Capturing the Diversity – Wideawakes

Stedson had a right to grumble about the plants playing second fiddle to other efforts, especially on my earlier visits.  Much of the conservation effort on Ascension Island had been focused on the birds.  The island had been a massive breeding ground for several species of sea bird; one of which, the Ascension Frigate Bird, was endemic.  But first sailors taking eggs and birds, then the animals that humans introduced, particularly rats and feral cats, did more damage to these colonies.  The evidence that Ascension once had even larger bird populations is seen particularly on those ghost colonies in the lava fields on the north of the island. Because of the years of build up and the dryness of the climate, the guano deposited by ancient birds still whitens the black rocks for several square kilometres.

An indication of what a massive colony looks like could be found at a number of sites to the south of the airfield.  Anselmo took Edsel and myself to visit one of these, the Wideawake Fairs, from which the airport gets its name.  To get there he had to get permission from the US base which runs the airfield, and we drove down the far end of the huge runway, built they say to take space shuttles overshooting from Cape Canaveral.  Conservation were allowed to unlock the gates and drive across the runway, checking with ground control that there were no movements (considering there were only a maximum six scheduled landings and take offs a week, it was highly unlikely) and we headed on to a rough track down through the lava fields.  The larger colonies of birds appear to favour this terrain, the jagged rocky surface provides both little nooks and crannies for nests and look out points against predators.  The most useful guard against invasion is safety in numbers, and when we got to the edge of the colony, I could see why.  The squawking mass of birds in there was not a place I wanted to venture too far into.

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Crossing the runway

Wideawake Terns, or sooty terns as they are more usually known, come to nest on Ascension Island, as they do on many remote islands around the world.  Their breeding timing is a confusion; they do not breed at the same point of the calendar year, but between every 10-11 months.  I suppose that being very close to the equator, there is little evidence of seasons; the sun goes down within half an hour of 6pm every day and rises again around 6am local time.  The temperature varies little from its balmy 27 degrees and there is no distinctive wet or dry period, deluges do occur sometimes but cannot be forecast by time alone.  So what does a sooty tern use to decide when to breed?  Probably something internal that works on a slightly shorter year.

The only time a sooty tern will come in to land is during the breeding season, and until recently, very little was known about where the Ascension wideawakes would go for the rest of the time.  They spend a lot of time flying and may sit on the surface of the sea, or dive in to catch their food, mainly fish and crustaceans.  Once their offspring had fledged they would leave quite quickly over the course of a few weeks.

The monitoring of these birds for Conservation was quite low key.  Assisted by the British Army Ornithological Society, they would map the boundary of the colony each year to see if it was contracting or expanding, or maybe even shifting along the coast.  Counting individuals was not an option – there are frequently over half a million adult birds, but spot checking for breeding success was carried out.  And any evidence of predation by cats or rats was looked at.  But getting in amongst the birds to monitor the nests is a risky business.  Sooty terns are very territorial beasts and will bomb any intruders.  They drop down aggressively from above, swooping closer and closer to you, maybe pecking at your head or squitting faeces over you.  The piercing shrieks of one aggressive bird is likely to attract its mate and maybe others until you are driven away to a safe distance.

More recent tagging and tracking of wideawakes are beginning to shed light on the vast distances of ocean they can cover between breeding seasons.

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