Wednesday, 8 March 2017

Migratory birds and sea turtles on Denis Island

Northern Wheatear on Denis Island
Denis Island geographic location in the northern Seychelles archipelago, right on the edge of the Mahe Plateau, makes it a very important resting and overwintering site for migratory birds. 

Northern Wheatear at Belle Etoile
Numerous species of birds are regular non-breeding migrants to Denis Island and they include waders, seabirds and ducks. The waders and ducks fly to Seychelles from the northern hemisphere to overwinter and are mainly present from October- April although first year birds may stay all year round (e.g. the Ruddy Turnstones) rather than migrating to their breeding grounds in Europe, the Middle East Asia, North Africa, Madagascar or Australia.

Northern Wheatear

Vagrant species are those that have been blown from their normal migration routes and so, like regular migrants, they are usually seen between October – April, especially after stormy weather and strong winds. Most vagrants stay for a short period before moving on or succumbing to exhaustion, but a few stay for prolonged periods.

Recently, after abatement of the recent regional stormy event, the Denis Island environment team spotted an unusual bird along the eastern part of the island. After careful observations using a high definition Steiner binocular we agreed that it was a Northern Wheatear.
Literature review suggests that Northern Wheatear is a vagrant throughout Seychelles, mainly to the Aldabra group, and that most sighting occurs in December –March. Northern Wheatear likes to frequent open areas with low bushes for perches, they are known to be solitary birds with low rapid flights.  One of the bird distinguishing features is its Black T- shape tail tip.

Taking measurements of nesting Green Turtle
The Denis Environment team was also delighted to encounter a nesting Green Turtle on the East Coast beach of Denis Island. Two species of turtles nest on the beaches of Denis Island, namely the endangered Green Turtle (Chelonia mydas) and the critically endangered Hawksbill Turtle (Eretmochelys imbricata). The former species, the Green Turtle, nests all year while the latter, the Hawksbill Turtle, nests from September to February. 
Denis Island is an important nesting habitat for Green Turtles

Turtle nests are marked so that information can be gathered when the hatchlings will emerge. To date a few turtle nest have been recorded and some hatchlings have also emerged as well which shows that Denis Island is a very important turtle nesting ground; some of its bays also provide good feeding grounds, especially the green turtles which feed on the seagrass.
Data collected sporadically at Denis Island since 2002 indicate that, in addition to hosting nesting hawksbill turtles, Denis also hosts one of the three largest nesting populations of Green Turtles remaining in the Inner Islands of Seychelles. Green turtles of the inner Seychelles islands have been nearly extirpated due to over-exploitation for meat.

Denis Island hosts exceptionally important near-shore foraging aggregations of immature green turtles, plus smaller numbers of immature hawksbills—especially along the east coast in the vicinity of Belle ├ętoile, just south of the airstrip. Denis is also associated with beautiful dive sites inhabited by both species of turtle.

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