Last year, around this time a large cloud of Dragonflies was observed along the west coast near Colombo which could be part of an amazing Dragonfly migration. With the rains, could Dragonflies too appear as a wave this year?
his wave of Dragonflies was first reported moving toward the South in large numbers on October 20 (morning) last year. Nashath Haffi of the Field Ornithology Group of Sri Lanka (FOGSL) who had witnessed the flight said that he had observed this wave around 7.00 in the morning along the coast, continuously from
Moratuwa
to Kollupitiya while he was travelling on the train. Susequent
investigations confirmed this phenomenon as the beach community in
Dehiwala and the west coast also confirmed seeing the large number of
Dragonflies. Some of the residents living near the beach said this swarm of Dragonflies appears with the change of wind or goda sulan most of the years. Further investigations also revealed that a Dragonfly Migration from the Maldives to Africa was reported by a well known naturalist, Dr. Charles Anderson. Dragonfly larvae can survive only in freshwater pools, but there are no freshwater pools in the Maldive islands. So the dragonflies that are present in the Maldives have to migrate.
Dr. Anderson had noted the dates when the dragonflies were seen the first time in the Maldives, and then compared the data with the appearance of Dragonflies in South India. He found a clear sequence of dates of arrival from the north to the south. According to these data, dragonflies first arrived in Southern India and then in the Maldives. According to his research, each year, dragonflies first appear in Maldive's capital, Male, between October 4-23, with a mean arrival date of October 21. Quite interestingly, the sighting of the dragonfly wave in the west coast of Sri Lanka was reported on October 20, which is quite close to the dates they had arrived in the Maldives. Therefore one can speculate that the dragonflies seen in Sri Lanka must also be those that were involved in this migration.
Dr. Anderson also attributes the wind pattern that helps them in this journey. In October, and continuing into November and December, a weather system called the Inter-tropical Convergence Zone moves southwards over the Maldives. Dr. Anderson suggests these dragonflies must be flying on these winds at an altitude
above
1000m. “Ahead of the ITCZ the winds blow towards India, but above and
behind it, the winds blow from India. So it seems that the dragonflies
are able to reach the Maldives by flying on these winds at altitudes
above 1000m,” he stated. This would probably assist them to visit Sri
Lanka too. In the past week there was rain in many parts of Sri Lanka. So perhaps the time is right for this interesting phenomenon, and the dragonfly swarm could be seen any time these days.
The Field Ornithology Group of Sri Lanka that first studied this phenomenon is now looking for more data of the presence of Dragonflies to solve this mystery. The society seeks the support of the general public to collect data on the sighting of large movements of dragonflies.
Migrant Birds too are here now…
Among the many types of birds that migrate are some of the common species such as the Blue-tailed Bee-eaters that can be commonly seen even in Colombo. It is also a fun exercise to note down the days these migrants first appear and the days they disappear at the end of the migration season. FOGSL that is based in the University of Colombo asks the general public to keep a log on the common migrants that can be seen and share the information with everyone at the end of migration season. Some of these migrant birds find their journey across hundreds of miles, exhaustive. Last year, as per the announcements through MigrantWATCH, the lives of some of the troubled migrants were saved. FOGSL invites the public to be vigilant this year too.
MIGRANT WATCH – You too can support science
Much research is needed to solve the mysteries of migration. The first step would be to monitor where the dragonflies have been seen in large numbers, which will give the coordination of a possible map. FOGSL that initiated a programme called MIGRANT WATCH also invites the general public to send information on the movements of dragonflies.
The Migrant Watch mainly aims at observing migrant birds and dragonflies as a Citizen Science project. The power of observation, even by non-experts, can contribute towards collecting information in this regard. FOGSL invites all to participate in MIGRANT WATCH. The data can be emailed to fogsl@slt.lk or by post to: FOGSL, Dept. of Zoology, University of Colombo, Colombo 3. Further details can be obtained by calling 2501332 or 0712543634.
Published on LakbimaNews on 14.10.2012 http://www.lakbimanews.lk/index.php?option=com_content&view=article&id=7203:could-there-be-a-dragonfly-migration-across-sri-lanka&catid=41:mag&Itemid=12
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