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A Little Bit More

All birds have a higher normal body temperature than humans, with a typical range of from 38°-44°C (100°-112°F); smaller birds tend toward the higher temperatures. Like mammals, birds are warm-blooded animals (endotherms) and must maintain a relatively stable body temperature regardless of their environment.

Black-capped Chickadee

Black-capped Chickadee © Solon Morse

Larger birds have an advantage over smaller ones, since their ratio of body surface (where they lose heat) to total volume is less than that of smaller species. The larger birds have proportionately less surface area from which to lose heat and thus do not have to eat as much, in proportion to their weight, as the smaller birds. If we take this to its limits to help us visualize, we can compare a hummingbird and ostrich. The hummingbird has much, much more surface area compared to its own body mass than does the ostrich – therefore a hummingbird loses (or gains) heat much more quickly than an ostrich would. If you want to visualize this with mammals, you can compare a mouse to an elephant. The elephant although much larger, has less surface area proportionately compared to the mouse for its given volume.

Darkeyed Junco on cold winter day

The insulation of feathers and body fat, and the energy obtained from that fat are not the only factors that help a bird survive winter weather. Acclimatization (gradually getting used to an environment) is also important. A bird removed from a warm environment and thrust into a winter one is unlikely to survive even though a slow adjustment to those same conditions would not be a problem. Well-meaning people who have rescued injured birds from outdoors in the winter do a disservice when they bring these birds into a warm house for any length of time. Once the bird is returned to the outdoors, if its indoor stay was of any length, it is unlikely to survive when released – it is no longer acclimatized to the winter weather. Winter convalescence is best conducted in an unheated garage or shed rather than in a heated building.

Activities

Science – Surface Area

Objectives: See how much difference surface area makes

Materials: 2 Ice cubes of identical size, ability to grind one into pieces, 2 plates

It’s one thing to discuss surface area and what that means to animals but it can be very different to see it in action. This is an easy-to-do activity that anyone can use to help demonstrate the effect surface area can have on gaining or losing heat – it goes both ways.

  1. Make 2 same-size ice cubes in an ice cube tray (any size will do as long as they’re identical)
  2. Once frozen, remove one ice cube and place on a plate
  3. Remove the second ice cube and break it into many different pieces and place all of these onto an identical plate. Place the plates next to each other in an obvious location for viewing
  4. Note the beginning time on a piece of paper and allow the two ice cubes (one whole and one crushed) to melt at room temperature
  5. Time the melting and note on paper when the crushed ice cube is completely melted.
  6. Continue monitoring the whole ice cube and note on paper again when it is completely melted.
  7. There should be a marked difference in the melting times between the two ice cubes

Here are some questions you may want to ask:

  1. Why did the crushed ice cube melt more quickly than the whole ice cube? By crushing the one ice cube, you dramatically increased its surface area. This allowed it to absorb heat more quickly than the solid cube and speeded up the melting process.
  2. How might you have speeded up the melting process of the crushed ice cube beyond what we did? You could have crushed the one ice cube even more to further increase its surface area.
  3. Can you think of a drink you might purchase in a fast-food restaurant that uses the concept of surface area to cool their drinks quickly? Drinks that have highly crushed ice — even a slurry of ice — cool very quickly because the surface area of the ice is so large.

Key Concepts

Behavior and Regulation, Adaptations and Diversity

Questions

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Filed under: Birds