Species Up­date

Dun­lins con­gre­gate in their thou­sands on the Bri­tish coast­line – but num­bers of this small wader are de­clin­ing

Bird Watching (UK) - - Contents -

Breed­ing num­bers of the Dun­lin are de­clin­ing

MANY WADERS OC­CUPY the shift­ing in­ter­face be­tween the sea and the land, for­ag­ing in the rich in­ter­tidal zones that are ex­posed to both the sun­shine and the marine cur­rents. On a global scale these habi­tats are al­most one-di­men­sional; thin lines run­ning along the edges of con­ti­nents, and waders track the sea­sonal pulses of their food sup­plies up and down these coast­lines in marathon in­ter­na­tional mi­gra­tions. The Star­ling-sized Dun­lin is one wader that makes epic mi­gra­tions along our coasts ev­ery year, con­gre­gat­ing in tens of thou­sands at par­tic­u­larly rich sites. They breed in the Arc­tic tun­dra and up­land ar­eas in north­ern Europe, and win­ter along north­ern-hemi­sphere coast­lines across the globe. Num­bers spend­ing the win­ter in the UK vary from year to year, but cur­rently av­er­age about 360,000, mak­ing this one of our most com­mon win­ter­ing coastal waders. Jan­uary is the peak month for win­ter­ing birds, ac­cord­ing to the Wet­land Bird Survey, and the greatest con­cen­tra­tions are on ma­jor es­tu­ar­ies in­clud­ing the Sev­ern, the Hum­ber, the Thames Es­tu­ary and More­cambe Bay, though smaller num­bers can also be found at in­land wa­ter­bod­ies. Ring­ing re­cov­er­ies have shown that once win­ter­ing Dun­lin have ar­rived at their fi­nal des­ti­na­tion they are very site-faith­ful, not mov­ing much over the course of the win­ter, and of­ten re­turn­ing to the same site year af­ter year, mak­ing them vul­ner­a­ble to de­vel­op­ment and habi­tat change. In April and May, Dun­lin start mov­ing north, joined by oth­ers that had spent the win­ter fur­ther south along the coasts of south­ern Europe and West Africa, in preparation for their late, high lat­i­tude breed­ing sea­son. By mid-july, re­turn­ing mi­grants once again ap­pear on our coasts, and this pas­sage con­tin­ues through Au­gust and Septem­ber. Dur­ing this non-breed­ing sea­son, we see Dun­lin of three dif­fer­ent races, schinzii, arc­tica and alpina, which can vary markedly in size and bill length, mak­ing iden­ti­fi­ca­tion con­fus­ing. About 10,000 pairs of Dun­lin of the schinzii race are es­ti­mated to breed in the UK; their strongholds are the North­ern Isles and the Outer He­brides, as well as the flow coun­try and up­lands of main­land north­ern Scotland, with good DUN­LIN You could see these in their tens of thou­sands on Bri­tain’s coast­line. The BTO runs vol­un­teer sur­veys to mon­i­tor and ex­plain changes in bird pop­u­la­tions. To find out more about the Wa­ter­ways Breed­ing Bird Survey visit num­bers also found in the Pen­nines. There is a tiny breed­ing pop­u­la­tion on Dart­moor, con­sist­ing of about 15 breed­ing pairs, and these have the dis­tinc­tion of be­ing some of the most southerly breed­ing Dun­lin in the world. In con­trast to their non­de­script grey win­ter plumage, sum­mer Dun­lin are beau­ti­fully pat­terned in ru­fous, black and white, with a dis­tinc­tive black belly patch. Un­for­tu­nately, num­bers of breed­ing Dun­lin in the core pop­u­la­tion in the Outer He­brides de­clined by 50% dur­ing 1983–2000, and by a fur­ther 15% from 2000–07. In­tro­duced Hedge­hogs are thought to have con­trib­uted to these de­clines through egg pre­da­tion, while habi­tat changes are shown to have played a part in de­clines in other parts of the UK. As well as de­clines in breed­ing birds, the num­bers spend­ing the win­ter here have also been fall­ing, and the cur­rent es­ti­mate of 360,000 win­ter­ing birds is only half of the num­bers recorded in the 1970s. The rea­sons for this de­cline in win­ter­ing num­bers are not clear, but are thought to be due to an over­all change in win­ter­ing dis­tri­bu­tions, with more birds spend­ing the win­ter in con­ti­nen­tal Europe, nearer to their breed­ing grounds, due to warmer win­ters, re­cently. Kate Risely is the Bri­tish Trust for Or­nithol­ogy’s Gar­den Bird­watch Or­gan­iser

Ring­ing re­cov­er­ies have shown that once win­ter­ing Dun­lin have ar­rived at their fi­nal des­ti­na­tion they are very site-faith­ful

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