Purpose

Overview

As a class, watch video from the Macaulay Library (http://macaulaylibrary.org) of Eastern and Western Meadowlarks and Blue- and Golden-Winged Warblers and discuss the fact that one pair of species hybridizes freely while the other does not. Students will then break into groups, with half the students examining the vocalizations of the meadowlarks and half examining the vocalizations of the warblers. After determining whether they think their species pair is likely to be the one that hybridizes, the groups will reconvene to discuss their findings and to discuss the implications for their results for how we understand species concepts.

Essential Questions

What is a species?
What are the practical implications of the species definitions we choose?

Learning Objectives

Students will be able to:

• Explain the difficulties of defining a species.
• Describe some potential conservation implications of the ways species are technically defined.
• Describe the role of song in mate selection. Explain why characteristics of sound would have the potential to allow species to either hybridize or be behaviorally reproductively isolated.
• Be able to interpret a spectrogram (or sonogram) view of sound.
• Define and measure quantitative traits in bird song.

Extensions:

• Evaluate multiple sources of data and weigh conflicting definitions to develop a coherent argument based on theory and evidence.
• Conduct basic statistical analyses and create graphs

Materials

Computers (one per student group) with Firefox browser and QuickTime, RavenViewer plug-in, and Flash player pre-installed
Internet access
Projector
1 pair of speakers (to play videos for class)
Student Sheets (best printed in color)
RavenViewer At-A-Glance guide (best printed in color)
Powerpoint slides introducing the Macaulay Library (provided) 

Optional:

Earbuds for each student group (if noise from multiple groups is a concern)
Access to the Birds of North America Online website (small cost)

Setting

This investigation is intended for introductory courses for majors or non-majors, as well as upper-level Evolution, Ecology or Conservation courses. It could be used as a laboratory or recitation activity, as well as in longer lecture periods. 

Preparation

The data analysis and interpretation for this investigation hinge on students having some understanding of the variety of species concepts that exist, as well as the concept of reproductive isolation. While the initial discussion asks students to define a species in their own words, if this is the first time species concepts have been introduced, you may want to allow extra time for discussion. A possible pre-lab activity would be to assign students to a jigsaw, where each group is responsible for becoming the expert on a different species concept or isolating mechanism and then teaching their classmates about it.

The instructor should be familiar with some of the basic background information on the species of birds being considered. If your institution’s library has access, you could consult the relevant species accounts on the Birds of North America Online site: http://birds.cornell.edu/bna.

The more familiar the instructor is with sound visualization and analysis, the easier it will be to help troubleshoot with the various student groups during the data collection period. For information on how to download the free RavenViewer plug-in for QuickTime, as well as helpful guides to interpreting sound visualizations, please see: http://macaulaylibrary.org/help/ravenViewer/index.do.

If desired, an inquiry-based pre-lab activity could be used to familiarize students with looking at and interpreting sound spectrograms. See http://birds.cornell.edu/orb/investigations for ideas.

You may wish to ask the students to explore Macaulay Library and install RavenViewer software on their laptops before coming to class. Alternatively, you could use the provided PowerPoint to give a brief introduction to the Macaulay Library and the visual representation of sound.

Time

This investigation will take approximately two and a half hours of in-class time, best done in a computer lab with a white board and projector to facilitate both whole class discussion and individual work.

If students have not worked with sound spectrograms before, extra time may be required for them to develop their spectrogram skills.

Depending on the level of interpretation and writing assigned, this module take could 9+ hours of total student time. An estimate of the various parts follows:

Prelab (Optional):

• Pre-lab activity on sound analysis (30-45 min)
• Jigsaw on species concepts and reproductive isolation (30-45 min)

1-1.5 hours

In class:

• Introductory discussion and engagement (30-45 min)
• Exploration and measurement (45-90 min)
• Collecting class data and debriefing (30 min)

2-3.5 hours

In or out of class:

• Answering discussion questions individually or as a group (30 min)
• Data analysis and graphing (1-1.5 hours)

1.5-2 hours

Extensions/Out-of-class (Optional):

• Selecting and measuring additional species (45-90 min)
• Researching descriptions of the species' song, behavior, morphology, and ranges or species concepts (1 hour)
• Writing a scientific report (3-5 hours)

5-7.5 hours

Total time = 9.5-14.5 hours

Extension(s)

1. You may wish to have students investigate the natural history and breeding ranges of the species in greater detail in the authoritative species accounts in the Birds of North America Online. It might be particularly illuminating to review the sections on song and hybridization for the Golden-winged Warbler and the Blue-winged Warbler.

2. Students could be assigned to write a longer-form lab report, creating graphs of their data and doing basic statistical analyses (e.g., a t-test reporting p-value). See Assessment for more ideas on evaluating these reports.

3. This investigation could easily fit in with other lessons using the Macaulay Library and Raven sound analysis software. You could assign or have students choose other pairs of species, both ones that do hybridize, and ones that don’t, to conduct additional analyses.

See the Instructor Guide for examples of additional bird species pairs that do and don't hybridize.

4. Students could read a paper dealing with the practical/conservation sides of defining species to prepare for arguing an (assigned position) in a class debate following this activity. See Assessment for examples of follow-up questions relevant to the nature of science or conservation implications.

5. Students could read about and the class could discuss the “universal species concept” (de Queiroz 2007) as a means of building a stronger case for species definitions on the basis of multiple lines of evidence.