Guest Blog – Of nests and nets by Dave Leech (BTO)


Dr Dave Leech is a Senior Research Ecologist at BTO, where I oversee the Nest Record Scheme (NRS) and the two standardised ringing projects, the Constant Effort Site (CES) scheme and the Retrapping Adults for Survival (RAS) scheme.

My job involves developing survey methodology, analysing data and communicating the results to volunteers and the general public.

I’m particularly interested in exploring the responses of breeding birds to climate change and finding out how birds in urban environments fare relative to those in the wider countryside.









Of nests and nets: why we still count eggs and ring birds

In a post on this blog on November 13th, Mark made some very nice comments about the BTO Regional Meeting in Nottinghamshire. He also presented a list of things that we, as an organisation, ‘could do better’, which included communicating the benefits of bird ringing and nest recording to an audience beyond our volunteers. As someone involved in the Nest Record and Ringing Schemes as both staff member and participant for over a decade now, I couldn’t agree more. We should be shouting from the rooftops about the achievements of the 3,000 ringers and 600 nest recorders who spend a combined 0.6 million hours each year collecting data that underpins much of the bird conservation work in the UK. So, let’s get the ball rolling………

Surely we know where birds go in winter by now?

When at a twitch (I do partake, occasionally), I like to start talking about ringing and nest recording at the first opportunity, to stimulate discussion and gauge attitudes amongst my fellow birders. The commonest misconception voiced is that the main purpose of ringing is to identify the wintering grounds of migrants. While that may have been the original intention when the Ringing Scheme was set up over a century ago, the chances of ringed birds being located in Africa are slim at best and satellite tracking is fast proving a more reliable method of specifying destinations, as well as routes and flight speeds.

A matter of life and death

IMG_1014So why do the Government (through the Joint Nature Conservation Committee), the BTO and the ringers themselves (who buy all their own rings and equipment) stump up the cash? What bang does their buck provide?

The true value of Ringing and Nest Record Scheme (NRS) data is the role they play in understanding species declines. ‘Population modelling’ may sound complex, but the basic principle is pretty straightforward – bird numbers are determined by the number of fledglings raised, the subsequent survival of those youngsters and that of the adults that produced them. Nest recorders collect data on productivity and ringers collect data on survival, allowing the relative influence of each on population trends, generated by thousands of volunteers like Mark taking part in the BTO/JNCC/RSPB Breeding Bird Survey (BBS), to be assessed. This is essential information for conservationists attempting to reverse declines (after all, there’s no point providing better nesting habitat if numbers are dropping due to starvation over winter) and the subject of many scientific papers written by my colleagues, the most recent by Rob Robinson et al. (but see also the NRS publications list).

So why don’t we focus efforts on declining species?

In the words of the great Joni Mitchell, “You don’t know what you’ve got ‘til it’s gone”. It’s not easy to predict what species may decline in future (I, for one, wasn’t expecting a crash in the Greenfinch population given it was one of the main species on which I cut my teeth as a ringing trainee), and you can’t investigate the factors driving the fall in numbers if you don’t have baseline figures – this is why long-term datasets are so valuable to conservationists. The information presented in the BTO’s BirdTrends report summarises the annual NRS results going back to 1966, alongside data collected by a number of ringing projects and population trends generated by BBS. And if you, like me, you can’t wait to find out whether the next point on the graph conforms to your gut feeling of how birds fared in 2014, we have a sneak preview of where it might fall in the preliminary trends, released this week.

The future of ringing

IMG_1416The way in which we use ringing to monitor survival is constantly adapting and improving. A decline in the number of reports of dead birds in the late 20th Century could have been catastrophic (and we still need more folk to report rings found on dead birds []) but thankfully statistical developments have allowed us to make more use of data from birds retrapped by ringers – and so the focus shifts from the dead to the living. The problem with relying on retraps is that the chance of recapturing a bird is dependent on a ringers’ effort, so a network of Constant Effort Sites (CES) have been established to standardise this effort across sites and years.

The use of colour rings reduces the need to recapture birds as individuals can be identified remotely, which is less time-consuming and also means that non-ringers can help collect survival data (my own, non-ringing mother does 90% of the fieldwork for my Holt Blackbird Project and her neighbours do most of the rest!). Increasingly, Passive Integrated Transponder (PIT) tags, similar to the chips vets place in cats and dogs, are fitted to rings, allowing a birds’ presence to be detected by automated recording systems.

It’s not just about survival, though. The ratio of juveniles to adult birds caught by CES ringers allows us to measure annual variation in breeding success, with trends again displayed in the BirdTrends report. Dispersal is another key variable, determining the ability of birds to colonise new breeding sites – thanks to ringing, we know that Marsh Tits are not one of nature’s explorers, but Pied Flycatchers fledged in the UK will happily move to foreign climes to rear their first broods. Ringers at bird observatories record the timing of spring and autumn migration each year, which has real implications for the ability of species to adapt to new situations – how early/late can our migrants shift their laying dates in response to climate change, for example? And catching birds regularly opens up a whole range of new data collection possibilities that we’re only just starting to explore, from disease to population genetics.

People power

I hope this post at least gives a taste of the role these demographic surveys play in modern conservation (and if you won’t take my word for it, check out recent editorials penned by John Eyre  and Ian Newton in the ever-excellent British Birds). As with all monitoring, there is no definitive ‘end’ product, no leather-bound tome sitting on a shelf in a dusty library – ringing and nest recording are part of an ongoing, proactive commitment to chart the health of our wildlife. And given the ever increasing list of potential threats, from climate change to habitat destruction, the efforts of citizen scientists across the globe are more valuable now than ever before.

Not only are ringing and nest recording worthy pursuits, they’re great fun and guaranteed to change your perspective on the birds around you, as focus shifts from the species to the individual and the interpretation of behaviour becomes key. Visit the NRS and Ringing Scheme webpages to find out how you can contribute.


21 Replies to “Guest Blog – Of nests and nets by Dave Leech (BTO)”

  1. That is a brilliant blog post Dave and it is all the reasons you mention that make me volunteer every weekend. Doing this makes me feel like I can doing something positive to help with the conservation of our birds.

  2. Excellent post, Dave. Sound conservation policy depends on a clear knowledge and understanding of what is happening to the populations of species that make up our fauna and flora and you give a clear exposition of how ringing and nest recording contribute to this. The UK has an enviable tradition of amateur naturalists collecting huge volumes of data on a wide range of different taxa and obtaining the most benefit from this effort requires the organisation of well designed schemes. The BTO sets a very high standard in this respect. Keep up the good work!

  3. A really interesting blog from Dave Leech. I do admire the BTO and their scientific approach. Lyn and I are greatly looking forward to the Annual Conference at Swanwick this weekend, always a fascinating meeting with great speakers.

  4. Excellent post Dave, made with your usual enthusiasm. Never waste a sentence by not including as much information as possible! Seriously though, the need to keep ringing for demography is so important. Constant Effort Site ringing is fascinating just on the local level – of seeing the same birds returning year after year. Getting the odd recovery from abroad is just a nice bonus.

  5. Now I know why I struggle to find Reed Warbler nests. I’m wearing my hat the wrong way round! Great blog Dave.

  6. Excellent post Dave. The BTO should have you on the staff/committee to extract more money from the Government Agencies. With your persuasive enthusism for ringing and nest record recording backed by scientific methodology and facts – you could not fail. See you at the conference.

  7. An interesting guest blog but I am afraid I am not convinced. I am quite uneasy about bird ringing; it seems to be a jolly day out but also seems to be morally and perhaps scientifically questionable. We all feel free to take the moral high ground about people, such as the “shooting set”. who persecute and kill our birds of prey for instance, so perhaps we should be thinking about the stress and trauma ringed birds must suffer and whether the data obtained compensates for this. I hesitate to say it but I sense similarities between the “shooting set” and the “ringing set”, not least in wondering if the importance of their jolly day out blinds them to the damage they may be doing. There must be other negatives arising from bird ringing but information on them does not seem to be readily available. I am, of course, no expert, so I would like to ask a few questions that occur to me that perhaps Dr Leech or some other knowledgeable person would answer. This would enable me to make a more balanced decision rather than the instinctive one I have already made.

    1. The BTO website shows that 950822 birds were caught and ringed in 2013. 244,028 were then retrapped. What percentage of caught birds were injured and put down, died or predated whilst trapped in the nets? Does retrapping increase the chances of injury/mortality and are specific species more liable to be injured or die than others? I have a vague recollection of reading that up 80000 birds die each year in the US during ringing for example. I am more than happy to be told my memory has failed me!!

    2. The BTO data shows huge numbers of juveniles ringed. I assume many of these are ringed in the nest, am I correct in this assumption and if so what is the survival rate of these juveniles compared to unringed juveniles?

    3. What effect does trapping have on the subsequent behaviour of birds? Are they for instance more likely to be predated than untrapped birds? Do they resume their normal behaviour or is their behaviour confused? I would think this is of special relevance regarding birds on migration. What control is used to compare the behaviour of caught birds with birds that are not caught? If no control is used or available then is not the scientific basis of ringing deeply flawed?

    4. On a moral point has the stress and discomfort of a caught bird been calculated or considered? Has anyone considered ringing may be inherently cruel?

    5. Regarding nest recording, there must be some disturbance to the nesting birds. Indeed the photo accompanying the blog shows Dr Leech wading through a reed bed, presumably in search of nests. Is any data available on subsequent failure of recorded nests?

    6. One piece of data on a specific species did catch my eye in particular. The BTO website shows that in 2013 a colossal 106,173 blue tits were ringed, which appears to be in excess of 10% of the yearly total of all birds ringed. It shows that almost 4,000,000 blue tits have been ringed in total. I suspect that the blue tit is a well studied species. How much extra knowledge about blue tits will be gleaned from the ringing of these 106,173 and the similar total that will have surely been ringed in 2014? Is it possible in the case of the blue tit ringing is utterly pointless?

    7. On a lighter note where the hell are all the tens (at least) of millions of rings that have not been recovered? Almost as bad as ring pulls I would think.

    As I have written earlier I am no expert and am quite happy to be corrected on any points I may have made. I do feel however that perhaps the people who take part in ringing do need to be a little more introspective about their actions and consider whether the end justifies the means.

    1. tony – thank you for taking the trouble to make that comment. Let’s see what answers you get. i could answer a few of your points but I’ll leave it top others for a while. Thank you again.

    2. Dear Tony,

      Many thanks for a really helpful email – lots of points here that warrant further discussion. I’ll start by addressing the philosophical issue and then move to your specific questions about the impact of ringing and nest recording.

      In your introductory paragraph and again in question 4 you raise the issue of morality, asking whether ringers have the right to catch birds if there is the potential to cause stress to the individuals caught. My response is that every action we perform and every decision we make at any part of our day, no matter how small, has implications for individual birds; did we drink environmentally friendly coffee, did we leave the video on standby, did we drive to work, did we eat meat for lunch, etc? I strongly believe that we do have a moral responsibility to all wildlife that involves quantifying the costs of all our actions and minimising their impact on the natural world – both ringing and nest recording help us to do that in the ways outlined in my post.

      The wording of your question suggests that some might favour the welfare of an individual over the future prospects of a population; my moral compass, and I suspect that of many conservationists, tends to point in the opposite direction. This is not to say that we don’t continually evaluate the pros and cons of the way we ring and work to minimise impacts, both as an organisation and as individual ringers; welfare is certainly utmost in the minds of the volunteers I’ve worked with during my ringing ‘career’ and where problems are identified, we work quickly to address them. The scheme is developing into a much more structured format, with the development of schemes such as CES and RAS maximising the value of each capture, and this is an ongoing process.

      You also raise the issue of motivation, highlighting the fact that many ringers enjoy catching birds. I can’t help but think this is a good thing as long as the outputs are of value. People who enjoy their work tend to do a better, more efficient job of it – just look at teachers. And when you’re talking about a volunteer survey, this is self-selecting; credit to those who devote their spare time to collecting data purely through a sense of duty, but it’s much easier to roll out of bed at 3.00am if you’re looking forward to it. The crucial point is that a sense of enjoyment doesn’t negate the value of the information collected – if anything, it’s likely to enhance it.

      In terms of your specific points:

      1.) A recent study in the US that looked at mortality of birds during ringing activities (, which they quantified at 0.23%. There are c. 1.2 million birds ringed in the US each year, so the resulting mortality figure stands at just under 3,000 individuals per annum. We have no comparable figures for the UK yet, but colleagues of mine are analysing the information as I type with the aim of publishing the results in a peer-reviewed journal and disseminating them more widely. Some species are more susceptible than others and guidance is provided to ringers.

      2.) Anecdotally, many birds ringed as pulli are relocated as breeding adults, often several years later, but recruitment is difficult to quantify as juvenile birds tend to disperse widely before they raise their first brood. We do calculate daily survival rates of nests at chick stage from NRS data, so if there are sufficient numbers of unringed broods in the sample, we might be able to compare this up to the point of fledging – I’ll certainly look into this. It is, unfortunately, impossible to directly measure the survival rates of unmarked nestlings once they have fledged as we have no means of identifying them subsequently, but see my response to the question below re. impacts of ringing more generally.

      3.) There are certainly some studies showing that handling can influence bird behaviour during and after the event (e.g.,, although there are other published studies that don’t find an effect (and possibly many more we are unaware of as it can be very difficult to publish negative results). As mentioned above, it is impossible to follow individual birds without marking, so we don’t have a true control, but the results of population modelling undertaken by many researchers (Michael Schaub’s work is a good example) show that that the survival rates generated by ringing are a good fit to observed population changes – this suggests that ringed birds are representative of the wider population in terms of the probability of mortality. It’s worth noting that the impact of all ‘special’ marks, e.g. satellite tags, is assessed by a panel of experts, with survival compared to that of unmarked birds.

      4.) I think I’ve addressed moral issues in the opening paragraphs.

      5.) The impact of nest visitation has been the subject of much research. The most recent review is linked from the NRS webpages ( and shows no overall negative effect of visitation on outcomes. There is, in fact, some suggestion of a positive impact, which is potentially problematic from a scientific standpoint, but does not have welfare implications. All nest recorders are asked to adhere to a Code of Conduct to minimise disturbance, also on the website (

      6.) Huge numbers of Blue Tits are indeed ringed annually, although some of these will not be targeted and will be caught when focusing on other species. As I mentioned in my post, we do need to keep an eye on species that are currently widespread in case they decline in future, but in the case of the Blue Tit the primary value of the dataset is as a model for other, rarer species. Having a really large, well distributed dataset for a single species enables us to look at impacts of pressures such as weather conditions, fine-scale habitat features, food availability and habitat connectivity in detail to help understand causes of population change, so the results can have implications that range far beyond the species itself.

      7.) We do receive records of rings found by members of the public using metal detectors from time to time, so they are out there, but I suspect ring pulls still outnumber them!

      Apologies for the long response, but you posed some very pertinent questions and I agree with you that transparent discussion really is the way forward. Balancing the good of the individual against that of the population will always be, to some extent, a subjective activity, but everyone needs to be aware of the evidence that feeds into decisions made.

      1. Well, Dr Leech , I must thank you for your reply. I not studied it fully at the moment-it may take me some time to digest it fully and to see if you have converted me! One perception of mine has probably already changed, perhaps Bird Ringing is a more rigorous scientific discipline than I realised.

        I tend to ask a lot of questions of conservationists on forums such as this and on social media, as well as writing a few letters. I am especially suspicious of the need to “manage nature” for instance. I often question the status quo and maybe play Devils Advocate a little! Usually the answers are brief, abrupt and obviously toe the party line. However that is not the case this time. It is so refreshing to receive such a detailed reply as the one you have given. You are clearly passionate about your field of study and thank you for taking the trouble to reply to my questions.

        PS I am SURE ring pulls outnumber bird rings!

        1. Well, Mr. Phillips, have you had time to study and fully digest Mr. Leech’s reply? He took the time to put together his very detailed reply, it would be a shame if you disregarded it for its length.

  8. Brilliant blog Dave. This confirms why we turn out on cold and frosty mornings before the Sparrows have arisen. I can use your comments effectively when briefing the casual visitors we have on many of our public sites in Birmingham and the surrounding area. Well done.

  9. A very good blog post Mark, I enjoyed reading it especially as I am a ringer myself and think it is every bit as important as every other research.

  10. An excellent post but also an excellent email from Mr Phillips. Only by having this discussion can we reassure others of the scientific benefit of ringing. As for being akin to the shooting set the ringers I have met (and I include myself) are in general much scruffier not a barbour jacket in sight. Why should anyone dislike the Mr Phillip’s post by the way are these not questions we should answer

  11. What a refreshing change. Proper honest questions to be asked openly and given non-defensive well thought out answers in reply. If only we could have this sort of discussion about more things. Thank you to both Tony and Dave. I will go out ringing tomorrow with good heart.

  12. Brilliant blog Dr Leech. I have been ringing since 2009 and in that time have ringed over 2,000 Blue Tits and retrapped over 1,000 of them in my main study area. One of the key areas of interest to me is the proposal that Great Tits usurp Blue Tits from an area over time, primarily by out-competing them for nesting areas. In one of my sub-site areas there has definitely been a shift in bias towards Great Tits and away from Blue Tits, but not in others. To make my point: even what might be seen as the most mundane of captures can add to our sum total of knowledge of the pressures affecting the commonest of species.

  13. Dr Leech.
    I have just your article on bird ringing after a discussion on the Stockport nature watch Facebook site.
    What interests me as a nature lover is whether ringing causes distress to birds, after they are caught in nets or taken from their nests. Your thoughts on the morality of ringing in response to Tony Phillips, to quote, ‘In your introductory paragraph…you raise the issue of morality, asking whether ringers have the right to catch birds if there is the potential to cause stress to the individuals caught. My response is that every action we perform…., no matter how small, has implications for individual birds; did we drink environmentally friendly coffee…etc? I strongly believe that we do have a moral responsibility to all wildlife that involves quantifying the costs of all our actions and minimising their impact on the natural world – both ringing and nest recording help us to do that in the ways outlined in my post’ Interesting answer.
    As a bird expert can you please answer this simple question? Does catching birds in nets or taking them from their nests to put rings upon them, cause them distress or pain?
    Many thanks.

  14. Doctor Dave Leech.
    Specifically, why do Dippers still need to be rung, anything up to 4 bands/rings ?
    10,000 have been rung in the past five years in the UK.
    I find the number of leg bands disturbing, for a little aquatic songbird to have to stand and swim against strong currents for twelve hours a day or more wearing several leg bands clearly must cause discomfort and distress. Common sense surely would suggest the forces of water impacting against legs with bands is an unwelcome burden, basic physics/drag theory would support this. They use their legs actively when swimming so any additional drag on the legs would inhibit this bird.
    I look forward to your reply.

    Thank you

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