Exercise 14 Aves: Observations and Classification of Specimens

EXERCISE 14 AVES: OBSERVATIONS AND CLASSIFICATION OF SPECIMENS Structure 14.1 Introduction Objectives 14.2 Material Required 14.3 General Characters and Classification of Aves 14.4 Observation of Museum Specimens Milvus migrans Bubo bubo Dicrurus adsimilis Dendrocopos mehrattensis Psittacula eupatria Eudynamys scolopacea 14.5 Terminal Questions 14.1 INTRODUCTION Birds occupy all continents, oceans and islands, penetrating the Arctic and the Antarctic and live from sea level to above timberline on the Everest. They are well adapted to migratory habits. They are the best known and most easily recognised animals being unique in having feathers for flying and also cover to insulate their bodies and provide them with distinctive colouration. The body weight is reduced for flight by elimination of some bones and fusion of others and by presence of some air filled cavities and spaces in many bones. High metabolic rate, and raised body temperature, strong flight muscles and advanced respiratory mechanism with air sacs and lungs provide necessary strength for the flight. They have highly developed voice, sight and hearing but poor sense of smell. Class Aves is made up of 28 orders of living birds and a few fossil orders. More than 9600 species have been named so far and only a few species remain to be discovered. Of the 28 orders, four or five (depending on the classification system) are ratitae or flightless birds, the remaining orders are carinate birds with keeled sternum. In this exercise you will observe and classify some representative specimens of class Aves. You are advised to come prepared for this exercise by reading Unit 16 of Block 4, Animal Diversity course. In this exercise you will study six common birds from different orders. Objectives After completing this exercise you will be able to: • identify and give scientific and common names of some of the avian species, • classify the identified genera upto the level of order, • list the characters justifying the classification of the identified specimens Aves : Observations and Classification of and mention special features if any, Specimens • mention the habitat and geographical distribution, • draw labeled diagram of each of the identified genera, and • mention the economic importance if any, of each of the given genera. 14.2 MATERIAL REQUIRED 1. Stuffed specimens of: Kite (Milvus migrans ) Owl (Bubo bubo ) Drongo (Dicrurus adsimilis ) Woodpecker (Dendrocopos mehrattensis ) Large Indian parakeet ( Psittacula eupatria ) Koel (Eudynamys scolopacea ) 2. Hand lens. In the absence of stuffed specimens good large sized photographs may be provided. 14.3 GENERAL CHARACTERS AND CLASSIFICATION OF AVES Let us recall the general characters that distinguish class Aves from all other classes. i) Endothermic tetrapod vertebrates with feathers . ii) Forelimbs modified into wings each bearing three digits and feathers for flight. iii) The hindlimbs are modified for walking, perching or swimming and bear four toes. iv) No glands in the skin except for oil gland in the tail . v) Bones are strong fully ossified, though light, provided with air cavities . vi) Skull bones fused, bearing single occipital condyle as in reptiles. This makes it possible for birds to rotate their heads almost 180 °. vii) Modern birds have no teeth, only horny beak is present. viii) Pelvis is fused to many vertebrae but open ventrally, small ribs with strengthening processes; sternum is broad, well developed usually with median keel or reduced with no keel; flight muscles attached to keel. 187 Animal Diversity: ix) The sacral vertebrae are fused with lumber, last thoracic and last caudal Laboratory vertebrae to form synsacrum . x) Posterior caudal vertebrae fused to form pygostyle . xi) Gullet has crop to store food, muscular gizzard in the stomach to masticate food. xii) Lungs spongy, attached to air sacs that extend into various parts of the body. xiii) Voice produced by syrinx situated at the junction of the trachea and the bronchioles. xiv) Heart four chambered. Classification Class Aves comprises two sub-classes. Subclass Achaeornithes: Ancestral birds of the late Jurassic and early Cretaceous period. They retain many reptilian features including jaws with teeth, a long tail, unfused carpals and metacarpals, and three fingers, each bearing a claw. Archaeopteryx. Subclass Neornithes: Extinct and living birds. Birds with well developed sternum usually with keel. Tail reduced with reduced number of caudal vertebra; metacarpals and some carpals are fused together; the three fingers are reouced and clawless. Birds of Cretaceous to recent times are represented by the following 3 super orders. Superorder Odontognathae: Cretaceous birds retaining teeth. Hesperornis, Ichthyornis. Superorder Paleognathae: Modern birds without teeth, but retaining a primitive archosaurian palate. The ratites (with unkeeled sternum) and tinamous (with keeled sternum). Superorder Neognathae: Modern toothless birds with a flexible palate. (We are following Olson [1985] in listing neognathous bird orders by phylogenetic position and major adaptive radiations rather than in the usual linear sequence from aquatic through terrestrial groups.) 14.4 OBSERVATION OF MUSEUM SPECIMENS Look at the given specimens of birds carefully, use the hand lens wherever you need to see any details and note down all the characters. Compare your observations with the characters given in the text as you draw the given specimen. 14.4.1 Milvus migrans Special Characters i) Pariah kite or Milvus is a large bird about 45-60 cm in length. 188 ii) The plumage is reddish brown streaked with dark brown in both the Aves : Observations and Classification of sexes. Specimens iii) It is distinguished from all similar birds by its forked tail. iv) The toes are elongated bearing sharp pointed claws for grasping and capturing. v) The beak is sharp pointed and hooked, very well adapted for tearing the flesh of the prey. Fig. 14.1: Milvus migrans. Habit and Habitat Milvus is largely a scavenger bird feeding on rodent pests, reptiles, small birds, earthworms and garbage etc. It can be seen soaring around villages and towns at all times. It boldly swoops down to snatch food from the busiest street or market. Geographical Distribution: Milvus is found throughout India, Pakistan, Bangladesh, Sri Lanka and Myanmar. Classification and its Justification Kingdom Animalia Animals, multi-cellular organisms with cells that lack a cell wall, many capable of movement or movement of some of their body parts or capable of movement at some time of their life cycle; heterotrophic nutrition. Phylum Chordata Dorsal tubular nerve chord; notochord and paired gill slits present. Group Vertebrata Notochord is replaced by vertebral column; (Craniata) two pairs of appendages; circulatory system closed; hepatic portal system present; RBCs present in blood. Class Aves Endothermic with feathers; forelimbs modified into wings, claws absent; hind 189 Animal Diversity: limbs adapted for climbing, perching or Laboratory swimming; skull with single occipital condyle; beak present; sternum well developed; amniotic; oviparous. Subclass Neornithes Tail short, ends in pygostyle; metacarpal fused with distal carpals to form carpometacarpals; sternum well developed with keel. Superorder Neognathae Skull neognathus; feathers with interlocking mechanism; wings well developed. Order Accipitriformes Beak short and curved at the tip; mandibles sharp-edged; feet with sharp curved claws; diurnal strong flier. Genus Milvus Species migrans Common Black Kite Name 14.4.2 Bubo bubo Special Characters i) Barn owl is a large and robust bird, measuring upto 60cm in length. ii) Beak is short sharp and decurved and adopted for tearing and piercing. iii) The colour is dark brown streaked with tawny buff and black. iv) The head is large and has two black ear tufts or horns. v) The eyes are large, round and directed forwards. vi) The legs are fully feathered. vii) Feet adapted for grasping and claws sharp pointed. 190 Fig. 14.2: Bubo bubo . Habit and Habitat Aves : Observations and Classification of Barn owl is nocturnal but can be seen frequently during the day time. It spends Specimens the day resting on the ground under the shelter of a bush or on some shady projection of a rock near a river. Its food consists of small mammals, birds, lizards, and other reptiles; also feeds on small insects as well as on fish or crabs. Best known for its deep double hoot. Geographical Distribution : Barn owl is found throughout India, Pakistan and Myanmar. Economic Importance The barn owl is a farmer’s friend, for it kills a large number of crop pests like rodents and other vermin. It deserves the strictest protection. Classification with Justification Kingdom Animalia Animals, multi-cellular organisms with cells that lack a cell wall, many capable of movement or movement of some of their body parts or capable of movement at some time of their life cycle; heterotrophic nutrition. Phylum Chordata Dorsal tubular nerve chord; notochord and pharyngeal gill slits present. Subphylum Vertebrata Notochord is replaced by vertebral column; two pairs of appendages; circulatory system closed; hepatic portal system present; RBCs present in blood. Class Aves Endothermic (warm blooded) with feathers; forelimbs modified into wings, claws absent; hind limbs adapted for climbing, perching or swimming; skull with single occipital condyle; beak present; sternum well developed; amniotic; oviparous. Subclass Neornithes Tail short, ends in pygostyle; metacarpal fused

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