Fun without the sun in the Okanagan
unravelling some of the mysteries about bats and goatsuckers

(For informative captions click on photographs.)

The literal translation of the Latin name for the family of birds (Caprimulgiformes) to which familiar species such as Whip-poor-wills (Caprimulgus vociferus), European Nightjars (Caprimulgus europaeus) and nighthawks belong, means "goatsucker". The name goatsucker comes from European folklore which has it that these birds suckled livestock at night. Of course, like many of the best myths (e.g., blind rabid bats flying into people's hair), this notion is completely baseless. The huge mouth of most goatsuckers is used as an efficient "sweep net" to engulf flying insects. There are about 120 species found in all parts of the world except for polar regions and New Zealand. Virtually all of them are active at night and most eat nothing but insects, like most bats which are true flying mammals belonging to their own order called Chiroptera.

I well remember the night in May 1985 when I first stood on the bank of the Okanagan River in Okanagan Falls Provincial Park, just south of Skaha Lake, and beheld the aerial spectacle which occurs there most summer nights. Literally hundreds of nighthawks and Big Brown bats (as well as other bat species) filled the air, feasting on insects. I found out later that both the bats and the birds were principally consuming caddisflies emerging from the river. I am still in awe when I return to Okanagan Falls and enjoy the nightly display put on by those animals. In fact the Park now has a Wildlife Viewing sign, which encourages members of the public to enjoy the nightly display.

The essence of my PhD was that the bats and birds converged remarkably in terms of the insects they ate, how long it took them to find food, and from where they commuted to get to the river. I found that both species attacked a caddisfly on average every 3 seconds, a feeding rate that is still amongst the highest ever reported for either species! In fact, Dr. Hugh Aldridge from England, who was working as a post-doctoral fellow at the time, calculated that, based on the energy they require, nighthawks must be attacking and eating more than one insect at once, something that no other "aerial insectivore" is thought to do. Although we have not been able to verify this, it remains a question that I would love to answer at some point in the future. This example illustrates the fascination of Science for me and is what makes me look forward to going to work each day. Science is not so much about the compendium of facts held in textbooks and journal articles, as it is about the questions that remain unanswered and the mysteries of life that are still to be unraveled. Why is it that in the Okanagan, nighthawks and Big Brown bats eat mostly caddisflies whereas in other places, they eat predominantly moths and/or beetles? Why is it that most Big Brown bats in the Okanagan roost in dead Ponderosa Pine trees, whereas in the rest of North America they are commonly thought of as "house bats" based on where they roost.

In part because of the findings in the Okanagan Valley, there has been a flurry of recent research on bats in forests. Three hundred kilometres to the east near Nelson in the Kootenays, Big Browns use Douglas Fir, Western White Pine and large Aspen trees as roosts. In the Cypress Hills of Saskatchewan they use only Aspen trees, while in the coulees (small, steep-sided valleys) of the south Saskatchewan River near Canadian Forces Base (CFB) Suffield in Alberta, they use rock crevices as roosts. Is this roost-site flexibility the main reason for the virtual continent-wide distribution of these bats or are roost sites dictated simply by the types of sites available in a local area?

The British Columbia Ministry of Forests, amongst others, have sponsored projects evaluating the interaction between bats and forest habitats. Graduate students Scott Grindal, Maarten Vonhof, Matina Kalcounis, and Paul Bradshaw have subsequently conducted extremely thorough studies on bats' selection of certain tree and forest attributes for roosting and feeding in forests in both British Columbia and Saskatchewan (yes, believe it or not, Saskatchewan does have a significant forest component!). Grindal, for example, found that bats near Nelson concentrated their activity along forest edges, whether they be created by logging operations, road building or avalanches. Whether creating "edges" will actually help bats in the long run remains to be determined, however, scientists working in the state of Georgia and in the Netherlands have documented the same patterns Grindal uncovered. Bradshaw and Kalcounis have both conducted studies on bats' use of the space near or above the top of forest canopies as foraging sites. Whether it be in the canopy of a Sitka Spruce forest on Vancouver Island or above a Boreal Mixed-Wood forest in Prince Albert National Park, bats are commonly found using this part of the forest. In large part, our focus on the interaction of bats and forests can be traced back to my surprise at finding Big Brown bats in pine trees on the valley ridges above Okanagan Falls Provincial Park.

Partly out of my own curiosity, but mostly as a result of the exceptionally thoughtful mind of Robert Barclay, we designed a project to assess the prey-detecting abilities of echolocating bats and visually-orienting nighthawks. The Okanagan was the logical place for the experiment to take place. Barclay had always been struck by how a bat would occasionally attack a rock when it was thrown up into the air. That bats seemed to perceive rocks as insects flew in the face of data collected in the laboratory which suggested that echolocation should easily allow bats to discriminate between different insect species and perhaps even between sexes. In other words, reinforcing the notion that echolocation was a extremely sophisticated system that provided bats with very accurate acoustic "images" of their environment. Barclay and I tested bats' abilities under natural conditions (over the surface of the water) by presenting them with a variety of prey (e.g., small or large moths and beetles and non-prey, e.g., leaves). If echolocation was so good, we expected that only the most profitable insects would be attacked. Contrary to this however, we found that bats would respond to, and press home attacks on, virtually anything, especially if it was moving. Our best explanation for the apparent contradiction is that in real life, unlike laboratory experiments, bats have only fractions of seconds to decide whether or not to attack and since most small things moving in mid-air are insects, it rarely pays not to attack. Nighthawks foraging over the river at Okanagan Falls, behaved remarkably similar in the initial stages of an attack. The visually-orienting birds also responded to virtually anything (e.g., moth, leaf or stick) 3-30 mm long, especially if it was moving. The difference was that unlike bats, who actually attack sticks and leaves, nighthawks break off from attacking at the last instant, presumably when the visual information provided by their eyes is enough to positively identify targets as edible or inedible. We found no evidence that the birds could discriminate between insect types however. Thus, work in the Okanagan has shed at least some light on the question of whether bats or birds are able to actively select certain types of insect prey.

For me, perhaps the most exciting work that has come out of the time I spent in the Okanagan concerns the use of torpor and hibernation by birds. The ability of many mammals (e.g., bats, ground squirrels) to enter torpor for short periods of time or hibernate for long periods to save energy when food is in short supply is well known. However many people are unaware that some birds might use the same strategies. While doing my PhD, I can remember regularly hearing a bird at night calling "poor-will" in the vicinity of the University of British Columbia (UBC) Geology Field station on White Lake Road, northwest of Oliver, where we stayed during several summers. Having spent considerable time as a kid in the forested parts of northern Ontario, I was familiar with the night calling of Whip-poor-wills and thus I knew it was another goatsucker, but I was astonished when I read that Common Poorwills (Phalaenoptilus nuttallii) had been documented to be able to lower their metabolism and body temperature when brought into the lab. Torpor is a valuable energy-saving strategy. It has been estimated that a torpid poorwill which allows its body temperature to fall to 10°C, uses only 5% of the energy required when fully active. Torpor should make it relatively easy to survive periods of inclement weather without feeding. Further, poorwills are supposedly the only bird in the world which can hibernate. In essence, hibernation means an animal remains in torpor for weeks or even months at a time. The published evidence that poorwills can really do this is, so far, anecdotal and no birds had ever been followed through a winter under natural conditions.

Daily torpor is a strategy commonly employed by many temperate bats to survive occasional periods of bad weather in a summer when insects are scarce. Many of the same bats also hibernate as a means to cope with long periods of winter when there is no food available rather than migrate, which is the typical strategy of most birds. I was intrigued to learn more about if, how, when, and why, free-living poorwills specifically, and goatsuckers in general, used torpor and/or hibernation. This research was the focus of my post doctoral work with Robert Barclay from the University of Calgary and remains a focus of my research to the present. The Okanagan seemed the best place to do the field work because poorwills were common. In the spring and fall, the weather is often such that conditions where torpor might be useful, regularly occurs.

As with all field-oriented projects, when I say that I spent from 1988 to 1990 studying the ability of free-living poorwills to enter torpor, it must be recognized that I had a great deal of help. Without the assistance of numerous students, the friendship and help of many Okanagan residents, the financial and collegial support of Robert Barclay, and the sacrifices made by my family, the research would never have happened. Few words are required to convince anyone with an inkling about the place, that spending a summer in the Okanagan Valley is a coveted opportunity. However, consider this from the perspective of a new mother living under the same small roof with her husband who works "nights" and several students. In 1989, my wife Anne, with our one year old son, joined me and the "crew" for July and August. She helped with the field work directly only occasionally, but her contribution was monumental nevertheless. How else could one characterize her willingness to get out of the house shortly after we came home at some ungodly hour in the morning so that our son Tony's vocal practice sessions did not keep sleeping field workers awake. Not only that, but Anne also has the remarkable ability of alerting rattlesnakes to the presence of a bunch of plodding biologists. At the cost of regular "frights", she kept the rest of us from inadvertently stepping on the poor snakes!

I spent two summers catching poorwills (which no one had ever really tried to do before) and affixing radio transmitters to them with little backpacks. These radio-transmitters "beep" at different rates depending on temperature, allowing me to measure the body temperature of the birds without having to disturb them. A reduced body temperature is indicative of torpor and thus an easy way to measure its use. We amassed some fascinating data showing that in the Okanagan, poorwills do regularly use torpor. This "state" usually occurs during the spring and fall, before and after the nesting season. Only rarely do birds enter torpor when incubating eggs or brooding chicks. Torpor bouts typically occurred after a short period of foraging at dusk, with the bird arousing shortly after sunrise in the morning. We still don't know precisely how, or if, birds "decide" to enter torpor. On some nights, individuals only 100 metres apart would employ different strategies, some using torpor and some not. The use of this strategy probably reflects a combination of weather conditions (the cooler or windier it is, the less likely that foraging will be productive) and the condition of a particular animal (fit and fat birds likely have less incentive to enter torpor if the assumption that torpid birds have a higher risk of being preyed upon is correct). Perhaps most astounding was the fact that I found poorwills could drop their body temperature to less than 5°C, more than 35°C below their normal temperature of 40°C. To put this in perspective, if a human being's temperature falls 2-3 degrees below the normal value of 37°C for mammals, they can die! Body temperatures of 5°C in torpid poorwills are, to my knowledge, the lowest recorded for any bird.

My finding that poorwills commonly entered torpor has led to a number of other projects on this and other goatsuckers both in the Okanagan and in other places. Ryan Csada, did his MSc research on the use of torpor by poorwills in the Cypress Hills of Saskatchewan (SK), the only other place in Canada outside of the Okanagan, and nearby areas of the southern interior of British Columbia (BC) where these birds occur. The weather in the Cypress Hills is much more unpredictable and insects not as abundant, but Csada found that the birds use torpor in precisely the same way as poorwills near Oliver. I will forever carry the image in my mind of Ryan digging through 15 cm of snow dumped by a mid-August storm, to find a torpid (body temperature of about 7°C), but otherwise perfectly healthy, bird. Two nights later when the cold front had blown through, the bird was out catching insects like nothing had ever happened.

An undergraduate student from the University of Calgary, Mitchell Firman, found no evidence that nighthawks, which are closely related to poorwills but slightly larger (80 versus 45 g), ever enter torpor. This work was done in the Okanagan. Whether this is due to the differences in size (torpor is more common in small animals than larger ones) or whether some other factors are important was unclear.

Currently, Chris Woods, a PhD student in my lab, is studying poorwills in the vicinity of Tucson, Arizona. His focus is on the question of whether these amazing birds really can hibernate for the winter like many mammals do, or if they are restricted to short bouts of torpor like we have found in the Okanagan and the Cypress Hills. Poorwills migrate to British Columbia and Saskatchewan during the summer months to nest. They leave for points unknown in the fall. Woods has succeeded in finding a population near Tucson that remains resident all year. At the time of this writing, he is still gathering data but the clear indication is that the birds can, in fact, hibernate and may not move for weeks at a time during the winter. One doesn't normally think of Tucson as cold, but presumably some combination of low insect numbers and cool temperatures makes actual hibernation in this area worthwhile.

My studies of torpor by birds in the Okanagan was significant with regards to the decision of where to take my first sabbatical leave. I spent a year working with Dr. Fritz Geiser, an internationally recognized expert on hibernation and torpor, at the University of New England in Armidale, Australia. Until my visit, his work had focused exclusively on mammals, but the data on poorwills convinced him that "birds were worth a look". Along with his post-doctoral fellow, Dr. Gerhard Körtner, we found evidence that two Australian goatsuckers, the Australian Owlet-nightjar (Aegotheles cristatus) and the Tawny Frogmouth (Podargus strigoides) regularly enter daily torpor. Appropriately, Aegotheles is literally Greek for goatsucker! Body temperatures of the Australian birds typically fell to 20 - 25°C for 3-5 hours, not as impressive a drop as Okanagan poorwills but an exciting finding nevertheless. Interestingly, the Australian birds differed substantially regarding when they used torpor. Like poorwills, frogmouths foraged for a short time at dusk and then entered torpor whereas Owlet-nightjars foraged all night, even when the weather was miserable, but regularly entered torpor at dawn. Why the difference remains unknown. The data for frogmouths are illuminating in that these animals are quite large, as much as 400 g, which strongly suggests that body size is not the only variable affecting the ability to use torpor.

To ensure that the bat side of the ledger was not neglected, Geiser and I also collected data which showed that several species of Australian long-eared bats (Nyctophilus spp.) can, in the lab at least, drop their body temperatures to as low as 1°C. Currently an undergraduate student of Geiser's is following up on this, studying free-ranging bats in the same forest where we studied the birds. It is my hope that with time we can build up a picture of the similarity of bats and birds in their use of torpor. Townsend's Big Eared bat (Corynorhinus townsendii), which physically resembles the Australian long-eared bats and lives in the Okanagan, would be an obvious candidate for a comparative study about the use of torpor.

Recent research in the Okanagan has also had an explicit focus on aspects of conservation. While studying poorwills and nighthawks, I was successful in being awarded some money by the World Wildlife Fund and the British Columbia Ministry of the Environment to increase basic understanding of the importance of unique Okanagan habitats for endangered species of bats. During the early 1990s we conducted considerable work on Spotted bats (Euderma maculatum) and Fringed bats (Myotis thysanodes) with the goal of providing recommendations to ensure protection for these animals whose Canadian range is restricted entirely or mostly to the Okanagan. During the course of our research, we also documented the presence of a reproductive population of Pallid bats (Antrozous pallidus) between Oliver and Osoyoos. Up until 1990, there were only six records for this species in Canada, all in the Okanagan south of Okanagan Falls. Our data show that a small resident population does exist. These data are important for the formulation of management plans to help ensure that these animals remain a viable part of the Okanagan ecosystem.

The results of our research find their way into a variety of places. Aside from the technical reports and scientific papers, much of the basic information collected in the Okanagan has been used to help write books on "nocturnal critters". David Nagorsen, from the Royal BC Museum, and I published a book in 1993 entitled The Bats of BC, which is aimed at a general audience. Much of the information about bats in British Columbia comes from work done in the Okanagan. In 1998, a book by Nigel Cleere from England focussed on the World's Caprimulgiformes and, partly by virtue of work done in the Okanagan, the two North American species which receive the most detailed treatments are the poorwill and the nighthawk.

Not all of my trips to the Okanagan have focussed only on research. In 1995, in collaboration with Drs. Fenton and Barclay and Dr. James Fullard from Erindale College of the University of Toronto, we offered a field course on bats and birds. About twenty undergraduate university students from Ontario, Saskatchewan, Alberta and British Columbia spent nearly two weeks in the Okanagan learning about the region's unique nocturnal flying critters. As a result of acquiring a greater appreciation for this part of Canada and some of the fauna that lives there, these young people got credit towards their degree programs. Science in general also benefited, given that data the students collected on flight speeds of Nighthawks and new records for bats have subsequently made it into the scientific literature.

I have been fortunate to spend time with some fascinating people in the Okanagan and have learned a lot about some of its inhabitants. It is my hope that with further studies both in the Okanagan and elsewhere, my students, collaborators and I will be able to piece together a more complete picture of the behaviour and ecology of the bats and night birds which live there. However, no matter what we learn, I will always look forward to each summer when I can return and be mesmerized by nighthawks and bats wheeling through the night sky from the bank of the Okanagan River.

I am grateful to the Natural Sciences and Engineering Research Council (Canada) for generously supporting my research over the past fifteen years.