It feels now that winter has truly arrived, the temperatures are plunging and the nights are drawing in and the clocks are about to go back. A chilling sentence for anyone who lives in the British Isles.
It was therefore nice to get an update on the movements of the ringed gull chicks on Havergate this year. Those who have read previous blogs will know that in July the landgard ringing group came out to ring the young nestling Herring gulls, Lesser Black backed gulls, Great Black backed gulls and Common gulls in early and mid July. The final totals are in, 245 Lesser Black backed gulls where ringed including 5 adults, 81 Herring gulls, including 4 adults, 2 greater black backed gulls all juveniles and finally 3 Common gulls, again all juvenile.
Giving a grand total of 335, more than three times what was ringed last year. Largely due to the team making two visits as opposed to the normal one.
Due to virtual collapse of the colony on Orfordness, dropping from a peak of 25,000 in the late 80’s to less than 500 pairs this year. Havergate is now a nationally significant gull colony, especially noteworthy for its high population of Lesser Black backed gulls. It is therefore important to be able to ring large totals on Havergate to continue advancing the knowledge for the reasons in the decline of Herring gull numbers and to advance the studies in the ecology of Lesser Black backed gulls.
So, now comes the exciting time when the results start coming in. It is still early in the season but this year’s juvenile lesser black backed gulls have been seen in Portugal (18), Spain (10) and France (1). Whilst unusually a Herring gull has been seen in Belgium.
Picture courtesy of Michael Davies
Lesser Black backed gulls movements have gone through a rather significant change in the last 50 years or so, revealed by observations and ringing data. Previously the entire species was migratory, in winter it would be relatively unusual to see a “British” Lesser Black backed gull as most would migrate to Spain or even as far as Morocco. However, now the species can be best described as a partial migrant. The juveniles still head south, wintering in Southern Europe, whilst adults see out the winter on estuaries and rubbish dumps in England. This is quite a radical shift in ecology and the reasons behind it are not fully understood.
Herring gulls are not migratory and can be found all year round. However, despite being considered relatively common they are now a red listed species, due to a 53% decline in their breeding population since 1969. Like the Lesser Black backed gull recent changes are not fully understood but it is believed disturbance, predation, disease and changes in availability of food from waste tips have had an impact. It could even be that the numbers are returning to a more “natural” level. However, these declines are masked by an incredible 570% increase in Herring gulls nesting in urban areas. The RSPB is now involved in determining the reasons for the decline and what can be done to aid previously healthy populations of Herring gulls.
So, if you see a colour ringed gull remember to report it in and think about all the migratory species when its snowing and freezing outside.