It’s been a while since a migration update so it’s clear nothing dramatic has happened!
Although, if you take the long view, there is something very significant. Just look at these two heatmaps prepared by Paul Wildlifewriter.
Seeing the data presented in this innovative way truly highlights 7H’s shift of focus. We don’t believe heatmaps have been used in Europe on bird tracking data before now; Paul wrote an article in his own blog with more about the work involved. He has to process literally thousands of fixes from a GSM tracker. His presentation of results of data analysis in highly accessible graphics including the heatmaps is greatly appreciated.
Apart from the obvious reduced activity near the mouth of the river (although ironically 7H did go there yesterday!) what else can we learn?
Firstly, 7H is tending to travel further each day than over her first few months near Azemmour. She is still favouring roosts on or near the pylons to the west, yet her hunting focus is further east. The heatmap is red near her roosts because of the daily movement in that area.
Secondly, her trips further upstream are far from daily but are frequent enough to show red on the heatmap. As noted previously, she is often flying at too high an altitude to be hunting during on these outings. The next image shows her heights ASL on a flight upstream on 4 May.
Most upstream outings end roughly where this one did, or just a little further upstream. You can see she flew out at altitude but not in a straight line, then she flew lower as she tracked back along the river. Is she assessing water levels, perhaps – dropping at this time of year – to identify areas which will be shallower for fishing? And then taking a closer look for fish on the return journey? Because she seldom behaves as if she is hunting when on these trips reconnaisance appears the most probable reason for them.
Thirdly, on the Spring heatmap the ‘spike’ from the area around the weir to the farmland she likes to sit in is very prominent. Quite why the farmland is so attractive is a mystery, but it definitely appeals to 7H even more than the wood by the weir.
To end – something not visible on the heatmap is 7H’s choice of a good place to sit early on the morning of 13 May.
Here is a photo of the railway bridge where she was on top of one of the poles enjoying a panoramic view!