GEOG/ES&P 330
PigeonWatch Hypotheses for Group Projects
PROJECT PIGEONWATCH GROUP TOPICS:
Team Zeta: Natural Selection in Columba liviaThis project will analyze the Fall 2021 field data, which will be integrated with the Fall 2000 through Fall 2020 field data for possible signals of natural selection in the distribution of grouped pigeon morphs by the kinds of habitats in which they were observed. Pigeons are subject to predation by cats and various raptor species. Pigeons feed in social flocks and, when a hawk or falcon goes after them, they scatter in all directions. The raptor will try to focus on one distinctive pigeon in all the confusion. Anything that makes an individual pigeon stand out, like odd coloring, will create a disadvantage and, so, pigeons may be subject to what's called "stabilizing selection" (look that up). Stabilizing selection penalizes morphs that diverge from a common pattern, enforcing greater uniformity in prey species. Think about how all mourning doves and English sparrows look pretty much alike. Feral pigeons, however, are very diverse because they descend from domestic flocks that have been selected by humans to have all kinds of crazy colors and patterns. Why doesn't stabilizing selection drive them back to the wild morph (the blue-bars)? Maybe it's because stabilizing selection operates differently in different environments and, so, selects for different morphs in different places, exploiting that genetic diversity brought in from domestic flocks. Perhaps different backgrounds make one morph less conspicuous than another. Pigeons roam over different locations, though, exposing themselves to different risks. Since they do tend to hang out mostly in about a one kilometer radius, maybe stabilizing selection is "tuning" them to those territories, so that we might see somewhat different mixes of morphs in different kinds of landscapes.
To get at this, you can model your analysis loosely on what you did in Lab 7 by cross-tabbing morphs into different general habitats. Instead of using the two habitats in Lab 7, which you also see cross-tabbed in the PigeonWatch00-21.ods database, I'd like you to work with the cross-tabs provided below those. The birds are cross-tabbed into three habitats:
Do a Chi-square with all 7 morphs by the 3 habitats. Is there a significant difference in the distribution of morphs by these 3 core habitats? If so, try to figure out which morphs are over- and under-represented (or roughly proportionately represented) in the three habitats. Create pie charts or bar charts to show the comparison and contrast. Maybe there is something about these environments that make different morphs more survivable in different places.
- urban (including downtowns, industrial, and commercial), habitats with a lot of light grey rooves, sidewalks, and aging asphalt and a lot of humans going about their workaday rounds and leaving garbage
- residential (including both suburban and urban residential), habitats with more trees and lawns, a great diversity of roof materials (tile rooves, dark comp rooves, white rock rooves, etc.), fewer humans and their messes (I guess we don't like to mess where we live!)
- more natural areas (including beaches and parks), habitats with open spaces, greenery, lake or ocean water surfaces, sand, and often a lot of people and their messes and some people who actually feed birds
Team Zeta should do this analysis using
https://home.csulb.edu/~rodrigue/geog330/PigeonWatch/F21/ChiSquare3x72000-2021Habitats.ods. I have integrated all the data for all the semesters that your predecessors have done PigeonWatches (Fall 2000 through Fall 2020). You will need to incorporate the Fall 2021 data, so you have the complete set.To do this, enter all the collected data into another spreadsheet:
https://home.csulb.edu/~rodrigue/geog330/PigeonWatch/F21/PigeonWatch00_21.ods. When you open this one, you'll see all the PigeonWatch data entered by habitat and, over to the far right, their courtships, too. Don't touch this tab! It has the formulas that will be updated when you enter your own data. To do that, open the tab called F2021. That is where you only need to enter all the pigeons from this semester's fieldwork, classified by habitat. You'll notice the tab will do all sorts of magic, creating counts by itself. Don't touch anything but the cells you need to put F/21 counts in! When you're done, you can revisit the Summary tab and all your data will now be in there now, too.At this point, you can manually enter the data from the Summary tab into the ChiSquare3x72000-2021Habitats.ods spreadsheet. Use the F21 data entry tab. When you enter the Fall 2021 habitats data there, they will be integrated with the F/00 through F/20 data in the 3x7 and 3x4 tabs automatically. You can now use the 3x7 and 3x4 tabs to test your null hypothesis that there is no predation and stabilizing selection affecting the mixes of morphs by the three habitats.
Also, if the results are significant, try to figure out the pattern of allocation of morphs to habitats. For each morph, is it much more common or much less common than expectation in a particular habitat; others may be somewhat more common or less common in particular habitats; and others may be pretty close to expectation. A color-coded table could do the job, either a second copy of your Chi-square table but with the cells' backgrounds given different colors for much more, more, roughly equal, less, much less common. Or you could create a new table filled with plusses and minuses of various font sizes.
Team Zeta will also prepare three comparison graphics showing the proportion of the seven morphs among the urbanized, residential, and "natural" landscapes. Either three pie charts or one stacked bar chart (where the three stacks are the same height for 100%) would work.
Team Delta (repurposed from Charmlee Park's coyotebrush): Sexual Selection in Columba livia
Sexual selection is another theme. Do male pigeons "cruise" potential hens who are similar to them or different from themselves? That is, can we see signs of "assortative mating" among pigeons? Assortative mating occurs when organisms mate with individuals who resemble themselves more than the rest of their species, so that reproductive isolation among lineages can eventually develop even as far as new species. There may be some limitations to this in particular species, if the in group is small enough for inbreeding errors to accumulate (homozygous exposure of deadly recessive genes, which is one reason all human societies have some kind of incest restriction). If there is a tendency to assortative mating, however, it might explain why feral pigeons show such sustained morphic diversity around the world. Maybe this is what is countering stabilizing selection back toward the wild blue-bar morph. This is a key argument that LaBranche makes in the 999 PigeonWatch backgrounder on the course home page. So, let's see if our data show a significant tendency towards assortative mating.
Use the PigeonWath00_21.ods spreadsheet at https://home.csulb.edu/~rodrigue/geog330/PigeonWatch/F21/PigeonWatch00_21.ods. On the Summary tab on the far right, you'll see how the courtships over the last two decades have been entered. Don't touch anything on that tab! Instead, go to the F2021 tab and enter the Fall 2021 courtships there on the far right. The numbers you enter there will be automatically transferred to the Summary tab.When you're done entering the data for Fall 2021 courtships, you will manually transfer them to another spreadsheet that will allow Chi-square analysis of the targets selected by the cruising males in comparison with the morphs of the males themselves. The second spreadsheet is the CourtshipChiSq00-21.ods one at https://home.csulb.edu/~rodigue/geog330/PigeonWatch/F21/CourtshipsChiSq00-21.ods
Use the F21 data entry tab on the left. When you enter the various observed courtship attempts for this semester, the data will be automatically transferred to the 00-21 7x7 tab (and all the other tabs, too). You'll be able to test the null hypothesis that the males show no particular preference in their targets. With a 7 x 7 Chi-square contingency table, it is important to evaluate, not only whether the null hypothesis can be rejected but also whether the data stay within the Chi-square "guardrails" (no expected values below 1; ≤ 20% of expected values under 5). Power should be ≥ 0.800, and make sure to evaluate the effect size. If there are problems (which the spreadsheet will tell you), then use the 4 x 4 or 3 x 3 or 2 x 2 tabs to see if the analysis can stay within the guardrails.
Also, the spreadsheet allows you to evaluate whether the different male morphs prefer females like themselves or different from themselves. Is there a difference among the male morphs in this preference for similar or dissimilar mates? The pink tabs on the right, 00-21 SameDiff 2x7, 00-21 SameDiff 2x4 and 00-21 SameDiff 2x3 will let you evaluate that. You can test the null hypothesis that the male morphs do not differ among themselves in their tendency to seek mates like themselves or different from themselves. Illustrate your work with graphs, such as pie charts or stacked bar charts for each male morph (or four grouped male morphs) as to their mix of targets and another set of graphs showing the balance of "same" or "different" courtship targets.
So, what do you suppose is going on with the assortative mating hypothesis? Was Cornell University's Ornithology Lab onto something explaining the sustained morphic diversity of feral pigeon flocks? Or not? Or what?
For both groups:
Be sure to do searches in Google Scholar on appropriate search terms: "Project PigeonWatch," "assortative mating" (maybe focussing only on "pigeons," "stabilizing selection," "balanced selection," "predation on pigeons," "sexual selection in pigeons," and similar. You are trying to find a handful of appropriate refereeed sources to build your introduction past LaBranche (1999). You need to factor in time to read these sometimes dense papers to "digest" them enough to explain the importance of your projects and set a context for them.