Thursday, January 31, 2013

Robben 2012 Penguin Foraging Data Collected, Analysis Ahead!

Thanks to the help of all assistants we achieved the collection of foraging track and dive data from 35 different breeding African penguins at Robben Island in 2012.  Kate is now busily conducting data exploration, analysis and write up.

·        From April to August, Global Positioning System Temperature and Depth (GPS-TD) data loggers were equipped to a total of forty-two breeding African penguins, for one foraging trip. From those deployments, a total of 35 birds successfully equipped yielded useful GPS foraging data and thirty seven complete data sets of dive data. On four occasions, unfortunately the devices failed to start and record data. These were sent to Germany for repairs. One of the equipped birds did not go to sea; the logger was removed on the third day the bird was at the nest. In two cases, no GPS data was recorded while the bird was at sea perhaps due to the way the bird was swimming. We were lucky to retrieve all the GPS-TD logger devices.  The longest time that a penguin spent away from its nest when on a recorded foraging trip this year was 26.5 hours and the shortest was 9.7 hours. One bird made an usual trip that circled the island. The majority of foraging trips were on the eastern side of the island, predominantly in Table Bay only a few trips were made west of Robben Island.  Nest visits continued after logger retrieval to assess breeding success and bird behaviour. The main foraging grounds are being mapped. Comparisons of inter- and intra-annual variation of foraging parameters such as trip duration, path-length, dive rate, dive efficiency, bottom phase time and maximum distance from colony are underway.
·         The dates at which penguins were at sea with a logger device coincided exactly with eight of the hydro-acoustic pelagic fish surveys.  There were also other deployments that corresponded with dates closely. This data will be overlaid to ascertain whether penguins are foraging in the areas where the pelagic fish are locally densest and whether the distance from those areas to the island affects the foraging range of penguins. Pelagic fish data has been received from the Department of Agriculture, Forestry and Fisheries. The mapping of penguin foraging grounds with local prey distribution and analysis has begun.

Best wishes for 2013 to you and the penguins!

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