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Pecking Order: What Types of Post-Fire Snag Areas Do Woodpeckers Prefer?

Trees that are dead but still standing are called snags. Even though snags are dead, they are still are important parts of the forest. Snags provide benefits to the environment, especially to the animals that live nearby. Because the population of Black-backed woodpeckers had fallen in the Sierra Nevada, scientists wanted to study what types of postfire habitats this woodpecker liked best.

Pecking Order: What Types of Post-Fire Snag Areas Do Woodpeckers Prefer?

Meet the Scientists

Chad Hanson

Fire Ecologist | Forest Ecologist

Malcolm North

Forest Ecologist

Thinking About Science

As scientists continue to do research, they learn new things. In the past, for example, scientists believed the best thing to do after a severe wildfire was to cut down and remove most of the snags. Snags are dying or dead trees that are left standing after a fire, flood, wind, disease, or insect damage. More recent research, however, has shown that snags may provide ecological benefits to an area.

When science is used to solve a problem or make something better, it is called applied science. In this study, the scientists were doing applied science. This is because their research could be used to help forest managers take better care of the forest after a wildfire occurred.

Thinking About the Environment

Think about your friends at school. They may seem similar to each other, but none of them are alike. This is true, even though they may like the same activities and laugh at the same jokes. Like your friends at school, all wildfires may seem alike, but they can actually be very different. One of the ways that wildfires are different from each other is that they burn at different severity levels. Wildfires are classified as low-, moderate-, or high-severity fires. High-severity fires are where most or all of the trees are killed by the fire (figure 1). Low-severity fires still have trees that are living (figure 2).

Because wildfires do not burn evenly, a patch of forest that has experienced a high-severity burn may be almost surrounded by areas that have experienced low or medium severity wildfire.

A forest area where trees are dead from being burned — **Figure 1**. A high-severity wildfire burned this area. You can see that most or all of the trees are dead. Photo by Randall
Whitehall, Forest Service.

Trees in a forest with very little burn damage — **Figure 2**. A low-severity wildfire burned this area. Although some of the trees’ needles or leaves may be brown, few trees have been damaged by the wildfire. Photo by Randall Whitehall, Forest Service.

Introduction

Trees that are dead but still standing are called snags. Even though snags are dead, they are still are important parts of the forest. Snags provide benefits to the environment, especially to the animals that live nearby. Some of the benefits include providing a home for birds, mammals, reptiles, and amphibians. Snags also are used as hunting perches by birds and perches for songbirds. Snags are a good source of food for some animals because snags provide habitat for insects, mosses, lichens, and fungi. Some woodpeckers use snags for food. The Black-backed woodpecker is one of the animals that needs snags to survive (figure 3).

A black-beaked woodpecker pecking a tree — **Figure 3**. Black-backed woodpecker. Photo by Terry Spivey, Forest Service, courtesy http://Bugwood.org.

The Black-backed woodpecker is considered a keystone species. A keystone species is one that can indicate problems in the environment. This is because these species
are sensitive to environmental changes. If their population numbers fall, for example, this might mean that other species needing that same environment are in danger also. For example, in the 1870s there were a lot of Black-backed woodpeckers in the Sierra Nevada (figure 4). By the 1920s, however, there were relatively few of these woodpeckers. This drop in woodpecker population indicated that there was something changing in the environment that was causing problems for the woodpecker. There were probably
problems for other species living there as well.

A map of the U.S. highlighting California and the Sierra Nevada. — **Figure 4**. The Sierra Nevada is located in the Western United States.

Forest managers usually leave between three to six large snags per acre after a wildfire. The rest are cut down and removed. Past records had showed that the Black-backed woodpecker seemed to live in forest areas with a lot of snags. Because the population of Black-backed woodpeckers had fallen in the Sierra Nevada, scientists wanted to study what types of postfire habitats this woodpecker liked best. In this study, the scientists wanted to know what types of post-fire snag forests were best for the Black-backed woodpecker’s foraging.

Reflection Section

Methods

The scientists studied several different patches of forest in the Sierra Nevada (figure 5).

A map of the U.S. highlighting the Sierra Nevada and stars marking the study sites within it. — **Figure 5**. The location of the study sites in the Sierra Nevada.

Each patch was at least 12 hectares in size. The study took place from 2004 through 2006. Each patch was labeled as having experienced a moderate-severity or high-severity wildfire. The scientists also noted whether or not the area had any of its snags removed and how many snags were in each hectare (figure 6).

Figure 6. The scientists studied four different post-fire conditions.
Habitat Condition	Number of Patches Studied
Unburned	9
Moderate-severity and all snags left standing	8
High-severity and all snags left standing	10
High-severity and only 8-15 large snags left standing per hectare	9

The scientists walked through all of the patches and recorded the presence or absence of the Black-backed woodpecker. The scientists started their observations 100 meters from the edge of the patch and moved toward the center (figure 7). Every 200 meters the scientists stopped and recorded the presence or absence of the woodpecker during an 8-minute time period. The same method was used in each patch.

A illustration of each patch that waws surveyed showing how it was surveyed — **Figure 7**. Each patch was surveyed in the same way for the presence or absence of the Black-backed woodpecker.

Number Crunches

Reflection Section

Findings

The scientists reviewed all the information they collected. They put their observations into a computer program to help them analyze the data. When they analyzed their observations, the scientists found that Black-backed woodpeckers were found in only one type of patch. The woodpeckers were found only in patches that had experienced high-severity wildfires and where all of the snags were left standing.

The scientists found that there was a difference between the number and size of snags in each type of patch (figure 8).

Figure 8. The average number of snags per hectare in each of the patch types.
Habitat condition	Number of patches studied	Average number of medium size snags per hectare	Average number of large snags per hectare
Unburned	9	13.9	7.4
Moderate-severity and all snags left standing	8	110.8	53.4
High-severity and all snags left standing	10	127.5	124.2
High-severity and only 8-15 large snags left standing per hectare	9	169	18.5

Reflection Section

Discussion

The Black-backed woodpecker clearly prefers one type of habitat for foraging. Patches that experienced high-severity burns with snags left standing were the favorite areas for the woodpecker. This research suggests that, if forest managers want to support the population of Black-backed woodpeckers, they should not remove snags from patches that had experienced high-severity burns.

Reflection Section

Adapted from Hanson, C.T. and North, M.P. (2008). Postfire woodpecker foraging in salvage-logged and unlogged forests of the Sierra Nevada. The Condor. 110 (4):777-782. http://www.treesearch.fs.fed.us/pubs/33988

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Wildland Fire 2 - Vol. 13 No. 1

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What Is a Natural Inquirer Journal?

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A Natural Inquirer journal is a collection of 4-8 articles on a related science topic. Journals are written for a middle school audience, but they can also be adapted for both high school students and advanced upper elementary students. Some journals are particularly suited to high school students; you can find our grade level recommendations in the tags on the product page or by filtering journals by grade level.

Journals include:

Four to eight articles based on published, peer-reviewed research papers; the articles keep the research paper format (see more below) but are written in language students can understand.
A FACTivity for each article, which is an activity to complete after reading the article. The FACTivity helps reinforce major science concepts from the article. These activities are designed to be easy to implement, with few material requirements and options for adapting them for your audience or available resources. Some articles in a journal may have two FACTivities.
A short “Welcome to the journal” article about key background information and science concepts that unify the articles included in the journal
A glossary of new terms for each article and the introductory materials.
A list of related Natural Inquirer publications for each article as well as outside references.
Standards correlations, including Next Generation Science Standards, addressed in the articles and the FACTivities.

Journals may also include additional essays (called spotlights), other activities (like crossword puzzles or vocabulary challenges), and more.

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Reading Modes

Journals are available in three different formats:

Hard copies can be ordered from the website and shipped, all free of charge.
PDF versions of the printed journal can be downloaded free on the website. The PDF version directly replicates the content and layout of the printed version. You can also download individual articles as pdfs.
The “Read Distraction Free” option allows the individual articles to open in their own window, without the rest of the website being visible. These articles can be found under the “Articles” tab. This version allows readers to scroll to particular sections of the article using the sidebar menu on the left side of the screen. This version also has interactive Reflection Sections and Number Crunches. Students can enter their answers, submit them, and then receive the correct answers to double-check their work. Submitted answers are not saved on the website and will disappear once the window is closed.

What's in a Natural Inquirer Article?

Here, we'll go into more detail about the parts of a Natural Inquirer article and give you some ideas about how they can be used.

Meet the Scientists
This section introduces the scientists (and others) who worked on the study. In their own words, they each share a memorable science experience, a favorite research project, or something they learned during the course of their education or research.

Use this section to:
- Introduce kids to the variety of people who work in science
- Introduce kids to the variety of scientific fields and give brief descriptions of science-related jobs
- Explore ways that people interact with science every day
Next Generation Science Standards (NGSS) applications:
- Science and Engineering Practices
- Crosscutting Concepts: Influence of Science, Engineering, and Technology on Society and the Natural World
Note that specific standards for this particular monograph are linked on this educator guide tab.

Other resources:

Many of the scientists and engineers featured in this section are also featured on our collector cards. Learn more about their work, how they got interested in their fields, and interesting projects they worked on. Cards can be printed as posters, too.
Thinking About Science
This section briefly describes a concept about science or scientific research. This overview can touch on topics like
- study type (longitudinal study, quantitative vs. qualitative data),
- behaviors of scientists (conducting literature reviews, collaborating with other specialists, replicating earlier studies),
- the practice of science (the scientific method, engineering design, data collection, randomization, controls and variables),
- or other aspects of science (bias, correlation vs. causation).
Use this section to:
- Reinforce steps in the scientific method and the process of science
- Encourage students to think about the practice of science and what it can and cannot tell us
- Consider the many types of scientific study and what information each type can provide
Next Generation Science Standards applications:
- Science and Engineering Practices
- Life Science Disciplinary Core Ideas (depending on topic)
- Most Crosscutting Concepts (depending on topic)
Note that specific standards for this particular monograph are linked on this educator guide tab.

Other resources:

You can use key words to search for other or related scientific topics on our website (e.g. “longitudinal study,” “bias,” or “sampling”).
Thinking About the Environment
This section provides a brief overview of a topic or concept in environmental/life science. The topic or concept is directly related to the research study that follows. Examples of topics include the carbon cycle, the water cycle, habitat fragmentation, phenology, biodiversity, and ecosystem services.

Use this section to:
- Provide important background information to help students understand the research study
- Serve as a quick reference during reading or class instruction
- Connect the research article with other activities or media on the same topic
Next Generation Science Standards applications:
- Life Science and some Earth Science Disciplinary Core Ideas (depending on topic)
- Most Crosscutting Concepts (depending on topic)
Note that specific standards for this particular monograph are linked on this educator guide tab.

Other resources:

You can use key words to search for more resources on life or earth science topics on our website (e.g. “habitat,” “carbon,” or “genetics”).
Introduction
This section begins the scientific article format. Much like the published, peer-reviewed study this article is based on, the introduction provides background information for the study – what is currently known and what remains unknown. The introduction culminates in the question(s) the study hopes to answer.

The introduction is also the first section with a Reflection Section. This section includes two or three questions to help kids reflect on what they’ve just learned in the Introduction. If they are using the online distraction-free reading mode, they can answer these questions directly on the website.

Use this section to:
- Review important background information that kids need to understand the study
- Connect the study to the concepts addressed in the Thinking About Science and Thinking About the Environment sections
- Understand research questions and hypotheses, including generating their own hypotheses given what they already know
Next Generation Science Standards applications:
- Life Science and some Earth Science Disciplinary Core Ideas (depending on topic)
- Most Crosscutting Concepts (depending on topic)
Note that specific standards for this particular monograph are linked on this educator guide tab.

Other resources:

Use one of the guided reading lesson plans to help kids follow the format of a scientific paper.
Methods
This section is the nuts and bolts of the study design – the who, what, when, where, why, and how of the research. Contained within the Methods section are usually maps of the study location or the set-up of study plots, as well as details about what data was collected and how.

The Methods section also ends with a Reflection Section – two or three questions to help students think through what they just read. These questions are interactive on the distraction-free reading mode.

Use this section to:
- Show students how experiments and studies are designed and carried out
- Explore sampling methods and randomization
- Introduce various data collection tools (e.g. camera traps, surveys, insect collection tools, weather stations, etc.)
- Explain bias and how studies are designed to remove bias
- Help students gain experience with map reading
Next Generation Science Standards applications:
- Life Science and some Earth Science Disciplinary Core Ideas (depending on topic)
- Most Crosscutting Concepts (depending on topic)
Note that specific standards for this particular monograph are linked on this educator guide tab.

Other resources:

Many Methods and Findings sections contain Number Crunches, which are simple math exercises designed to help students interact with the data from the study.
Findings
This section summarizes the data collected during the study. The Findings section usually includes data tables or graphs and highlights the significant data points from the study. This section often mentions statistical analysis or the use of computer programs to model or analyze the data, though these methods are only discussed generally.

The Findings section also ends with a Reflection Section – two or three questions to help students think through what they just read. These questions are interactive on the distraction-free reading mode.

Use this section to:
- Have students practice reading and interpreting graphs and tables
- Compare results between variables and controls
- Explain the concept of statistical significance
- Discuss how no data or negative results still provide valuable information
Next Generation Science Standards applications:
- Life Science and some Earth Science Disciplinary Core Ideas (depending on topic)
- Most Crosscutting Concepts (depending on topic)
Note that specific standards for this particular monograph are linked on this educator guide tab.

Other resources:

Search the website for “map” or “graph” to find activities where students can practice making and reading maps and graphs.
Discussion
This section concludes each article. In it, we summarize the main findings of the scientists’ study. Additionally, we present the scientists’ ideas about the limitations of their study, the big-picture impacts of their research, and the scientists’ plans for future study or action.

The Discussion section ends with a Reflection Section – two or three questions to help students think through what they just read, especially general take-aways from the study. These questions are interactive on the distraction-free reading mode.

Use this section to:
- Discuss what conclusions can and cannot be drawn from the available data
- Explain the difference between correlation and causation
- Explore study limitations and opportunities for further study
- Brainstorm ways the study findings could be applied to real-world situations
Next Generation Science Standards applications:
- Life Science and some Earth Science Disciplinary Core Ideas (depending on topic)
- Most Crosscutting Concepts (depending on topic)
Note that specific standards for this particular monograph are linked on this educator guide tab.

Other resources:

Use the “Designing Your Own Study” resource page for videos of scientists discussing their own research studies. The page also includes educator resources to help students plan their own scientific studies.

Additional Resources on the Website

A screenshot of the product tabs for an NI monograph On the website, we pair each journal with a variety of other resources, as well. Use the tabs on the product page to browse through the following:

Related activities, including the FACTivity for each article
An “About” essay that gives some larger context for the research the scientists conducted or more information about the science topic from the journal
A glossary of all boldfaced terms from the journal
A “Scientists and Collaborators” page that lists the people involved in the studies in the journal; click on a researcher to reach their bio page and see what other articles they might be featured in
A “Related Content” page that lists both Natural Inquirer resources about similar topics and also outside reference materials

Article Selection and Review

Natural Inquirer partners with the USDA Forest Service, so we source research studies by Forest Service scientists that have been peer-reviewed and published in reputable journals. Some of our articles have also been created in collaboration with scientists from other Federal agencies, such as U.S. Geological Survey and the United Nations Food and Agriculture Organization, universities, and other non-profits.

All journal articles are reviewed by scientists who conducted the original research study to verify scientific accuracy. Journals are also reviewed by student editorial review boards of middle or high school students before publication. Additionally, all journals are reviewed by the Forest Service and the U.S. Department of Agriculture before publication.

A screenshot of the citation for "Lights, Camera, Tracks" Every journal article includes a citation of its source study. Many educators pair the original research paper with our article to help more advanced students learn how to read formal research papers. The journal article then serves as adapted primary literature, bridging the two articles.

Lessons

In small groups (or individually), students will read a Natural Inquirer or Investi-gator article and write a letter to the scientist, asking for clarification on at least four questions. This...
Lesson Plan – Letter to a Scientist
In small groups (or individually), students will read a Natural Inquirer or Investi-gator article and write a letter to the scientist, asking for clarification on at least four questions. This...
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Wildland Fire 2 - Vol. 13 No. 1
The purpose of this lesson plan is to give students a chance to reflect on their reading and create poems to express what they have learned. The lesson plan is...
Lesson Plan – Forest Poems
The purpose of this lesson plan is to give students a chance to reflect on their reading and create poems to express what they have learned. The lesson plan is...
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Wildland Fire 2 - Vol. 13 No. 1
This lesson plan introduces students to the different sections of a Natural Inquirer article. Additionally, it helps the students understand the content of the article through the use of graphic...
Lesson Plan – Reading a Natural Inquirer Article – FACELook
This lesson plan introduces students to the different sections of a Natural Inquirer article. Additionally, it helps the students understand the content of the article through the use of graphic...
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FACELook! Exploring the Relationship Between Carbon, Photosynthesis, and the Roots of Trees

Education Files

Project Learning Tree

If you are a trained Project Learning Tree educator, you may use “Living with Fire” and “Trees as Habitats” as additional resources.

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FACTivity – Pecking Order

Glossary

analyze

ecological

forage

habitat

lichen

sample

severity level

species

Chad Hanson

Malcolm North

Standards addressed in this Article:

What Is a Natural Inquirer Journal?

Reading Modes

What's in a Natural Inquirer Article?

Meet the Scientists

Thinking About Science

Thinking About the Environment

Introduction

Methods

Findings

Discussion

Additional Resources on the Website

Article Selection and Review

Lessons

Lesson Plan – Letter to a Scientist

Lesson Plan – Forest Poems

Lesson Plan – Reading a Natural Inquirer Article – FACELook

Education Files

Project Learning Tree