Tern season 2005

bubiCurrently the tern season 2005 is coming to an end on Aruba. Few tern species are laying now and most of them are rearing their chicks. Some tern species already have fledging chicks and are in full preparation to migrate. The tern season on Aruba is from March till August. In March experts assume that the birds are searching for probable nest sites. During daytime they are foraging out on the sea. In general the public sees the birds at lay in April and May. The critical period for breeding terns is when they are searching for a nesting site, are in lay and when they are rearing their chicks. If at the site there is too much nuisance like a prolonged presence of humans, the birds may nest elsewhere or abandon their eggs or even chicks. In the past nest site abandonment has been noticed on Aruba as a result of a firework show held on the reefs. This year chick abandonment has been observed in terns nesting near a fishermen hut on a reef. Different tern species have different breeding periods and even within a specie there might be a difference in the breeding period. The latter can occur with birds that have abandoned a previous nesting site and are nesting over again. Therefore it is difficult to define the critical period for nesting terns on Aruba

Tern species

bubiAbout 10 tern species nest on Aruba, of which 4 are regionally or globally threatened. The specie that nests in highest numbers on Aruba is the Sooty tern (Sterna fuscata); they can nest in pairs up to 6000. The tern specie though for which Aruba is an important bird area is the Cayenne tern (Sterna sandvicensis eurygnatha). They nest in pairs up to 5000 and experts believe this is about 30% of their world population. The Least tern (Sterna albifrons), Bridled tern (Sterna anaethetus) and Brown Noddy (Anous stolidus) nest on Aruba up to pairs of 100. The other tern species, like the Common tern (Sterna hirundo) and the Roseate Tern (Sterna dougalli), nest in pairs lesser than 100.

Nest results 2005

This year the tern study revealed the changes caused by Hurricane Ivan to the main reef Isle of San Nicolas Bay. This is the reef where most of the terns nest. The big waves washed the shores of the reef away, depositing much sea debris on the reef. The abundant rain enabled the vegetation to grow vigorously. These changes affect the nesting habitat for the ground-laying terns like the Cayenne, but also the Bridled as most of their habitat has been removed. Only the Brown Noddy seemed to benefit as they nest in the vegetation and this has increased vigorously. In preliminary numbers of pairs about 4,200 Sooty terns, 3,700 Cayenne terns, 190 Brown Noddies, 80 Least terns, 32 Commons, 19 Bridled terns and 4 Sandwich terns nested this year. Like mentioned before the Roseate terns also nested, but the chicks were abandoned. The number of nesting Least terns might be higher, but a colony has been reported destroyed as they nested on the dunes near the Lighthouse. In general the 2005 season was a poor year for the Cayennes, Bridleds, Leasts and the Roseates.

For more information call +297 585 6473 or email Department of Agriculture, Husbandry and Fisheries directly.

[Information courtesy of Mr. Facundo Franken of the Department of Agriculture, Husbandry and Fisheries (DLVVM) - Nature Management]

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