day at Boston's Logan Airport. In the great gray owl irruption of 2001, birders in
southeastern Manitoba spotted more than 100 in a single day.
50 Given that northern owl populations naturally experience large fluctuations
in size, it's hard for wildlife managers to determine whether species are stable or
To further complicate matters, the main source of data on North American
bird population trends, the volunteer-based Breeding Bird Survey (BBS)-a
collaboration between U.S. Geological Survey and the Canadian Wildlife
Service-collects almost no data on northern owls. Relatively few humans, much
less willing volunteers, live in the Canadian regions where these owls breed.
In the United States, data on northern owl populations are being collected
through the survey and management program of the Bureau of Land Management's
60 (BLM) Northwest Forest Plan, which requires land managers to assess potential
impacts on rare and sensitive species whenever timber sales are proposed in old-
growth forests. In May 2003, however, the Forest Service and BLM proposed
eliminating some of the survey requirements. At presstime a decision was still
With scientists unable to get a fix on owl numbers, conservationists worry
that loss of habitat-whether from natural disasters or human actions such as
logging-could seriously harm owls without anyone noticing.
"Great grays often nest in the tops of dead snags, so they require fairly good-sized trees," says Priestley. Boreal owls nest in cavities excavated by pileated woodpeckers and northern flickers and also require big, old trees. The problem is that big trees also attract timber companies. A recent report published in Conservation Ecology predicted that most of the old-growth boreal forest in western Canada will be completely gone by 2065 if logging and drilling for oil and natural gas continue at current rates.
"Cool Operators" by Cynthia Berger. Reprinted with permission from the February/March 2004 issue of National Wildlife magazine. Copyright 2004 by the National Wildlife Federation.
____ 1. Based on lines 3-11, you can infer that great gray owls
have a keen sense of sight
use snow banks to cool off
have difficulty finding food
use burrows to escape the cold
____ 2. Monitor your understanding of lines 17-21. Great grays are protected in harsh weather because they have
large nests made of twigs and bark
fluffy feathers that protect their ankles
highly developed immune systems
special diets that build layers of fat
____ 3. What key idea from lines 26-30 contributes to the main idea of the selection?
Birdwatchers enjoy witnessing the adaptations of many owls.
Irruption is another name for the sudden dive an owl makes to get food.
Long- and short-eared owls often show up in unexpected places.
Some types of northern owls move south when food is unavailable.
____ 4. According to the article, one cause of the loss of owl habitats is
____ 5. Berger most likely included the map to provide information about the
Directions Read the following selections. Then answer the questions that follow.
from Owls Aren't Wise and Bats Aren't Blind
Warner Shedd Snowy owls evolved as hunters on the vast, barren Arctic tundra, where they
prefer to perch on the highest point around and wait until they spot their prey—then
glide down to seize their victims by stealth. Thus, when they visit southern Canada
and the United States, the big predators favor wide-open spaces (airfields such as
Boston's Logan Airport are often preferred hangouts) and high perches, where they
can approximate tundra hunting conditions.
Snowy owls do much of their hunting diurnally. This is no great surprise,
considering that there is daylight almost twenty-four hours a day during their high
Arctic breeding and nesting season. Conversely, they must also be efficient Night
10 hunters during the long stretches of almost total Arctic darkness.
Summer prey for snowy owls consists almost entirely of mammals—
mostly small, with lemmings making up the bulk of their diet. In
winter, especially for those owls that migrate south, their meals are far more varied.
Hares and ptarmigan help carry the owls through the winter in the Arctic, when
lemmings are mostly active beneath the snow. Owls wintering farther south have
proved quite adaptable when it comes to prey. Mice are a staple, but Norway rats are
also prime fare. For that matter, so are pigeons, rabbits, dead fish, and almost
anything else of suitable size that comes to the owls' attention.
It was once thought that these white visitors from the Arctic came south in
20 winter because of the shortage of lemmings. Although it's a complete myth that
lemmings periodically commit suicide by throwing themselves off cliffs into the sea,
where they drown en masse, the plump little rodents are notoriously cyclical, going
from almost unbelievably high populations to extreme scarcity every four or five
years. Unquestionably, lemming numbers have an effect on snowy owl populations,
but biologists are learning that the interrelationship between these two species is far
more complex than has heretofore been suspected.
For one thing, there's no evidence that lemming cycles are synchronized throughout the Arctic, and they may be quite regional. Since snowy owls by nature are great
travelers, it's no special feat for them to move from an area of lemming scarcity to
30 one of abundance. For another, large numbers of snowy owls migrate annually
to the Great Plains area of Canada and the United States without apparent reference
to lemming cycles. Much remains to be learned about the dynamics of the
lemming/snowy owl relationship.
From Owls Aren't Wise & Bats Aren't Blind by Warner Shedd. Copyright (c)2000 by Warner Shedd. Used by permission of Harmony Books, a division of Random House, Inc.
____ 10. The author's main purpose for writing this article is to
____ 11. According to lines 7–10, one effect of the snowy owl's Arctic habitat is that the owls
choose lemmings over other mammals
have the ability to hunt day and Night
sleep during months of total darkness
migrate to warmer climates in winterigan
____ 12. Monitor your understanding of lines 13–15. In the winter, snowy owls
change their diet because lemmings are harder to catch
stop eating mammals and mostly eat plants
hunt exclusively at night to avoid predators
travel across the tundra with hares and ptarm
Directions Answer these questions about "Cool Operators" and the excerpt from Owls Aren't Wise and Bats Aren't Blind. ____ 13. What conclusion can you draw about the owls discussed in the two articles?
Northern owls migrate because they are ill-suited to survive the extreme weather of their harsh environments.
Bird watchers are more interested in the migration patterns of snowy owls than of other northern owls.
Most northern owls have been forced to migrate because of the destruction of their natural habitat in the boreal forest.
More research is necessary to fully understand the migration patterns of northern owls.
____ 14. How are the main ideas in the two selections different?
Berger discusses many types of owls, but Shedd focuses solely on the characteristics of great gray owls.
Shedd thinks that the snowy owls are better hunters, and Berger thinks that great gray owls are better hunters.
Berger only provides information, but Shedd stresses that readers should take action to protect owls.
Shedd addresses the relationship between predator and prey, but Berger focuses on the ways northern owls adapt.
Directions Answer these questions about the photograph.
____ 15. The photograph most likely shows a cracked egg in the setting to