The last update on UV described some unsettled behaviour. Here is more detail from Paul Wildlifewriter on what may be the cause.
Ospreys are creatures of habit, and so any observed departure from their usual routines is a cause for interest. UV’s recent unsettled behaviour – particularly around his habitual evening roost sites – has no obvious explanation, but it might be just the time of year that is affecting him… Many species of migratory birds exhibit zugunruhe (migratory restlessness) at certain times of the year. Research has shown that this happens in accordance with “built-in” circannual rhythms, although modified by external influences such as the varying lengths of day. Recent studies suggest that this behaviour is an intrinsic part of being a bird, and even some non-migratory species can exhibit it. If this is true, then we might expect a first-year osprey to feel some of the effect – even though it is not actually required to undertake a full migration until another twelve months have passed. This is yet another aspect of osprey ethology that is being highlighted by GSM tracking technology – it would not normally be observed in the wild. It will be interesting to see how this develops as the season goes on. Citation: “Zugunruhe of migratory and non-migratory birds in a circannual context” B. Helm, 2006, DOI: 10.1111/j.2006.0908-8857.03947.x
Many thanks to Paul for the insight. 7H has been more markedly unsettled than UV as recent updates have highlighted. On the whole this continues to be the case, although just after the last post she appeared to have ceased her explorations. It was rather worrying at first because on 21 March, a day of rain, she sat on the beach a little north of her usual positions from 10.30 GMT until just after 18.00.
Although the eagle eyed will notice the time slider at the top reads 16.02 it was 18.18 before there was a fix away from the area as she returned to a Eucalyptus tree for the night. You can see the place she sat looks very bare; was 7H injured or ill to sit so long in an apparently inhospitable spot? Pip and Vic were consulted and provided some reassurance. They remembered a bit more vegetation when they visited at the end of February. Presumably 7H did find a ‘comfortable’ place to sit out the rain. On 22 March she was relatively quiet again (it was still rainy), staying around the Eucalyptus trees until a data point at 12.14 showed her flying quite near the mouth of the river. She may well have caught lunch because the tracker temperature dropped 12°C between 12.05 and 12.17, suggesting possible immersion. She returned to the Eucalyptus trees until later in the afternoon when she went across to the pylons for the rest of the day and night. On 23 March 7H went up to the beach near the gravel extraction site after sitting near the wreck at the mouth of the river on the southern side. She left there in mid afternoon and had a wide sweep round the farmland on the east side of the river.
7H went up to 374m ASL to survey her surroundings and beyond as she headed south towards her new favourite spot near the bridge over the A5. Her most adventurous day was 24 March when she flew mainly along the winding river further upstream than previously.
A straight line from the A5 bridge to her furthest point is about 21 km. Paul has researched whether some anadromous fish species may have migrated upstream and she was following a food source but this seems unlikely at this stage of the season. Mostly her altitude was too high to have been hunting although she circled lower examining the terrain a few times.
Just as this post was being completed a partial data download arrived; at some point yesterday 7H went south to the area around Jorf Lasfar – she was still there at 17.30 today. Zugunruhe indeed! There will be a further update in the next couple of days.