By Julie Brown, National Geographic’s Great Nature Project
Winter time in the northern hemisphere is a great time to observe animal behavior and work on your species identification skills.
When the trees are bare and snow comes and goes from the landscape, it is easier to see organisms whose physical appearance starkly contrasts with their habitat. Birds are easier to see without the cover of foliage, especially when they make frequent visits to feeders to fuel their bodies in cold weather.
Northern Cardinals are frequent feeder visitors and bring to mind some of my favorite topics to discuss with students– evolution, sexual selection, and sexual dimorphism (males and females of the same species look noticeably different).
When I was a classroom teacher, I would begin my lesson by asking students to look at images of sexually dimorphic species and identify which picture was of a male and which was of a female. At first students would identify the “prettier” of the two organisms as the female. Then I would explain the importance of camouflage to the survival of nesting and caregiving females. I would once again ask them to identify the sex of the organisms in the same images. The students would correctly identify the organism with more ornate plumage of the two shown as the male.
I emphasized that female humans are among the only organisms that dress up to attract males. Why is it that we have chosen to behave this way?
Students quickly learned that in nature, males are the organisms that are all “dressed up” to attract female mates. I would point out how this differs from human dress and behavior. I emphasized that female humans are among the only organisms that dress up to attract males. Why is it that we have chosen to behave this way?
This discussion led to lots of laughter and discussions about how we should change things. Young ladies would make the case that men should be the ones wearing makeup and caring about fashion! The conversation always led back to sexual selection criteria in other species. Students thought about a species, its habitat, and how its phenotype helps it survive. This line of questioning sparked curiosity in the role of sexual selection in species evolution.
There are many different types of organisms that have evolved with sexually dimorphic phenotypes; many species of birds, reptiles, fish, insects and mammals. Sometimes females are much larger than males, which is the case with blue whales and some species of spiders and insects. Other times, the males are much larger than the females, which is the case with several species of fish as well as some mammals.
I offer you this topic as an engagement piece to get students outside making observations, documenting them in some way (preferably with photography or video), and thinking about what they see.
Get outside, take pictures, share what you see with the world, and spark conversations that help young minds think about the world around them as informed critical thinkers. Share your observations with National Geographic’s Great Nature Project!
More to Learn and Do
Use this lesson plan to delve deeper into the topic of sexual selection and evolution with students.
Check out how birds of paradise have evolved with this interactive.
Julie Brown is a conservation biologist, certified teacher, and project manager at National Geographic Society. Julie can be found throughout our collection of educational media and curriculum for classroom use, and has frequently facilitated our online and in-person professional development opportunities.