Author: Andrew Rush
Overview: This lesson introduces students to how birds obtain and digest food. The first part explores the structure of the digestive system. The second part of the lesson focuses on different types of bills and how they function in collecting different types of food. This is done by examining specimens or pictures showing variation in bill shapes, and through a simulation game in which students, using everyday objects that model different bird bills, try to gather different types of food.
Birds have unique digestive systems that allow them to get energy from food.
Bird bills are important tools that allow them to get the food that they need.
Some bills are adaptations that allow birds to specialize on specific types of foods.
Scientists record drawings and information in field notes that allow them to share and use important information.
Life Sciences Standard 2c: Students know the sequential steps of digestion and the roles of teeth and the mouth, esophagus, stomach, small intestine, large intestine, and colon in the function of the digestive system.
Investigation & Experimentation Standard 6a: Classify objects in accordance with appropriate criteria.
Investigation & Experimentation Standard 6f: Select appropriate tools and make quantitative observations.
Investigation & Experimentation Standard 6g: Record data by using appropriate graphic representations and make inferences based on those data.
Grade span: 5
- Chicken gizzards (one per class, or more if available)
- Beak tools:
- Pliers (two pairs per class)
- Needlenose pliers (one pair per class)
- Clothes pins (three per class)
- Tweezers (three pairs per class)
- Chopsticks (three pairs per class)
- Eyedropper (one per class)
- Pipette (one per class)
- Aquarium net (one per class)
- Envelope (one per class)
- Bird "food":
- Sunflower seeds (in shell)
- Test tube (stabilized with clay) or small graduated cylinder with
colored liquid (nectar)
- Styrofoam studded with whole cloves
- Potting soil
- Paper cups (five to ten per class) ("bird stomach")
- Paper plates (five to ten per class) (surface for bird food)
- Small bowl for potting soil and raisins
- Chart paper for graphs
- Data sheets (pdf)
- Paper plates (five to ten per class) (surface for bird food)
- Specimens from a natural history museum (at UC Berkeley, from the Sagehen Creek Field Station collection and Museum of Vertebrate Zoology teaching collection) or a variety of pictures or slides showing variation in bill shape and size
The feeding stations for the bird beak buffet will have to be set up ahead of time (including data sheets in manila folders). Chicken gizzards can be purchased at a grocery store, and should be thawed overnight if frozen.
Time: 50 minutes
Grouping: Students work in groups of three
Part I: Digestive system of birds (10 min)
Begin by asking students how they get energy. [By eating food]
Ask how they would eat if they had no teeth. How do birds get energy from food with no teeth?
Different birds eat very different types of food hawks eat meat, sparrows eat seeds, hummingbirds eat nectar.
Birds need a lot of energy to maintain their high metabolism (flying takes a lot of energy). Birds eat constantly and have a very efficient digestive system that extracts the energy from food very quickly.
Sequence of digestive system of birds:
- Mouth no digestion
- Crop food storage (like chipmunk mouth pouches)
- Esophagus lubrication and transport
- Two-chambered stomach
- Proventriculus chemical digestion, followed by …
- Gizzard physical digestion. Show students chicken gizzard cut it open to show strong muscles
- Birds eat sand and small stones that act as 'teeth' in gizzard to grind up food
- Gizzard is more muscular in birds that eat hard food
- Gizzards can crush walnuts (turkey), metal needles (turkey), acorns (band-tailed pigeon), and small clams (canvasback duck)!!
- Intestine food absorbed into blood stream
- Cloaca exit
Optional: Owl pellets In some birds (e.g., owls), things that cannot be digested are regurgitated. Break apart owl pellet for students to show contents.
Part II: Bird bills
- Introduction (five minutes)
- Ask students how birds get their food with no hands. [Pick up/catch food with bills]
- Bird bills are often specialized for the type of food they eat. (can examine real bird skins or pictures)
'Bird beak buffet' activity (20-25 minutes)
Set up five stations ahead of time with: (1) a container or paper plate containing food items, (2) a paper cup to function as the student's bird stomach, (3) three implements to use to gather food, as listed below:
Food: Nuts/seeds (sunflower seeds; students must crack the shell to get the seed)
Beak tools: Pliers, clothes pin, tweezers
Food: Insects (raisins in potting soil)
Beak tools: Pliers, tweezers, chopsticks
Food: Nectar (water in a graduated cylinder)
Beak tools: Clothes pin, medicine dropper, pipette
Food: Flying insects (toss popped popcorn in the air)
Beak tools: Envelope (or aquarium net), tweezers, chopsticks
Food: Insects in bark (whole cloves embedded into a piece of Styrofoam)
Beak tools: Needlenose pliers, clothes pin, chopsticks
(Alternative foods: yarn, gummy worms, uncooked shell macaroni, goldfish crackers, etc.)
When students arrive at a station, they will hypothesize which beak will be the most effective with that food type.
At each station, one student at a time will have 20 seconds to try to get as much food as possible into the cup using one of the implements. Students must keep their free hand behind their back. Because there are three implements at every station, each student will be able to do a trial at each station. (We will not do multiple trials per implement, but we could).
The number of stations each group gets to depends on the amount of time you have. The first round will take longer.
- Students log results (number of food items or milliliters of liquid collected by each beak type) on data sheets.
Graphing and discussion (10 min)
At the end of the exercise, graph and discuss the class results. Did they match the students' predictions?
Show stuffed bird specimens or pictures as examples of birds that eat different foods, for example:
Crossbill pries pine seeds from between scales on cones
Hummingbird sucks nectar from flowers
Bushtit picks small insects off of leaves and twigs
Brown creeper picks small insects out of cracks on tree trunks
Evening grosbeak seed eater, note strong bill
Black phoebe a flycatcher that catches flying insects out of the air
Curlew or whimbrel invertebrates in sand
Duck filter feeder, note lamellae on sides of bill
Avocet sweeps invertebrates from water
Wrap Up: (5 min)
Describe a food type/feeding style to students and see if they can describe the bill/body of a bird that would have that feeding style. Then show them examples (specimens or slides) of birds that actually do have that feeding style.
Bird that picks snails out of shallow water and eats them [limpkin]
Bird that dives into water and catches fish [kingfisher, osprey two 'designs' that work osprey has added feature of rough spicules on its feet that allow it to hold slippery fish]
Bird that eats dead carcasses [vulture, stork have different types of strong bills to tear flesh both lack feathers on head that would get covered in gook]
Bird that catches flying insects (think of grasshopper exercise) [swift, swallow, nighthawk, flycatcher broad-based bills that function like sweep nets]
And what about FEET?! How do birds' feet help them acquire food? [talons hold food down for raptors while they tear with their bills, sparrows and chickens scratch in the dirt to find food, woodpeckers cling to the sides of trees, some herons are thought to use their brightly colored feet for fish lures, etc.]