Colour Ringed Mediterranean Gulls at Heysham

The numbers of Mediterranean Gulls appearing in late summer to mid/late September around Heysham outfalls has increased markedly in recent years, in contrast to the status at other times where there has in fact been a decline (spring passage) or no change (winter) for many years.  At least 70 birds were involved in 2017 and an absolute minimum of 74 have been seen in 2018.  This figure is reached by adding together the maxima for each age class with the highest day count of 62 being in early August 2018.

Unfortunately, as regards deciphering the darvic numbers, the immediately local birders/ringers have struggled with ring reading and we have had to rely on better eyesight and better optics/cameras from outside in order to read all but the very occasionally obliging individuals.  Double-figures of Mediterranean Gulls were read in the "Bonaparte's Gull year" of 2013, where the occurrence pattern of this vagrant mirrored the moulting Med Gulls.  In the absence of any subsequent notable mid-summer 'draws', ring reading has been very intermittent and this explains the 'gap years' for some of the returning birds.

They are quite difficult, even for the best optics, especially on Red Nab where they tend to congregate on the south-western area of the rocks and any attempt to approach them leads to mass flushing of eg closer Black-headed Gulls and they are also disturbed by the alarm-calling habits from recently nesting large gulls being difficult to break!  They also tend to clear off south well before the tide reaches the rocks.  The most favoured ring-reading area is on the mudflats between Heysham one outfall and the wooden jetty but even here a lot of patience and luck as they move closer on the incoming tide instead of flying off is needed

However, the rewards for a successful ring-read have been very interesting.  There are clearly a number of adults, third and second calendar years which move in a north-westerly direction in late June/July from breeding areas between France and Poland, including Czech Republic, and complete their moult at Heysham Power Station outfalls and surrounding areas (eg outer Lune Estuary where Heysham birds are displaced on high spring tides). Slightly later in the summer, we receive decent numbers of juveniles which often remain to partially moult into first winter plumage.  Logic might then suggest that these birds move onwards at a similar latitude and become part of Ireland's significant wintering population.  However, this has not been the case with any of the Heysham ringed birds, although the vast majority, of course, are not ringed.  After moving north-west to moult, several have been traced back south to the French and Iberian peninsula coasts during the winter months.  Why do they come so far NW to moult!

Note that one of the dispersing juveniles in 2003, ringed in he Czech Republic, has returned here outside the breeding season every year but it is going to be hard to locate in 2018 with access changes (and absence of food from anglers) in its favoured location on the north harbour wall

Please do visit Heysham at or near low tide or the early stages of the incoming tide - not at high tide on a spring tide when you will see a big fat zero - and try and check the Med Gulls for rings.  Thanks to Richard du Feu, Pete Woodruff and Margaret and Mark Breaks for efforts in 2018 and many others (including Ian Hartley, Mark Nightingale, Mark Prestwood, Jon Carter, Gav Thomas, Chris Batty) for efforts in previous years    


Pete Marsh