Ornithology Fall 2013 BIOL 456 UNCW

LAB HANDOUT I Avian Topography, Anatomy, and Paleontology

The primary reference for this lab will be your lab manual: Manual of (1993) by N. S. Proctor and P. J. Lynch. This handout will help guide you through the sections you need to study on avian anatomy. The major sections to read in the manual are:

Chapter 1: pp. 7-9 Chapter 3 Chapter 4: pp. 81-87; 92-97 Chapter 5

Station 1: Avian Topography

Become familiar with the terms for describing external features of the . Knowledge of these terms will help you identify in the field and to understand descriptions of birds in the text of your field guide. Begin by reading over the anatomic terminology on pp. 7-8 in your manual and become familiar with their use when describing characters of a bird as shown in the figure on p. 9.

Next, read Chapter 3 and use the mounts provided to become familiar with topographical features of the bird. Learn those features illustrated in the figures on p. 49 and note the description for each feature on p. 50 and 52 to help you identify the correct feathers on the mounts. Note how some of these features (e.g., supercilium) will be present in some birds, but not others. Pp. 56-65 provide additional details on the topography of the wing and head that will help you get familiar with the terminology.

Station 2: Feathers

Feathers are the single most characteristic feature that defines the Class Aves and are shared with no other vertebrate group. Feathers probably are derived from reptilian scales, but the manner in which they evolved from scales is still largely unknown. Use the microscope provided to look at the slides that show a developing feather in cross-section. Be sure to identify the dermal and epidermal cells, pulp, feather follicle and papilla. Use pp. 86-87 in your manual to help you locate structures in these slides.

Examine the structure of a flight feather and become familiar with the terms on p. 85. In particular, you should be able to locate the vanes, rachis, calamus or quill, barbs, and barbules. Examine a feather under the stereomicroscope and carefully separate and view a single barb. Note the hooklets and barbules and how they connect. Do you see how they function to give the feather flexibility as well as strength? Can you see the difference in structure between distal and proximal barbules?

Feather types are defined by their structure and location on the body. The major types are:

Flight feathers or remiges Semiplumes Tail feathers or rectrices Filoplumes Contour feathers Bristles Down (including natal, powder, and adult)

Can you find these feathers on the skins provided? See the figures provided in the lab manual (pp. 94-95) and your text (Chap. 4, pp. 69-73) for descriptions of these types. Notice that flight feathers are further 2 divided into primaries and secondaries. Look at p. 61 in your manual to see how these feathers are numbered and arranged on the wing. This numbering system is standard in birds and aids in studying molt patterns. What wing bone supports the secondaries? What bone supports the primaries? Although not illustrated in the manual, the rectrices also are numbered from medial to lateral. What bone supports these feathers?

Feathers also do not grow all over the body in most birds, as hair does in mammals, but along specific feather tracts, or pterylae. Bare areas between tracts are called apteria. Look at the figures on p. 99-101 in your manual and become familiar with these tracts. You do not have to learn the different tract names, just know that they exist. Not all birds have feather tracts and instead grow feathers all over the body, such as penguins, to facilitate insulation in cold marine waters.

Station 3: Avian Adaptations

Birds have numerous morphologic variations in relation to specific modes of locomotion (different types of flight, swimming, and running) and feeding (bills and feet). Penguins, for instance, are flightless and have highly modified wings that act as their primary means of propulsion when they dive underwater seeking prey. Their tail is reduced to a rudder-like appendage to aid in steering. Their legs are short and their feet also aid in propulsion. Note these features on the penguin wing and skin provided.

Other birds have their feet modified for swimming such as in grebes, with expanded skin flaps on each digit, or in ducks with webbed feet. The toe arrangement also varies in birds with the first toe (big toe or hallux) usually directed backward. There are at least five types each of toe arrangements and webbing found in birds (see pp. 72-73 in your manual, plus Fig. 3-7 in your text). What types of toe arrangements and webbing can you identify in the lab specimens?

Bill shape also varies considerably among birds in relation to diet (see pp. 66-69 in your manual). The horny covering of the bill, the rhamphotheca, can add to the shape of the bill for specific diets as well as display color and appendages for sexual recognition and communication. The rhamphotheca can keep growing to account for bill wear and in some species has external coverings that are shed annually or seasonally depending on the function of the bill in communication. Seasonal ornaments or appendages also may grow on the bill, such as the knobs or humps at the base in coots or the horns in hornbills. Based on bill size and shape, what diet would you predict for the specimens provided in lab?

Except for passerines, many birds have a salt or nasal gland on the top of the head near the orbit (see p. 227 in your manual). This gland helps the bird to excrete excess salt from its body - to do so with their kidneys alone would take too much fresh water not available to the bird – and aids in osmoregulation. Salt is excreted from these glands in a highly concentrated solution that is drained either along a groove on the side of the bill or through the nasal passages and off the tip of the bill. It gives these birds a ‘runny nose’ look when excretion is occurring. In the Procellariformes or "tube noses," the solution is drained via a special tube on top of the bill. Only birds in this have this special structure. Find the tube on the specimen provided in lab.

In seabirds the salt gland is large and sits within a pocket in the bone, usually located above the eye. Locate this pocket on the penguin skull provided. Other birds, such as gulls, have large salt glands but lack the pocket in the skull or have just a small pocket. Cormorants house this gland in a pocket within the orbit of the eye.

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Station 4: Avian skeleton

Use the diagram on p. 119 in your lab manual to become familiar with the avian skeleton. You will be expected to know all the major skeletal elements given on this diagram. You do not need to learn individual digits of the wing and foot. Note how not all of the avian skeletal elements match those of mammals. They are still homologous (same embryonic origin), but some bird bones are a fusion of two or more bones that are separate in mammals. For example, the tibiotarsus includes the bone homologous to the tibia in mammals, but also is comprised of fused tarsal bones. The carpometatarsus and tarsometatarus are the middle three metacarpals and metatarsals fused into one bone, with some of the carpals and tarsals, respectively.

You also need to learn how the bones are articulated (e.g., proximal versus distal ends, which element is proximal to the tibiotarsus, etc.). Use the mount of the chicken skeleton to help you with this. As you learn the different bones or elements, note the variations in morphology that are apparent in the specimens provided. Also locate on the mount the trioseal canal (see pp. 136-137). This opening, formed at the articulation of the scapula, coracoid, and humerus, is an important feature for avian flight and will be discussed in class later. Most birds can be identified from a single bone from their skeleton (exclusive of ribs, toes, and other minor elements). These species specific characteristics also have allowed avian paleontologists to track the evolution of different orders and families of birds through time. After this class, perhaps you'll be able to identify bones you find in the field.

Read through the rest of chapter 5 and note the different skeletal elements in the skull and palate (p. 125 and 129). The palate especially has been important in avian systematics and classification, but you do not need to learn all of these elements here. However, you should be able to find and recognize the premaxilla, maxilla, pterygoid, occipital condyle, and foramen magnum.

Station 5: Origin and Evolution of Birds

See pp. 18-21 in your lab manual to help guide you through this section.

Archaeopteryx

The fossil record of birds begins with lithographica from the Jurassic (150 million years ago, Ma) of Bavaria and Germany. Archaeopteryx means "ancient wing" and ten specimens, plus an impression of a single isolated feather, have been found since the original discovery in 1860.

Examine the casts of the Berlin and Eichstätt specimens of Archaeopteryx. Can you see where the feather impressions are located? What other characters do you see that are avian? What characters are reptilian?

The discovery and description of Archaeopteryx initiated two debates that continue today: from which reptilian group did birds (including Archaeopteryx) evolve, and how did flight evolve? Shown here is just some of the prolific amount of literature that has been published on this fossil. Thomas Huxley (1868) first proposed that Archaeopteryx was related to small bipedal . Later, Gerhard Heilmann (1927) proposed that birds evolved from Pseudosuchian Thecodonts (a basal group of reptiles that also gave rise to dinosaurs). John Ostrom (1976), in a detailed analysis of all fossils of Archaeopteryx, revitalized the theory that birds are derived from dinosaurs though many still disagree with this origin. Recent discoveries of well-preserved fossil birds from China that are 120 Ma are described as supporting the hypothesis (see National Geographic, July 1998), but do they? Another Chinese fossil described as a relative to Archaeopteryx was recently published (July 2011) and is still under review by paleontologists. Thus, the debate and controversy on the origin of birds from either reptiles or theropod dinosaurs continues. 4

The first true birds after Archaeopteryx do not appear in the fossil record until the Cretaceous, or about 135 Ma. Many toothed birds are present during this period, including marine diving birds. By the early Paleocene, the first modern orders of birds appear in the fossil record. See p. 21 for a geological timeline of fossil birds.

Paleocene Birds

The publication by Peter Houde (1988) illustrates well-preserved skeletons of birds from the Paleocene of Wyoming. The skeletons were found inside nodules of rock that were being discarded by other paleontologists searching for mammals until Peter cracked one open and found bird bones and even articulated skeletons.

The significance of this find is that these birds have a paleognathous palate (bottom of skull below the bill) and could fly. Previously, some paleontologists thought that this of palate was found only in ratites - flightless birds - which indicated a common ancestor for these birds. This discovery indicates that a palaeognathous palate is a primitive character and cannot be used to suggest that ratites form a monophyletic (or related) group.

Vultures and teratorns (Order Ciconiiformes)

The fossil record of New World vultures (Vulturidae or Cathartidae) is interesting because this group appears to have originated in the Old World, but today is found only in the New World. Examine the cast of the earliest fossil now known for the group from the early Oligocene (~ 30 Ma) of Mongolia. What element is it? The opposite pattern occurred with Old World vultures (Accipitridae, Falconiformes). They evolved in the New World, but are found today only in the Old World.

Many unusual groups have evolved and become extinct over the course of avian history. One such group, the teratorns ( Teratornithidae), was related to New World Vultures and probably evolved in South America. Examine the casts of various wing and leg bones of a teratorn from North America, Teratornis merriami. It had a wing span of 12-15 feet (3-4 meters) and went extinct only 10,000 years ago. Can you identify the bones of this species provided in lab?

Teratorns also include the largest flying bird ever known, Argentavis magnificens from the late Miocene (about 7 Ma) of South America. It had a wing span of up to 25 feet (7-7.6 meters) (see photo provided) and must have depended on coastal winds to fly.

Phorusrhacidae (Order Gruiformes)

Another unusual group is the phorusrhacids, known primarily from South America. This group includes all the giant flightless birds, now extinct, that evolved in South America beginning in the early Oligocene (35-38 Ma). They were large carnivorous and scavenging birds that had a long evolutionary history, reaching North America just prior to their extinction. The last known species, Titanis walleri, occurred in Florida and Texas at 2.0-2.5 Ma. After that, the group disappears from the record.

Examine the casts of Phorusrhacos logissimus and Titanis walleri. The skull of the former species indicates that this was a large predatory bird. Compare the tarsometatarsus of Titanus with that of a rhea, an unrelated ostrich-like bird found in South America today. Note the size differences and similarity in features probably due to parallel evolution. The carpometacarpus of Titanis is reduced relative to the rest of the skeleton since this species was flightless. However, as with all other flightless birds, the presence of this unique element in the wing shows that it evolved from a flying ancestor.

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Other avian fossils

An excellent summary of the fossil history of birds was published by (1980, revised 1996). Look at the photos of Presbyornis (p. 92-93), a duck/shorebird ancestor that Feduccia studied from the Eocene (55 Ma) of Wyoming. This fossil had a mosaic of features that suggests it was ancestral to both Anseriformes and Charadriiformes. Also, on p. 146 note the diversity of birds (extant and extinct) that are known from the late Pleistocene (>10,000 years ago) of California (Rancho La Brea Tar Pits). These pits, located in Los Angeles, contain thousands of well-preserved bones of mammals, birds, and other vertebrates that lived in California only 10,000 years ago. The birds include condor, teratorn, extinct Old World vultures, extinct hawk-eagles and caracara. Examine the selection of casts from fossil material of condors. Can you identify the skeletal elements represented here? Why are there so many predators and scavengers in this assemblage?

By 10,000 years ago, many birds (and large mammals) became extinct in North America. Avian diversity probably declined by 10-15% compared to modern avifaunas. These extinctions may have been caused by climate change or other factors, but resulted in the disappearance of many scavenging and raptorial birds including teratorns, some condors, Old World vultures, and some hawks and eagles. Why would these birds be more susceptible to extinction at that time?

In other parts of the world, avian extinctions occurred much more recently. For example, the , a large flightless pigeon, disappeared from Island soon after humans first became aware of this island and the ease of killing for food. In , (Dinornithiformes) were once a large and diverse group of giant flightless birds related to kiwis. Hundreds of well preserved skeletons of these birds have been recovered from swamps and bogs in New Zealand, giving us an excellent record of this group. Examine the cast of a skull of Pachyornis elephantopus and note the palate area. It has a typical paleognathus palate, similar to many other flightless birds, with more fusion of skeletal elements in the palate area than found in flying birds. They were hunted to extinction by Maoris by about 400 years ago.