TOPICS:  Animal behavior, birds, ecology, energy, homeostasis, weather

LEVEL:  High school and advanced placement

TIME:  Compiling data will take a few minutes of class time over one or more weeks.  45 min for data analysis and discussion.  Optional preactivity discussion takes less than one class period.

ADVANCE PREPARATION:  Purchase luggage tags from a stationary or office supply store.  You may wish to make a few observations several weeks in advance to obtain supplemental data on especially cold or warm winter days

.

PREDICTIONS: In class discussion, encourage creative, logical, and critical thinking.  We recommend that you introduce the following ideas if they are not suggested by students:  On cold days, the chimney supplies heat to the bird by convection, conduction, and radiation.  On windy days, birds may prefer sheltered perches because body heat is lost quickly on an exposed chimney (wind chill) and heat from the chimney is dissipated more rapidly; thus, the bird may prefer a perch sheltered from the wind.  Cloudy days reduce available solar radiation in all locations; chimney may be the only external source of heat in the environment, increasing chimney perching behavior.  Precipitation increases loss of body heat; bird may prefer sheltered perch .

PROCEDURE: Try to collect bird data on both colder and warmer days by making observations several days apart.

SAFETY NOTE:  Appropriate dress for winter .

STEP C: Record temperature and wind speed; accurate hourly temperature and wind speed information is often available in the newspaper on the following day. An appropriately sited thermometer and wind gauge at the school might add to the interest .

PROCEDURE: Step F and question 11 focus on an important process scientists use in data analysis.  However, you may wish to omit these steps for less advanced classes or to save time.  The scatterplot in step F is simply a graph of all data on number of birds per chimney (step C) collected by all students (see example).

GOING FURTHER:  For advanced classes, you may wish to have students divide the class data into high and low wind speed observations and make two bar graphs (windy, calm) of number of birds per chimney versus temperature.  What is the effect of wind speed on the relationship between temperature and number of chimney perching birds?  Have students use the energy flow diagram to explain their results.

QUESTIONS 2-11 require higher-order thinking skills.  We recommend that you discuss these questions with your class before having students write out their answers .

2. Data should show that more birds perch on chimneys when the weather is cold.  When air temperatures are high, birds do not lose body heat as quickly, and may not need chimney heat to maintain body temperature. Also, chimneys may be cold when weather is warm! It is possible that no clear relationship between number of birds and temperature will be found.  If so, you may wish to discuss the following possibilities with the class (see Teacher Background):

o The birds really do perch on chimneys without regard to temperature.  Perhaps the birds only use the chimneys as a lookout point or a place to socialize.

o The weather did not vary widely enough over the data collection period.  If the temperature had been above freezing or very cold, the bird and weather data would have shown a different relationship.

o The factors which influence chimney perching are complex.  Perhaps wind, wind chill, precipitation, cloudiness or other factors not on the graph are important .

3. Increasing wind should decrease chimney perching behavior in birds, because wind increases loss of body heat from exposed bird .

4. Clouds reduce transfer of sunlight to bird and absorbing surfaces in the environment; chimney perching should increase .

5-6. Answers will vary .

7. Answers will vary.  On a sunny windy winter day, heat from the sun can reach a bird sheltered from the wind on top of the window .

8. The behavior of seeking a warm micro- environment may be innate; seeking chimneys must be learned since chimneys are recent man-made inventions. In concert with 10 this would be a good place to bring up social facilitation or initiative behavior. This leads off into the field of social behavior. The bird winter ecology teacher background discussed the habitat modification aspects of social behavior (flock roosting) as well as the foraging and predator protection aspects .

9. Answers will vary.  More observations will always give better data .

10. Accept reasonable answers that use data for support .

11. Points representing different number of birds at the same temperature may reflect differences due to weather (cloud cover, wind, precipitation), location (type of chimney, amount of heat coming from chimneys, etc), time (morning or afternoon, different days), observer error (two observers looking at same chimney at same time may count different numbers of birds by mistake), or chance. Observations made 10 min later under identical conditions show different numbers of chimney perching birds since birds come and go.

OPTIONAL DISCUSSION:  While the data are being collected, you may wish to consider the following information on the energy balance of birds in winter.  This background will help students make predictions and interpret the class data.  Underlined questions may be used to start student discussions.

RADIATION:  If the air temperature is the same, why do you feel warmer outside on a sunny winter day than on a cloudy winter day?  A body can gain or lose heat by electromagnetic radiation.  The wavelengths of interest are visible light from the sun and infrared radiation which is given off by all bodies at environmental temperatures.  On clear days, the most important source of radiant energy is the sun.  Even on cloudy days, a body will give off and receive infrared radiation from surrounding objects.  The amount of radiation given off is a function of the temperature: hotter objects give off more infrared radiation.  Most objects not in direct sunlight are approximately air temperature, unless they have an internal source of heat such as a building or animal.  On a cloudy day, if an object is warmer than its surroundings it will cool off because it loses more radiation than it receives.  The greater the difference between the temperature of the air and the object, the greater the heat loss.  A sunlit roof can be considered a warm body unless it is white or covered with snow. 

RADIATION:  How does the color of your summer and winter clothing affect heat gain or loss?  Dark colors tend to absorb more light and thus heat up; light colors tend to reflect more light and thus absorb less heat. 

CONDUCTION:  How is heat transferred when you fall on the ice or sit in the snow?  When two objects with different temperatures are in contact with each other, heat is lost or gained by conduction.  When perching on chimneys, the feet and/or bodies of the birds are in contact with the chimney material which may be warmer or colder than the birds. 

CONVECTION:  Why is the air near the ceiling of a room often warmer than the air near the floor?  When two regions at different temperatures are separated by air space, heat is transfered by convection.  Convection is caused by warmer air rising and cooler air sinking. Warm air rising up a chimney is another example of convection. 

INSULATION:  How do people and birds reduce heat loss outside in the winter?  People wear specialized clothing (hats, gloves) and additional layers of clothing.  Bird feathers, especially those fluffed up to create dead-air space, provide excellent insulation to reduce heat loss.  

WIND CHILL:  How does the wind affect your comfort level when you go outside in the winter?  Wind chill is a form of convection.  A heated body warms the surrounding air layer.  If there is a wind, the warm air is replaced by colder air, and more heat must be produced to maintain body temperature.

RESPIRATION:  When you use your breath to warm your hands in the winter, where does the heat come from?  Cellular respiration is the metabolic process that provides energy for all body activities, including maintenance of body temperature.  This process uses oxygen and produces carbon dioxide.  During breathing, cold oxygen-rich air is inhaled, and warm, carbon dioxide-laden air is exhaled; thus the body loses heat. 

EVAPORATION:  Why do your hands feel colder when they get wet in winter?  Explain the flow of heat from your hands to the environment.  Why can you see your breath on a cold winter day? Heat energy is lost when water changes from a liquid to a gas.  In winter, the major source of evaporation is respiration; cold dry air is not only heated, but moisturized, in the lungs.