Scarce passage migrant and winter visitor. Records for all months but most July to March and a peak in late winter/early spring. Up to five pairs have bred or attempted to breed since 2007 but with limited success.

An analysis of the status of Mediterranean Gull in the West Midlands Region up to 1988 was published in the West Midland Bird Report for 1988 (Dean 1989). At that time there were only 46 records of the species. Even so, there was evidence of increasing numbers, with around a dozen in both 1987 and 1988 compared with only 2 or 3 per year during earlier years of that decade.

Arrivals of first-years were well-distributed through the year with records in all months except April, June and August. Peak arrivals, however, were in mid-winter, with 54% in November, December and January.

Arrivals of adults were less evenly distributed, with 43% in November or December, 36% in February, and single arrivals in just three other months.

Updated analysis for 1989 - 2010 (with comments for subsequent years)

In the ensuing 22 years, 1989 - 2010, records of Mediterranean Gull in the region have continued to increase, accumulating a total of around 1400 individuals, with a mean of 29 per year in the period 1989 - 1994, 41 per year in the period 1995 - 2000, 72 per year in the period 2001 - 2005 and 123 in the period 2006 - 2010. Since 2010, published data have been too 'condensed' to enable an accurate assessment of numbers but suggest annual totals remaining between 100 and 150 during 2011 - 2015. Despite increasing numbers reaching the West Midlands region, the scale of increase does not match that apparent in several south coast counties of England, where three-figure and even four-figure counts are now quite regular. On that basis, the species arguably remains less-numerous than might be anticipated in the midlands. At Draycote, traditionally among the most productive sites, a decline has been noted, with the WMBC Annual Report for 2017 noting that individuals on spring passage were much scarcer than in earlier years. Conversely, a few pairs now breed in the region each year though with limited success.

Annual Distribution.

The annual distribution of records during 1989 - 2010 is shown in figure 1:

Figure 1. Annual distribution of Mediterranean Gulls in the West Midlands Region, 1989 - 2010

Age Distribution.

The age distribution of Mediterranean Gulls recorded between 1989 and 2010 is presented in Table 1. Prior to 2006 most published records were accompanied by details of age but, with increased numbers and increasing use of tabulated data, subsequent reports have included a significant number of individuals for which no age data was provided. Thus, the column for 2006 - 2010 excludes 265 individuals (43% of the total) recorded during that 5-year period. During the late 'eighties and early 'nineties, first-years outnumbered adults. As well as a significant increase in numbers in all age-categories, it is also evident that the proportion of adults has increased since the mid 'nineties (Table 1) and adults now outnumber first-years.  Since 2010 it seems likely that the proportion of first-years has declined further. Juveniles and early first-winters still occur regularly in late summer but mid-winter records of first-winters are now relatively few.

Table 1. Age Distribution of Mediterranean Gulls in the West Midlands Region, 1989 - 2010
(* Note: individuals not aged are excluded from the table and this is a significant number for 2006 -2010)
 

Monthly Distribution

The monthly distribution during 1989 - 2010 is shown in Figure 2, plotted from summer through winter:

Figure 2. Monthly distribution of Mediterranean Gulls in the West Midlands Region, 1989 - 2010

August has become marginally the most productive month for first-years, reflecting the now regular appearance in the region of juveniles during July and August. This phenomenon reflects the increasing breeding success of Mediterranean Gull on the near continent and also in England. Juveniles or first-winters have been recorded in the West Midlands bearing colour rings which show they have originated from France, Belgium or the Netherlands.

The distribution of adults has apparently changed somewhat, with arrivals in all months and numbers increasing through the autumn and winter, to peak in February and March. February remains a significant month but, unlike the earlier period of analysis, there are also significant arrivals in January and March.  (In recent years, the pattern of records indicates that several adults have wintered in the area, at sites such as Draycote Water and the Tame Valley in Warwickshire and Chasewater in Staffordshire. It should be noted that the histograms display arrival dates and not the totals present in any given month.)

In contrast with the earlier analysis, the period 1989 -2010 produced sufficient numbers of second-years to be of statistical significance and in this category March emerges as the peak month for arrivals, when numbers may approach those of first-years.

Discussion

Discussing the national distribution of records for birds of all ages, Bourne (1970) detected three periods in the year when new records reached a peak, namely July/August, October, and April. He deduced that Mediterranean Gulls must often undertake three migrations annually: a post-breeding dispersal to regular late-summer quarters where they probably completed the moult, followed in some cases by a late-autumn movement to regular winter quarters elsewhere before the return to the breeding grounds in spring. Examination of Bourne's figures showed that the spring peak was not abrupt and, for adults in particular, encompassed the period February to April and not just the latter month.

The more-recent pattern of arrivals in the West Midlands also shows a subsidiary July/August peak, but dominated by first-years (with juveniles now appearing annually). After a decline in arrivals during September, there is a steady increase in overall numbers from September through to a peak in March. For first-years there is little evidence of individual 'peaks' during this period, but October is marginally the most productive month. For adults, by contrast, there are increasing arrivals during October to March, with February and March the most productive months.

Although there are some similarities, the pattern in the West Midlands cannot be said to match unequivocally the movements proposed by Bourne. However, it does seem likely that three factors are involved in the arrivals of Mediterranean Gulls in the region:

• Post-breeding season dispersal, for juveniles and first years in particular, during July and August.
• Winter arrivals from September to January (February), involving birds of all age categories - this may perhaps involve a secondary relocation to winter quarters as suggested by Bourne but also perhaps involves cold-weather movements.
• Spring passage in February and March (early April), particularly involving adults.

Origins

Mediterranean Gulls are breeding in the UK in increasing numbers, with a very few pairs even in the West Midlands region (see below). Such British breeding birds no doubt contribute to the increased numbers observed in the West Midlands at other seasons but no doubt most continue to originate from further afield, in mainland Europe (and perhaps Russia). Ringing recoveries indicate that Mediterranean Gulls reaching the West Midlands region include individuals from quite a wide area of Europe, with a majority having been ringed in the Low Countries and France (see comment on juveniles above) but other individuals from further east in Hungary and Poland.

Adult Mediterranean Gull, West Midlands, August 2014. This individual had been ringed in Poland. Note coded colour ring on right leg.

Breeding in the West Midlands region

With increased numbers of Mediterranean Gulls visiting the region since 2000, and breeding increasing nationally, it was expected that nesting might be attempted in the West Midlands. Occasional individuals had been noted frequenting colonies of Black-headed Gulls in the Tame/Trent Valley system and in 2007 breeding attempts occurred for the first time in Warwickshire (one pair) and in Staffordshire (three pairs). Unfortunately all were flooded out following heavy summer rains. The first successful breeding occurred the following year, when two pairs nested in Staffordshire and one successfully fledged two young. In 2009 a single pair again reared two young, in 2010 three pairs fledged at least three young and in 2011 one pair reared a single young. Since then up to five pairs have attempted to breed in Staffs, N Warks and West Midlands combined but with very limited success.

References

Bourne, W.R.P. 1970. Field characters and British Status of Mediterranean Gulls. British Birds 63: 91-93.

Dean, A.R. 1989. Status of Mediterranean Gull in the West Midlands Region. West Midland Bird Report (for 1988) 85: 34-39.