Phenology: Spring Leaf Index

A Carolina Essentials™ Activity

Total Time: 45-60 MIN

Prep: 15 | Activity: 30-45

Life Science


High School


The study of related events, particularly between plants and animals that occur on a predictable or periodic cycle, is called phenology. Phenology studies are crucial to determining disruptions in environmental relationships as climate patterns shift, and phenology studies provide evidence of environmental changes.

In this activity, students interpret a Spring Leaf Index Anomaly map from the National Phenology Network and determine the areas of the country with the greatest anomalies. Then they identify the seasonal relationships between blue jay food gathering and ripening fruit on the northern red oak using an activity curve. After examining data from the different sources, students should be able to support or refute claims of climate change and its possible effects.


Every spring, ruby-throated hummingbirds migrate from Central America to the southern and eastern part of the United States. Before migrating, a hummingbird consumes enough nectar and small bugs to store half its body weight in fat. During migration, the birds fly nonstop across the Gulf of Mexico, about 500 miles in about 20 hours. On an average day, hummingbirds consume double their weight.

Watch the short video and think about this question: What would happen if a late spring freeze killed the flowers? Jot down your thoughts.

Essential Question

How can nationwide data be used to support claims of environmental changes?

Activity Objectives

  1. Interpret a Spring Leaf Index Anomaly map.
  2. Interpret activity curves for the blue jay and northern red oak.

Next Generation Science Standards* (NGSS)

HS-LS4-5. Evaluate the evidence supporting claims that changes in environmental conditions may result in: (1) increase in the number of individuals of some species, (2) the emergence of new species over time, and (3) the extinction of other species.

HS-ESS3-5. Analyze geoscience data and the results from global climate models to make an evidence-based forecast of the current rate of global or regional climate change and associated future impacts to Earth systems.

Science & Engineering Practices

Engaging in Argument from Evidence

Analyzing and Interpreting Data

Disciplinary Core Ideas

LS4-C: Adaptation

ESS3.D: Global Climate Change

Crosscutting Concepts

Cause and Effect

Stability and Change

Safety Procedures and Precautions

No PPE is required for this activiy.


Teacher Preparation and Disposal

Prepare colored copies of the student pages if the activity is not delivered digitally. If copying is limited, copy a class set or project the map and chart for student use. No disposal of materials.


Map-Spring Leaf Index Anomaly

1.  Examine the map for patterns and relationships between the onset of spring and geography, biomes, regional weather, ground cover, water availability, and anything else you can think of that may affect the onset of spring.

2. Make a list of your patterns and relationships and the evidence for each. Share your findings with the class. 

Graph-Activity Curve for Blue jays and Fruiting Read Oaks

1. Using the Activity Curve for the Northern red oak and blue jay, describe the annual cycle of acorn production, (ripe fruit), for the Northern red oak. What evidence supports your claim? 

2. Describe the annual feeding pattern, (nut gathering), for the blue jay. What evidence supports your claim?

3. Make a list of your descriptions and share them with the class.


Map-Spring Leaf Index Anomaly

1. Review with students what the term anomaly means and that when working with climate data averages or means are calculated over a 30-year period. That means spring leaf index of 2018 is being compared to the average of spring leaf index of 1981-2010.

2. Students can share ideas orally, on a master list or spreadsheet, or possibly as a gallery walk.

Graph-Activity Curve for Blue jays and Fruiting Red Oaks

1. Make certain that students are identifying the curves correctly. 

2. Students can share ideas orally, on a master list or spreadsheet, or possibly as a gallery walk.

Data and Observations

Analysis and Discussion

  1. Summarize the onset of spring for the contiguous United States. Address the regions of the country, whether spring was early, late, or on time and the evidence that supports your claim.

    “Spring leaf-out has arrived in all of the Continental US and most of Alaska. Spring arrived 1-3 weeks late in the Southeast, northern Great Plains, Midwest, and Northeast and 1-3 weeks early across the central Great Plains, Ohio Valley, and mid-Atlantic compared to a long-term average (1981-2010). The west is a patchwork of early and late arrival.* Accessed June 14, 2018.

  2. Using the activity curve, describe the Blue jay’s annual feeding relationship with the Northern red oak. What evidence supports your claim?

    The peak of Blue jay nut gathering is in November slightly after the peak of Northern red oak ripe fruit from about mid-September to mid-November. In early spring, mid-March, there is a smaller peak in Northern red oak ripe fruit that coincides with a gathering peak in the Blue jays.

  3. How might the Blue jay’s feeding habits have to adapt if there is an unusually early spring? What impacts might this have on the food web?

    If the Northern red oak produced early ripening nuts there may not be an adequate food supply for the Blue jay. The Blue jay population would have to seek nuts from other trees. The food web would be altered as the Northern red oak nuts would be removed as a link in the Blue jay’s food chain. Students may say that some Blue jays may starve to death.

  4. How might the Blue jay’s feeding habits have to adapt if there is an unusually late spring? What impacts might this have on the food web?

    If there is an unusually late spring, mid-May, Northern red oaks would be producing ripe fruit during a time when Blue jays were not gathering. Maybe fallen nuts could produce sapling trees, and maybe other birds would eat the nuts ripening later. The Blue jays, however, would not have spring Northern red oak nuts to gather. Blue jays are not normally gathering the Northern red oak nuts during late spring so their food chain would be unchanged. Other bird or small mammal species may add a link to the Northern red oak nuts increasing the number of links in the food web.

  5. If spring were to come three weeks early to the Southern and mid-Atlantic states for the next 20 years, how might this affect the hummingbird, and what far-reaching effects on the ecosystem may occur? Use evidence to support your claims.

    If spring were to come three weeks early for 20 years, the migrating hummingbirds would have to find new food sources that were blooming when they would normally arrive, they would have to adjust the time they migrated, or they may adjust their destination and migrate further North where spring is “on schedule”. Hummingbirds rely on tubular flowers that hold nectar and in turn, the flowers rely on the hummingbirds for pollination. If the flowers and birds are not in sync, then new relationships between flowers and hummingbirds will have to be established. Other animals could replace the hummingbirds as pollinators and the birds could find alternate food sources. If altering the relationship is not possible, it may be both the flower species and the hummingbird species go extinct in their original location. If the birds move farther North, they may displace other birds or insects as pollinators or may have to share food supplies. Less than adequate food supplies may result in a decrease in the population of hummingbirds and the displaced species. individual food chains and food webs will be disturbed as relationships change.

*Next Generation Science Standards® is a registered trademark of Achieve. Neither Achieve nor the lead states and partners that developed the Next Generation Science Standards were involved in the production of, and do not endorse, these products.

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