Tag: Q&A

This book (or rather book series, since it will be more than just one book) has been an incredibly long time in the making, and the sheer scale of the project alone makes it a huge achievement. What were the main challenges you came across and how were they overcome? 

Our project began in 1998 when the French publisher Delachaux et Niestlé requested us to create a new feather identification guide based on colour photos. The illustrations of feathers in our Atlas are arranged according to a unique, recognisable pattern on a standardised grey background, each of them depicting the feathers of an individual bird, which allows readers to grasp the essence of different feather types at a glance. We use a method of directly scanning feathers on a flatbed scanner that was developed at the University of Amsterdam. But printing costs were prohibitive. Print-on-demand technology made it possible to produce smaller, more affordable print runs. We used this technology to produce our first collective work of the Feather Research Group titled The Tail Feathers of the Birds of Central Europe. We also produced two feather calendars with a series of colour plates that were composed for our Atlas of Feathers for Western Palearctic Birds as a test run to see how the colours came out in print.     

In 2009, after 10 years of intense work, we produced a DVD with 1,280 colour plates featuring illustrations of feathers for 330 Passerine species. This compilation from many sources resulted in a wave of interest in our project. Meanwhile, the number of Passerine species for which colour plates were ready had nearly doubled to more than 600 species. We decided to publish our collective work under the name The Featherguide rather than any individual names. In this way, everyone in our group can identify with this eponym and no one needs to feel that anyone is adorning themselves with borrowed plumes.  

The most time-consuming aspect of our work is the composition of feather images for bird species that are not found in any feather collections. Thanks to the kind support of the Feather Identification Laboratory at the Smithsonian Institution, and generous curators at Natural History Museums, it was possible to develop a technique that allows us to extract depictions of isolated feathers from photographs of bird skins. The missing part of the feather that remains in the skin is digitally added in a seamless way. A single colour plate produced in this way from many different puzzle pieces takes up to one week. With 1,350 bird species to be covered in our Atlas and our goal of illustrating all important plumages, you can imagine how many months and years this adds up to. We thank readers for their patience and interest.  

Our project has inspired a number of off-shoots that will be welcome by most readers. For example, the French feather identification book by Cloé Fraigneau, which is now available  under the title An Identification Guide to the Feathers of Western European Birds, emerged from the initial planning sessions we had with the director of Delachaux et Niestlé. The series of books on feather identification by Professor Hans-Heiner Bergmann was inspired by our flyer distributed at the International Ornithological Congress in 2006. A book titled Feathers: Displays of Brilliant Plumage by world–renowned photographer Robert Clark features several photographs of original feather sheets that were mounted for our Atlas of Feathers for Western Palearctic Birds, each depicted on a full double page. Even Audubon Magazine featured a series of photographs of original feather sheets from our Atlas of Feathers for Western Palearctic Birds. The Feather Atlas for North American Birds, published online by the Forensics Laboratory of the U.S. Fish and Wildlife Service, was inspired by our original project description in the Conference Proceedings of the International Bird Strike Committee. The Featherbase website, which gets several million visitors per year, adopted the same grey background colour that we had chosen for our illustrations and also adopted the idea of depicting wing and tail diagrams in the way that we presented in our original project description.

The study of feathers has an obvious application for species identification, particularly when dealing with bird remains. But can a study of feathers also provide us with an insight into bird evolution and taxonomy, or indeed other areas of research? 

Yes, indeed, much can be learned on these topics through the study of feathers. Subtle variations in the phenotype constitute the raw material for natural selection to act upon. Through the study of feathers, we can gain a deeper understanding of evolution. The high amount of phenotypic plasticity in bird wings is a clear example of evolution in progress. Many species exhibit subtle fluctuations in the extent and depth of emarginations on their primaries, resulting in different numbers of slots in their wings between different individuals. Another area of phenotypic plasticity is unusual variations in the number of flight-feathers. Our Feather Research Group compiled a large body of such variations from scientific literature and from our own research. 

While feathers were not unique to birds, emarginations are. Birds as we know them today are thought to have evolved from Mesozoic stem birds that coexisted with feathered dinosaurs. The only line that survived the cataclysmic event on Yucatan 66 million years ago evolved emarginations in their wings. If we consider birds as a class of their own, then the feature that distinguishes birds from feathered dinosaurs is the presence of emarginations. The evolution of emarginations can bring clarity into today’s scientific discussion on the origin of birds, which largely portrays birds as living dinosaurs, thereby blurring the line between reptiles and birds. Emarginations make birds unique. Neither bats nor insects nor pterosaurs have emarginations in their wings. Not all bird families living today have emarginations in their wings, giving rise to the question whether these bird families never evolved emarginations or whether their emarginations disappeared during the course of evolution. Emarginations can be lost either through the evolution of very narrow, pointed wings or through devolution into flightlessness. 

Whether our findings have any relevance for taxonomy is up to taxonomists to decide. In the past, taxonomy was entirely based on phenotype, while today it is largely based on  genotype. Phenotypic variations do not play a significant role in current taxonomy, unless one is interested in the possible inheritance of epigenetic switches that regulate the expression of the genotype into the phenotype. For example, it is not clear whether the fine-tuning of the gradient in retinoic acid that is linked to two genes on the sixth and eighth chromosomes (and is responsible for the regulation of the vane width of feathers) was already inherent in the genome of Mesozoic stem birds and was activated through one of these epigenetic switches, giving rise to emarginations in modern birds. This question may be possible to answer by looking at the genome of bird families that appear to have never evolved emarginations so far, such as rails. 

Who do you think these books will appeal to and who will benefit from such a comprehensive and high-quality atlas? 

Anyone who visits the Featherbase website and finds the scans of feathers depicted there to be useful or interesting will also benefit from our work. If only 1% of the millions of visitors to this website see any value of having a printed Atlas with feather images of similar or even higher quality, this will make our  Atlas of Feathers for Western Palearctic Birds worthwhile.  

Many of the scans shown on the Featherbase website are from the collection of Dr. Wolf-Dieter Busching, the former director of the Naumann Museum in Köthen, Germany, who built up the largest scientific feather collection in the world, comprising feathers of around 2,500 bird species. During the time of the former communist regime in East Germany, it was difficult for Dr. Busching to obtain paper of a consistent colour for mounting the feathers in his collection. Therefore, his feather specimens are mounted on paper of many different colours, sometimes blue, sometimes red, sometimes yellow. Since the vanes of feathers are semi-transparent, the colour of the paper they are mounted on influences the colour of the feathers. In addition, the feathers in Dr. Busching’s collection often overlap each other, thereby hiding parts of the neighbouring feathers. In our Atlas of Feathers for Western Palearctic Birds, we show all feathers on the same standardised grey background and without overlap. In this way, each feather is fully visible and the colours of the feathers can be reliably compared.  

Of course, the production of a series of books with high-quality colour plates is more expensive than running a website. The cost of such a series in printed form will limit the number of potential buyers compared to the number of visitors to the Featherbase website. We will keep the cost as low as possible to maximise the  number of people able to afford our series in printed form.  

The first volume in the series provides readers with a global overview of feather characteristics. Were there any particularly surprising data or revelations that resulted from compiling such a comprehensive collection? 

There were several surprises indeed. Two of the most peculiar discoveries, or rather rediscoveries, were made in the families Tityridae (tityras, becards and allies) and in the family Trochilidae (hummingbirds). In the families Tityridae, two genera, Tityra and Pachyramphus, have a small, crippled primary number 9 in between normally-sized neighbours in the wings of adult males, while females and juveniles have normally formed wings. The function of the reduced-sized P9  may be related to sound production (sonation) during the display of adult males, but so far, we could not find any references in the scientific literature that would substantiate such an assumption. Amazingly, this peculiar phenomenon had even escaped the attention of Dr. Wolf-Dieter Busching, who devoted his entire life to the study of feathers, and none of our other collaborators in the Feather Research Group noted this phenomenon. 

There are currently three mounted feather specimens of adult males of these two genera on the internet, one of them from the collection of Dr. Busching and two from other feather collections. In each of these three feather collections, the reduced-size P9 was mistakenly glued in front of P10 rather than in its correct position between P8 and P10, indicating that the respective feather researchers had no clue where this feather belongs and seem to have misjudged it to be a reduced outer primary, as is found in many passerines. However, when we consulted an older publication on feathers from 136 years ago, it turns out that this odd, reduced-size feather was already noted by Hans Gadow in 1888, at least in the genus Tityra, while its presence in the genus Pachyramphus seems to have escaped his attention, too.  

The second peculiar discovery in the family of hummingbirds concerns the presence of emarginations at the tips of the outer primaries in males of 22 species from five genera. Most of us in the Feather Research Group had assumed by default that none of the hummingbird species have any emarginations, based on our experience with the many species for which we had examined feathers. The great majority of the 377 extant hummingbird species do not have any emarginations, as in the related family of swifts. So, it would have been easy to miss these exceptional few species if the effort had not been made to look at every single hummingbird species based on photographs of live birds. Again, the fact that only males of these exceptional species have emarginations, while females are missing them, leads to the assumption that these emarginations have something to do with the display flight of males. In this case, there is indeed a scientific paper dating back to 1983, which confirms this assumption for just one of the 22 hummingbird species in which males have emarginations. The only feather experts who knew about this study are Professor Lukas Jenni and Dr. Raffael Winkler from Switzerland. The authors of this study found that males create noises with their emarginated primaries and that these noises are used to protect nectar resources. Filling the slot between emarginated primaries with a glue film or clipping the distal 2–3 mm of these primaries caused males to sing more to protect their territories. We can deduce that the other hummingbird species in which males have emarginations use them in a similar way to produce sound. There is, however, a sixth genus of hummingbird in which males have inverse emarginations at the base of the primaries, not at their tips. This phenomenon of emarginations at the feather bases instead of at their tips does not make any aerodynamic sense, so it is likely that these inverse emarginations have some type of ornamental function in males.  

These two discoveries, or rather rediscoveries, in the families Tityridae and Trochilidae teach us to remain open and not adhere to preconceived ideas. They also teach us to consult old literature that may have been forgotten or considered outdated.  

The first volume will initially be published in black and white to make it affordable to as many people as possible. The online database of feathers is also available to everyone in the hopes that citizen scientists and members of the public will help to verify and correct the results. Given that birdwatching is such a popular pastime, do you think that there is a large body of untapped knowledge within the birding public? 

There definitely is a large body of untapped knowledge within everyone, not only within the birding community. The key is to allow everyone to express their inner potential themselves. We are in favour of encouraging birders to publish their own data under their own names. Professor Peter Finke, who advises our Feather Research Group, calls this approach of empowering citizens to publish their own data Citizen Science Proper. What has been prevalent so far is Citizen Science Light, in which so-called experts scoop off the knowledge of the public and make a name for themselves with borrowed plumes, so to speak. Professor Finke published a book titled Citizen Science: The Underestimated Knowledge of Laymen (, which answers this question in much greater depth, giving many examples for birdwatchers in particular.  

With regards to the global survey of emarginations in all bird species of the world, that became possible on the basis of photographs of live birds, which citizen scientists generously share on the internet. Our approach of opening our research findings on the number of emarginations in all bird species of the world by listing the internet links of the original photos that were used for this study is a way of thanking  these many thousands of photographers. They all deserve to be mentioned as co-authors of our study. By sharing our findings and providing the original links to the photos that were used, we offer these photographers a way to give us their feedback on what we discovered thanks to their generosity. Anyone else who likes to share their observations on the photographs of live birds and scans of feathers that were used for our study is also welcome. We greatly value this interaction with birdwatchers and the general public. 

How many volumes will the series eventually comprise, and do you know when they are due to be published? 

After our last meeting in 2016, the World Feather Atlas Foundation purchased ten large scanners for our Feather Research Group. Five of these scanners went to the Featherbase team to support their endeavour of creating a World Feather Atlas. The remaining five were given to other collaborators in our group. The Featherbase team adopted the same grey background for newly mounted feather specimens as we adopted in 1998 for our Atlas of Feathers for Western Palearctic Birds. This unified the backgrounds on all scans,  creating the basis for a potential cooperation to speed up the work on our Atlas of Feathers for Western Palearctic Birds.  

The production of colour plates for the passerines took 24 years because they were all produced by only one person. If the work on the colour plates for the non-passerines is divided up by the holders of these ten scanners, it will be possible to produce the remaining colour plates more quickly. At the same time, the holders of these scanners can use them for their own projects.  

Most important to us is to respect the copyrights of everyone who produces scans of feathers. Any contributions to our Atlas of Feathers for Western Palearctic Birds must be based on mutual respect for everyone’s free will. Those who contribute scans of feathers are treated at an equal level to those who contribute text. In the past, illustrators of bird guides were often underappreciated compared to the authors. All too often, illustrators were not even mentioned on the book cover. We feel that this relationship between illustrators and authors needs to be amended. Illustrators deserve to be cited alongside authors. In our Atlas of Feathers for Western Palearctic Birds, the work of those who produce scans of feathers is even more important than those who write the texts, because the texts can only be written on the basis of these scans. 

The Full Edition of our Atlas of Feathers for Western Palearctic Birds will comprise a total of ten volumes including the introductory volume. Each of the subsequent nine volumes will cover about 150 bird species, adding up to a total of about 1,350 bird species. The Concise Edition will consist of two volumes. . The most precious thing we have to offer are the large-size colour plates in the full edition. The illustrations of feathers in the Concise Edition will be a cut-down version of the original colour plates and considerably smaller.

Atlas of Feathers for Western Palearctic Birds, Volume 1: Introduction is available to pre-order from our online bookstore.

This is the first comprehensive guide to bird pellets showcasing a wide range of pellets produced by different species, including owls, hawks, waders and various garden birds. Author Ed Drewitt offers a methodical introduction to pellets, outlining what they are, how they’re formed, dissection methods, analysis and common findings, accompanied by an array of detailed illustrations and photographs. Bird Pellets provides a closer look at those produced by each species in turn and outlines how to identify the remains of small mammals, which can be an important tool for discovering what a bird feeds on, understanding dietary change over time and other aspects, making this an invaluable resource in ecology.

Ed Drewitt is a professional naturalist, wildlife detective and broadcaster for the BBC who specialises in the study of birds and marine mammals. He studied Zoology at the University of Bristol, before working at Bristol’s Museums, Galleries and Archives for numerous years. He is now a freelance learning consultant who runs bird identification courses, provides wildlife commentaries on excursions, writes for wildlife magazines and is involved in bird ringing studies. Ed is also the lead researcher in a study focusing on the diet of urban-dwelling peregrines in the UK and author of Urban Peregrines.

Firstly, can you tell us a little bit about yourself and how you came to write a book about bird pellets? 

I have been interested in wildlife, particularly birds, since I was six or seven. Back then I would love collecting feathers and skulls, and bird pellets. I remember being excited at finding a Sparrowhawk plucking–perch in the woods where I lived in Surrey and finding small pellets – packed full of small feathers – from the hawk. Much of my career has involved developing and delivering learning workshops and resources for school-aged students and my public engagement work involves communicating science in plain English. Therefore, I am well versed in writing a book that appeals to families, schools and researchers alike. For several years I worked part-time in the teaching laboratory for the School of Biological Sciences at the University of Bristol. Each spring I would help oversee students dissecting several hundred Barn Owl pellets; I also arranged for a live owl and Kestrel to come in, to bring the practical ‘alive’. I have also been studying what urban-dwelling Peregrines eat (and am author of Urban Peregrines and Raptor Prey Remains) over the past 26 years. Therefore, I was in a brilliant and timely position to tap into my own pellet and bone collection, and source more material from others across the country and beyond, to write the ultimate bird pellet book!

Most people are aware that owls and raptors produce pellets, but are there any pellet-producing species that we’d be more surprised to hear about?

Absolutely – any bird that eats something that is indigestible and unable to pass through the intestines and out the other end, will produce a pellet. People are always surprised when I explain that even Robins and Blackbirds produce pellets, often made up of bits of woodlice and beetles. Interestingly though, two raptors, that you might expect to produce pellets do not: the Osprey and the Honey Buzzard. Both eat foods that either are digested or picked at, meaning harder parts, such as bones, are not swallowed.

I was interested to read in your introduction to the book that pellets can be used to study what birds were eating thousands or even millions of years ago. Are bird pellets generally well represented in the fossil record?

The brilliant thing about pellets is that, while their general structure may break down, their contents, for example, mammal and bird skulls, may accumulate in one area, even if they get buried over time. While some bits will slowly decay or move over time, others may remain in situ and intact. Palaeontologists and archaeologists often study how animals decay; it is known as taphonomy. It can also be applied to pellets. While complex, researchers can work out which species has produced a pellet and what happens to its contents with time. In turn, researchers can determine previous assemblages of prey species, such as small mammals, and how these have changed over time depending on environmental and ecological conditions. This type of study can also work out which species are more (or less) likely to be found in such accumulations and therefore how the fossil record may be biased towards particular prey species.

Many of us will be familiar with the technique of using the visual observation of bones and other remains in pellets to study what was in a bird’s diet. But are there more advanced laboratory methods that are now being used to study them in more detail? 

Yes, although I don’t think they are quite as fun or smelly! In essence, taking swabs from pellets can reveal the DNA of what has been eaten, including things that may not otherwise be detectable, although some of these items may have been eaten by the prey itself, if the DNA is intact enough. It can work the other way though; well digested food remains may mean the DNA of prey is undetectable or so degraded it cannot be assigned to a species or taxa, while traditional visual techniques may be able to confirm its identity.

Can pellets be useful for studying the presence of pollutants in the environment, such as plastics and microplastics? 

Absolutely, and this is not a new thing, although it is now more topical in the media. Some seabirds, such as terns and gulls, have been producing pellets with polystyrene particles going back to the 1970s. However, now we have a better idea of just how much plastic is in our environment, we are now looking for it more in the stomachs and pellets of birds. Dippers are a very good example. Small invertebrates, such as stonefly larvae, ingest microplastics. They are then eaten by Dippers and the plastics accumulate in the pellets they regurgitate. Of course, the cumulative health effects that ingesting plastic has on birds such as Dippers is difficult to ascertain. Even Barn Owl pellets may contain microplastics, ingested from the stomachs of small mammals they are eating.

What is the most surprising or unusual thing you have found in a bird pellet to date?

Gull pellets are often the most interesting, mostly because of the litter they contain, from plastic particles and bags to condoms! On a more natural note, the most spectacular pellet I have found was on the Flannan Isles, a remote island west of the Isle of Lewis, Scotland. The pellet was from a Great Skua, and it contained a whole Leach’s Petrel, which also live on the island. The petrel had gone down into the stomach where it had been digested. It was then regurgitated as a pellet, pretty much as a whole bird including intact wings, just minus any flesh! Skuas and Great Black-backed Gulls will also do the same thing with young rabbits and Puffins. Pellets can also be useful for finding the rings of wild birds and discovering that a bird has eaten another bird with an interesting origin of ringing, such as Norway or Russia!

Finally, what’s keeping you occupied this summer, and do you have further books in the pipeline that we can look forward to?

During the summer I am busy taking people out to see wildlife, especially in the Forest of Dean, where I live. I especially love birdsong and helping others to hear it. I am also working with the RSPB on the Gwent Levels, doing some training courses on identifying saltmarsh plants and wildlife. My wife, Liz, and I have two children, aged four and seven, so we will also be busy keeping them occupied! They love the outdoors and enjoy seeing wildlife just like we do. I have some papers in the pipeline as I am halfway through a part-time PhD at the University of Bristol. My 26-year study of the diet of urban-dwelling peregrines has given me plenty of data to analyse and write into chapters for my PhD. 

Bird Pellets will be published by Pelagic Publishing and is available to pre-order from our online bookstore.