UV has had a quiet time since the last update. In fact he has been at roost so much that some days the number of fixes are seldom as often as every 30 minutes or so, and on 12 January he wasn’t flying at any of the data points! Usually he is quite late leaving his inland roost site for fishing grounds – on 11 January he probably didn’t go to the water until after 15.00 GMT. But on 14 January he was flying over the sea near the Bajo Tortugo lagoon at 7.53. So he is not totally predictable. He didn’t have an active day despite the early start. The number of fixes reached 1-2 minutes but he was never moving on any of them between the first point at the lagoon (8.31) and 15.30. Here is an image of his whereabouts during that time.
Low tide would have been within about 15 minutes of 12.43 but there is no indication that UV took advantage of the shallow water around that time. If he did it was in the hour before when there were less fixes. You can see at the last fix above he appears to be roosting in the water. The ‘current’ image on Google Earth is from June 2012 and the sand bars are likely to have altered since then. But perhaps not too much around that particular channel. The remaining data for 14 January arrived the following day and for the rest of the afternoon UV had roosted near that ‘last fix’ point. The image below shows subtle changes in his exact position.
In the 15.49-16.02 ring he was moving slightly further north in most of the fixes – he then shifted 20m to the 16.04-16.29 ringed area. So maybe there is still a channel in that part of the lagoon and he was avoiding the incoming tide.
UV’s lack of activity is reassuring. It indicates he is finding it relatively easy to get fish and can spend the rest of the day at roost rather than needing to look for new foraging areas like some juveniles. Readers may recall that when UV arrived at the Gulf of Cintra he spent time at the northern end but then went south for a few days before concluding the best area was around the lagoon. Paul has made an animation which illustrates better than words how he explored then settled in his current territory. You can view it here. Many thanks to Paul, it took a long time to create but is well worth his effort.
7H is also spending most of her time roosting so there are less fixes to analyse. She is still moving between the river and pylons most days for a spell and the gravel extraction area east of the river mouth sees her a few times a week. The poplars remain a favourite daytime spot. Here is an image of her range from the afternoon of 10 January to the end of 15 January.
Several times a day she flies up and down the short stretch of river between just north of Azemmour and the sea. Sometimes she could be hunting but not every time and she also fishes at sea. Paul has dredged up a possible reason for her behaviour on the river – following a dredger!
In the historical images on Google Earth a dredger is normally visible. The ‘current’ image which appears on most of the graphics in the blog doesn’t show it because it was in its maintenance dock when the imagery was captured. Estuarine fish often follow dredgers because the activity stirs up food, much like flocks of birds follow a plough, and 7H could well be checking for some well fed fish! There could be a tasty reward for not much energy expenditure over a few minutes. It is ‘only’ a theory but a plausible one; on the historical images the dredger is always working in the area preferred by 7H. Here is a photo from Google Earth/Panoramio showing the dredger at work with an inset of what it looks like from the sky.
The forecast for the Azemmour area from today for the next week is mostly showery with Sunday likely to be the wettest day. So 7H may hunker down even more!