ground nests at or below the high water line, low chick survival rates occur, often due to environmental conditions and predation. This situation makes it necessary for more data to be collected on Aldabra’s Caspian tern population of Aldabra.
An experimental research project, initiated in 1995 by Augeri and Pierce, to test and analyse human/boat induced abandonment behaviour in frigate birds (Fregata ariel, F. minor), boobies (mainly Sula sula rubripes) and brown noddy (Anous stolidus) around the atoll, revealed very high abandonment by frigates, especially by females, when approached within 30m by boats with the engines on. Although fewer impacts were observed with some silent approaches at close distance, these inevitably led to even more abandonment because of the necessity to suddenly restart the boat engines due to currents or when leaving the area.
Abandonment of nests by frigate birds is potentially detrimental to both individual birds and to some of the colonies on Aldabra. Specific surveys at the more highly visited sites, conducted regularly, should reveal over time any changes in abundance or shifts in populations which might be due to the impact of visitation by humans.
Aldabra brush warbler
The Aldabra Brush Warbler (Nessilas aldabranus) is one of only two fully confirmed endemic avian species on Aldabra. It was last sighted in 1983 and may be extinct. If not, it is certainly one of the rarest birds in the world. The habitat in which it is found is densely covered with scrub vegetation, making sighting difficult. There is therefore a possibility the brush warbler still exists. The method recorded here is modified from the one developed by Augeri and Pierce (in which a warbler’s call was played continuously along the whole length of a transect as well as at 20m intervals).