DOCSLIB.ORG

Ornithology Group, Institute of Biomedical and Life Sciences, Graham Kerr Building, University of Glasgow, Glasgow G12 8QQ U.K

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Ornithology Group, Institute of Biomedical and Life Sciences, Graham Kerr Building, University of Glasgow, Glasgow G12 8QQ U.K SEPTEMBER 2007 SHORT COMMUNICATIONS 235 J. Raptor Res. 41(3):235–238 E 2007 The Raptor Research Foundation, Inc. WHY DO CONDORS AND VULTURES EAT JUNK?: THE IMPLICATIONS FOR CONSERVATION DAVID C. HOUSTON1 Ornithology Group, Institute of Biomedical and Life Sciences, Graham Kerr Building, University of Glasgow, Glasgow G12 8QQ U.K. ALLAN MEE Zoological Society of San Diego, CRES, 2920 Zoo Drive, San Diego, CA 92101 U.S.A. MIKE MCGRADY Natural Research Ltd., Am Rosenhu¨ gel 59, A-3500 Krems, Austria KEY WORDS: vulture; condor; conservation; diet; junk; trash. fulvus) at the Gamla Golan Heights colony. Most nests The seven species of New World condors and vultures are strewn with junk; such quantities have been found in and the 15 species of Old World vultures are taxonomically the stomach of chicks that it can easily be felt, and heard, unrelated, being descended from ancestral storks and ea- by gently palpating the stomach, and this condition has led gles, respectively (Feduccia 1996). They occupy identical to at least one known gut blockage: (Ferro 2002, B. Wood- scavenging roles in their respective ecosystems, being clas- ley and O. Bahat pers. comm.). In Armenia, a griffon vul- sic examples of convergent evolution. Species specialize on ture (G. fulvus) chick ejected 34 g of junk including sheep different parts of carcasses (Kruuk 1967, Hertel 1994) with wool (Fig. 1), and junk is common in and below nest condors [Andean Condor (Vultur gryphus) and California ledges (M. Ghasabian pers. comm.). Junk is routinely Condor (Gymnogyps californianus)] and griffon vultures (all found at nests of G. bengalensis in Pakistan (M. Gilbert pers. eight species of Gyps) taking muscle and viscera from large comm.) In southern Africa, Benson et al. (2004) docu- mammals: our speculation here is mainly concerned with ment the extensive range of junk eaten by Cape Griffon these species, not other vulture species. Among the many (G. coprotheres), and review other studies from this region. similarities between these two groups is the unusual behav- As far as we know, comparable behavior has not been de- ior of swallowing indigestible, nonfood and often human- scribed on this scale for any other birds of prey or owls, made objects. For brevity we call this ‘‘junk.’’ Junk in- despite much intensive pellet analysis which would be ex- cludes fragments of glass, china, and plastic, metal objects pected to reveal such activity (e.g., Yom-Tov and Wool such as bottle tops, small rocks, sticks, grass, wool, and fur, 1997, Akaki and Duke 1998, Redpath et al. 2001). In this among other things. The scale of this behavior has only paper we speculate on the evolutionary function of this become apparent in recent years with the intensive surveil- unusual behavior, and the implications for conservation. lance necessary in conservation projects. In North America We suggest three possible functions for ingesting junk, the critically endangered California Condor has hatched which are not mutually exclusive. Firstly, as is often as- 17 chicks in the wild since the first breeding efforts of sumed, junk may be swallowed in the mistaken belief that reintroduced populations in California and northern Ari- it is a bone fragment. Condors and the larger vultures are zona (2001–2006). Of 10 nestlings hatched in the wild in unusual among birds of prey in that they feed mainly on California (2001–2005), only one survived to fledging the soft tissues (i.e., muscle and viscera) of large ungulate (Mee et al. 2007a). Seven of eight wild-hatched chicks in carcasses. Unlike some other birds of prey, which feed on California examined between 2002–2005 were found to small mammals or birds, they cannot consume their prey have consumed junk, and all nest sites contained this ma- whole. Bones are the primary source of calcium in the diet terial; six chicks had large quantities (30–204.5 g) of junk of birds of prey, but the large mammal carcasses on which in their guts, and three of these died in the nest area (Mee large vultures and condors feed have few bones small et al. 2007b). A fourth was later euthanized and two others enough for them to swallow, other than carpals, tarsals, were released back to the wild after 1.5–2.5 yr recovering at and phalanges. Their diet, if confined to soft tissues, may Los Angeles Zoo (U.S. Fish and Wildlife Service unpubl. therefore be deficient in calcium (Houston 1978). Adult data). This is also a common phenomenon in some Old birds probably can maintain calcium balance on such a di- World griffon vulture colonies. In Israel, there has been et, but, during the breeding season, females need to form heavy nestling mortality among Eurasian Griffons (Gyps eggshells and the chicks need higher calcium levels to mineralize their growing bones. The larger vultures have 1 Email address: [email protected] an unusually slow nestling growth rate, compared to other 236 SHORT COMMUNICATIONS VOL. 41, NO.3 cause of their long necks, condors and griffon vultures may find pellet ejection more difficult than do species with short esophagi. Those vulture species which consume large quantities of skin, such as the Old World Cinereous Vul- ture (Aegypius monachus) and Lappet-faced Vultures (Torgos tracheliotus) or the smaller New World Turkey Vulture (Cathartes aura) and Black Vulture (Coragyps atratus) are able to form large pellets regularly from the substantial quantities of hair they consume, in which smaller undigest- ed objects are embedded (Rea 1973, In˜igo Elias 1987). But vulture species such as condors and griffon vultures, which do not consume such large quantities of skin, may not always have sufficient material to form into functioning pellets, and in our experience do not produce pellets reg- ularly. When these vultures have small, undigested items lodged in their stomach they may deliberately seek other Figure 1. Junk (34 g) regurgitated by a Gyps fulvus nest- indigestible objects to swallow to enable them to accumu- ling in Armenia. Photo by Mike McGrady. late a sufficient volume of material for peristaltic action to eject it all as a pellet. This probably requires both material birds of their size, a growth strategy that may have evolved of sufficient mass and bulk against which the muscular as an adaptation to their low-calcium diet because it re- contractions of the esophagus can act, and sometimes also duces the daily calcium requirements of the chick (Hous- fibrous material to bind such junk together into a single ton 1978). Because of this low-calcium diet, vultures may functional pellet. Both vultures and condors apparently seek out small bones lying on the ground as alternative eat indigestible fibrous material such as grass, leaves, twigs, calcium sources, as is well known for many other bird spe- bark of shrubs, and hair, and such material can be found cies (see references in Ramsay and Houston 1999). Bone incorporated into their pellets together with solid objects can be digested readily in the acidic conditions of the (Koford 1953, Benson et al. 2004). The consumption of stomach (Houston and Copsey 1994). This need to find small, indigestible objects may therefore have been a be- calcium sources might account for condors’ and vultures’ havior that originally had clear adaptive value for condors consumption of pieces of white china, white PVC piping, and griffon vultures, and any naturally occurring junk plastic, glass, and similar white- or brown-colored junk in items swallowed would not normally have been life-threat- the mistaken belief that it is bone. However, it is perhaps ening, but would have assisted in pellet production. How- unlikely that this explanation alone can account for the ever, the situation has changed because humans have now consumption of metal bottle-tops, washers, electrical items, littered the environment with items that have sharp edges brightly colored or clear glass, ammunition casings, rub- which can lodge in, or even penetrate, the gut, and items ber, grass, sticks, and the other bizarre objects vultures which are toxic. These items probably are given to nest- regularly swallow (Collins et al. 2000, Ferro 2000, Benson lings unintentionally. When adults disgorge food from et al. 2004, Mee et al. 2007b), which could not be mistaken their crops into the mouths of the chicks, this transfer is for bone. indiscriminate; the bone fragments taken from the crops A second explanation may also be a consequence of of Cape Griffon chicks are not statistically different in size feeding on the soft tissues of large ungulate carcasses. It from those taken from the crops of adult birds (Benson et concerns the need to form pellets. No vertebrate gut con- al. 2004). But chicks might have weaker muscles in their tains an enzyme to digest keratin, so any keratin structure esophagus walls than do adults, and may not be able to that a bird swallows, including hair, horn, and hoof, will expel pellets as readily. This might explain the accumula- remain undigested once it reaches the stomach. All vul- tion of junk in the stomach of some chicks. In addition, tures will inadvertently eat some such keratin items, and because these species usually nest on rock ledges, chicks some species will consume more than others, depending have little opportunity to seek out fibrous indigestible ma- on the part of the carcass for which they are specialized. terial to help in the deliberate formation of a structured These will impede digestion if they are not ejected from pellet that can be expelled. This may be especially true for the stomach, and this is done through the production of nestling condors, usually confined to inaccessible cave pellets. In the stomach, pellets are formed from all mate- nests.
Load more

Recommended publications
  • Owl Pellet Dissection Activity
    Owl Pellet Dissection Activity: Background: Owl pellets are neat little packages of fur, bones, and other indigestible stuff that are regurgitated (spit up) sometime after an owl has finished digesting several meals. You can find owl pellets on the ground under trees where owls like to roost or nest. All owls cough up pellets as a part of how they digest their food. Most of the time, they swallow their prey whole without chewing or tearing the flesh apart. This means that owls naturally have a lot more bones, feathers, and fur in their diet. Owls can digest only the soft muscles and organs of their prey. The bones, teeth, fur, feathers, scales, or insect skeletons are too dense and cannot be converted into energy. The harder parts may also puncture an owl’s soft, curved intestines if passed through its digestive tract. Instead, the waste material is formed into a pellet in the gizzard, a muscular pouch in the owl’s digestive system. The gizzard operates like a trash compactor, pressing all the bones, fur, feathers, or other indigestible stuff into a firm, oval-shaped ball. When the pellet gets big enough, it is passed back up the esophagus to be cast out (thrown up) about twelve hours after eating. Although other birds, like eagles and hawks, also regurgitate pellets, owls are more efficient at it and they regurgitate more frequently. Owls swallow their prey whole, ingesting the entire skeleton. Other raptors selectively tear at their prey, eating only the soft digestible parts and leaving the indigestible bones. Also, unlike other birds, owls do not have a crop, which is an organ that holds food until the stomach is ready to receive it.
    [Show full text]
  • Additional Specimen of Microraptor Provides Unique Evidence of Dinosaurs Preying on Birds
    Additional specimen of Microraptor provides unique evidence of dinosaurs preying on birds Jingmai O’Connor1, Zhonghe Zhou1, and Xing Xu Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China Contributed by Zhonghe Zhou, October 28, 2011 (sent for review September 13, 2011) Preserved indicators of diet are extremely rare in the fossil record; The vertebral column of this specimen is complete except for even more so is unequivocal direct evidence for predator–prey its proximal and distal ends; pleurocoels are absent from the relationships. Here, we report on a unique specimen of the small thoracic vertebrae, as in dromaeosaurids and basal birds. Poor nonavian theropod Microraptor gui from the Early Cretaceous preservation prevents clear observation of sutures; however, Jehol biota, China, which has the remains of an adult enantiorni- there does not appear to be any separation between the neural thine bird preserved in its abdomen, most likely not scavenged, arches and vertebral centra, or any other indicators that the but captured and consumed by the dinosaur. We provide direct specimen is a juvenile. The number of caudal vertebrae cannot evidence for the dietary preferences of Microraptor and a nonavian be estimated, but the elongate distal caudals are tightly bounded dinosaur feeding on a bird. Further, because Jehol enantiorni- by elongated zygapophyses, as in other dromaeosaurids. The rib thines were distinctly arboreal, in contrast to their cursorial orni- cage is nearly completely preserved; both right and left sides are thurine counterparts, this fossil suggests that Microraptor hunted visible ventrally closed by the articulated gastral basket.
    [Show full text]
  • Wildlife Center Classroom Series Owl Pellets: Little Packages of Owl Puke
    Wildlife Center Classroom Series Owl Pellets: Little Packages of Owl Puke Wednesday August 10, 2016 Raina Krasner, WCV: Hello, everyone! Welcome to today’s Wildlife Center Classroom Series! Raina Krasner, WCV: Today, we’re talking about something that I think many of you are familiar with – owl pellets! Otherwise known as owl puke, little furball gifts, tiny packages of bones. But let me stop myself before I give away too much of the good stuff. Comment From caleb (͡๏̯͡๏) WOO HOO! Kids think this may be one of the BEST Classroom Series EVER ~~ we LOVE to dissect Papa G'Ho pellets! Comment From Dave in Missouri Oh, oel puke, this will go good with my lunch!:) Raina Krasner, WCV: :) Raina Krasner, WCV: First, what is an owl pellet? Eagle Owl Pellet in Germany, Martin Lindner Wildlife Center Classroom Series: Owl Pellets: Little Packages of Owl Puke Page 1 Raina Krasner, WCV: When an owl eats its prey, it consumes most, if not all, parts of the animal. Raina Krasner, WCV: If you order a fast food hamburger (or a veggie burger!) and it comes to you in a neat little wax paper package, and on the hamburger there is lettuce, tomato, and pickles, you have the luxury of using your utensils or fingers to pull back the wax paper wrapper, and then pick apart the burger and pull off the parts you don’t like, don’t want, or can’t eat. Raina Krasner, WCV: An owl, however, has to eat everything – “wrapper”, toppings, and all. Raina Krasner, WCV: No handy little thumbs and fingers to pick apart the food.
    [Show full text]
  • For Creative Minds
    For Creative Minds The For Creative Minds educational section may be photocopied or printed from our website by the owner of this book for educational, non-commercial uses. Cross-curricular teaching activities, interactive quizzes, and more are available online. Go to ArbordalePublishing.com and click on the book’s cover to explore all the links. Biologist or Paleontologist? Scientists who study living things (biologists) often observe animals to learn about them. If they are working in the field, they might even see different animal signs (nests with eggs, footprints, or poop) that help them to better understand the animal they are studying. Scientists who study dinosaurs (paleontologists) learn about the animals by studying body or trace fossil clues. They sometimes use knowledge of today’s animals to help them understand the dinosaurs. Identify whether you think the following statements describe the work of a biologist or a paleontologist. Can you explain “why” to someone? 1. The scientist dissected the owl pellet to see what it had eaten. 2. The scientist discovered that the round-looking rock was fossilized poop (coprolite) containing bits of bone from a plant-eating dinosaur. 3. In 2011, scientists found several dinosaur feathers trapped in amber. 4. In 2007, scientists found a duckbilled dinosaur that was so well preserved that even the skin had fossilized. 5. Scientists watched the birds care for their young. 6. Scientists found fossils of an animal sitting on eggs in a nest in Mongolia. 7. Scientists used medical scanners to see inside fossils of a dino skull. Inside the crest were hollow passages similar to the inside of a horn.
    [Show full text]
  • P0549-P0553.Pdf
    SHORT COMMUNICATIONS 549 The Condor 99549-553 0 The Cooper Omithologlcal Society 1997 COMPARISON OF PELLETS VERSUS COLLECTED BIRDS FOR SAMPLING DIETS OF DOUBLE-CRESTED CORMORANTS CLAYTONE. DERBY AND JAMES R. LOVVORN~ Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071 Abstract. For many fish-eating birds, two types of sample sizes of colonial diving birds in given months samplescan be usedto determine diets of adultsduring or years are usually < 25 and often < 10 (e.g., Baltz both breeding and nonbreedingperiods: esophagus and and Morejohn 1977, Kennedy and Greer 1988, Otten- gizzard contentsof birds collected at feeding sites,and bather et al. 1994), althoughgreater samples are some- pellets (indigestible residue) cast up at roostsor breed- times possibleat wintering concentrations(Glahn et al. ing colonies. We compared these two methods for 1995). Collecting birds also requiresthat all important Double-crested Cormorants (Phalucrocorux auritus) feeding sites be located and sampled. collected on the North Platte River, Wyoming and Gathering pellets at colonies or roosts does not re- nesting at a nearby colony both before and after fin- quire killing birds, can provide integrative samplesof gerling trout were stockedin the river. Before stocking, all feeding sites, and can result in larger sample sizes there were no significant differences between pellets with less time and effort (Veldkamp 1995, Warke and and collected birds in percent massesof different fish Day 1995). However, this method cannot be used if types in different length classes. After stocking, the colonies or roosts are inaccessible(e.g., on cliffs), are two methodsyielded similar resultsfor different length directly over water where pellets cannot be retrieved classes,but differed in relative proportionsof suckers (on pilings, etc.), or have too few birds to yield enough and trout.
    [Show full text]
  • A Curious Pellet from a Great Horned Owl (Bubo Virginianus)
    University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln USGS Staff -- Published Research US Geological Survey 2005 A Curious Pellet From a Great Horned Owl (Bubo Virginianus) Neal Woodman USGS Patuxent Wildlife Research Center, [email protected] Carla J. Dove National Museum of Natural History, [email protected] Suzanne C. Peurach USGS Patuxent Wildlife Research Center, [email protected] Follow this and additional works at: https://digitalcommons.unl.edu/usgsstaffpub Woodman, Neal; Dove, Carla J.; and Peurach, Suzanne C., "A Curious Pellet From a Great Horned Owl (Bubo Virginianus)" (2005). USGS Staff -- Published Research. 619. https://digitalcommons.unl.edu/usgsstaffpub/619 This Article is brought to you for free and open access by the US Geological Survey at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in USGS Staff -- Published Research by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. 2005NORTHEASTERN NATURALIST 12(2):127–132 A Curious Pellet From a Great Horned Owl (Bubo Virginianus) 1, 2 1 NEAL WOODMAN *, CARLA J. DOVE , AND SUZANNE C. PEURACH Abstract – One of the traditional methods of determining the dietary preferences of owls relies upon the identification of bony remains of prey contained in regur- gitated pellets. Discovery of a pellet containing a large, complete primary feather from an adult, male Ring-necked Pheasant (Phasianus colchicus) prompted us to examine in detail a small sample of pellets from a Great Horned Owl (Bubo virginianus). Our analyses of feather and hair remains in these pellets docu- mented the presence of three species of birds and two species of mammals, whereas bones in the pellets represented only mammals.
    [Show full text]
  • Owl Pellet Project Review
    Owl Pellet Project Review: What have we learned about barn owls so far? Use this slideshow to quiz yourself. Write down the answers in your Journal in complete sentences that restate the questions, then check the next slide to see if you are correct. If you are incorrect, be sure to fix your answer! Owls are a type of carnivorous bird that is sometimes called a “bird of prey.” Q1. What term did we learn that means bird of prey? A1. A bird of prey is called a raptor. Q2. What are some other raptors besides owls? This is my friend Megan with an Eagle Owl. She works at the Cincinnati Zoo. Other raptors are eagles, hawks, ospreys, and falcons. Red-tailed Hawk Bald Eagle Falcons Osprey This Secretary Bird is also a raptor. I saw some of these crazy-looking birds in Namibia. Although they can fly very well, they usually hunt on the ground. These guys even kill and eat snakes! Q3. Are all carnivorous birds raptors? Support your answer with evidence! Pelicans eat fish. So do Penguins! FACTS: 1. A carnivorous animal eats other animals. 2. A raptor has sharp talons with which to catch its prey and a sharp beak for tearing it up. A3. Possible answer: Raptors are carnivorous birds of prey with sharp, hooked beaks and talons. There are some carnivorous birds which are not raptors. For example, penguins and pelicans eat fish, which are animals, but they do not possess sharp talons or beaks specialized for tearing. Make sure the question is restated and that you provided supporting evidence! An adaptation is a physical or behavioral trait which helps and organism survive in its environment.
    [Show full text]
  • AN ANALYSIS of BIRD PELLETS FOUND on LUNDY by ALAN ROWLAND Mole Cottage, Chapel Close, Woodford, Morwenstow, Cornwall, EX23 9JR E-Mail: [email protected]
    Journal of the Lundy Field Society, 4, 2014 AN ANALYSIS OF BIRD PELLETS FOUND ON LUNDY by ALAN ROWLAND Mole Cottage, Chapel Close, Woodford, Morwenstow, Cornwall, EX23 9JR e-mail: [email protected] ABSTRACT Bird pellets are a potential source of information on food preferences and composition of local fauna. Sixteen pellets from three different bird taxa (raptors, gulls, corvids) were collected from Lundy over a period of two years and the contents subsequently analysed to identify prey and predator. Keywords: Lundy, bird pellets, raptors, gulls, corvids INTRODUCTION Owl pellets, especially those of owls such as Barn Owl (Tyto alba), are a useful source of identifying mammal distribution as well as predation statistics. Owls swallow their prey whole and eject the indigestible remains. These remains can be teased apart to reveal the bird’s choice of diet as well as the composition of the local small mammal, bird and invertebrate population. Some species, like Barn Owl, have preferred perches where they regularly return to digest their food. These perches are often inside barns or other buildings, or within sheltered areas, so the ejected pellets can be easily found and suffer minimal damage from wind and rain. Such devotion to a perch means that pellets can usually be identified to species with some degree of certainty (RSPB, undated). The pellets of species other than owls are occasionally described. Witherby et al., 1963, gives pellet sizes of Peregrines to be 40-45mm in length by 22-25mm in diameter though they can be much smaller and often taper at one end; Kestrel pellets are typically 30-35mm in length by 9-15mm in diameter and Sparrowhawk pellets 21-40mm long by 10-12mm in diameter.
    [Show full text]
  • Pellet Egestion in Modern Carnivorous Snakes
    Current Zoology, 2020, 66(5), 593–595 doi: 10.1093/cz/zoaa009 Advance Access Publication Date: 7 March 2020 Letter to the Editor Letter to the Editor Pellet egestion in modern carnivorous snakes a,b, c Stanisław BURY * and Agnieszka DROHOBYCKA-WAWRYKA aInstitute of Environmental Sciences, Jagiellonian University, Gronostajowa 7, Krako´w, 30-387, Poland, bNATRIX Herpetological Association, Legnicka 65, Wrocław, 54-206, Poland and cMedicavet Veterinary Clinic, Kapelanka Downloaded from https://academic.oup.com/cz/article/66/5/593/5799074 by guest on 01 October 2021 13c, Krako´w, 30-347, Poland *Address correspondence to Stanisław Bury. E-mail: [email protected]. Handling editor: Xiang Ji Received on 7 January 2020; accepted on 2 March 2020 Food resources vary in terms of digestibility and constraints in food mass: 23.4 g), 7 days after ingestion of a vole, prior next feeding, a processing are an essential factor driving the evolution of adapta- compact mass of distinguishable shape was palpated. The location tions to cope with them, for example, a complex morphology of of the object in the mid-body at approximately half of the snout– gastric tract, symbiosis with microorganisms, enzymatic specializa- vent length indicated its location in the stomach, which was further tion (McNab 2002). Pellet egestion is another important adaptation confirmed by the X-ray examination (performed in MedicaVet that enables to remove indigestible food particles and is observed in Veterinary Clinic, Cracow, Poland; Figure 1A). One day later the several vertebrate taxa. Pellets are most commonly reported in sau- specimen was observed to eject orally a structure resembling avian ropsids, particularly birds, but published records indicate pellet for- pellet, that is, containing bones and fur, being dry and lacking any mation also in the 2nd groups of sauropsids, that is, nonavian soft tissues (Figure 1B).
    [Show full text]
  • Discovering Owl Pellets
    Discovering Owl Pellets Essential Question: Location: Indoors Do all animals digest their food in the same way? Objectives: Learners will At a Glance: 1) dissect an owl pellet and Learners will dissect an owl pellet and interpret clues to owl interpret clues to owl eating and digestion habits. eating and digestion habits. Next they will identify small 2) identify small mammal skulls mammal skulls and bones using a bone identification chart. and bones using a bone identification chart. Background: More than 300 species of birds in several different orders are Skills: communication, observation, data collection, known to regurgitate pellets of indigestible material listening, analysis including all owl species. Owl pellets are very useful in understanding owls’ feeding habits. Supplies: owl pellets (easy to locate Owls, like other birds, cannot chew their food. Small sources on internet) dissecting tools (toothpicks, prey is swallowed whole, skull intact. Larger prey, like a tweezers) skunk eaten by a Great Horned owl, may be torn into smaller paper plates pieces before being eaten. owl pellet bone ID sheet Discovering Owl Pellets Unlike most other birds, owls have no crop, and the Worksheet food passes straight into the foregut (they do not possess a Pencils gloves true stomach). The acid in the owls gut is rather weak with a pH of 2.2 - 2.5 which is the same as vinegar. This compares Subjects: science to diurnal birds of prey which have a pH of 1.3 - 1.8, which is approaching the pH of concentrated hydrochloric acid. Time: 40 minutes This means that only the soft tissues are digested; the bones and even fur and feathers remain virtually intact.
    [Show full text]
  • Diet Composition of Common Ravens Across the Urban-Wildland Interface of the West Mojave Desert
    Diet 244 RAVEN DIET AND URBANIZATION Diet composition of common ravens across the urban-wildland interface of the West Mojave Desert William B. Kristan III, William I. Boarman, and John J. Crayon Abstract Common ravens (Corvus corax) are human-subsidized scavengers and predators in the Mojave Desert. They have increased dramatically in number and have been implicated as contributors to the decline in desert tortoise (Gopherus agassizii) populations. Known patterns of increased fledging success near human developments suggested that food was the most likely resource subsidy received by ravens. Because ravens are opportunistic foragers with a generalist diet, we predicted that the types of resource subsidy provided by different kinds of human developments should be reflected in measures of diet com- position of breeding ravens. We estimated diet composition from contents of raven pel- lets collected at nests and related diet composition to distance of the nests from roads and point sources of resource subsidies, such as towns or landfills. Ravens that nested close to point subsidies far from major roads had the greatest incidence of trash in their diets. Ravens that nested close to roads but far from point subsidies had a low incidence of trash and a higher incidence of presumably road-killed mammals and reptiles. Ravens far from both roads and point subsidies had more plant material and arthropods, and ravens close to both roads and point subsidies had more birds and amphibians. Diet diversity was not related to distance from roads or developments. Fledging success was correlated with diet composition, such that birds with diets consistent with trash or road-kill subsidies fledged the greatest number of chicks.
    [Show full text]
  • Pedagogical Guide: the Raptor Pellet
    PEDAGOGICAL GUIDE: THE RAPTOR PELLET PEDAGOGICAL GUIDE : The Raptor Pellet TABLE OF CONTENTS PELLET PRELUDE Introduction…………......……………………………….............2 Formation of the raptor pellet….......…..............................….2 Pellet analysis ……………………….......…...............…....…..3 Amazing pellets!…………………………......……................…3 THE PELLET DISSECTION ACTIVITY Preparation.........………………………………………..…........4 List of materials......................................................................4 Dissection Instruction Sheet...................................................5 Activity wrap-up…………………………………….….....…...…6 SCIENTIFIC METHOD OPTION The Scientific Method....……............................................…..6 Scientific Report Worksheet...................................................7 Appendix I: THE BIRD DIGESTIVE SYSTEM..........……………..8 Appendix II: REFERENCE BOOKS......………..……………...…..9 © All rights reserved –Falcon Environmental Services, inc. 1 www.falcon.bz PEDAGOGICAL GUIDE : The Raptor Pellet PELLET PRELUDE INTRODUCTION Birds of prey are carnivorous birds that possess 3 important adaptations for hunting. They have an excellent vision which allows them to see prey a great distance away. They have powerful feet called talons which they use to catch the prey, and they have a hooked beak to break their prey’s neck and tear off meat. FORMATION OF THE RAPTOR PELLET Most raptors eat their entire prey. Some owls even eat them whole, in one gulp, when they are small enough of course! The bird’s stomach can digest the meat, the fat and other tissues but not the feathers, fur or bones of the prey. All these non-digested parts create a pellet in the bird’s gizzard, an organ of the digestive system. The process of digestion and of forming a pellet can take between 6 and 24 hours depending on the type and the size of the prey eaten. It is important the bird coughs up this mass of non- digested parts because it could get in the way of the absorption of nutrients and cause certain health problems.
    [Show full text]