Crow Scientistby Phaela Peck

Crow Scientistby Phaela Peck

© 2018 by The Regents of the University of California. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage or retrieval system, without permission in writing from the publisher.

These materials are based upon work partially supported by the National Science Foundation under grant numbers DRL-1119584, DRL-1417939, ESI-0242733, ESI-0628272, ESI-0822119. The Federal Government has certain rights in this material. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

These materials are based upon work partially supported by the Institute of Education Sciences, U.S. Department of Education, through Grant R305A130610 to The Regents of the University of California. The opinions expressed are those of the authors and do not represent views of the Institute or the U.S. Department of Education.

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Grade 4 Crow ScientistISBN: 978-1-945192-50-0

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Contents

A Crow Is Watching You 4

Surviving in an Environment with Humans 6

What a Crow Sees 8

Investigating Crows 10

How Scientists Change Variables 11

Changing Faces 12

What Marzluff Found Out 14

More Questions and More Investigations 15

Glossary 16

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A Crow Is Watching You

You’re going down the street, minding your own business. Then you see it: a crow perched on a sign, staring straight down at you. It watches with interest and almost seems to recognize you. That’s not possible, though, is it? Can crows recognize humans?

That’s the question John Marzluff (MARS-luf) asked after years of observing crows. Marzluff is a wildlife biologist. Wildlife biologists study animals, how they behave, and how they interact with their environment. For many crows, that environment is a busy city or town. Marzluff is especially interested in how crows interact with one very important part of their environment: humans.

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Marzluff says crows are fun to study because many people see them every day. “Everyone knows what a crow is,” he says. Crows have shiny black feathers and are about half a meter (1.5 feet) long. They will eat anything from insects to eggs to scraps of food that humans throw in the trash. They can even catch and kill rats to eat! Unlike many animals, crows are able to survive in places where lots of humans live.

Marzluff is curious about how crows manage to survive so well around humans. He wonders: What makes crows so successful in a city environment? How closely do they pay attention to humans? How does noticing humans help crows survive in their environment?

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Surviving in an Environment with Humans

“You may not think of yourself as part of a crow’s environment, but you are! Crows are very aware of you and are reacting to you,” says Marzluff. From a crow’s point of view, humans can be dangerous. Some humans chase crows away from gardens and farms, or even hunt crows. Other humans feed crows, even though crows can find plenty of food on their own. Of course, many humans simply leave crows alone. Different humans may treat crows in very different ways.

Humans are part of the environment for many crows. Crows can get food from humans. They sometimes eat seeds that humans plant in fields and trash that humans throw away. On the other hand, humans can be dangerous to crows. Some humans hunt crows.

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Marzluff noticed that crows seem to treat humans in different ways, too. He noticed crows “scolding” some humans. When crows scold, they call loudly, flap their wings, and sometimes even dive and chase. Marzluff noticed that crows often scolded the wildlife biologists he worked with. He wondered if that was because the biologists on his team often trap crows. Trapping crows lets biologists observe them closely and mark them with tags. The biologists don’t harm the crows, and they let them go afterward, but to a crow, being trapped seems like an attack. Marzluff noticed that crows often scolded biologists who had trapped them. He wondered whether the crows could actually recognize the biologists.

When a crow calls loudly and tries to chase a person away, it is called “scolding.”

What a Crow Sees

A crow has to see someone in order to recognize that person. Like many other animals, crows rely on vision to find food and avoid danger. Light reflects off objects (such as humans) in the environment, and some of that light enters a crow’s eyes through the pupils. The light carries information about the environment. Light receptors in the crow’s eyes respond to the light and send information to the crow’s brain. The brain processes the information and forms an image. Then it compares that image to memories and decides what to do next.

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light (which provides information about the environment) enters eye through pupil

receptors respond to light

information goes to brain

brain processes information

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Investigating Crows

To find out whether crows can recognize humans, Marzluff chose to focus on faces. He decided to investigate this question: Will crows recognize the face of a dangerous human?

Marzluff thought of a way to test this. First, a human would have to trap some crows so that the crows would think the human was dangerous. Later, that same human would have to walk by the same crows. If the crows scolded the human, that would give Marzluff evidence that the crows remembered that particular human was dangerous. But how could Marzluff know for sure it was the human’s face the crows recognized? Maybe they could smell the human, or notice the human’s clothing or way of walking. To make sure he was testing just the face, Marzluff made masks of human faces. That way he could be sure the face was the only variable he changed.

Marzluff made masks to use in his investigation.

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How Scientists Change Variables

A variable is something that can change in an investigation. Scientists set up investigations so that they are only changing one variable at a time. By changing only one variable at time, scientists can tell how that variable affects how the investigation turns out. If scientists changed too many things at once, they wouldn’t be able to learn from their investigation. They couldn’t tell which variable affected how the investigation turned out.

In Marzluff’s crow investigation, the mask would be the only variable he changed. He would keep everything else the same, including smell, clothing, and way of walking. He made masks of two different faces: Face 1 and Face 2. Marzluff and his team wore both masks where crows could see them. They wore Face 1 to trap crows so that the crows would think Face 1 was a dangerous human. When they wore Face 2, they ignored the crows and did not trap them.

One of the biologists on Marzluff’s team wears Face 1 while trapping a crow.

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This crow is scolding and chasing a person wearing the mask of Face 1, the face that traps crows.

Changing Faces

Once Marzluff’s team had introduced the crows to Face 1 and Face 2, they were ready to find out whether the crows would react differently to the two faces. A person walked past the crows wearing the mask of Face 1. The crows scolded Face 1 and even swooped down to try to chase Face 1 away.

Then the person walked into a building where the crows couldn’t see him. The crows stopped scolding. He switched masks so he was wearing Face 2. When he came out of the building wearing Face 2, the crows did not react. They did not scold Face 2 at all.

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Marzluff and his team repeated this investigation many times. They repeated it with different crows in different places. They repeated it with different masks. They observed how the crows reacted to each mask. Almost every time, the crows scolded the face they had learned was dangerous.

Marzluff was able to figure out that the crows remembered faces because he changed only the masks in his investigation. If he had changed other things at the same time, he would not have been able to tell whether it was the masks that the crows were reacting to. The investigation gave Marzluff evidence that crows learn, recognize, and react to human faces. The crows remembered the faces that trapped them. They scolded people wearing masks of those faces.

Here the same person is wearing a mask of Face 2. The crows are not scolding him.

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What Marzluff Found Out

Marzluff learned a lot about how crows survive in an environment filled with humans. Crows pay attention to the humans around them. Light reflecting off a face carries information about that face. Some of the light enters a crow’s eyes through the pupils. Light receptors respond to the light and send information to the brain. The brain compares the face to other faces in the crow’s memory. Crows can remember which faces mean danger. The crow’s brain uses its memories to guide the crow’s next action. Recognizing dangerous faces helps crows avoid dangerous humans—and survive.

Working with brain scientists, Marzluff made this image using a machine that can show inside a crow’s head. The bright areas show where the crow’s brain is responding to the sight of a human face that the crow recognizes.

brain

beak

eyeeye

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More Questions and More Investigations

Marzluff and his team have done many other investigations about how crows interact with humans. They studied crows using machines that can make images of brain activity. They made lots of different masks and did tests with different crows in different places. In every investigation, Marzluff thought carefully about what information he needed and what variable he would change.

While Marzluff’s investigations answered his question about whether crows can recognize faces, they have also led him to ask many more questions: Do crows learn about dangerous humans from other crows? How long do crows remember faces? What parts of a human face do crows recognize?

Maybe Marzluff will be able to answer some of these questions in future investigations. In the meantime, if you see a crow, remember: It’s not just looking back at you. It might even recognize your face!

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Glossaryenvironment: all the living and nonliving things in an area

evidence: information that supports an answer to a question

interact: to affect one another

investigate: to try to learn more about something

investigation: an attempt to find out about something

observe: to use any of the five senses to gather information about something

process: to change information from one form to another

pupil: the hole that lets light into the eye

react: to do something because of some information or event

receptor: a structure that responds to information coming in from the environment

reflect: to cause light to bounce off a material

respond: to change because of some information or event

survive: to stay alive

variable: something that can change in an investigation

vision: the ability to see

Books for Vision and Light: Investigating Animal Senses

I See What You Mean

Crow Scientist

Seeing Like a Shrimp and Smelling Like a Snake

Handbook of Animal Eyes

Lawrence Hall of Science: Program Directors: Jacqueline Barber and P. David PearsonCurriculum Director, Grades K–1: Alison K. BillmanCurriculum Director, Grades 2–5: Jennifer Tilson

Lead Book Developers: Ashley Chase and Chloë Delafield

Vision and Light Book Development Team:

Amplify:

Design and Production: Fran Biderman-Gross, advantages.net

Credits:Photographs: Cover, Pages 1, 12, 13: Keith Brust; Pages 4, 6, 15: Shutterstock; Page 5: Theresa Moran; Page 7: Ken Shults/Flickr Flash/Getty Images; Page 8: Nancy Mulvaney/EyeEm/Getty Images; Page 10: John Marzluff; Page 11: Ila Palmquist; Page 14: Robert Miyaoka

Leah B. AndersonRanem AtiaBryan FlaigAri Krakowski

Andrea MarksJulia D. NealCatherine ParkPhaela Peck

Michelle M. SelvansElizabeth Shafer

Irene Chan Samuel Crane Shira Kronzon

Charvi Magdaong Thomas Maher Rick Martin

Matt Reed Eve Silberman Steven Zavari

Could a crow recognize you?This scientist investigates crows and their amazing abilities. He and his team have discovered that crows can recognize different people, and they remember who treats them well and who does not.

Special thanks to John Marzluff, Professor of Wildlife Sciences at the University of Washington.

Vision and Light

Published and Distributed by Amplify.www.amplify.com

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