Friday, 12 January 2018

Hoo island Herons

Another of my speck shots, just under the kilometre from Finsborough to Hoo island where, especially at this time of year, Grey Herons assemble. Several spread along the revetments as far as Folly Point, but the gathering at the old pier, a dozen in all today, always intrigues me.

Voisin's family monograph, 'The Herons of Europe', points to there being little known on courtship behaviour away from colonies- essentially, even though the species has recognised 'gathering grounds', sexual behaviour (courtship displays) do not take place on them. However, the book describes the little known dance display (perhaps little known because it is all rather unimpressive and over in a flash, a bit of one foot in, one foot out, shake it about, flap wings once and over). I've been watching, but not seeing. Makes you then wonder whether, like the Berengrave non-breeders' spring roost, these might be younger birds, not about to pair. Whatever the answer, now is the time of year for peak counts along the southern Medway. Counting gatherings here, and elsewhere, plus the routine feeding flights to inland ponds, soon provides a thirty-plus figure, a little higher than the WeBS current five-year average for the whole estuary of 21.

The other puzzling thing is still how infrequent flights between the north and south shores are. Perhaps because individual, perhaps because often pre-dawn? Certainly true flocks most often encountered in the autumn. Additionally mapping year round flightlines, the preference for avoiding the largest stretches of open water remains:

The question is how much of a role does the south Medway have as a core area for birds from the large Northward Hill heronry (circled, just north of the estuary). Data collected to date may not reflect how much local populations rely on the estuary at this time of year. The latest BTO Birdtrends results state the causes of the recent decline in breeding populations to be as yet unknown. And more notes from the head of the estuary, around St Mary's would be something to consider in the future in relation to routine crossings- I have a hunch that area could yet prove as busy as just east of Hoo Island.

And of course, as discussed recently, there could also be a few continentals hanging on- and definitely one Scandi bird has been found on the estuary before.

So many questions..

No comments:

Post a Comment