Hoopoe – A blog by nhbs

The Sensory Ecology of Birds is a fascinating new work that explores the sensory world of birds from an evolutionary and ecological perspective. The author Professor Graham Martin gives us some insights into his inspiration, the incredible diversity of avian sensory adaptations, and how studying sensory ecology can help in developing practical conservation solutions.

How did you first become interested in bird senses?

Through owls. As a child I used to listen to tawny owls calling all through the night in a nearby wood and I wanted to know what they were doing and how they did it. My father took me round the woods at night and that experience led me to wanting to know more about the eyesight of owls.

What inspired you to write the book and what kind of readers do you think would find it useful?

I have been studying bird senses all of my working career. Nearly 50 years ago I started to get paid for looking into bird senses; it has been a strange and exciting way to spend my time. After such a long time of investigating the senses of so many different birds I wanted to bring it all together, to provide an overview that will help people understand birds from a new perspective. I think anyone interested in birds will enjoy the book and find it useful. No matter which group of species intrigues you most, this book will enable you to see them from a new perspective. Understanding bird senses really does challenge what we think birds are and how they go about their lives.

Sensory ecology is a relatively new field of research; could you explain a little about what it is and what makes it particularly relevant today?

Sensory Ecology is basically the study of the information that birds have at their disposal to guide their behaviour, to guide the key tasks that they perform every day to survive in different types of habitats.  Different habitats present different challenges and to carry out tasks animals need different sorts of information. Birds have at their disposal a wide range of different sensory information, they are not just reliant upon vision. However, each species tends to be specialised for the gaining of certain types of information. Just as each species differs in its general ecology, each species also has a unique suite of information available to them. Sensory ecology is also a comparative science. It compares the information that different species use and tries to determine general principles that apply to the conduct of particular behaviours in different places. For example how different birds cope with activity at night or underwater.

Sensory Ecology also looks at why evolution has favoured particular solutions to particular problems.  I think the major result of this kind of approach is that it certainly challenges our assumptions about what birds are and also what humans are. We do not readily realise that our view of the world is very much shaped by the information that our senses provide. We are rather peculiar and specialised in the information that we use to guide our everyday behaviours. My hope is that people will come to understand the world through birds’ senses, to get a real “bird’s eye view”. In doing so we can understand why birds fall victim to collisions with obvious structures such as powerlines, wind turbines, motor vehicles, glass panes, fences, etc. We can then work out what to do to mitigate these problems that humans have thrown in birds’ way.

An understanding of how a species perceives its environment can be very useful in designing practical conservation measures. Could you give us some examples?

Yes, I have been involved in trying to understand why flying birds apparently fail to detect wind turbines and power lines, or diving birds fail to detect gill nets.  These investigations have led to a number of ideas about what is actually happening when birds interact with these structures and what we can do to increase the chances that birds will detect and avoid them.

How do you think that studying avian sensory ecology can enhance our understanding of our own sensory capabilities and interaction with the world?

It gives a fresh perspective on how specialised and limited our own view of the world is. We make so many assumptions that the world is really as we experience it, but we experience the world in a very specialised way. Sensory ecology provides lots of new information and facts about how other animals interact with the world, what governs their behaviour, but equally importantly sensory ecology questions very soundly our understanding of “reality”, what is the world really like as opposed to what we, as just one species, think it is like. This is quite challenging but also exhilarating. We really are prisoners of our own senses, and so are all other animals. Sensory ecology gives us the opportunity to understand the world as perceived by other animals, not just how we think the world is. That is really important since it injects a little humility into how we think about the way we exploit the world.

Could you give us some insight into how birds can use different senses in combination to refine their interpretation of the world around them?

Owls provide a good example. Their vision is highly sensitive but not sufficiently sensitive to cope with all light levels that occur in woodland at night, so owls also rely heavily upon information from hearing to detect and locate moving prey. The nocturnal behaviour of owls requires these two key sources of information but even these are not enough. To make sense of the information that they have available to them the woodland owls need to be highly familiar with the place in which they live, hence their high degree of allegiance to particular sites.  Other birds, such as ducks, parrots and ibises rely heavily upon the sense of touch to find food items. The degree to which this information is used has a knock on effect on how much the birds can see about them. So a duck that can feed exclusively using touch, such as a mallard, can see all around them, while a duck that needs to use vision in its foraging cannot see all around. This in turn has implications for the amount of time birds can spend foraging as opposed to looking around them, vigilant for predators. In many birds the sense of smell is now seen as a key source of information which governs not just foraging, but also social interactions.

Are there interesting examples of species that are specialists in one particular sense?

Usually birds rely upon at least two main senses that have become highly specialised and which are used in a complementary manner. For example, in ibises it might be touch and vision, in kiwi it is smell and touch, in some of the waders it is touch and taste, but in other waders touch and hearing.

Probably the most obvious single sense specialisations are found among aerial predators such as eagles and falcons, they seem to be highly dependent upon vision to detect prey at a distance and then lock on to it during pursuit. However, we really don’t know anything about other aspects of their senses and there is a lot left to learn about them.

Can you tell us about any species that you have studied that you find particularly fascinating?

Oilbirds; they are really challenging to our assumptions about what birds are, how they live and what information they have available to them.

Oilbirds are the most nocturnal of all birds, roosting and breeding deep in caves where no light penetrates, emerging only after dusk and then flying over the tropical rain forest canopy to find fruit. But they are a form of nightjar! In the complete darkness of caves they use echolocation to orient themselves and calls to locate mates. When searching for food in the canopy they use their sense of smell to detect ripe fruits, they have long touch sensitive bristles around the mouth. And their eyes have sensitivity close to the theoretical limits possible in vertebrate eyes.  They seem to rely upon partial information from each of these senses, and use them in combination or in complementary ways. They really are marvellous, but in truth the senses of any birds, and how they are used, are fascinating and intriguing, it is a matter of delving deep enough, and asking the right questions.

In what kind of direction do you think future sensory ecology research is headed?

We now have available a lot of techniques to find out about the senses of birds, from behavioural studies, to physiology and anatomy. Armed with these techniques, and also with ways of thinking and measuring the perceptual challenges of different tasks and different environments, there are so many questions to investigate. We have some fascinating findings but we have only just scratched the surface with regard to species and it does seems clear that senses can be very finely tuned to different tasks. I like to compare the diversity of the bills that we find in birds with the same diversity in the senses in those species.

Every bill tells a story about form and function, about evolution, ecology and behaviour. The senses of birds show the same degree of diversity and tuning. So to me sensory ecology is a wide open field with lot of questions to investigate. To appreciate the world from a bird’s perspective will, of course, give us a much better understanding of how to mitigate the problems that humans have posed to birds by shaping the world for our own convenience.

The Sensory Ecology of Birds is available now from NHBS

Birds of the Indonesian Archipelago: Greater Sundas and Wallacea is a new field guide dedicated to this major region which contains a massive 13% of the world’s avian biodiversity. Featuring over 2,500 illustrations, it describes all 1,417 bird species known to occur in the region.

Co-authors James Eaton and Nick Brickle share some of their birding insights and in-depth knowledge of the region’s avifauna in this interview with NHBS.

Could you tell us a little about how you became interested in birding and what drew you to this region in particular?

James – My Grandmother gave me a copy of Benson’s Observer’s Book of Birds when I was six, and, wanting to see some of the birds in the illustrations in real life, my father agreed to take me to the local nature reserve to look for them, and from that point on it became an obsession!

Nick – Similar story. I got hooked before I was 10 years old, partly thanks to Choughs, Peregrines and my dad’s old binoculars on family holidays to Pembrokeshire. Ten years later and I found myself surveying White-winged Ducks in Sumatra and never looked back.

What inspired you to create a field guide that covers the entire Indonesian Archipelago? It must have been quite a challenge to cover such a diverse region.

All four of us are pretty obsessed with the region’s birds, both as a hobby and professionally, and all of us have travelled pretty widely in the region over many years. During this time the region has gone from having no bird field guide at all, to having a variety of books covering different parts of it; some now already long out of print. We all decided it was time to put our passion into a project that could do justice to the spectacular diversity to be found here, and so agreed to work together to create the new guide.

Could you explain a little about the unique biogeography of the region which makes it such a biodiversity hotspot?

Hard to sum it up in a sentence! It’s a fantastic combination of Asian and Australasian bird families, spread across 1000s of islands, with Wallace’s famous line running down the middle, and spectacular endemism throughout. For more, read the biogeographical history section in the introduction to the field guide!

Who is your target audience for the book?

Anyone with an interest in the birds of the region! Visiting and resident birdwatchers are the obvious user, but given that it includes over 13% of the world’s birds, anyone with an interest in birds should enjoy it. In due course we also hope to produce an Indonesian language version of the guide, so as to make it more accessible to the growing number of local birdwatchers.

For someone visiting the area for the first time, what are some of the most exciting sites, and the key species that you recommend looking out for?

Where to start! Within Indonesia, the best places for an introduction are probably the mountains and forests of West Java, which are easy to visit from Jakarta, and where many of the most sought after Javan endemics can be seen; or perhaps North Sulawesi, where a trip to see hornbills, endemic kingfishers and Maleo can be combined with beaches and diving; or Bali, where one of Indonesia’s rarest and most spectacular birds – the Bali Starling – can be seen with a short trip from the beach resorts.

Another choice for an easy introduction is the Malaysian state of Sabah in the north of Borneo. Here many spectacular and endemic birds can be seen from the comfort of first-rate hotels, including Great Argus and the completely unique Bristlehead. After that, the opportunities are limitless!

How do you kit yourself out for a birdwatching trip to the region, and can you recommend a great birding gadget or app?

At the simplest, you don’t need much more than a pair of binoculars (and maybe a rain coat or umbrella!). Beyond that it depends a bit on where you are going and what you’d like to see: a telescope can be useful, but is rarely essential, sound playback or recording equipment can be very useful, a camera if you like to take photos, camping equipment if you plan to visit very remote regions. If you plan to explore off the beaten track (and there are lots of parts of the region that qualify as this!) then a phone and google maps can be a surprisingly useful way to look for patches of forest, and then all you need to do is try and make your way towards them!

Do you have any favourites among the species in the guide? Are there any that proved particularly elusive or challenging to observe?

James – Difficult question, can I give two answers? One would be Helmeted Hornbill. Such an iconic bird that symbolises the region’s rainforests. You know when you hear the bird’s incredible mechanical laughing call you are in the rainforest, but equally you are reminded how it is disappearing from many areas due to illegal hunting for its casque. Another would be Bornean Ground Cuckoo. Once a mysterious bird, largely unknown due to its shy nature, feeding on the rainforest floor, but now as our understanding of the species has grown it is possible to see it. Nothing gets the adrenalin pumping quite as much as looking for this species.

Nick – Too many to choose from! For me it would have to be something that walks on the ground… pretty much any pitta, pheasant or partridge is a candidate. Maybe Banded Pitta (any of the three species…)? Or the spectacular Ivory breasted Pitta? Then of course there is Rail Babbler… Actually, more often than not my favourite is the last new species that I have seen, or the next new one that I want to see!

With so many endemic species, there must be some that fill very specific ecological niches?

Endemism is very high in the region, and many species are only found within very small ranges, such as Boano Monarch on an island only 20km wide, or Sangihe Island, only 40km long at its widest point, and with five endemic bird species. Damar Flycatcher too, found in the dark understorey of a tiny island that requires two days’ boat travel from the nearest city. Kinabalu Grasshopper Warbler is only found on the top of two mountain tops in Borneo. When it comes to specific niches, however, small island endemics are often the opposite, in that they often expand their niche due to the absence of competitors. Birds filling very specific niches are probably more a feature of the large islands groups like Borneo and Sumatra, where the overall diversity is much greater.

It is quite well publicised that one of the biggest threats to the conservation of all Indonesian species is rapid deforestation to create palm oil plantations. Are there other threats to bird species which also need to be highlighted?

Deforestation is a big issue. There has been a huge loss of forest over the last decades, but vast areas still remain, and their value is finally starting to be more widely recognised. Hunting for the captive bird trade also remains a huge threat, particularly to those species most desired as pets, such as songbirds and parrots. Local and international groups are working hard to try and reduce this trade, in particular the public demand, but there is still much work to be done to change attitudes.

How can the international community help to support conservation efforts?

As birdwatchers one of the simplest and best things you can do is to visit the region and go birdwatching! Coming here, spending time, spending money, staying in local hotels, eating local food, using local guides, all serves to create a value to the forests and the wildlife that lives in them. This is not lost on local people or the regional governments. Beyond that think carefully about the products you buy from the region, to make sure they come from sustainable and fair sources. If you have money invested make sure that is not going to support destructive or exploitative practices in the region. Finally, support a good cause! There are many, many local NGOs established and emerging in Indonesia and the wider region, all working and lobbying hard to protect the region’s forest and wildlife. Your support will help them achieve this.

Birds of the Indonesian Archipelago: Greater Sundas and Wallacea is available now from NHBS