WHEN A HOUSEFLY LANDS on the ceiling, does it execute a wing-over, a slow roll or a half-loop? Do rattlesnakes bite? Can the fast deerfly break the sonic barrier? For answers to such questions a good man to consult is Walker Van Riper of Denver, Col., who has been tracking down odd facts concerning animal behavior ever since he retired from the investment banking business 17 years ago. His high-speed camera has proved that rattlesnakes do not bite—they stab [see "How a Rattlesnake Strikes," by Walker Van Riper; SCIENTIFIC AMERICAN, October, 1953]. It has also shown that the deerfly is easily outstripped by many other insects. Van Riper does not yet have a final answer on the housefly's landing performance, but he is currently studying the matter.

He does much of his work at the Denver Museum of Natural History, where he is an honorary curator. "Van Riper," says A. M. Bailey, director of the museum, "is the sort of fellow who is the perfect answer to the small museum director's prayer. You couldn't possibly pay him what his extraordinary skills are worth, yet he does the job for the joy of doing it, and does it better than anybody else could do it." Van Riper is inclined to take a more modest view of his accomplishments: "Anyone can help chip question marks from the rough edges of natural science if he puts his mind to it. Take hummingbirds, for example."

Van Riper has written us the following account of his hummingbird studies.

"Probably no other bird is so amenable to intimate observation as the hummingbird. Fairly accurate answers can be obtained to such questions as: What does it eat and how much? How fast and in what manner does it fly? What is its size and weight? How are the young cared for? Besides its convenience as a subject, the hummingbird is the most beautiful, vivacious, bold and interesting of birds.

"These words may sound a bit extravagant, but they are well backed by authority. John Gould, the great British ornithologist of the 19th century, loved the hummers beyond all other birds. His five-volume A Monograph of the Trochilidae, or Humming-Birds testifies to this. Eugene Simon, head of the Entomological Society of France, produced a highly valuable work on the classification of hummingbirds which took 60 years in the making. Simon had dedicated his life to the study of spiders, but during an expedition to Venezuela to collect spiders he was 'seduced' by the hummingbirds and decided thereafter to divide his labors between his first love and his second. Considering that there are some 600 species of the Trochilidae, more than in any other bird family, their taxonomy is no mean task. In fact there is a word for a specialist on hummingbirds—'trochilidist.'

"The rufous and calliope hummingbirds show up here only during their return migration to Mexico from the north, where they breed in the summer. The rufous probably has the longest migratory movement of any hummingbird: it nests as far north as southern Alaska. It also has another distinction: it was first described by none other than Captain Cook. On his third and last voyage he was given some rufous hummers by the natives of Vancouver Island.

"Usually by mid-July a fair number of the migrants from the north arrive here. The mature males come first and stay only two weeks or so. They are followed by females and the young. The young males often stay into September, sometimes outstaying the resident broadtails. The calliope is the smallest of our hummers, weighing about 2.5 grams–the weight of a dime. You could send about a dozen of them by first-class mail for a three-cent stamp!

"The amenability of hummingbirds to close-up observation and experiment is due primarily to the fact that they are extraordinarily fearless, probably because they have no natural enemies of importance. Coupled with their eagerness for food and readiness to accept artificial food, this makes them excellent laboratory residents.

"The artificial food for hummers is a syrup comparable to the flower nectar on which they usually feed. Hummingbird fanciers have a great variety of notions about the best kind of syrup. I recently made a preference test with a mature female broadtail. I set up a series of bottles side by side with different mixtures: sugar solutions in water at various concentrations; sugar, orange juice and water; honey and water; honey, orange juice and water. The bird showed a clear preference for the syrup made of ode part sugar to one part water (i.e., equal proportions by weight). Incidentally, the feeding bottles were in my garden: to keep out bees and wasps the aluminum cap had only a tiny hole (an eighth of an inch) which was big enough for the hummingbird's bill; to keep out ants I smeared a band of sticky material around each bottle.

"I next set up an experiment to determine the amount of syrup consumed daily by my bird, together with its relationship to her weight. The hummer fed from a single bottle while resting on a wire perch hanging from a postal scale. By remote control I tripped a camera to photograph the scale reading and record the weight of the bird. It averaged 4.3 grams (less than one sixth of an ounce), and the bird consumed each day an average of 1.8 grams of sugar–42 per cent of her weight.

"Intake of fuel at this rate is astonishing. Oliver Pearson has show, n that the hummingbird has the highest metabolic rate of any warm-blooded animal so far measured [see "The Metabolism of Hummingbirds," by Oliver P. Pearson; SCIENTIFIC AMERICAN, January, 1953]. In calories my bird ate 1.7 calories of sugar per gram of its body weight per day–more than 30 times the daily rate of food intake needed by a man doing moderately hard physical labor. And this bird by no means limited her feeding to my bottle: she also ate insects and flower nectar each day!

"For several years I have maintained a hummingbird feeding station in a bit of rough yellow-pine and scrub-oak country on a ranch 25 miles south of Denver, where it is possible to assemble many more birds than can be attracted to a single city garden. I was able this past summer to take a census of the hummingbird population on the ranch. Early in May I put out some feeders of a new type designed by Erwin Brown [see photograph in Figure 1]. It was made of a five-ounce jelly container with a red lock-top. A hole in the center of the lid admits the neck of a pop bottle, and four eighth-inch holes are spaced around the perimeter. These holes admit the hummingbird bill, but not bees or wasps. The lid is fastened to the bottle with a couple of three-quarter-inch hose washers, one above and one below. The bottle is filled, the cup fastened to the lid, then the whole is inverted and hung. There is little evaporation, and it may be assumed that the entire output of this feeder goes to hummingbirds alone.

"On June 20 I had half a dozen of these feeders distributed in an area about a mile square. I estimated that the number of hummers, all broadtails, then feeding at my station was 66. A few nests had been found and, judging from these, most of the hens in the area were sitting on eggs at the time. By July 11, as these hatched, the population rose to 118.

"At this point the first migrating rufous appeared. The coming of the first male rufous is always an exciting event, for he is spectacularly beautiful. The rufous is sometimes called the golden hummingbird. His back is the color of burnished copper, and he has a gorget (throat patch) which is described as 'of a surpassingly vivid fiery red or metallic scarlet changing to crimson, golden and even brassy green.' The metallic shine and changing hues of the gorget are due to refraction and reflection of the light by minute elements in the structure of the scale feathers.

"The rufous is the most pugnacious and aggressive of our hummers. A bit smaller than the broadtail, but meaner, he takes little time to demonstrate who is boss. Within 24 hours after arrival the rufous males have taken over command of every feeding bottle. In flight they make a distinct buzz, like that of a bumblebee, in contrast to the whistle of, the male broadtail. The young male broadtail at first flies with a hum, like his mother, but he acquires whistling wing slots when his second set of feathers develops.

"With the coming of the migrants my hummingbird population jumped to 132. As more broadtail young joined the feeders, it increased gradually to a high of 166 on July 24. The population then declined steadily and was down to 70 by the end of the month. It stayed at that level for most of August, dropped to 39 by September 4 and to zero by the 11th.

"During July, when the population was at its peak, I occasionally supplied only a single feeder, generally a red bowl, in order to concentrate the birds for observation and pictures. This often brought together a flock of 25 or 30 hummers–fighting, chasing, diving and investigating around the bowl. When I sat in my car, some would 1Hy in the window and hover a foot from my nose to look me over. When I put up my photographic apparatus, the birds investigated the camera, lights, lens–everything shiny, and especially everything red. If I held the red bowl in my hands, half a dozen birds would alight on my hands, or the rim of the bowl to feed at once.

"It was an easy matter to get pictures of my subjects in all positions–flying, feeding, sitting. Exact positioning is important, especially for color shots of the brilliant male gorgets, which Hash in full glory only when the bird is turned toward the light and head-on to the camera. The photography of hummingbirds is a highly interesting art. A few of my friends and I have formed the most exclusive of all scientific societies–the Society of Trochilidographers (photographers of hummingbirds). The art requires the special high-speed electronic flash invented by H. E. Edgerton of the Massachusetts Institute of Technology. An exposure of one 5,000th of a second will stop a hummingbird's wings fairly well; a 20,000th of a second stops them cold. We usually use three lights–two at the camera and one on the background, which would be black without it. Color, as well as black and white, is practical, and successful with this setup.

"The pictures on these pages showing hummingbirds in flight were made at a 20,000th of a second. One of them is a rare photograph of a male calliope [see Figure 3]. This little rascal is rather uncommon in our parts, only a few coming through in migration. I had not had more than a bare glimpse of two or three and had never got a chance at a picture until R. J. Niedrach, curator of birds at the Denver Museum, discovered one feeding on a patch of matrimony vine last summer. We tried every trick in our repertoire to introduce the calliope to a feeding bottle, but he was single-mindedly intent on the matrimony vine and would not be enticed. So I

finally had to set up my camera and lights near a prominent plant and wait him out. I made myself as comfortable as possible with a camp chair and umbrella (it was hot) and sat 25 or 30 feet away with a remote-control button on my hand. In a week's waiting I managed to get three or four good shots. I had to take him on a dark background, because a background light spooked him just enough to keep him away from the target spot.

"There 'is an old argument about whether a hummingbird can fly backward. The Duke of Argyll, in a Victorian work of some merit, held that it was physically impossible for any bird to do this and that observations to the effect that the hummingbird did were purely illusory. The dispute is comparable to the modern one about whether a baseball curves. In both cases the high-speed flash has given a clear answer: a curve can be thrown; the hummingbird can fly backward.

"One of our pictures shows the hummingbird in the act [see Figure 4 above]. Three flashes were set off in rapid succession. We used a black velvet background–an essential in multiple-exposure photography. The camera shutter was open for a few seconds. The first flash shows its bill dipped in the feeding bottle and starting to withdraw backward; the next two catch it backing up.

"A pair of successive flashes can determine the speed of a flying bird, and three or more will give both speed and acceleration. C. H. Greenewalt, a member of our society, has published some interesting results for nuthatches and chickadees flying to and away from a feeding table. These measurements are of some importance, for ornithological literature is loaded with inaccurate and contradictory figures. I recently looked up the speed of the duck hawk in three natural history books which happened to be lying on my reading table. One gave the speed as 80 miles per hour, another 180 and the third 270! My own incomplete experiments have so far failed to show the duck hawk diving at more than 57 miles per hour.

"Various speeds have been reported for the flight of the hummingbird. My guess is that most of these are greatly exaggerated. In this field it is fairly safe to assume that the better the observation, the slower the speed. Ordinary experience shows that we are very likely to overestimate the velocity of small objects nearby. A bee seems to zip past your nose at bullet-like speed, but it actually does not exceed 10 miles per-hour.

"The dive-bombing flight of the male broadtail hummer, probably shows him at his greatest speed. A well-known ornithologist once told me that he thought this was the highest velocity attained by any bird. A male broadtail in courtship display before a female flies past her, generally near the ground, soars straight up 40 to 50 feet, poises there for a moment, and then swoops down past her and soars again, tracing a deep U-shaped J arc. He repeats this performance several times. His fast power dive produces a loud tinkling whistle, which rises in pitch with increasing wingbeat until he reaches his greatest velocity at the bottom of the dive.

"I set up my camera with the electronical flash timed to go off twice, the interval being a hundredth of a second. This system works satisfactorily to time the diving speed of a barn swallow, but in many trials I was unable to get an accurate measure of the hummer's dive. You have to be a super wing-shot to hit a diving hummer on the nose.

"I was, however, able to get a good measure of the hummer's speed in straightaway flight as one chased another away from his feeding bottle. This maneuver looks faster than it really is; actually it does not exceed the hummer's speed in ordinary level flight. In 14 measurements the chasing speed ranged from around 18 to 24 miles per hour. I think the reason it does not go higher may be that the bird is slowing up as it approaches the intruder, the objective being not to hit him but to make him fly away.

"I attacked the problem of the diving speed in another way, without the camera. I noticed that a female would often perch on a bush near a feeding cup, and this pause would stimulate a male to do his stuff. The male generally soared to the height of the highest tree at the place before diving. After measuring the height of the tree, T timed a considerable number of dives by different birds with a stop watch. Assuming that the velocity reached at the bottom of the dive is twice the average for the whole dive, I calculated the hummer's top speed to be 61.2 miles per hour.

"The hummingbird has been called the most aerial of all birds. It never walks or hops. To turn around on a perch, it takes wing for the turn. If it wishes to move half an inch to one side. it flies there. Sometimes a mother bird will even feed its nestlings on the wing, hovering above the baby instead of alighting on the nest. In order to photograph this I had to lower a nest from a tree to a convenient position near the ground. I sawed off a limb containing a nest of fledglings 25 feet up on a yellow, pine, and with ropes I lowered the limb by four stages on successive days. The little hen was a bit disturbed by all this, but not too much. I have tried this nest-lowering stunt several times. It can be done with other birds, but I know of none that will sit as tight as the hummer 53 sometimes does. After I got the limb ,~ down to a convenient level, I found that to train my camera on the nest I had to move a branch on the upper side of the nest out of the way. I sawed it through and attached a hinge, so that it could be kept in the accustomed position but could be swung out of the way when I wanted to take pictures of the nest. It turned out that this fold-back of the branch excited the hen just enough so that she fed her babies on the wing more often than not. All of which was just what I wanted.

"The broadtail hen builds the nest, incubates the eggs and raises the babies with no assistance of any kind from the male. In fact, there is some evidence that she selects the nest site and starts building before she picks out a mate, and, after the briefest possible association with him, returns to the nest and resumes her domestic duties. The mating is so brief that in many years of hummingbird watching I have never seen it, and it has been seen only a few times by others. These little birds are independent individuals save for the mother's care of the young, they show little tolerance for one another's company.

"The male is never allowed to perch near the nest. Nor is any other bird, for that matter. The female's attack is a kind of dive-bombing: she zips down on an intruder from a couple of feet above, just brushing its back. No harm is done, but the repetition of the act–zip, zip, zip, back and forth–soon drives the objectionable one away. I have seen female broadtails chase many kinds of birds in this way.

"For aggressiveness, though, the males take the prize. Chasing and fighting are the order of the day around the feeding bottles. Occasionally the sound of contact between two birds can be heard, and two or three times I have known of birds being knocked out. The male will peck at its mirror image, at a stuffed hummer and even at just the stuffed head and gorget of a male hummer. Females also fight sometimes with other females. But in both sexes the belligerency usually goes no further than threatening behavior. Its purpose seems to be to chase away an intruder or rival, rather than direct combat.

"Some years ago a party of us trochilidographers, camping in the Huachuca Mountains in southern Arizona, found a young male blue-throated hummingbird which we named 'Junior.' One evening an approaching hawk caused a clatter in a chicken yard about 50 yards away. Tiny Junior, seeing the hawk from his lookout atop a nearby apple tree, went for the hawk and actually put it to flight!

"The life span of the hummingbird is still unsettled. I have known of one which lived five and a half years in captivity and have an unconfirmed report of another that lived to 11. One of my friends had a hummer nest in his garden seven years in succession.

"The act of mating, as I mentioned, has rarely been observed, and the few accounts of it differ greatly. It has been reported to take place both on the wing and on the ground. One report of the calliope says: 'As he passed the female, she fluttered and hung head downward on her perch. The male alighted above her, with vibrating wings, and coition took place in that position.'

"There are still many questions to be investigated. I hope the day will never come when I am satisfied that I know all the answers about the life history of this most fascinating of all birds."

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