Larus argentatus, Pontoppidan, 1763.

So here's a second synanthrope for the day:

Juvenile, Brighton, East Sussex, U.K, in July 2012, using Olympus E-420 and Zuiko 70-300mm lens.

This is a member of the most frequently cited example of species ring - essentially, when a more-or-less continuous band of a specific environment exists (as in the near-arctic and arctic coasts of Europe, America and Asia) - a species that becomes adapted to that specific environment will eventually spread through and colonise the whole area but, if the ring is large enough that genetic flow between populations are incomplete, then genetic drift can cause the two ends to be genetically incompatible when they eventually close the ring.

This particular ring closes in the UK, which is probably why it's so frequently cited, with the Lesser black-backed gull, and the silver-backed, or Herring gull,

Larus argentatus

(Pontoppidan, 1763)

Which, when it grows up, should look like these little fellows from Priory Park in Chichester, West Sussex, UK: 

Photographed in Priory Park, Chichester, West Sussex, UK, in January 2012, using Olympus E-420 and 40-150mm Zuiko lens.

 And it belongs to:

- Laridae         

-Lari                 

See also Sterna hirundo.

- Charadriiformes

See also Burhinus vermiculatus.

- Neoaves             

See also Troglodytes troglodytes, Megaceryle maxima, Ardea goliath, Chalcophaps indica, Stigmatopelia senegalensis  and Tockus alboterminatus.

- Neognathae          

- Neornithes              

- Euornithes                

- Aves                           

- Maniraptora                  

- Coelurosauria                  

- Tetanurae                          

- Therapoda                           

- Saurischia                              

- Dinosauria                                

- Avemetatarsalia                           

- Archosauria                                   

- Archosauromorpha                           

- Sauria                                                 

See also  Thelotornis capensis, Trachylepis varia, Zootoca vivipara and Lygodactylus capensis.

- Diapsida                                                

- Romeriida                                                

- Reptilia                                                       

- Amniota                                                        

- Reptiliomorpha                                                

See also Syncerus caffer and Hipposideros vittatus.

- Tetrapoda                                                          

See also Rana temporaria, Breviceps poweri and Chiromantis xerampelina.

- Sarcopterygii                                                        

- Osteichthyes                                                           

See also Synchiropus splendidus.

- Teleostomi                                                                

- Gnathostomata                                                            

- Vertebrata                                                                     

- Craniata                                                                          

- Chordata                                                                           

- Deuterostomia                                                                     

- Nephrozoa                                                                            

See also Burtoa nilotica, Ligia oceanica, Dicranopalpus ramosus, Hyllus argyrotoxus, Alopecosa barbipes, Enoplognatha ovata, Argiope bruennichi, Pardosa amentata, Enallagma cyathigerum, Pseudagrion hageni, Lestinogomphus angustus, Rhyothemis semihyalina, Humbe tenuicornis, Lobosceliana loboscelis, Cyathosternum prehensile, Heteropternis thoracica, Stictogryllacris punctata, Enyaliopsis, Tettigonia viridissima, Sibylla, Pephricus, Grypocoris stysi, Ranatra, Anoplocnemis curvipes, Synagris proserpina, Vespula germanica, Astata tropicalis, Anthophora furcata, Andrena nigroaenea, Zebronia phenice, Crambus pascuella, Nemophora degeerella, Sphinx ligustri, Laelia robusta, Acada biseriata, Metisella willemi, Anthocharis cardamines, Papilio demodocus, Panorpa germanica, Chloromyia formosa, Senaspis haemorrhoa, Helophilus pendulus, Episyrphus balteatus, Metadon inermis, Diasemopsis meigenii, Dolichotachina caudata, Megistocera filipes, Hagenomyia tristis, Phyllobius pomaceus, Otiorhynchus atroapterus, Malachius bipustulatus, Oedemera nobilis, Melolontha melolontha, Cheilomenes lunata, Neojulodis vittipennis, Demetrias atricapillus, Anthia fornasiini and Lophyra cf. differens.

- Bilateralia                                                                                

- Eumetazoa                                                                                

- Animalia                                                                                     

- Eukaryota                                                                                     

And that, folks, is all!