Strutting Grouse and Chokecherry Pits

Use refuge survey data to explain how behaviors and fruit structures help living things reproduce.

Answer Key

Dawn on the lek

Read the passage and Table 1. Then answer questions 1–4.

A Spring Survey at Antelope Draw

1Every spring, the crew at Antelope Draw National Wildlife Refuge surveys its greater sage-grouse, large birds that live on the sagebrush plains of the western United States. The refuge, the people and the numbers here are made up, but they are based on real wildlife studies. This year, sixth grader Kenji Abernathy joined refuge biologist Dr. Lucía Begay for the survey.

2Before sunrise on spring mornings, male sage-grouse gather on an open patch of ground called a lek. Each male fans his spiky tail feathers, puffs out his white chest and struts. As he struts, two bare yellow air sacs on his chest swell and then snap back, making popping sounds that carry across the plain. Females walk among the displaying males, watching and listening, and each female mates with just one or two of them. The males give no help with nests, eggs or chicks.

3From a parked truck, Kenji and Dr. Begay watched one lek for five mornings. They sorted the 24 males by where on the lek each one usually displayed, counted how often the males strutted and recorded every mating they saw.

4After mating, each female nests alone. She scrapes a shallow bowl in the ground under a sagebrush shrub and lays her eggs. While she sits on them, her mottled brown and gray feathers blend with the shadows, and she stays still even when a coyote walks nearby. Ravens often hunt for nests from the air. Later in the spring, the crew checked nests that it had found by following hens with radio collars.

5Chokecherry shrubs grow along the refuge's creek. In late summer, each small fruit turns from green to dark purple. While the fruit is green, the single seed inside is not yet ready to sprout. The seed has a hard, stony coat and is wrapped in sweet pulp. Birds such as robins swallow the ripe fruits whole. The pulp is digested, and the hard seed passes out in the bird's droppings, often far from the shrub where it grew.

6To learn more, volunteers set a trail camera on one chokecherry shrub whose branches held both green and dark fruits. They also planted seeds in the refuge nursery. All the seeds they planted came from ripe fruits of the same creek shrubs, except one group of seeds that they picked out of bird droppings under nearby fence posts.

Table 1. One Lek, Five Mornings
Where males displayed	Males	Struts per 10 min (avg.)	Matings seen
Center of lek	3	18	24
Middle ring	8	11	5
Outer edge	13	4	1

Use Table 1.

What percent of all the matings seen went to the males at the center of the lek? 80%

Use Table 1.

On average, how many matings did each male at the center of the lek have over the five mornings? 8 matings per male

Which conclusion does Table 1 best support?

A. Males that strutted more often tended to get more of the matings.
B. Each male got about the same number of matings over five mornings.
C. Females mated at random, since each group had at least one mating.
D. Edge males got the most matings, since there were 13 of them on the lek.

Use paragraph 2. A male sage-grouse gives no care to eggs or chicks. Why can hours of strutting each spring still help him reproduce successfully?

A. Strutting shows young males where the hens have hidden their nests.
B. Strutting raises his chance of being chosen, his only way to have chicks.
C. Strutting warms the ground on the lek, so eggs laid there hatch sooner.
D. Strutting scares coyotes away from the nests that hens build on the lek.

Hens and their nests

Use paragraph 4 and Table 2 to answer questions 5–8.

Table 2. Sage-Grouse Nests Checked This Spring
Shrub over the nest	Nests	Eggs per nest (avg.)	Nests that hatched
Tall, thick sagebrush	20	7	14
Short, sparse sagebrush	10	7	3

What percent of the nests under tall, thick sagebrush hatched? 70%

Which explanation of Table 2 fits paragraph 4 best?

A. Hens in short sagebrush left their nests each dawn to strut on the lek.
B. Hens in short sagebrush laid fewer eggs, so fewer of their nests hatched.
C. Males guarded the nests in tall sagebrush but left the other nests alone.
D. Thick cover hid the sitting hen and her eggs from predators that hunt nests.

The refuge wants more sage-grouse chicks to hatch next spring. Based on Table 2, which plan would most likely help the most?

A. Count the males on the lek every morning so the crew knows the best strutters
B. Protect the tall, thick sagebrush near the lek from clearing and fire
C. Mow the sagebrush near the lek so the males have more ground to strut on
D. Plant short grass in place of sagebrush so hens can see coyotes coming

Sort each sage-grouse trait or behavior from the passage by how it most likely helps reproduction.

A male's air sacs swell and pop as he struts.A hen scrapes her nest under a tall, thick shrub.A female walks among the males, watching and listening.A sitting hen stays still while a coyote walks nearby.A male fans his spiky tail feathers at dawn.

Helps a bird win or choose a mate	Helps eggs survive until they hatch
A male's air sacs swell and pop as he struts. A female walks among the males, watching and listening. A male fans his spiky tail feathers at dawn.	A hen scrapes her nest under a tall, thick shrub. A sitting hen stays still while a coyote walks nearby.

Chokecherries along the creek

Use paragraphs 5 and 6 and Tables 3 and 4 to answer questions 9–13.

Table 3. Trail Camera on One Shrub, One Week in August
Fruit color	Visits taking a fruit
Dark purple (ripe)	46
Green (not ripe)	3

Table 4. Chokecherry Seeds Planted in the Nursery (50 in each group)
How seeds were planted	Sprouted next spring
Inside the whole fruit	6
Pulp removed by hand	27
Picked out of bird droppings	30

The seeds picked out of bird droppings sprouted how many times as often as the seeds planted inside the whole fruit? 5 times

10.

Which explanation fits all three rows of Table 4 best?

A. Pulp left on a seed held back sprouting, and removing it, as a bird's gut does, helped.
B. A bird's gut cracked the hard seed coats, and cracked seeds were the ones that sprouted.
C. Bird droppings fed the seeds extra nutrients, and that food made most of them sprout.
D. Birds picked out the strongest seeds, and seeds left in fruit were the weak ones.

11.

Use paragraph 5 and Table 3. How does a chokecherry fruit turning dark purple only once its seed is ready most likely help the shrub reproduce?

A. Dark fruits stay on the branch longer, so their seeds sprout right under the shrub.
B. The color change keeps robins from swallowing the seeds along with the pulp.
C. Birds mostly carry off fruits whose seeds can already grow into new shrubs.
D. Dark fruits taste bitter, so birds leave them alone until the seeds drop to the soil.

12.

Match each structure or behavior from the refuge to the way it most likely helps reproduction.

The hard, stony coat of a chokecherry seedC
The sweet pulp of a ripe chokecherryD
A male grouse's popping air sacsA
A hen nesting under tall, thick sagebrushB

A. Draws the attention of females on the lek
B. Hides the eggs from predators hunting from the air
C. Lets the seed survive the trip through a bird's gut
D. Draws in birds that carry the seed away

13.

A visitor says, "Robins harm the chokecherry shrubs, because they eat the fruit that holds the shrub's seeds." Do you agree? Write a claim, give evidence from Table 3 and Table 4, and explain your reasoning about how the fruit's structures and the birds' behavior affect the shrub's reproduction.

I disagree: robins most likely help the shrubs reproduce. Table 3 shows that birds took 46 ripe dark fruits but only 3 green ones, so they mostly take fruits whose seeds are ready to sprout. Table 4 shows that only 6 of 50 seeds sprouted inside whole fruit, but 30 of 50 seeds from bird droppings sprouted, about the same as the 27 seeds with the pulp removed by hand. The sweet pulp draws birds to eat the fruit, the hard seed coat lets the seed pass through the bird's gut, and the bird drops the seed away from the parent shrub with its pulp removed. So the birds' eating behavior spreads the seeds and helps more of them sprout.