Birds and Theropods

1. Birds and Theropods • The Theropods had these traits that are similar in some ways to birds • Elongate, mobile and S-shaped neck • A foot with 3 toes pointed forward and one extending backward (tridactyl foot) • Digitigrade posture (I.e. with toes bearing the weight of the body • Ankle joint between tarsal bones (inter-tarsal joint) rather than between tarsals and tibia and fibula • Hollow pneumatic bones • Fused bone sternum • A furcula (wishbone) formed from fusion of the clavicles

2. Earliest Bird: Archaeopteryx • Archeopteryx is believed to be the the earliest known bird • Oldest fossil belonging to the class Aves • Dates to late Jurassic • But its structures seem to be intermediate between Theropods and birds. • Birds defined as Archaeopteryx + extant birds and all descendants of their most recent ancestor

3. Earliest Bird: Archaeopteryx • Flight feathers on wings had asymmetrical veins suggesting that they had been shaped by aerodynamics forces associated with flapping flight • The retrices-(tail feathers) are arranged in 15 pairs along the sides of the 6th thru 20th caudal vertebrae • Had a large furcula • Fused clavicle • Rectangular sternum • Wings very large, to contribute acceleration as it ran

4. Earliest Bird: Archaeopteryx • Evidence suggest it could fly by taking off the ground and rapidly fly for several hundred meters • Well defined as a ground dwelling cursorial predator that could leap into the air to seize flying insects and fly rapidly to escape from predators • Could not land in trees due to its foot structure.

5. Chapter 17: Extant Birds: Characteristics • Major characteristics of birds are modifications for flight which is the central trait of birds • Feathers represent modified epidermal scales • Are used for a variety of functions • Insulation, airfoil, streamlining, waterproofing, reflecting/absorbing solar radiation, tactile senses and display

6. Feathers and Flight • In general, feathers grow in tracts called pterylae over the birds body. • Unfeathered areas are called apteria • A typical feather has a • calamus, which is a short tube attached to the bird; • rachis, which is the main support in the middle of the feather; • vane, which is made up of barbs that are held together by barbules (Figure 17-2).

7. Types of feathers • contour feathers • have a large vane and are found in the wing and tails • Have interlocking barbs and barbules • Used as airfoil, flight • Remiges are the wing feathers • Retrices are the tail feathers

8. Types of feathers • down feathers– • The rachis is shorter than the longest barb and there are no barbules, • Thus the feather seems very disorganized. • Soft and fluffy • This feather is used for insulation and covers the body of the bird.

9. Types of feathers • Semiplumes (fig 17.4 a) • are intermediate between a contour feather and a down feather . The base of the feather is like a down feather but the rachis is longer than the longest barb. Provides shaping and insulation

10. Types of feathers • powder down feather – • these produce an extremely fine powder as they break up. The powder helps to keep the feather dry. • bristles – • have a stiff rachis and no barbs (figure 17.4 b). Generally used for protection around the eyes, nose, mouth and they are also tactile sense organs. • filoplumes • are very fine feathers with a few barbs at the distal end (figure 17-4 C). • They are sensory in nature and provide information about the position of the flight feathers.

11. Musculoskeletal system • Bones have been lightened via inclusion of large air spaces (pneumatic bones) • feathers may weigh more than skeleton • Pneumatization better developed in large birds than small ones • Diving birds have less pneumatization • Skull is greatly pneumatic, sternum, pectoral girdle and pelvic girdles are all pneumatic

12. Musculoskeletal system • Skeleton is strengthened by extensive fusion of bones • loss of teeth and heavy jaws; replaced by horny beak -- lighter • specialization of forearm bones to support flight feathers • loss of tail: pygostyle--fused 5 remaining caudal vertebrae; platform for tail feathers.

13. Musculoskeletal system • furcula - fused clavicles, only in birds [and theropods]--"wishbone"; provides extra bracing for shoulder girdle • synsacrum: fused pelvis • Hind legs used for body support and locomotion (bipedal walking, hopping, perching) • Fore-limbs modified as wings

14. Musculoskeletal system • Thoracic vertebrae are joined by strong ligaments that are often ossified- immobile • Resists collapse during flight • Sternum bears an enlarged process= keel for the origin of the flight muscles (the Pectoralis) • Furcular and procoracoids brace the sternum and prevent it from collapsing the chest during contractions of flight muscles • Ribs overlap, forming light, strong cage protecting heart, viscera, during contraction of flight muscles

15. Femur is robust to support major muscles • Bones of shank, ankle, foot elongated for efficient locomotion • Ankle joint is mesotarsal ( inside the tarsals)5th toe is lost • Tarsometatarsus formed by fusion of distal tarsals and metartasals of the remaining toes • Knee is between thigh and drumstick and is hidden between contour feathers of the body • The tibiotarsus is the lower leg (drumstick)

16. Avian Wing • Serves as an air foil (lifting surface) and propeller for forward motion • Equipped with primary feathers that propel the bird and the secondaries that provide lift. • Primary feathers responsible for flying..

17. Flight terminology • Reaction: • Force produced by flow of air and composed of • Lift: vertical force opposed to gravity • Drag: backward force opposed to forward motion • Angle of attack: the angle above the horizontal of the leading edge of a bird,s wing. A larger angle ideal for generating lift

18. Flight terminology • Cambered airfoil • A structure of a wing that is convex dorsally and produces lift when air flows across it or • The degree to which the ventral surface of the wing is concave. • The more camber the more lift that is developed at low speed. • Can compensate for high wing loadings, low aspect ratios

19. Flight terminology • Angle of attack • The angle that the wing is tilted above horizontal as is moves into the air. • If the angle of attack is too high, turbulence results across the wing and the lift decreases to the point that it can not keep the bird in the air. At this point the bird stalls. • The angle at which this occurs is called the stalling angle. • See figure 17.8

20. Flight terminology • Alula • The tuft of feathers on the first digit of a bird’s wing that reduced turbulence in airflow over the wing

21. Flight terminology • Aspect Ratio: ratio of wing length to width • Long narrow wings • have high aspect ratio and high lift to drag ratios (L/D) • These wings allow fast flight and dynamic soaring • E,g sailplanes, albatrosses: AR = 18: 1; L/D = 40:1 • Short broad wings • Have low aspect ratio • Slow flight speeds without stalling • Good maneuverability • E.g. pheasants, woodland dwelling birds

22. Flight terminology • Wing Loading • Mass of bird divided by wing area • The lighter the load, the less power is needed to sustain flight (e.g in small birds) • The larger the load, the more power needed to sustain flight ( as in larger birds) • See table 17.1 • Heavier birds, in general, have higher wing loadings than lighter birds

23. Flight terminology • Induced drag • is the result of airflow from beneath wing around the distal tip to the upper surface of the wing. (picture an airplane landing on a dusty runway).

24. Flapping Flight • The shoulder joint of a bird involves the Humerus, scapula, and Coracoid. • The muscles that power the wing are on the ventral surface. • The muscles on the dorsal surface are very weak and are not used to power the wing. • The downstroke is powered by the Pectoralis major (largest breast muscle).This muscle originates on the keel of the sternum and inserts on the ventral surface of the Humerus.

25. Flapping Flight • The upstroke is powered by the supracoracoideus. This muscle also originates on the keel of the sternum and is deep (or beneath) to the pectoralis major. • A tendon runs from the supracoracoideus, though the foramen triosseum and inserts on the dorsal surface of the humerus.

26. Flapping Flight • Strong fliers have as much as 20% of their body weight made up by breast muscle (pigeons), • Some birds have the breast muscle make up only 10% of the body weight (owls). • During takeoff birds usually strongly power both the upstroke and the downstroke.

27. Four Types of wings • high-speed wing – fast flying birds such as pigeons and falcons moderately high aspect ratio tapered to a point at the distal end • very little camber (almost flat on the ventral surface) • no slots in the outer primaries

28. Four Types of wings • dynamic soaring birds have – • long narrow, flat wing, no slots in the outer primaries; very high aspect ratio (18:1) • Albatrosses and shearwaters (figure 17.12)

29. Four Types of wings • elliptical wings – • Low aspect ratio (length to width ratio is small). E.g in pheasants & grouse • highly cambered; slotting in the outer primaries • highly maneuverable wing, relatively slow speed, commonly found in woodland species, constantly flapping to produce lift.

30. Four Types of wings • slotted high-lift wing – • Highly maneuverable wing, with high lift at slow speed. intermediate aspect ratio, deeply cambered • These birds engage in static soaring where they ride thermals or other air currents while gliding. • marked slotting in the outer primaries (the slotting reduces induced drag and provides lift at slow speed with each feather acting as an airfoil)

31. The hind Limbs • Hind limbs are adapted for walking, running (cursorial adaptation) as follows • an increase in the length of the distal elements of the leg • a decrease in the surface area of the foot that makes contact with the ground • a decrease in the number of toes (for example, ostriches have 2 toes) • See figure 17.13

32. hopping This is a specialization in which both feet move together. A succession of jumps • This is typical of smaller birds (songbirds) • In larger birds hopping becomes energetically unfavorable (for example among the corvids, blue jays hop but ravens walk).

33. Perching on trees/ branches • Usually birds have three toes forward and one back (called ansiodactyl) : produces a large grip • Typical of passerines which perch on their limbs, • Parrots & woodpeckers have two toes forward and two toes backward (called zygodactylus) • Special arrangements of tendons creates a pulley system such that the weight of the perching bird tightens the tendons and curls the toes tightly around the perch • Means no muscular energy expended, bird will not fall of when off when it sleeps

34. Climbing • Relatively short legs for climbing • Feet often with 2 toes in front and 2 to rear • Often accompanied by tail with especially stiff feathers to act as prop

35. Swimming • Feet either webbed or lobed • webbing or lobbing between the toes • legs positioned toward the back of the bird • muscle mass for the limbs is more streamlined into the body • wide body for stability when floating • dense plumage for buoyancy and insulation • preen gland that produces oil that waterproofs the feathers

36. Feeding & digestion • Feeding habits are reflected in beak morphology • Short, deep curved beaks: seed eating • Short pointed shallow beaks: insects • Long slender pointed beaks: fish spears • Spoon bills flattened with broad tips: for aquatic feeding • Long broad, flattened bills with ridges along the sides: Filter feeding (water strainer, mud sifter)

37. The digestive system • The digestive tract of birds has some interesting adaptation for holding food and for mechanical digestion • teeth are absent, hence no processing of food in mouth

38. Esophagus & Crop • crop is basically a pocket in the esophagus. • The function is • to hold food, • transport food to nest, adult regurgitates food • Produces crop milk in doves that is fed to the young. Rich in lipids and proteins

39. Stomach: Has two parts • Proventriculus: anterior • Secrete enzymes and acid • Large in spp that swallow whole fruits • Gizzard: Posterior muscular stomach • Has a thick lining and is very muscular. • Birds eat small bits of gravel and the gizzard grinds the food with the gravel. • The function is for mechanical digestion of the food and basically replaces the chewing as birds do not have teeth, Also food storage; chemical digestion

40. Intestines, Ceca, Cloaca • small intestine primary site if chemical digestion and absorption of nutrients. • Enzymes produced by small intestine & pancreas • large intestine is short and is for storage of wastes and water absorption. • Pair of ceca at the junction of the small and large intestines. small in carnivores, insectivorous & seed eating spp, large in herbivores • Contain symbiotic microorganisms that ferment material

41. Intestines, Ceca, Cloaca • cloaca is the very last section and receives wastes from the excretory system as well. • Water absorption also occurs in cloaca • In birds, the feces is composed of urate salts from the excretory system (the white stuff) and indigestible matter from the food (the dark stuff).

42. Mating Systems, Reproduction & parental care

43. Colors & Patterns • Colors of patterns are determined by a combination of pigments and structural characteristics • Three types of pigments • Eumelanin: produces black, gray, dark brown color • Phaeomelanin: reddish brown & tan shades • Carotenoid pigments: red, orange, yellow

44. Vocalizations • Birds use color, vocalizations and posture for sex, spp, and individual identification • Bird songs are long and complex • In many spp, songs are produced by males only and during the breeding season • Song is a learned behavior controlled by many song control regions (SCRS) in the brain

45. PROPERTIES OF BIRD SONG • Series of notes with intervals of silence • More than one song type for many spp • Show regional dialects • Individual variation • Spp specific

46. Mating systems • Monogamy • A pair bond between one male and one female • Pairing may last for a part or entire breeding season, or for a lifetime • Both parents care for the young • Infidelity may still occur (extra-pair copulation) • Social monogamy • Male and female share responsibility for a clutch of eggs but do not demonstrate fidelity

47. Extra-pair copulation • See advantages on page 470-471 • Polygamy: • Second most common mating system for birds, accounts for 6% of the extant birds • 2 types • Polygyny: a male to many females • Polyandry: a female to many males

48. Resource defense polygyny • Males control access to females by controlling critical resources such as nest sites • Its it a high quality territory, females settle for a male with other mates already. • Male dominancy polygyny • Males compete for females by establishing patterns of dominancy, or displays

49. Reproduction & Parental Care • Oviparous • Sex determination is genetic • Heterogametic sex chromosomes • Female is heterogametic: WZ • Male is homogametic: ZZ • Sex Biased Broods • Sex biased hatching is not well understood • Females hatch first the sex that is a higher chance of survival • Eggs hatch in the sequence of laying

50. Reproduction & Parental Care • Nesting • Nests protect eggs not only from physical stresses as heat, cold and rain • But also from predation • Most birds nest individually but a few are nest in colonies, many nests put together at a distance of two necks • Nests vary in quality and materials • Shallow holes in the ground • Cup shaped nests made from plant materials woven together • Stems of aquatic plants- floating nests