SPECIES UP­DATE

Bird Watching (UK) - - Your Birding Month -

MY FIRST EX­PE­RI­ENCE of bird ring­ing was at uni­ver­sity, when I worked on a win­ter re­search pro­ject study­ing Chaffinches. We were in­ves­ti­gat­ing the ef­fects of feather mites on wild birds, and my job was to in­spect the wing feath­ers of each bird for the tiny mites. How­ever, the birds them­selves, so briefly held and then re­leased, were of far more in­ter­est to me than the par­a­sites. Even in win­ter, the black, blue and brick-red heads of the males, their green lower backs and in­tri­cately pat­terned wings were stun­ning. For me, as per­haps for oth­ers, the amaz­ing de­tails of these com­mon gar­den birds had pre­vi­ously passed me by, but those ring­ing ses­sions were an education in tak­ing a closer look, and were my first steps to a ca­reer in or­nithol­ogy. As well as re­ceiv­ing a les­son in the plumage and anatomy and won­der of birds, I did also learn about feather mites. Our mea­sure­ments didn’t find any link be­tween num­bers of mites and body con­di­tion, and it ap­pears that these par­a­sites, which live be­tween the fine fil­a­ments of the feath­ers and feed on the oil pro­duced by the preen gland, are rel­a­tively harm­less pas­sen­gers. How­ever, Chaffinches do suf­fer from other, more se­ri­ous, par­a­sites and dis­eases. One of the most vis­i­ble con­di­tions is swollen, scaly legs and feet, known as leg mange or scaly leg. There are ac­tu­ally two main causes of scaly leg: an in­fes­ta­tion of Cne­mi­do­coptes mites, or a vi­ral in­fec­tion known as pa­pil­lo­mavirus, which both have sim­i­lar ef­fects. Birds with these con­di­tions gen­er­ally ap­pear oth­er­wise to be in good health, though as the con­di­tion wors­ens they may be­come lame, less able to for­age and vul­ner­a­ble to preda­tors. The BTO col­lects in­for­ma­tion on dis­eased gar­den wildlife through the part­ner­ship pro­ject Gar­den Wildlife Health, and are mon­i­tor­ing the pres­ence of scaly leg in Chaffinches across the UK. Chaffinches are also af­fected by tri­chomono­sis, the par­a­sitic in­fec­tion that emerged sud­denly a decade ago and has led to a crash in Green­finch pop­u­la­tions. While re­ports made to Gar­den Wildlife Health show that Chaffinches of­ten suf­fer from this dis­ease, they ap­peared to have avoided the se­vere mor­tal­ity suf­fered by OB­SERVED Chaffinch breed­ing num­bers and re­ports of dis­eased birds are be­ing closely mon­i­tored Green­finches, and over­all pop­u­la­tions had been hold­ing up. How­ever, Breed­ing Bird Sur­vey re­sults from 2013 and 2014 showed that num­bers of breed­ing Chaffinches dropped sharply in those years and, as I write, we are await­ing the fi­nal fig­ures for the 2015 breed­ing sea­son. Could this be an ef­fect of dis­ease, or could there be an­other cause? Per­haps this is merely a dip, and num­bers will be back up again be­fore long, but we will be mon­i­tor­ing both Chaffinch breed­ing num­bers, and re­ports of dis­eased birds. De­spite the re­cent down­turn, Chaffinch num­bers are still much higher than they were at the start of rou­tine mon­i­tor­ing in the 1960s, hav­ing shown fairly con­sis­tent in­creases from the 1970s to the 2000s. We have an es­ti­mated 6.2 mil­lion breed­ing pairs in this coun­try, mak­ing this our third most nu­mer­ous breed­ing bird be­hind Robin and Wren, and num­bers swell fur­ther in win­ter by ar­rivals from north­ern Europe and Scan­di­navia. Though orig­i­nally a wood­land species, Chaffinches have adapted well to sub­ur­ban and gar­den habi­tats, as well as to frag­mented wood­lands and hedgerows, and it ap­pears that, at least un­til re­cently, the changes in our coun­try­side have been to their ben­e­fit.

Kate Risely

FW1F 2 3 4M 5 6W 7 8F 9 10 11M 12 13W 14 15F 16 17 18M 19 20W 21 22 23 24 25M 26 27 28 29F 30Sa 31 6.54 6.68 6.89 7.08 7.23 7.32 7.31 7.19 6.95 6.66 6.38 6.14 5.93 5.83 5.87 6.07 6.35 6.52 6.75 6.92 7.06 7.17 7.21 7.13 6.94 6.71 6.48 6.30 6.24 6.28 6.44 6.67 6.84 6.96 7.04 7.07 7.03 6.88 6.67 6.45 6.24 6.01 5.83 5.80 5.95 6.23 6.61 6.78 6.90 14:54 6.98 7.03 7.01 6.93 6.80 6.65 6.50 6.37 6.37 6.49 6.70

Even in win­ter, the black, blue and brick-red heads of the males, their green lower backs and in­tri­cately pat­terned wings, were stun­ning

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