D4.5.6-8: Critiquing the Structure of Explanations

Overview

Lesson Procedure

65-70 minutes of class time across 5 phases.

1. Warm-Up10 minutes
2. Direct Instruction20 minutes
3. Guided Practice15 minutes
4. Independent Practice10-15 minutes
5. Closure10 minutes

1. Warm-Up10 minutes

   Warm-Up Prompt

   "A classmate explains why the school play was canceled: 'The play was canceled. The lead actor is tall. Then the stage lights broke. So the play was canceled.' What is missing or out of place? Write a better version in three sentences."

   Collect answers. Students usually notice that "the lead actor is tall" does not help explain anything, and that the link between the broken lights and the canceling is missing (could the lights be fixed in time?). Name what they noticed: an explanation has parts, and the parts must fit together. Introduce the Explanation Blueprint (Diagram 1) and its five parts. Tell students that today they will critique explanations written about 120 years ago by people who disagreed about why a bird vanished.

2. Direct Instruction20 minutes

   Part 1: The question and the sources. The question is "Why did the passenger pigeon disappear?" Mershon, writing in 1907, says that "as recently as 1880" the birds still came "in countless millions" to parts of the Middle West, and his book collects the explanations people gave for their disappearance. Words to know: a nesting or brooding place is where flocks built nests and raised young; squabs are young pigeons; netters caught birds in large nets to sell; the telegraph sent messages over wires; a cyclone is a violent storm; a theory is a proposed explanation; and a species' range is the area where it lives.

   Source Information: who made each source, when, and from what position (from the sources and Mershon's notes)

   Source	Maker and position	When	What it explains
   1: Pokagon	Simon Pokagon, whom Mershon's note calls "the last Pottawattomie chief of the Pokagon band" of Michigan; he writes from decades of watching the flocks	1895, reprinted 1907	How professional netters caught the pigeons for market
   2: Ames	C. H. Ames of Boston, in a letter to Mershon; he saw large flights in northern Illinois in the 1860s	Letter of 1906, printed 1907	A theory that storms drowned the flocks
   3: Ridgway	Robert Ridgway, Curator of the Division of Birds, U.S. National Museum	1906, printed 1907	Why the storm theory is not needed
   4: Mershon	W. B. Mershon, a Michigan collector of pigeon accounts, who calls his book "scarcely more than a compilation"	1907	Several causes working together
   5 and 6	Invented drafts and an invented scenario written for this page	Invented	Practice material; two drafts in Source 5 are deliberately weak

   1White men commenced netting them for market about the year 1840, These men were known as professional pigeoners, from the fact that they banded themselves together, so as to keep in telegraphic communication with these great moving bodies. In this they became so expert as to be almost continually on the borders of their brooding places. As they were always prepared with trained stool-pigeons and flyers, which they carried with them, they were enabled to call down the passing flocks and secure as many by net as they were able to pack in ice and ship to market. In the year 1848 there were shipped from Catteraugus County, N, Y., eighty tons of these birds; and from that time to 1878 the wholesale slaughter continued to increase, and in that year there were shipped from Michigan not less than three hundred tons of birds. During the thirty years of their greatest slaughter there must have been shipped to our great cities 5,700 tons of these birds; allowing each pigeon to weigh one-half pound would show twenty-three millions of birds. Think of it! And all these were caught during their brooding season, which must have decreased their numbers as many more. Nor is this all. During the same time hunters from all parts of the country gathered at these brooding places and slaughtered them without mercy.

   [...]

   2These experts finally learned that the birds while nesting were frantic after salty mud and water, so they frequently made, near the nesting places, what were known by the craft as mud beds, which were salted, to which the birds would flock by the million. In April, 1876, I was invited to see a net over one of these death pits. It was near Petoskey, Mich. I think I am correct in saying the birds piled one upon another at least two feet deep when the net was sprung, and it seemed to me that most of them escaped the trap, but on killing and counting, there were found to be over one hundred dozen, all nesting birds.

   1Thanking you for your courtesy in the matter, I beg to say that I have long had great interest in the problem of the so sudden and complete destruction of this great species, and have from the first been quite unable to believe that the ordinarily assigned agencies for the destruction of the pigeon were adequate, or anywhere near adequate, to make a destruction so sudden and complete.

   [...]

   2Years ago—I cannot tell how many, but I am confident it must have been at about the time of the disappearance of the great pigeon flights—I read an account, either in or quoted from a New Orleans newspaper, giving the stories of several ship captains and sailors who had arrived in New Orleans from the Gulf of Mexico. They stated that they had, in crossing the Gulf, sailed over leagues and leagues of water covered, and covered thickly, with dead pigeons. The supposition was that an enormous flight of the pigeons crossing the waters of the Gulf had been overwhelmed by a cyclone, or some such atmospheric disturbance, and that the birds had been whirled into the surf and drowned.

   3[...] The whole theory stands or falls, as it seems to me, with the ascertainment of the southern limit of the migration of the great pigeon flight. If the birds did not cross the Gulf of Mexico there is far less likelihood of my theory being the correct one [...]

   1If Mr. Mershon will communicate on the subject of Passenger Pigeons with Mr William Brewster, 145 Brattle Street, Cambridge, Mass., he may get some data which will (or ought to) dismiss from consideration the idea that the passenger pigeon could have been exterminated in the manner suggested by Mr. Ames. During a visit to northern Michigan, Mr. Brewster talked with a great many pigeon netters. I have forgotten the figures, and may be very inexact in my recollection of them, but my recollection is that at one "roost" there were one hundred netters who averaged one thousand (it may have been ten thousand) pigeons per day. When it is considered that this was the rate of destruction at one locality in one State only, that the same was going on in other States, and that tens of thousands were being killed by hunters and others, and this year after year, I cannot see anything surprising in the eventual extermination of the species, no matter how numerously represented originally.

   2Nothing in the history of the Passenger Pigeon is more certainly known than the fact that its range to the southward did not extend beyond the United States.

   3There is a single Cuban record, but the occurrence was purely accidental. The migrations of the Passenger Pigeon were wholly different in their character from those of true emigrants, that is to say, they were influenced or controlled purely by the matter of food supply, as in the case of the robin and some other birds, and the flights were as often from west to east and vice versa as from south to north or north to south; in short, the flocks moved about in various directions in their search for food or nesting places. For myself, I do not believe in the story of drowning in the Gulf of Mexico for two reasons. In the first place the birds are extremely unlikely to have been there, a hurricane from the northward being absolutely necessary to explain their presence in that quarter, and, in the second place, no such explanation is needed in view of what is known to be the facts concerning their wholesale destruction by human agency alone.

   1Many theories have been advanced to account for the disappearance of the wild pigeons, among them that their migration may have been overwhelmed by some cyclonic disturbance of the atmosphere which destroyed their myriads at one blow. The big "nesting" of 1878 in Michigan was undoubtedly the last large migration, but the pigeons continued to nest infrequently in Michigan and the North for several years after that, and until as late as 1886 they were trapped for market or for trap-shooting. Therefore the pigeons did not become extinct in a day; nor did one tremendous catastrophe wipe them from the face of the earth. They gradually became fewer and existed for twenty years or more after the date set as that of the final extermination.

   [...]

   2The habits of the birds were such that they could not thrive singly nor in small bodies, but were dependent upon one another, and vast communities were necessary to their very existence, while an enormous quantity of food was necessary for their sustenance. The cutting off of the forests and food supply interfered with their plan of existence and drove them into new localities, and the ever increasing slaughter could not help but lessen their once vast numbers.

   3The Passenger Pigeon laid only one egg in its nest, rarely two, and although it bred three or four times a year it could not replenish the numbers slaughtered by the professional netters. Undoubtedly millions of the birds perished at various periods along the Great Lakes country, becoming confused in foggy weather and dropping from exhaustion into the water, while snow and sleet storms at times caused great mortality among the young birds, and even among the old ones, which often arrived in the North before winter had passed.

   Part 2: Model the blueprint. Work through the examples aloud. For each one, point to the part of the blueprint it tests. Stress that critiquing structure is not the same as deciding who is right: an explanation can have a clear structure and a weak cause, or a strong cause buried in a confusing structure. More words from the sources: a curator is the expert in charge of a museum collection; migration is the regular travel of animals from place to place; "myriads" means huge numbers; "extermination" means wiping out completely; "agencies" (Source 2) means causes; "the craft" (Source 1) means the netters' trade; trap-shooting is a sport of shooting at released birds; true "emigrants" (Source 3) are birds that travel to the same distant region every year; and "vice versa" means the other way around.

   • Sequence: steps in order, with links (Source 1)

     Pokagon explains how market netting worked (Source 1, paragraph 1). Put his steps in order and find the words that link them.

     Result: Steps: (1) "about the year 1840" white men began "netting them for market"; (2) the netters kept "in telegraphic communication" to follow the flocks; (3) trained "stool-pigeons" (captive birds used as lures) called flocks down to the nets; (4) the birds were packed "in ice" and shipped; (5) shipments grew from "eighty tons" in 1848 to "not less than three hundred tons" in 1878. The dates and the word "so" show the order. Strength: the steps follow one another in time. The link "which must have decreased their numbers as many more" is Pokagon's reasoning, not a count.

   • Supporting details: do the numbers fit? (Source 1)

     Pokagon estimates that "5,700 tons" of pigeons were shipped in thirty years and, "allowing each pigeon to weigh one-half pound", gets "twenty-three millions of birds" (Source 1, paragraph 1). Check the detail and critique it.

     Result: One ton is 2,000 pounds, so 5,700 tons is 11,400,000 pounds. At half a pound per bird that is 22,800,000 birds, which rounds to about 23 million: his arithmetic is right. Critique: the total "must have been" shipped is his estimate; the paragraph names no record for it, and the half-pound weight is an assumption he states openly. A detail can be correct arithmetic and still rest on an estimate.

   • A competing explanation: cause, details and a test (Source 2)

     C. H. Ames explains the disappearance by storms that drowned huge flocks at sea. Critique the structure of his explanation.

     Result: His cause is a storm over the Gulf of Mexico, and his structure has one strong feature: he names what would decide it, saying his theory "stands or falls" on how far south the flocks flew (paragraph 3). The weak part is a missing link: he moves from his doubt that hunting was enough to the conclusion that storms did it. His full letter adds other reports of drowned flocks (not printed here), but none of them shows that storms were big enough, or came often enough, to destroy a whole species.

   • Several causes working together (Source 4)

     Mershon names several causes (Source 4, paragraphs 2-3). Show how his explanation connects them instead of only listing them.

     Result: Chain: the birds "could not thrive singly nor in small bodies"; cutting the forests took away food and "drove them into new localities"; slaughter cut their numbers; and because a pigeon "laid only one egg in its nest, rarely two", the flocks "could not replenish" (make up) the losses. Weather deaths are added as one more cause. Strength: the one-egg detail explains why the losses added up. Weakness: Mershon never says which cause mattered most, so a reader cannot tell the main cause from a small one.

3. Guided Practice15 minutes

   Pairs read Source 5, three invented drafts. Tell students that two of them are deliberately weak. For each draft, pairs fill in the five rows of the blueprint, mark the part that fails, and rewrite one sentence to fix it.

   1These three drafts were written for this page by invented students who read Sources 1-4 and explained why the passenger pigeon disappeared. Two of them are deliberately weak, so that the class can find the problems in their structure. They are not models.

   2Rosa: "The pigeons disappeared. Pokagon says 5,700 tons were shipped. Pigeons have long, graceful necks. Also there were storms. So that is why."

   3Eli: "Then netters shipped tons of birds to the cities. In the end the pigeons were gone. First, people learned to send news of the flocks by telegraph."

   4Nadia: "Pokagon and Mershon explain the disappearance as a chain. Professional netters followed the flocks to their nesting places (Source 1). They caught nesting birds, which meant fewer young birds each year. Because a pigeon laid 'only one egg in its nest, rarely two' (Source 4), the flocks could not make up the losses. As forests were cut, the birds also lost food (Source 4). So the numbers fell year after year, not in one day."

   Teacher key (discussion points). Rosa's draft names the event but gives no causes in order: a number, an unrelated detail (long necks) and "storms" are listed with no links, and "So that is why" is a conclusion that nothing before it supports. Eli's draft has a cause but its sequence is scrambled: "First" comes last, so the reader cannot follow the chain; putting the telegraph step first and adding why shipping tons of birds made the flocks shrink would fix it. Nadia's draft is the strongest: it names a chain of causes, links them with "which meant", "Because" and "So", and backs steps with Sources 1 and 4. One improvement: it could say which cause mattered most, or admit that the sources do not say.

4. Independent Practice10-15 minutes

   Each student chooses one of Sources 1-4 and writes a blueprint critique: one sentence for each of the five parts, saying whether the part is present, clear and connected, with a quotation for each. Students end with one sentence on the strongest and one on the weakest part of that explanation's structure.

5. Closure10 minutes

   Exit ticket: "Which part of an explanation is easiest to leave out by mistake: the causes, the links between steps, or the details? Give one example from today."

   Teacher note on the sources: Pokagon writes as a Potawatomi witness and calls the netters' methods cruel; his account is the main Native voice here, and his estimates should be treated with the same care as the others. Other parts of his article, not printed here, use period terms for Native people and, once, a slur; this excerpt includes none of them. The sources use the word "slaughter" and describe killing birds for market; the lesson focuses on how the explanations are built, not on hunting today. The disappearance is documented in the sources; Mershon writes in 1907 that the pigeons "gradually became fewer", and Ridgway, a year earlier, already writes of "the eventual extermination of the species" (Source 3, paragraph 1).

   Quiz passage. Questions 11-14, 19 and 20 use Source 6, an invented civics scenario.

   1This scenario is invented for this page. The town, the bus line and all the numbers are invented.

   2The invented town of Millbrook runs a city bus line, Route 9. Its transit office wrote this explanation for the town council.

   3Section A: "Route 9 carried an average of 1,200 riders a day last year and 900 riders a day this year. This report explains why."

   4Section B: "In March, a new highway exit opened near the mall, and many shoppers began to drive there. In June, the town cut Route 9 buses from every 15 minutes to every 30 minutes to save money."

   5Section C: "Our drivers are friendly, and the buses were painted blue last year."

   6Section D: "A survey of 150 former riders found that 63 said the longer wait was their main reason for stopping, 41 said they now drive to the mall, and the rest gave other reasons."

   7Section E: "Therefore, the only reason Route 9 lost riders is the new highway exit."

Differentiation Strategies

Assessment Guidance

1. Question 1 of 20 · Multiple Choice

   Which of these statements is an explanation rather than an argument?

   AEveryone in town should read all of the library's new books BThe creek flooded because three days of rain filled it COur school's soccer team is the best in the county DThe town ought to build a second public pool soon

2. Question 2 of 20 · Multiple Choice

   In Source 1, paragraph 2, Pokagon describes the salted "mud beds" that netters made near nesting places. What does this add to his explanation?

   AA new cause that had nothing to do with netting BThe conclusion of his whole explanation CA step showing how netters drew whole flocks DA detail about what pigeons looked like

3. Question 3 of 20 · Multiple Choice

   Pokagon writes, "I think I am correct in saying the birds piled one upon another at least two feet deep when the net was sprung" (Source 1, paragraph 2). What kind of supporting detail is this?

   AHis own eyewitness estimate, with a hedge BA count of birds taken from a shipping record CA report he read in a newspaper DA number given by a museum curator

4. Question 4 of 20 · Multiple Choice

   Pokagon says the catch from one net was "over one hundred dozen, all nesting birds" (Source 1, paragraph 2). A dozen is 12. How many birds is that?

   AMore than 100 birds BMore than 112 birds CMore than 1,000 birds DMore than 1,200 birds

5. Question 5 of 20 · Multiple Choice

   Ames supports his storm theory with an account he read "Years ago"; he adds, "I cannot tell how many" (Source 2, paragraph 2). What is the main weakness of this detail?

   AIt is too new to tell anything about pigeons BIt is vague, secondhand and has no date CIt comes from a museum record of the Gulf DIt shows that hunting caused the decline

6. Question 6 of 20 · Multiple Choice

   Ames says he cannot believe that the usual causes of the destruction were "adequate" (enough) to explain it (Source 2, paragraph 1). What job does this paragraph do in the structure of his explanation?

   AIt states the problem his theory will solve BIt gives the main supporting detail of his theory CIt proves that storms killed the birds DIt names the ships that saw the pigeons

7. Question 7 of 20 · Multiple Choice

   Ridgway writes that he does not believe the drowning story "for two reasons. In the first place [...] and, in the second place [...]" (Source 3, paragraph 3). What does this wording do for the structure of his reply?

   AIt hides which reason he thinks is stronger BIt turns his reply into a story of one day CIt puts his two reasons in a clear order DIt shows that he agrees with Ames after all

8. Question 8 of 20 · Multiple Choice

   Ridgway admits, "I have forgotten the figures, and may be very inexact in my recollection of them" (Source 3, paragraph 1). What does this admission tell a reader?

   AHis numbers on netting are a weak detail BHis whole explanation has no structure CHis figures come from a careful count of the nets DHis reply is mostly about storms at sea

9. Question 9 of 20 · Multiple Choice

   Ridgway writes that the pigeon's range "did not extend beyond the United States" to the south (Source 3, paragraph 2). Which part of Ames's explanation does this challenge most directly?

   AAmes's statement that he saw large flights BAmes's step that flocks crossed the Gulf CAmes's claim that netters used telegraphs DAmes's conclusion that hunting was the cause

10. Question 10 of 20 · Multiple Choice

    In the middle of his numbers, Pokagon writes, "Think of it!" (Source 1, paragraph 1). What does this sentence do in his explanation?

    AIt adds a new cause of the decline of the flocks BIt gives an exact date for the start of the netting CIt asks readers to feel the size of the loss DIt corrects an error in his arithmetic

11. Question 11 of 20 · Multiple Choice

    What job does Section A do in the transit office's explanation (Source 6)?

    AIt gives the main cause of the change in riders BIt states what is explained, with numbers CIt gives the conclusion of the report DIt lists details that do not belong

12. Question 12 of 20 · Multiple Choice

    What is the main structure problem with Section C?

    AIt puts the report's conclusion before its causes BIt gives numbers that do not add up CIt names too many causes at once DIts details support no step of the explanation

13. Question 13 of 20 · Multiple Choice

    Section B says the town cut buses "from every 15 minutes to every 30 minutes". Which detail in Source 6 best supports this cause?

    ARiders fell from 1,200 to 900 a day BThe buses were all painted blue last year CA highway exit opened near the mall D63 of 150 former riders named the wait

14. Question 14 of 20 · Multiple Choice

    What is wrong with the conclusion in Section E?

    AIt ignores a cause its own survey backs BIt gives the rider numbers in the wrong order CIt comes before the report's causes DIt repeats Section A word for word

15. Question 15 of 20 · Short Answer

    Pokagon's paragraph 2 (Source 1) tells what he saw at one net in 1876. Explain how this paragraph supports his explanation in paragraph 1, and name one step or detail that is still missing.

    Show model answer

16. Question 16 of 20 · Short Answer

    Compare the structure of Ames's explanation (Source 2) with Ridgway's reply (Source 3). Which one supports its steps better? Use the blueprint and quote both sources.

    Show model answer

17. Question 17 of 20 · Short Answer

    Critique the structure of Source 4, paragraph 1. What does Mershon explain, which explanation does he reject, what details does he give, and where does his conclusion come?

    Show model answer

18. Question 18 of 20 · Short Answer

    Write your own short explanation (four to six sentences) of why the passenger pigeon disappeared, using at least two of Sources 1, 3 and 4. Then label each blueprint part you used.

    Show model answer

19. Question 19 of 20 · Short Answer

    Rewrite the conclusion in Section E of Source 6 so that it follows from Sections B and D. Include what share of the 150 former riders named each reason, as percentages.

    Show model answer

20. Question 20 of 20 · Short Answer

    Name two other structure problems in Source 6 besides Section E, and explain how to fix each one.

    Show model answer

These standards connect to D4.5.6-8: prerequisites to review first, parallel standards at the same level, and next steps that build on it.

Standard text: National Council for the Social Studies (NCSS), The College, Career, and Civic Life (C3) Framework for Social Studies State Standards: Guidance for Enhancing the Rigor of K-12 Civics, Economics, Geography, and History (Silver Spring, MD: NCSS, 2013). NCSS was not involved in the production of this lesson and does not endorse it.