Another winter season of gull roosting at Tophill Low NR, East Yorkshire drew to a close with the changing of the clocks to British Summer Time over the final weekend of March.
I’ve been observing the D reservoir gull roost since the turn of the millennia and every year has proved different with some good winter periods, while others have failed to live up to expectations. However, every year has to be put in context with the site history, time available for observations and the weather conditions – not only locally, but also much further afield.
The site history is interesting – 13 species have been recorded, but there does seem to be a rule that the scarcer large gulls rarely appear on consecutive evenings. For example, from what I understand of Tophill’s past, and again witnessed this winter, maybe only three of the ‘white-wingers’ recorded on the reservoir have ever returned the following evening – I can recall only one bird returning the night after over the last decade.
Winter 2013/14 roost observations started in late October, involving 56 afternoons and evenings over 24 weeks spent in the sheds overlooking D reservoir. Time wise that equates to over 200 hours in a variety of weather conditions, with a minimum of 850,000 gulls searched through. It is impossible to say how many birds actually use D reservoir over the entire winter period as there are movements both locally and on a bigger scale, but with roosting numbers averaging 15,000 birds per night during observations, if looked at as individuals, it gives a minimum of 2.5 million opportunities to find something different amongst the massed ranks of Black-headed Gull Chroicocephalus ridibundus and Common Gull Larus canus and lesser numbers of Herring Gull L. argentatus and Great Black-backed Gull L. marinus.
Given the mild winter, which resulted in little in the way of cold weather movements off the continent, the 2013/14 gull roosting campaign surprisingly has proved to be one of the best ones at Tophill Low since the site was created in 1959. A total of 10 species were recorded between October 25th 2013 and March 30th 2014 with the more scarce species recorded on over 49 days during the period.
The highlights involved Tophill’s third Caspian Gull L. cachinnans, while ‘white-wingers’ fared well with single Glaucous Gulls L. hyperboreus appearing on two evenings and four Iceland Gulls L. glaucoides– including the 2nd winter Kumlien’s Gull L. g. kumlieni wintering in the Barmston area on the coast north east of the site, which dropped onto the reservoir on three occasions. Plus, an unidentified juvenile ‘white-winged’ gull came into roost on the reservoir late on Dec 24th, but proved impossible to relocate. Yellow-legged Gull L. michahellis was once again scarce with only a couple of records.
The species recorded
Black-headed Gull C. ridibundus
Common Gull L. canus
Mediterranean Gull Ichthyaetus melanocephalus
Herring Gull L. argentatus
Yellow-legged Gull L. michahellis
Caspian Gull L. cachinnans
Great Black-backed Gull L. marinus
Lesser Black-backed Gull L. fuscus graellsii
Glaucous Gull L. hyperboreus
Iceland Gull L. glaucoides
One species which is still considered a Tophill scarity, but which has become more common over the last decade is Mediterranean Gull I. melanocephalus. A quick glance at the old site reports indicate how rare it was almost 20 years ago with only one recorded at Tophill in 1997 for example. Records have increased since then, though it still remained unusual to note more than a single bird in a roost up to the end of 2011/12.
The winter 2013/14 period bucked this trend, with multiple birds recorded in 50% of the roosts observed. These records could relate to only 10 or so individuals over the entire period, or if it is accepted birds move, then a minimum number of 31 birds appeared.
Observations suggest the numbers below
roosted over the 24 week period.
6-8 2nd winters
12-16 1st winters
But then gulls move and don’t use the same roost site each evening, so how many birds could have been involved, especially with some of the more obvious individuals noted on only single or two nights at most? When single Mediterranean Gulls I. melanocephalus depart, it isn’t just those that leave, more likely they move with a number of Common Gulls L. canus and Black-headed Gulls C. ridibundus and new birds come in to replace them. Conservatively, I’d suggest 31-38 birds were involved in the Tophill records over the winter, but 50+ perhaps isn’t out of the realms of possibility.
This gull below also provided some discussion – hybrid Lesser Black-back L. fuscus x Herring Gull L. argentatus argentatus seems to be favourite, but extreme dark Herring Gull L. a. argentatus and hybrid Herring Gull L. a. argentatus x Heuglin’s Gull L. heuglini have been mentioned. Whatever it was will never be known, but its good for the learning!
Given the selection of birds recorded, the 2013/14 gull roosting period was the best ever at Tophill since the site was created with the scarce birds recorded on more dates than ever before.
It is worth mentioning that between September 8th 2013 to March 30th 2014, 12 of the 13 gull species ever recorded at Tophill since 1959 appeared on D reservoir – the winter recording period allowed me around 850,000 opportunities to pick out the odd ones, but I will wonder what else could have occurred.