Species up­date

A nest­box scheme launched in Scot­land dur­ing the 1970s had a huge im­pact on breed­ing num­bers of Gold­en­eye

Bird Watching (UK) - - Contents - Kate Risely is the Bri­tish Trust for Or­nithol­ogy’s Gar­den Bird­watch Or­gan­iser KATE RISELY’S

Nest­boxes can be a game changer for Gold­en­eye, who nest high off the ground

CAN PUT­TING UP nest­boxes help birds? In many cases, the jury is out. Of course, a box will be very use­ful to those par­tic­u­lar birds that choose to nest in it, and the great value of nest­boxes is that they al­low the suc­cess or fail­ure of the nests to be mon­i­tored and recorded. In many cases, how­ever, bird pop­u­la­tions are lim­ited by the avail­abil­ity of suit­able food sup­plies, and sim­ply in­creas­ing the num­ber of nest sites avail­able, while it sounds like it should help, will not nec­es­sar­ily cause the over­all num­bers of birds to in­crease. While nest­boxes don’t al­ways make a dif­fer­ence, for some birds they are a game changer – and one of these, per­haps sur­pris­ingly, is a duck. Gold­eneyes are best known from our coasts and lakes in the win­ter, when the brown-headed fe­males and strik­ing black and white males stare back at us with their round golden eyes. Un­like most of our fa­mil­iar ducks, they nest high above the ground, in hol­low trees. The ad­van­tage of this strat­egy is that the eggs and duck­lings are hid­den away safe from ground preda­tors, though as all duck­lings leave the nest while they are still un­able to fly, it does mean a long drop when the time comes to fol­low their mother to water! An­other dis­ad­van­tage is that ducks, of course, can’t ex­ca­vate holes in trees, so the avail­abil­ity of suit­able cav­i­ties can limit the num­bers that can breed in a par­tic­u­lar area, par­tic­u­larly as modern, man­aged wood­land habi­tats don’t tend to con­tain much stand­ing dead wood. Gold­eneyes first bred in the UK in 1970, in Spey­side. Scot­tish or­nithol­o­gists, en­cour­aged by re­ports from else­where that Gold­eneyes had suc­cess­fully nested in ar­ti­fi­cial sites, be­lieved that a nest­box scheme could ben­e­fit the fledg­ling Scot­tish breed­ing pop­u­la­tion, and in­stalled a num­ber of boxes along­side lochs and rivers in the High­lands. They were not used straight away, but they were du­ti­fully mon­i­tored, and in 1974, two of the boxes were used. Af­ter this the scheme re­ally took off, and by 1982 there were 83 boxes sup­port­ing 41 pairs of Gold­eneyes. To­day, there are thought to be about 140 breed­ing pairs in the UK, prov­ing the value of a well-thought-out nest­box scheme. From Oc­to­ber to April, the UK num­bers are rather larger, an es­ti­mated 27,000 birds, which ring­ing re­cov­er­ies show are mainly from the Scan­di­na­vian pop­u­la­tion. They are found on lakes, large rivers and shel­tered coasts, though, as win­ter pro­gresses, they tend to leave in­land sites and re­turn to the ocean, per­haps as lo­cal food sup­plies are de­pleted or the fresh water freezes over. Males are heav­ier and larger than fe­males and are able to make longer dives to for­age for food; this dif­fer­ence in for­ag­ing abil­ity means that males and fe­males oc­cupy dif­fer­ent habi­tats, and it’s nor­mal to see groups that are dom­i­nated by one sex. Gold­eneyes breed across Eura­sia and North Amer­ica, with a world pop­u­la­tion num­ber­ing sev­eral mil­lion in­di­vid­u­als. They have been eval­u­ated as ‘se­cure’ both glob­ally and in Europe, and ap­pear to be do­ing well in Scan­di­navia, their main Euro­pean breed­ing area. How­ever, counts of Bri­tish win­ter­ing birds made through the Wet­land Bird Sur­vey show that num­bers have been de­clin­ing since the early 1990s, thought to be due to milder Euro­pean win­ters mean­ing that birds are able to stay closer to their breed­ing grounds, not need­ing to make the jour­ney to the UK.

Ducks, of course, can’t ex­ca­vate holes in trees, so the avail­abil­ity of suit­able cav­i­ties can limit the num­bers that can breed in a par­tic­u­lar area

GOLD­EN­EYE Who would have thought that such a duck would ben­e­fit from tree-mounted nest­boxes?

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