Currently 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
About 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
please call Department of Agriculture, Husbandry & Fisheries on 5858102.
[Information courtesy of Mr. Facundo Franken of the Department of
Agriculture, Husbandry and Fisheries (DLVVM) - Nature Management]
