Swansea Bay: some bird population trends

The following plots are made using figures for Swansea Bay published in the Gower Ornithological Society's annual report Gower Birds (Grenfell et al., 1994 to 2006). They were produced in 2009 as part of an impact assessment for a proposed development that potentially could affect Blackpill SSSI. The plots show population trends for a few of the species examined over a 13 year period:

Great Crested Grebe 
Plots show that numbers increased steadily over the period. A clear mid-winter peak with birds largely absent from April until October. It would be interesting to see how Baglan compares?

Oystercatcher
Again numbers increased steadily over the period. Birds arrive post breeding much sooner than the grebes with failed/non-breeders returning as early as June. Winter average around 3000 birds.

Common Gull
Clearly a species that has declined, possibly partly explaining the general lack of Ring-billed Gulls these days?  Winter maxima around 2000 birds.

Great Black-backed Gull
This is quite and interesting one as non-breeding birds either gather or pass through during the summer months, when the majority of other birds are absent. The July maxima averages over 100 birds.