How many of us ever got to know a wild animal? I do not mean merely to meet with one once or twice…but to really know it for a long time…and to get an insight into life and history.
- Earnest Thompson Seton in THE AMERICAN CROW AND THE COMMON RAVEN by Lawrence Kilham
Director and Amateur Ornithologist
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Bethlehem, PA 18015
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1. COMMON BIRD BEHAVIOR: Introduction
The study of animal behavior, or ethology, is called by the British “behavioral ecology”, a term I prefer personally because I believe it describes it best and is all-encompassing on
the subject. For instance, behavioral ecology also studies human behavior, though not often. It also is not afraid of biological theory (hence the journal, The Journal of Biological Theory). I have had the privilege of belonging to Oxford’s The International Society for Behavioral Ecology (ISBE), which publishes the good journal BEHAVIORAL ECOLOGY. Behavioral Ecology is not interested in “how”, morphological and physiological questions, but “why”, evolutionary adaptive questions. What is the selective reason for this behavior? How does it help the bird “cope” (adapt) to its environment? As you can see, behavioral ecology has helped the sciences of psychology and neuropsychiatry endlessly. The comparative method is widespread in organismal behavioral science. It allows scientists and amateurs to compare different species from different families, orders, and even classes (mammals, birds: higher vertebrates) if the evolutionary reason for the two similar behaviors is the same. Originally used by morphologists, Konrad Lorenz of Germany, one of two fathers of animal behavior, with Niko Tinbergen of Norway in mid-last century, applied it to the behavior of waterfowl and gulls, respectively. Another method is contentious among professional ornithologists: whether to "tame" your subject species, say with whole kernel corn with American Crows (Corvus brachyrhynchos), so they will act close and natural around you, or whether such taming causes them to act in unnatural ways. Many raptor biologists cite studying manned raptors in falconry, with its training, for hunting data, as artificial. I personally do not know the answer to the taming issue. It may depend on what species, what journal, how you write it and account for possible anthropomorphic effects, if you can account for them all, and whether the species has the intelligence to be tamed in the first place (more on cognitivity in birds later- see crow section).
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For further reading on behavioral ecology, start with BEHAVIOURAL ECOLOGY: AN EVOLUTIONARY APPROACH by John R. Krebs and Nicholas B. Davies. Then read ANIMAL BEHAVIOR: AN EVOLOUTIONARY APPROACH by
John Alcock. These are the best overviews. The Alcock book is more readable and palatable to the birder, but Krebs and Davies wrote BEHAVIOURAL ECOLOGY: AN INTRODUCTION for that purpose, too. For an understanding of animal signals, such as bird vocalizations, see THE BEHAVIOR OF COMMUNICATING: EA ETHOLOGICAL APPROACH by W. John Smith, the doctoral advisor at The University of Pennsylvania of Dr. Robert Ricklefs, the foremost avian ecologist in the United States. If you want an understanding of bird ecology, I suggest AVIAN ECOLOGY by Christopher Perrins and T.R. Birkhead. Dr. Perrins is the current Director of the Edward Grey Institute of Field Ornithology at Oxford. This book is quite understandable, and affordable, at www.buteobooks.com. For you closet ornithologists, try THE ECONOMY OF NATURE by Dr. Ricklefs. AVIAN ECOLOGY is more oriented toward field avian ecology, but this book delves into depth more what every serious student should know. (Bob Ricklefs and Sir John Krebs are very interested in helping the amateur. I will ask them if they can help you via email once I get five names- via email- no more, and if they are not too busy, they can converse with you and preview your papers prior to submittal.) Do not, I repeat, do not buy these books unless you are particularly flush and can afford it. If you can afford used textbooks, try www.harvestbooks.com. Otherwise, I always get them through Inter-library Loan from my public library and take notes and take down the
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citation. Simple as that: all I have to pay for is the minimal ILL fee. The general rule of thumb regarding textbooks is of two schools: one, newest editions have the most up to
date information, such as in biology, and two: subsequent editions don’t offer much m
information but, with the permissions of the authors, publishing companies make more business in a hard business by putting out more-and-more editions, like in statistics texts. It is subject-dependent, and up to the reader/user. Also, I suggest ON AGGRESSION, KING SOLOMON’S RING, and [book on ethology and the Greylag Goose] by Konrad Lorenz and THE CURIOUS NATURALIST and THE HERRING GULL’S WORLD by Niko Tinbergen. There are other important books by these two, and papers, in the textbooks’ bibliographies. But some of their material is out-dated. For an example, call The University of Oxford Press in the U.S. and request free sample of BEHAVIORAL ECOLOGY journal at 1-800-852-7323 (email@example.com). If you have the funds, a student membership to the ISBE is $38; a regular one is $65. I highly recommend Donald Stokes’s A GUIDE TO BIRD BEHAVIOR, VOLUME 1, of all common species; though some subsequent scientific published papers have altered some of the book’s information, much of it still holds true. Stokes was the first to write an entire book of avian behavior for popular consumption, and ILL can find it in public libraries and. As you know, the scientific process means it is constantly being rewritten: Stokes was the first compendium that updated the classics since Catesby, Bartram, Audubon, Wilson, and the 19th and 20th century classics like Ridgeway, Coues, Bendire, Baird, Cooper, Chapman, Grinnell,
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Griscom, Bent, Sutton, Griscom, Heinrich, Davies, Krebs, etc., in readable, palatable form for the public.
For a partial, scientific, short course-outline of ethological concepts and theory, see Appendix I. It may behoove you to take an undergraduate course in ornithology. Stephen Kress's out-of-print book THE AUDUBON SOCIETY HANDBOOK FOR BIRDERS has such a list of colleges and courses in the back (see libraries or Harvest Books website). Muhlenberg College has an ornithology course for biology majors during the day and a non-major BIOLOGY OF BIRDS course in the evening adult Wescoe School. Adults can take for credit or audit either. Cornell University offers a BIRD BIOLOGY course through the computer through its Cornell Lab of Ornithology. In order to take it, you must pay for it or get a full scholarship through the Lab. Or you can buy their book HANDBOOK OF BIRD BIOLOGY for $99.50 (65 pounds) from Princeton Universty Press (www.pup.princeton.edu).
Optimal foraging is a behavioral ecological term defined by Robert E. Ricklefs (1993, The economics of nature, W.H. Freeman, New York.) as “a set of rules, including breadth of diet, by which organisms maximize food intake per unit time or minimize the time needed to meet their food requirements; risk of predation may also enter the equation for optimal foraging”. Optimal giving up time (GUT) is “the time that an organism should remain within a patch of resources before moving onto the next in order to maximize its rate of food intake”. Optimization of foraging is discussed in detail by Krebs (1984, Behavioural ecology: an evolutionary approach, Sinauer Associates, Inc., Sunderland, MA, for newer editions, and Blackwell Scientific Publications, Oxford, for earlier editions) and Ricklefs (1993).
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Anti-predator behavior is avoidance behavior toward predators of all classes of animals based on species size: small species tend to forage, roost, and breed near or in foliage, middle-sized birds like American Crows (Corvus brachyrhynchos) tend to go to woody
foliage and also outmaneuver avian predators in flight, and larger birds like Common Ravens (Corvus corax) and gulls outmaneuver and the ravens will turn on aerial predators. There are exceptions to this observation for a lot of species. Perhaps the most exemplary is the White-throated Swift (Aeronautes saxatalis), which even escape the Peregrine Falcon (Falco peregrinus) out west (Lima, Steven L. 1993, Ecological and evolutionary perspectives on escape from predatory attack: a survey of North American birds, Wilson Bull. 105(1): 1-47.).
Part 1. Foraging Patterns
I observed American Robins (Turdus migratorius), n100, foraging for earthworms (Oligochaeta: Lumbricdae) on the suburban lawns of Cedar Beach Park in Allentown, Lehigh County, eastern-central Pennsylvania (40.5968N x –75.5124W), in 1992, in a small flock with Common Grackles (Quiscalus quiscula). Birds tended not to forage straighter and in shorter bouts after a successful encounter with prey (Mood’s Median Test, N=1, 2= 0.1, p= 0.05, df= 1). Birds also tended to turn less acute angles after a successful
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probe (median= 140; N=1, 2= 628.4, df= 1, p= 0.05). The mean angle degrees after a successful run was 134 (SE13, cv= 40%). The mean angle degrees after not catching a worm was also 134 (SE13, cv= 38%). The mean angle after a successful run was 141.7 (n= 16, SE11.7, cv= 33%). The mean angle between unsuccessful runs was 140.6 (n= 16, SE12.3, cv= 36%). Not all robins do this behavior (Sign Test, z= 10, p>
0.09, N.S. (non-significant)), but the observation was not unique (z= 0, p= 0.01). However, Sign Tests are low-powered statistically.
My next robin optimal foraging project at the following site (in Part 2) will involve this spring observing GUT with a stopwatch with microseconds, measuring time of foraging on micropatches of lawn before they give up and move between patches in four categories, individuals, pair-bonding pairs, small flocks ( 25 individuals), and large flocks ( 25 individuals), either due to predator presence or searching for more food. Summer breeding foraging dynamics may be different either in the incubation, nestling
or fledgling stage. Also, worm catch (after detection) and beak handling times in microseconds will be recorded. At least thirty samples each of these two variables will be recorded: a Spearman’s R will be done if the two samples are even in number, a Mann-Whitney U if uneven. Seed handling time in finches (Darwin’s Finches; Abbot, I., et al, 1975, Seed selection and handling ability of four species of Darwin’s Finches, Condor 77: 332-335; Grant, P.R., 1986, Ecology and evolution of Darwin’s Finches, Princeton University Press, Princeton, New Jersey.) and North American selected Fringillidae and Emberizidae finches (Willson, M.F., 1971, Seed selection in some North American
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finches, Condor 73: 415-429.). Dr. Willson examined fruit choices by robins (1994, Fruit choices by captive American Robins, Condor 96(2): 494-502.), but an average worm handling time has not been calculated, to the best of my knowledge. The average earthworm weighs about [0.2g] and is not “chewed” buy the upper and lower mandibles,
but the head is tilted back and the item swallowed whole, thus a thin beak (shallow depth). A rule to all evolutionary biology is: “form fits function”.
Part 2. Avoiding Predation
Anti-predator behavior is staying next to foliage while ground foraging, say J.O. Oyugi and J.S. Brown (2003, Giving up densities and habitat preferences of European Starlings and American Robins, Condor 105(1): 130-135.). But Lima (1993) points out they
often seen, including by me, singularly to large flocks in the middle of lawns. Why? Evolution should have an answer. I observed foraging spring and fall flocks since 1994 at the grounds of the Allentown State Hospital (ASH), Allentown, Lehigh County, Pennsylvania (40.6151N x –75.4293W), where, because I am on the Board of Trustees, the administration and security has so graciously allowed me to use it as a study site (Acknowledgements: Gregory Smith, President and CEO, and Ms. Tiffany Hudock, Administrative Assistant to Mr. Smith). The robin alarm note is a species-specific signal that is barely audible to the human ear (See: Caldwell, G.S. 1986, Predation as a selective force on foraging herons: effects of plumage color and flocking, The Auk 103: 494-505.).
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So I will purchase a Radio Shack or Sears sensitive pocket cassette recorder, or go on Ebay and see if they have plastic parabolic reflectors attached to amplified microphones attached to sensitive playback pocket recorders capable of making and playing continuous loop tapes or CDs. I saw flocks get up and shift places, a kind of “following-the-leader” to new found food patch or in response to human movement, but when they flew completely away, they seemed to be often with American Crows or European Starlings (Sturnus vulgaris), and
possibly Common Grackles and Red-winged Blackbirds (Agelaius phoeniceus), and even more remotely so, Brewer’s (Euphagus cyanocephalus) and Rusty (Euphagus carolinus) Blackbirds. (There was the chance for a rare Emberizine or House Sparrow (Plocidae: Passer domesticus), but I only remember a Grasshopper Sparrow (Ammadramus savannarum)-call in a field full of Red-wings, that was a filled-in wetland, in another part of the property. Please see that ASH is in the suburban buffer zone between Allentown and Bethlehem. I may start a spring hawkwatch there because it overlooks the Lehigh River and I’ve observed quite a bit of raptor migration activity from there (fortunately
the governor and state senate appointed me to the board there twice, making it Grant’s little private bird preserve with Mr. Smith’s kind permission.) Were they responding to cues, visual or auditory, from the other species? Or could the warn themselves? If so, was it with visual or auditory signals, or both? How did they react towards an avian or mammalian predator? Did they ignore them for a time? How long? (Predator Presence
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Tolerance (PPT)- my term- defined by time of ignorance, per separate taxa of predator, including hominid).
Part 1. Optimal Cooperative Feeding
I define optimal cooperative feeding in American Crows as the mutual use of sentinels as predator guards while others feed below, then after awhile they switch off, and the sentinels feed. It is optimal because all individuals get to feed while not worrying about “looking up” for predators, optimizing energy intake. European Starlings do it (), and an observer of Canada Geese (Branta canadensis) told me he feels a drake always watches for predators in a flock at Cedar Beach: as he gets closer, it honks loudly and repeatedly and the flock moves away from the intruder.
I have observed many instances of sentineling, but because I was going somewhere, I could not stick around for the switch-off. Sentineling in corvids is, though not well, documented. Lawrence Kilham observed this in only small groups (1989, The American Crow and Common Raven, Texas A&M University Press, College Station, TX.), but I have seen this behavior in mass winter roosts up to 50,000 birds (winter roosts have been observed up to 200,000 birds documented, they may go larger according to the carrying capacity of the habitat), the more birds on the ground, the more sentinels in trees. Winter roosts travel up to 81 kilometers a day in search of food (Terres, J.K., 1980, The Audubon encyclopedia of North American birds, Alfred A. Knopf, New York.). This is because Optimal Foraging Theory says once at a foraging habitat patch, it is the Law of Diminishing Returns. Eventually, it is worth the energy expenditure to travel elsewhere.
I have seen cooperative feeding in crows personally only once according to my mutualism definition because of my itinerant schedule. It occurred at a street in front of
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Cedar Crest College, on the southern border of Cedar Beach Park in Allentown. It involved only two crows, possibly cooperatively breeding yearlings from a nearby nest attended to by the parental pair. Both took turns sentineling and and feeding in the road for ten minutes per bout, sentineling from approximately the same distance and height, feeding on what I hypothesize to be road-cracked acorns. American Crows () and Japanese Jungle Crows (Corvus macrorhynchos japonensis) in Tokyo () have been shown to use automobiles as nutcrackers, as tools, including American Crows with walnuts (Juglans spps.; Black Walnut Juglans nigra). A Sign Test calculated that the probability of all American Crows cooperatively feed, by my definition and sample, is 99%, very significant (z= 1.41, p= 0.01).