I agree with Jonathan's point, sometimes that many people visiting throughout the month during the breeding season of a single pair of birds (for example Yellow-cheeked Tits 2 years ago? Hainan Blue Flycatcher this year and Black Drongo at MP a few years back) is itself a great disturbance, even though the birds may have fledged successfully in the end, this does not proof as support that the crowd have not caused any disturbance or that it did not affect the chicks. There are chances that chicks in disturbed nests are fed less then chicks in well hidden areas, therefore affecting their survival rate after fledging...This I can only speculate.
Personally, I uses playbacks and find it a very useful tool for birdwatching, mainly to bring in birds a little far away. For instance, I used playbacks for the Fairy Pitta I saw last month, which I believe would not have shown if I didn't use playbacks. If done correctly I don't think it will harm the birds in the long run, I only played the tape until the bird came into view and stopped once I got it's attention, it stayed long enough afterwards for me to enjoy great views. The problem is when playbacks are used during breeding season or close to a known nesting site, I completely agree this should be avoided, plus anyone who have tried should know that birds get more "jumpy" and alarmed when playbacks are used near nests and make them more difficult to photograph anyway. If the same bird is continually taped in day after day for a few weeks or months, I am sure this will cause problems, imagine hearing someone calling your name but never finding out who was calling you constantly! You will go nuts too! So, I agree playbacks should only be used sparingly and not in front of big crowds.
Disturbance of nesting birds should really be avoided, I never stay long if I find a nest, 10 - 15 minutes tops, and I rarely revisit the site. Staying there too long will not only increase the stress levels of the nesting birds but will likely attract the attention of crowds of photographers. I have seen people breaking off twigs and cutting off branches to get a good view of the nest, which will no doubt cause a lot of stress on the birds. 30 - 40 people all focusing on one nest is not a good practice and no doubt will attract unwanted attention. Some Taiwanese photographers told me last month a Fairy Pitta nest was raided after a few weeks of continued visits by groups of photographers, the chicks likely to have been taken away by bird catchers and sold for money. People could argue that they can protect the nest if photographers are there, but in reality once the nesting site's location is known, nest raiders can easily go back at night and snatch the chicks or eggs.
I know there's been a lot of debate going on with this issue, and have been going on for a long time. I just hope everyone can respect the birds that you are photographing, or else sooner or later there won't be any to photograph!
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Last edited by kmatthew at 3/06/2015 21:28 ]