1800 Upper Canyon Road
Santa Fe, New Mexico 87501
(505) 983-4609
nm.audubon.org

Birds for a Purpose

Teacher Activity Packet

Audubon New Mexico and the Randall Davey Audubon Center

Audubon New Mexico’s mission mirrors that of the National Audubon Society on a statewide basis: to conserve and restore natural ecosystems, focusing on birds, other wildlife, and their habitats for the benefit of humanity and the earth’s biological diversity. We aim to enhance the knowledge of New Mexico citizens to make informed decisions about the protection of wildlife and to empower them to be active stewards of the planet. This is accomplished through education, public policy and land stewardship intended to develop a culture of conservation throughout the state of New Mexico.

Nestled at the mouth of the Santa Fe Canyon, the Randall Davey Audubon Center encompasses 135 acres and includes hiking trails, a classroom, nature store, and historic site. The trails wind through pinon/juniper woodlands and reach ponderosa pine forests. There are a variety of bird species and the adjacent Santa Fe River provides habitat for a myriad of species. The Randall Davey Audubon Center is also home to a natural history lab, picnic area, gardens, and an orchard. Trails are open to day hikers yearlong and free birding walks are available every Saturday morning at 8:30AM. In addition to our school programs, the Randall Davey Audubon Center offers family programs, a summer day camp, and adult lectures. For more information, please visit our website at nm.audubon.org.

Why study birds?

Birds are everywhere, on every continent, in every city, schoolyard, and backyard. Without birds, we would be overwhelmed by insects and many plant species would be unable to reproduce since birds play an important role in pollination and in spreading seeds. Not only do birds provide a multitude of services in our ecosystems, they have been an inspiration for many generations of artists and engineers. Birds instilled in humans the dream to fly. From Leonardo da Vinci to modern engineers, birds have been used as a template to create a myriad of flying machines.

Besides the ecological and aesthetic value, birds and more specifically, bird watching, have an economic value. Bird watching has become one of the most popular outdoor activities nationwide for those of all ages. There are approximately 66 million wildlife watchers in the United States and it is estimated that approximately one-third of the population are bird watchers. Over $38 billion dollars per year is spent on wildlife watching with $558 million dollars per year spent in New Mexico (U.S. Fish and Wildlife Service, 2001 National Survey of Fish, Hunting, and Wildlife-Associated Recreation, library.fws.gov/nat_survey2001.pdf.

Bird Design

Birds, Class Aves, Subphylum Vertebrata, Phylum Chordata of the Animal Kingdom are distinguished from all other creatures by the presence of feathers. Other animals can fly or glide but only birds have feathers. These structurally strong, yet flexible coverings for the body, are thought to have evolved from the frayed ends of reptilian scales. Birds also have well-developed optic lobes and a comparatively large brain. They all lay eggs and most care for their young in specially constructed nests.

A bird's structural design has two purposes only, to reduce weight, and increase power production in order to fly. Flight opened up new sources of food, made escape from earthbound predators easier and increased the safety of living and breeding quarters. Impenetrable barriers such as mountains, oceans or rivers became easily navigable. To follow favorable climates and changing food sources, seasonal migrations became possible.

Feathers

Feathers serve several functions. They are a lightweight, yet durable. The shaft gives the feather stiffness while the vane, composed of barbs, barbules and barbicels, imparts flexibility and reparability to support the bird in flight. Feathers are waterproof and insulate against heat loss. Coloration and the presence of a feather muscle also allow movement aid in courtship displays and camouflage.

Coloration in feathers may be pigmentary or structural. Pigments are compounds, which absorb light from certain wavelengths. There are three basic groups of pigment. Melanin,like in the melanophores of our skin, produce dull yellows to red-browns, browns and blacks. Carotenoids impart yellow, orange or red coloration. Porphyrins may be red, green or brown. Blues in bird feathers are the result of scattering of the shorter wavelengths of light by small particles within the feather (the Tyndall effect). This structural color is the result of the same process that makes the sky or large bodies of water look blue. Iridescent or shimmering colors like on the gorget of a hummingbird are also structural in origin. They are the result of the reflection and refraction of light by tiny platelets on the exterior of the barbs. Unless the angle of incident light is correct, feathers relying on structural colors simply look gray or black. White feathers reflect all wavelengths of light. Dark colors are more resistant to wear so many birds have dark wing tips.

Feathers come in different shapes and sizes on the same bird. The most obvious are the contour feathers, arranged in specific tracts. They include the general body feathers, the remiges or flight feathers and the rectrices or tail feathers. Semiplumes have a prominent shaft and downy web and are interspersed with the contour feathers to insulate and increase buoyancy. Down feathers have a minute shaft and soft tuft of barbs from the end of the shaft. Not only do these feathers serve as the nata1 covering on newly hatched chicks but they are important for heat conservation in adults (and humans wearing down-filled clothing). There are also many other types of feathers, which serve as sensory structures.

Molting, or the shedding and replacement of feathers generally occurs annually, usually immediately after the breeding season. The timing and pattern of molt varies from species to species. Some species may molt again in the spring. The new developing feather pushes out the old worn feather.

Bones

Most bird bones are pneumatic, rather, they are filled with air sacs or hollow bones to minimize weight, and have internal struts for strength. Flightless and diving birds, on the other hand, have solid bones. As in all vertebrates, bones are necessary to protect and support the fleshy tissue and joints allow for freedom of movement in many different directions. Because most birds fly, a bird’s skeleton is rigid and organized in such a way to have a shorter body axis and centralized weight. These adaptations are accomplished by the elimination or fusion of many different parts that are not found in terrestrial and non-flying vertebrates.

Interior of a bird bone

Struts inside give strength.
Air spaces to minimize weight.

Bird Survival

Feeding

Unlike most vertebrates, there are no teeth within a bird’s beak and yet they are able to digest food rapidly and efficiently. Compared to the digestive system of humans, birds have several important differences. In many bird species there is a swelling or ballooning of the esophagus midway down to form a crop, which serves as a food storage receptacle. Given the feast or famine nature of many bird species, it is common for birds to gorge on a food supply. Raptors (birds that kill and eat their food) and scavengers are prime examples. Vultures, for instance, have been known to eat so much at one sitting that they cannot take off due to the excess weight in their crops. Many hawks that have just eaten can be also be readily identified by the large bulge in their upper chest and, pigeons are known to produce a nutritious secretion in their crops for feeding their young.

Another important difference can be found in the stomach. Bird stomachs are composed of two parts including the procentriculus and the ventriculus. The proventriculus, or anterior stomach is small and thick-walled, and serves to secrete gastric juices and initiate food breakdown. The posterior ventriculus, or gizzard, is very muscular and functions to crush and abrade food via the aid of small stones or grit. Acting similarly to teeth, the gullet also holds indigestables (usually fur and/or bones), which in the case of many predatory birds, are later regurgitated as “pellets.”

The intestines, while proportionately shorter in birds than in mammals, serve the same functions of absorption and waste elimination, and both the urinary and digestive tracts empty through the cloaca.

Communication

How do scavengers find their food? Vultures rely on both their sense of smell and flock communications. Their syrinx or voice box lacks the necessary muscles for verbal communication. Instead an efficient means of visual contact has been developed. In flight the underwing of a Turkey Vulture has a dark leading edge and light trailing edge. As it circles riding thermals skyward, the teetering movement causes the undersurface to be alternately visible and invisible. The resultant flashes of light color attract other individuals to the area, either just to catch the same thermal or to investigate whether or not carrion has been spotted on the ground. Eventually large numbers will gather in the same area.

Bird Reproduction

Nests

Eggs

Once mating has occurred, the next step is to lay the eggs. The eggs of birds have a hard and protective, permeable shell, which can be uniform or mottled in coloration. Inside the shell there is an embryo and a generous food supply, which provides the energy for rapid development. The exact number of eggs laid varies from species to species. Some birds, known as determinate layers, will only lay a certain number and then stop. Other bird species are considered indeterminate layers, and will continue to lay eggs until a definite number has been reached (like chickens).

The Fledgling Young

Many birds leave the nest before they can fly and it is quite normal to find fledglings or "baby birds" wandering about the ground, shrubs, or low trees in the springtime. These teenagers do not need our services to rescue them, as the parents will continue to feed and nurture them, however we can assist by keeping cats and dogs inside or away from the territory being used.

The Egg, Inside and Out

Life in the nest may not be pleasant for all members of the family. Generally it is the nestling sticking its neck out the farthest and making the most noise that will be fed. Once satiated, this youngster relaxes and its sibling(s) will be then receive the parental offering. In species with asynchronous hatching, where one hatchling is larger than the others, interactions are slightly different. The larger siblings exhibit varying degrees of aggression, and the smaller siblings are often coerced into submissive states, or killed. This siblicide may be obligate, that is the parents cannot raise more than one offspring, or it may be opportunistic. In the latter case, more than one offspring will survive if there are adequate food supplies available. If food is scarce, then survival of the fittest is ensured by either the smaller nestling being ejected from the nest, or by it becoming food for the larger.