Two scientists have collaborated in a study that suggests that the size of a bird’s beak is linked to the temperature of its natural environment.
We already know that a bird’s beak is adapted for the food it eats and sometimes to attract a mate, but now it looks like it is also a good way of regulating temperature. Large beaks, such as that of the toucan, have a large un-insulated surface area which is full of blood capillaries lying just under the surface. This makes them excellent heat-exchangers and help birds to thermoregulate.
The scientists carried out their study by comparing female birds of 214 species from around the world which lived in different climates but ate a similar diet. Averaged across all species, temperature explained 16 per cent of beak size variation. For gulls and penguins it accounted for 66 per cent and 43 per cent of the variation respectively.
This is a good example of adaptation in birds. The toucan could be looked at as an example of this and how it evolved its large bill can be discussed. What would the toucan look like if it evolved in Britain?
It is also a new example of Allen’s rule, which states that animals from colder climates have shorter appendages from the equivalent animals in warmer climates.
Looking at this method of thermoregulation in birds could also be used as an interesting starter when learning about human temperature control. Students could be asked where a similar method is used in humans (vasodilation in the skin).
In physics lessons, it is a good example of how a thermal energy transfer is maximised in an animal.
Finally, the study could be used as way of learning about making hypotheses from scientific questions and how these are converted into investigations. Students can examine the method of the study (from a simplified abstract from the journal) and comment on the quality of evidence gathered. For example, the scientists tried to control variables that could affect the outcome by only studying female birds (male birds may have larger beaks to attract a mate), and choosing birds from the same species who ate the same food. They also used a large sample size.
I’ve decided to concentrate on the science skills angle and have created a starter that could be used in any lesson where you want students to think about making hypotheses.
The published study: The American Naturalist
National Geographic – some great photos taken with an infra-red camera that shows the heat being lost from a toucan’s bill when it is in a high temperature environment.
Anything to add?
Whilst writing this post, it’s always a possibility that I missed some other great information or teaching ideas. Feel free to share your thoughts.