Red Knot Population Decline: Limiting Factors, Resources, and Food Webs
IB Assessment
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Grasp
Goal: Research and explain why red knot populations are declining by connecting the decline to limiting factors, food web disruption, and human impact, and propose a science-based recommendation to a conservation organization
Role: Junior Wildlife Scientist at a coastal bird conservation organization, tasked with producing an accessible but scientifically accurate briefing report on the red knot crisis
Product: A structured Wildlife Science Briefing Report (2–3 pages or equivalent) that includes: a labeled food web diagram showing the red knot's ecological position, a written explanation of at least three limiting factors affecting the population, an analysis of how human activities have disrupted the food web, and one evidence-based conservation recommendation with a scientific justification
Audience: Members of the Delaware Bay Shorebird Conservation Council — a group of informed non-scientists (local government officials, fishing community representatives, and environmental educators) who need clear scientific explanations to make policy decisions
Situation: Red knot populations along the Atlantic Flyway have dropped by more than 75% since the 1980s. Scientists have identified a key disruption: overharvesting of horseshoe crabs has drastically reduced the availability of horseshoe crab eggs — the primary food source red knots depend on during their critical Delaware Bay stopover. Without enough food to fuel the final leg of their Arctic migration, birds arrive underweight and fail to breed successfully. Additional limiting factors — including habitat loss from coastal development and climate change shifting the timing of crab spawning — compound the crisis. Your organization needs a clear, science-based briefing document to present at an upcoming policy meeting.
Criteria
Name: Knowing and Understanding
Level 0: The student does not reach a standard described by any of the descriptors above.
Criterion: A
Level 1 2: The student demonstrates limited understanding of ecological concepts relevant to the red knot scenario. The student attempts a food web diagram but it contains significant errors in organism relationships or energy flow direction, or is largely incomplete. The student uses minimal scientific terminology and shows limited ability to connect concepts such as limiting factors or food web interdependence to the red knot situation. Statements about the red knot decline are vague, inaccurate, or not connected to scientific concepts. Scientific vocabulary is largely absent or used incorrectly.
Level 3 4: The student demonstrates a basic understanding of some ecological concepts relevant to the red knot scenario. The student constructs a food web diagram that shows some correct relationships between organisms but may have missing or incorrectly directed arrows, or fewer than 4 organisms. The student identifies limiting factors and food web relationships but descriptions are general, relying on everyday language more than scientific terminology. The student states that horseshoe crab egg depletion is linked to red knot decline but does not clearly explain the mechanism or the chain of effects. The student identifies at least one limiting factor but descriptions lack scientific detail or accuracy. Scientific vocabulary is used occasionally but inconsistently or with notable errors.
Level 5 6: The student demonstrates a mostly accurate understanding of the key ecological concepts relevant to the red knot scenario. The student constructs a food web diagram with mostly correct directional arrows showing energy flow between at least 4 organisms, with the red knot correctly positioned. The student describes limiting factors and food web relationships using mostly accurate scientific terminology, with minor errors or imprecision. The student describes how horseshoe crab egg depletion affects red knot populations, identifying the connection between food availability and population decline, though the explanation of the mechanism across trophic levels may be incomplete or partially developed. The student identifies and describes at least two limiting factors with some scientific detail. Scientific vocabulary is used in most parts of the report with occasional lapses or minor inaccuracies.
Level 7 8: The student demonstrates a thorough and accurate understanding of all key ecological concepts relevant to the red knot scenario. The student correctly constructs a food web diagram with accurate directional arrows showing energy flow between at least 6 organisms, correctly placing the red knot within its trophic level. The student precisely defines limiting factors, carrying capacity, and food web interdependence using scientific terminology throughout the report with no significant errors. The student explains the mechanism by which horseshoe crab egg depletion reduces red knot survival — describing the chain of cause and effect across trophic levels (e.g., reduced food availability → insufficient fat reserves → failed migration → reduced breeding success → population decline). The student also explains at least three distinct limiting factors (e.g., food scarcity, habitat loss, climate-driven phenological mismatch) with accurate scientific detail for each. Scientific vocabulary is used consistently, precisely, and in context throughout the entire report.
Task Specific Clarification: For this task, Criterion A assesses whether students can accurately recall and apply ecological concepts — specifically food webs, limiting factors, carrying capacity, producers/consumers/decomposers, and interdependence — to the specific context of the red knot population decline. Students must use correct scientific vocabulary (e.g., 'limiting factor,' 'trophic level,' 'food web,' 'carrying capacity,' 'population,' 'resource') in their briefing report. The food web diagram they construct must correctly show directional energy flow using arrows. Written explanations must connect concepts to the red knot scenario specifically, not just define terms in isolation. At higher levels, students are expected to explain the mechanism of how disruption at one trophic level cascades through the food web, not merely state that it does.
Name: Reflecting on the Impacts of Science
Level 0: The student does not reach a standard described by any of the descriptors above.
Criterion: D
Level 1 2: The student provides a limited discussion of human impacts, making vague or general statements about harm to the environment without specific reference to the red knot scenario or supporting scientific concepts. The student may attempt a conservation recommendation but it is not connected to scientific reasoning or the specific ecological situation. There is little evidence of reflection on the role of science in understanding or addressing the problem. Responses are largely opinion-based with minimal use of evidence.
Level 3 4: The student provides a basic discussion of human impacts on the red knot population, identifying at least one human activity (e.g., overharvesting of horseshoe crabs) as harmful. The student states that this human activity has negatively affected red knots but the explanation of how or why is limited or partially inaccurate. The student proposes at least one conservation recommendation but the justification is general or not clearly connected to scientific concepts (e.g., 'We should protect the crabs so the birds have food' without further scientific reasoning). The student shows some awareness that science can help address environmental problems but this is not developed. Reflections draw minimally on scientific evidence.
Level 5 6: The student provides a clear discussion of how human activities have impacted the red knot population. The student explains at least two human-caused limiting factors (e.g., overharvesting of horseshoe crabs and coastal habitat loss) and describes their effects on the red knot population with some scientific reasoning. The student mentions the role of scientific knowledge in understanding or responding to the decline. The student proposes at least one conservation recommendation and provides a scientific justification for why it would help (e.g., 'Limiting horseshoe crab harvesting would allow crab populations to recover, increasing egg availability for red knots during migration'). The discussion acknowledges that human actions have consequences for ecosystems but may not fully evaluate trade-offs or limitations of the proposed solution. Reflections are mostly supported by evidence from the provided resources.
Level 7 8: The student provides a detailed and insightful discussion of how human activities have impacted the red knot population and the Delaware Bay ecosystem. The student explains the role of scientific monitoring and ecological research in identifying the crisis — for example, describing how population surveys and dietary studies revealed the horseshoe crab connection — and discusses how this knowledge has shaped conservation responses. The student evaluates at least one conservation recommendation (e.g., horseshoe crab harvest limits, habitat protection, or managed beach access during spawning season) by explaining the scientific reasoning behind it AND discussing at least one limitation, trade-off, or challenge to its implementation (e.g., economic impact on fishing communities, difficulty of enforcing regulations, time lag before population recovery). The student demonstrates awareness of multiple stakeholder perspectives and the complexity of balancing human needs with ecological sustainability. Reflections are consistently grounded in scientific evidence from the provided resources.
Task Specific Clarification: For this task, Criterion D assesses whether students can reflect on how human activities — specifically horseshoe crab overharvesting, coastal habitat development, and climate change — have impacted the red knot population and the broader Delaware Bay ecosystem. Students must discuss both the role of science in identifying and understanding this problem, and the potential consequences (positive or negative) of human decisions on the ecosystem. Students must also propose at least one evidence-based conservation recommendation and justify it using scientific reasoning. At higher levels, students are expected to evaluate the effectiveness or limitations of proposed solutions, consider multiple perspectives (e.g., fishing industry vs. conservation), and demonstrate awareness that science both reveals problems and informs solutions. The reflection section of the briefing report is the primary evidence for this criterion.
Myp Year
MYP 3 (Grade 8)
Task Steps
Step: 1
Title: Explore the Resource Pack and Activate Prior Knowledge
Description: Read through all provided resource materials: the food web data card, the red knot population graph, the horseshoe crab harvesting data card, the habitat and climate information cards, and the glossary. As you read, use the provided KWL-style organizer to note: (K) what you already know about food webs and limiting factors, (W) what you need to find out, and (L) what you have learned from the resources. Highlight or underline any scientific vocabulary you will need to use in your report. This step prepares you to write accurately and confidently.
Time Estimate: 20 minutes
Step: 2
Title: Construct the Delaware Bay Food Web Diagram (Section 1)
Description: Using the unlabeled food web template provided and the organism information cards, complete the food web by: (a) writing the correct organism names in each box, (b) drawing arrows in the correct direction to show the flow of energy (remember: arrows point FROM what is eaten TO what eats it), and (c) using a colored pencil or annotation to highlight the red knot and horseshoe crab and draw a box around the pathway most directly affected by horseshoe crab decline. Add a brief caption (2–3 sentences) below your diagram explaining what the food web shows and why the horseshoe crab is a critical link for the red knot. Use at least 3 science vocabulary words from the glossary in your caption.
Time Estimate: 25 minutes
Step: 3
Title: Explain the Limiting Factors (Section 2)
Description: Write Section 2 of your briefing report: 'What Is Causing the Decline?' Using the data cards and your food web, identify and explain at least THREE limiting factors that are reducing the red knot population. For each limiting factor, write a short paragraph (4–6 sentences) that: (a) names and defines the limiting factor, (b) explains specifically how it affects red knots (using evidence from the data cards), and (c) connects it to a concept from the food web or carrying capacity. You must use correct scientific vocabulary for each factor. Suggested limiting factors to consider: food availability (horseshoe crab eggs), habitat loss at stopover sites, and climate change affecting migration timing (phenological mismatch). Use the sentence starters provided in the scaffold sheet if needed.
Time Estimate: 30 minutes
Step: 4
Title: Discuss the Human Connection and the Role of Science (Section 3)
Description: Write Section 3: 'The Human Connection.' In 1–2 paragraphs, discuss: (a) which human activities are responsible for the limiting factors you described — be specific (e.g., commercial horseshoe crab harvesting for bait and biomedical use, coastal development, greenhouse gas emissions); (b) how scientists discovered and measured these impacts (e.g., population surveys, satellite tracking, dietary studies) — this shows your audience that the evidence is real and science-based; and (c) what the consequences could be if no action is taken. Remember your audience: write clearly enough for a non-scientist to understand, but use correct scientific terms and explain them when you introduce them.
Time Estimate: 25 minutes
Step: 5
Title: Develop an Evidence-Based Conservation Recommendation (Section 4)
Description: Write Section 4: 'Our Recommendation.' Choose ONE conservation action that you believe would most effectively help red knot populations recover. Write a recommendation paragraph (5–8 sentences) that: (a) clearly states your recommended action, (b) explains the scientific reasoning — how would this action address one or more of the limiting factors you identified?, (c) uses evidence from the data cards to support your reasoning, and (d) acknowledges at least one challenge or trade-off involved in implementing this recommendation (e.g., economic impact, time for recovery, need for international cooperation). This shows your council that you have thought carefully and scientifically about the problem.
Time Estimate: 20 minutes
Step: 6
Title: Review, Revise, and Submit
Description: Before submitting, use the self-assessment checklist provided to review your report. Check: (a) Is my food web diagram complete with correctly directed arrows and at least 6 organisms? (b) Have I explained at least 3 limiting factors with scientific vocabulary? (c) Have I discussed at least 2 human activities and connected them to scientific evidence? (d) Does my recommendation include a scientific justification AND acknowledge a trade-off or challenge? (e) Is my report clearly organized into the 4 labeled sections? Make any final corrections, then submit your completed briefing report along with your annotated food web diagram.
Time Estimate: 15 minutes
Description
This summative assessment places students in the role of junior wildlife scientists preparing a report for a coastal conservation organization. Students investigate why red knot (Calidris canutus rufa) populations have declined dramatically, connecting the science of food webs, limiting factors, and resource availability to real-world environmental disruption. The assessment is grounded in the well-documented ecological relationship between red knots and horseshoe crabs along the Delaware Bay, where overharvesting of horseshoe crabs has removed a critical food source during the birds' northward migration, with cascading effects on population survival.
Students will demonstrate their understanding of key science concepts — including food web structure, limiting factors, carrying capacity, and the interdependence of organisms — by analyzing a provided food web diagram and a set of data cards describing environmental pressures on red knot populations. They will then reflect on the role of human activity and scientific knowledge in driving and potentially reversing this ecological crisis. This task is designed at a foundation complexity level, meaning students are provided with structured scaffolding, guided prompts, and visual resources to support their responses.
This assessment evaluates Criterion A (Knowing and Understanding) through students' ability to recall, describe, and explain ecological concepts accurately using scientific terminology, and Criterion D (Reflecting on the Impacts of Science) through students' ability to discuss how scientific knowledge informs our understanding of human impact on ecosystems and propose evidence-based responses. ATL skills — critical thinking, information literacy, and communication — are embedded throughout the task steps.
Command Terms
define
identify
describe
explain
analyse
discuss
evaluate
justify
construct
suggest
Subject Group
Sciences
Teacher Notes
Ib Connections: Global Context: This assessment connects most directly to the IB MYP Global Context of 'Fairness and Development' — specifically the concept of sustainability and the stewardship of shared natural resources — and also to 'Globalization and Sustainability,' as the red knot's migration spans multiple continents and its decline reflects global environmental pressures. Key Concepts: The primary key concept engaged is 'Change' (population decline as ecological change driven by human activity) with strong connections to 'Relationships' (food web interdependence) and 'Systems' (the Delaware Bay ecosystem as a system where disruption in one component affects others). Related Concepts: The most relevant related concepts for Sciences are 'Consequences' and 'Interaction,' both of which are foregrounded in the food web and human impact analysis. IB Learner Profile: This task develops students as Thinkers (analyzing ecological data and evaluating solutions), Communicators (writing for a specific audience), Knowledgeable (applying science concepts to a real-world case), and Caring (reflecting on human responsibility for environmental stewardship). The task also connects to the IB MYP Sciences framework's emphasis on the Nature of Science — specifically the idea that scientific knowledge is used by societies to make decisions, and that scientists have a responsibility to communicate their findings to non-specialist audiences.
Differentiation
Advanced: Students who complete the task with ease can be extended by: (1) adding a second conservation recommendation and comparing the two options — which is more effective, more feasible, or more likely to gain stakeholder support, and why?; (2) researching and incorporating information about the international dimension of red knot conservation (the birds migrate from Tierra del Fuego to the Arctic, crossing multiple national jurisdictions — how does this complicate conservation efforts?); (3) designing a simple monitoring protocol that scientists could use to measure whether a conservation intervention is working, connecting to scientific methodology; (4) writing a counter-argument paragraph from the perspective of a fishing industry representative and then responding to it with scientific evidence — developing higher-order argumentation skills.
Struggling: For students who need additional support: (1) provide a partially completed food web template with some organism names already filled in, requiring students to add only 3–4 organisms and draw the arrows; (2) provide a sentence frame scaffold for each section — for example, for limiting factors: 'One limiting factor affecting red knots is ___. This is a limiting factor because ___. The data shows that ___, which means ___. This connects to the food web because ___'; (3) reduce the minimum number of limiting factors from three to two for students with IEPs or language support needs; (4) allow students to annotate their food web diagram with sticky notes or bullet points rather than writing full sentences for the caption; (5) provide a word bank of key scientific vocabulary terms that must be used in the report, helping students access the language without having to recall it from memory. Teachers may also read data cards aloud to students with reading difficulties, as the assessment is primarily measuring science understanding rather than reading decoding.
Facilitation Tips: Prepare a Resource Pack for each student or pair before the assessment. The pack should include: (1) an unlabeled Delaware Bay food web template showing boxes for organisms with blank arrows — suggested organisms: phytoplankton, zooplankton, horseshoe crab, horseshoe crab eggs, red knot, ruddy turnstone, laughing gull, striped bass, loggerhead sea turtle; (2) a red knot population trend graph (1980–2020 showing decline from ~100,000 to ~20,000 birds); (3) a horseshoe crab harvest data card showing peak harvesting in the 1990s and subsequent management measures; (4) a habitat loss data card describing beach development statistics along the Atlantic coast; (5) a climate change timing card describing the mismatch between crab spawning peak and bird arrival dates; (6) a glossary card with definitions of: limiting factor, carrying capacity, food web, producer, consumer, trophic level, population, interdependence, phenological mismatch. All resources should be clearly labeled with a source card name (e.g., 'Data Card 3: Horseshoe Crab Harvest') so students can reference them. The assessment can be completed individually or in pairs — if pairs are used, ensure each student submits their own written sections. Allow approximately 2 hours total (can be split across two class periods: food web and limiting factors in period 1, human connection and recommendation in period 2). During the task, circulate to check that students are directing food web arrows correctly (a very common error at this level) and that they are connecting their limiting factor explanations to the red knot specifically rather than writing generically about ecosystems.
Assessment Strategy: Use this summative assessment at the end of a unit on ecosystems, food webs, and human impacts. It is designed to replace a traditional written test with an authentic performance task that gives students more agency and context. When marking, assess Criterion A primarily through Sections 1 and 2 of the report (food web diagram and limiting factors explanation), and Criterion D primarily through Sections 3 and 4 (human connection and recommendation). However, note that scientific accuracy in Section 3 also contributes to Criterion A evidence. Mark each criterion holistically using the best-fit model — identify the band that most closely describes the student's overall performance across the criterion, then decide whether the work sits at the lower or upper end of that band. Provide written feedback that names one specific strength for each criterion and one specific, actionable target. Suggested feedback language: for Criterion A — 'Your food web correctly shows energy flow and you accurately defined three limiting factors. To reach the next level, explain the mechanism — describe the step-by-step chain of how reduced crab eggs lead to population decline, not just that they are connected.' For Criterion D — 'You clearly identified two human activities and proposed a reasonable recommendation. To reach the next level, discuss a trade-off or challenge with your recommendation and consider more than one stakeholder perspective.' This assessment can also be used as a collaborative moderation task — share 3–4 anonymized student samples with colleagues and practice applying the rubric descriptors before finalizing grades.
Atl Integration
Skill: Thinking: Critical Thinking Skills
Activities
In Step 3, students analyze population trend graphs and harvesting data to draw inferences about cause-and-effect relationships between horseshoe crab decline and red knot body weight loss — practicing evidence-based reasoning rather than assumption
In Step 5, students evaluate their own conservation recommendation by deliberately identifying at least one limitation or trade-off, requiring them to think beyond a simple 'solution' and consider complexity
Throughout the task, students use the KWL organizer to monitor their own thinking, identifying gaps in their understanding and adjusting their explanations accordingly — a metacognitive critical thinking practice
Description: Students practice critical thinking by analyzing ecological data from multiple resource cards, identifying cause-and-effect relationships within the food web, and evaluating the strength of their conservation recommendation by considering trade-offs and counterarguments. Rather than simply recalling facts, students must reason about how the removal of one species creates cascading effects across an ecosystem and assess whether their proposed solution addresses the root cause of the problem.
Skill: Research: Information Literacy Skills
Activities
In Step 1, students actively preview and annotate the Resource Pack using the KWL organizer, practicing the skill of identifying what information is relevant to their specific task rather than passively reading all materials
In Steps 3 and 4, students are required to cite specific evidence from named data cards when explaining limiting factors and human impacts — practicing the habit of grounding claims in identifiable sources rather than writing from memory alone
In Step 5, students must select the most relevant piece of evidence from the data cards to support their conservation recommendation, requiring them to evaluate the usefulness and reliability of different pieces of information for a specific purpose
Description: Students practice information literacy by navigating a structured Resource Pack containing multiple types of information — graphs, data tables, written descriptions, and a glossary — and selecting relevant evidence to support specific claims in their report. They must distinguish between scientific evidence (data, measurements, research findings) and general statements, and they must attribute information to its source card when using it as evidence.
Skill: Communication Skills
Activities
Throughout the report, students must introduce and explain scientific vocabulary (e.g., 'limiting factor,' 'trophic level,' 'carrying capacity') in a way that is accessible to their identified audience of government officials and fishing community members — practicing audience-aware communication
In Step 2, students write a diagram caption that synthesizes visual and written information, practicing the skill of communicating scientific meaning through multiple modes (diagram + text)
In Step 6, students use a self-assessment checklist to review the clarity, completeness, and organization of their own written communication before submission — developing self-editing and reflective communication skills
Description: Students practice communication skills by writing a formal science briefing report for a specific, non-specialist audience. This requires them to make deliberate choices about language — using correct scientific terminology while also explaining terms clearly enough for a non-scientist reader. The structured format of the report (four labeled sections) develops organizational communication skills, while the requirement to write a recommendation with a justification develops persuasive scientific writing.
Task Description
Imagine you are a junior wildlife scientist working for a coastal bird conservation organization. You have just been asked to prepare a Wildlife Science Briefing Report for an upcoming policy meeting of the Delaware Bay Shorebird Conservation Council. The council includes local government officials, representatives from the fishing industry, and environmental educators — people who care about the issue but are not professional scientists. Your job is to explain, clearly and accurately, why red knot populations are in crisis, using your knowledge of food webs, limiting factors, and the impacts of human activity on ecosystems.
You will be provided with a Resource Pack that includes: a simplified Delaware Bay food web diagram (unlabeled arrows version for you to complete), a data card set describing red knot population trends, horseshoe crab harvesting data, habitat loss statistics, and climate change timing information, and a glossary of key science terms. Using these resources and your science knowledge, you will build your briefing report step by step. Your report must be scientifically accurate, clearly written for a non-specialist audience, and grounded in evidence.
Your completed Wildlife Science Briefing Report should include four clearly labeled sections: (1) The Delaware Bay Food Web — your completed and annotated food web diagram; (2) What Is Causing the Decline? — a written explanation of at least three limiting factors; (3) The Human Connection — a discussion of how human activities have disrupted the ecosystem and the role of science in understanding this; and (4) Our Recommendation — one evidence-based conservation action with a scientific justification. You will be assessed on how accurately you apply scientific concepts (Criterion A) and how thoughtfully you reflect on the impacts of science and human activity (Criterion D).
Learning Objectives
Define and apply the concepts of limiting factors, carrying capacity, food webs, and resource availability to explain population changes in a real ecosystem
Describe the ecological relationships between red knots, horseshoe crabs, and other organisms in the Delaware Bay food web using accurate scientific terminology
Explain how the removal or reduction of one species (horseshoe crabs) creates cascading effects on other species (red knots) within a food web
Identify and describe how human activities — including overharvesting, habitat destruction, and climate change — act as limiting factors on the red knot population
Reflect on the role of scientific knowledge in understanding environmental problems and evaluate the potential impact of conservation actions on the red knot population
Submission Requirements
Completed Wildlife Science Briefing Report organized into 4 clearly labeled sections: (1) The Delaware Bay Food Web, (2) What Is Causing the Decline?, (3) The Human Connection, and (4) Our Recommendation
A completed and annotated food web diagram (hand-drawn or digital) with correctly directed energy flow arrows, at least 6 labeled organisms, the red knot and horseshoe crab highlighted, and a 2–3 sentence scientific caption
Written explanation of at least THREE limiting factors, each in a separate paragraph using correct scientific vocabulary and evidence from the provided data cards
A discussion of at least TWO specific human activities causing the decline, including a statement about how science has helped identify or measure these impacts
One clearly stated conservation recommendation with a scientific justification (minimum 5 sentences) and acknowledgment of at least one trade-off or challenge
Completed KWL organizer and self-assessment checklist (for teacher review — not assessed for grades, but required for submission)
All work must be the student's own; direct quotations from resources must be placed in quotation marks and attributed to the source card