In the March issue of BB, Richard Porter described his difficulties in hearing the calls of certain birds – and speculated about the potential effects of an ageing workforce on the results of bird surveys. Andy Musgrove, Head of Monitoring at BTO, penned a reply to Richard’s letters, and you can read those pieces here
The topic has caused plenty of interest among readers, and the responses received include the following. Leave a comment if you agree – or disagree!
I have used an internet-based test (see http://www.noiseaddicts.com/2009/03/can-you-hear-this-hearing-test/) to ‘rate’ my hearing – which, like Richard’s, has deteriorated recently to the extent that I now wonder how much I’m missing! A couple of years ago I became conscious that I could hear cicadas through one ear but not the other. A visit to my GP and then a specialist concluded that, as far as they were concerned, my hearing was fineâ€¦ but of course their tests were only concerned with my being able to hear what humans were saying, not other species.
According to the online test, I can hear up to 10kHz in my right ear – so locating high-pitched calls is a problem for me, even if I can hear them! I can’t hear 12kHz in either ear. (I do, therefore, have a reasonable excuse for selective deafness when my wife complains I haven’t taken any notice of her!)
Can I suggest a couple of ideas? BBS volunteers could be asked to give their age with their annual returns, or at least this information gathered as a one-off survey. Volunteers could also be asked to check their hearing (using the link above, or similar online test) and the data from these tests could then be analysed, together with age data, to look for any effects on numbers of birds of species with high-pitched calls they detected in the most recent year’s dataset. It would also be possible to look for any reductions in numbers of those species reported by surveyors who have contributed to BBS over a period of time. It may then prove possible, and maybe necessary, to apply correction factors to BBS indices. I think that this is just as pertinent as the analysis undertaken to test for effects of transect familiarity.
Dave Smallshire (aged 60 and starting to feel it), 8 Twindle Beer, Chudleigh, Newton Abbot, Devon TQ13 0JP; e-mail [email protected]
I have been profoundly deaf for many years, something caused initially by noise exposure and now exacerbated by ageing. When I was in Uganda a few years ago, our South African guide suggested I should try a gadget called the SongFinder (http://www.nselec.com). This works by shifting the frequency of sound by a half, a quarter or a third, thereby bringing most bird songs and calls within the threshold of my remaining hearing. The birds, of course, sound different and you have to start learning them all over again, though many are easily identifiable by their rhythm alone, such as Common Chiffchaff Phylloscopus collybita or Grasshopper Warbler Locustella naevia. When I first started to use the SongFinder, I was amazed to be surrounded by (unidentifiable) bird song after years of almost totally silent walks. It has transformed my birding, though it is still a challenge to identify some of the sounds such as the enormous variety of Great Parus major and Blue Tit Cyanistes caeruleus calls. Suggested rewording:’ I can now identify most of the common birds by song, though, because I am totally deaf in one ear, I cannot localise them; but if I had hearing in both ears,I would be able to localise the sounds with SongFinder because the microphones are located on each headphone.
Robin Cox, Linden House, Long Lane, Fowlmere, Royston, Cambridgeshire SG8 7TG; e-mail [email protected]
I was interested to read the correspondence on this subject in BB. It did not, however, mention the fact that women normally retain their high-register hearing much longer than men. If the number of women doing BBS and other survey work is increasing (is there any evidence?), this could cancel out the bias of the elderly male surveyors who are missng out on Goldcrests Regulus regulus.
Rowena Quantrill, 36 Newtown, Bradford on Avon BA15 1NF; e-mail [email protected]
Richard Porter, younger than me, now hears only half the number of birds that he used to. I have the same problem, but bypass it by using a SONG FINDER from the USA. This gadget reduces the frequency of high notes by up to four times. Now I can easily hear Common Swifts and the higher notes of warblers, and count many more birds.
Does this ‘ageing’ affect BBS surveys? I have in front of me the Cumbria Bird Atlas (2002) and the Norfolk Bird Atlas (2011). The latter lists about 900,000 breeding pairs of birds while the Cumbrian figure is about 2.7 million pairs. Cumbria is slightly larger than Norfolk, and has far more Meadow Pipits and Willow Warblers, but their numbers do not really alter the gap. Cumbria appears to have two or three times as many Blackbirds, Robins, Dunnocks and Wrens.
Could it be that Cumbria’s birders are younger than those in Norfolk and so hear far more birds? I doubt it. Cumbria’s farmland is for cattle and sheep, Norfolk mostly arable. There is not much difference in tree cover of length of hedgerows. Is the difference really the result of how BBS surveys are extrapolated? I expect so.
Julian Taylor, 4 High Green, Sandford, Appleby-in-Westmorland CA16 6NR
And finally… Richard Mabey, in his book Nature Cure, sums it all up so eloquently. The following is reproduced with his permission. Did Auric come before Songfinder?
â€¦The frustration and sense of loss – how many more springs had I got left? – drove me into a rare bout of technological busyness. I could do something about my attention, but for my hearing I needed help, some clever escape route out of my personal silent spring. I went to see my audiologist, who denied there was anything superior to my hearing aid. I thought of the ear-trumpet that was among Gilbert White’s effects, but felt such a thing might be a tad ostentatious for the Fens. Then David Cobham did some lateral thinking and suggested I went to a detective agency, but they informed me that portable devices for tuning in to distant sounds were just film-makers’ fiction. So it was down to me, and handful of specialist electrical shops, and the end result was a combination of a high-quality directional microphone, a digital voice recorder and a pair of Walkman headphones. I called it Auric. The first time I took it out was a revelation: the birds I thought might be stretched out between Baghdad and the Alps seemed to be singing exultantly only a few feet away. I heard properly, for the first time since my thirties, the little grace notes in Reed Warblers’ songs, the scratching of Whitethroats, and that thin, triumphant see-saw of the Chiffchaff. And, paying for that artificial recapturing of youthful senses, I also heard, enormously amplified, the shattering roar of distant aircraft and the hum of traffic. It was I felt, a fair swap, since these are the realities of the world to which our migrants return. But they’d made it back to where they belonged, and back, too, inside my headâ€¦