Nature Almanac, March 2021: Pampas Hawks Arrive on Schedule but Find Fewer Vacancies

For millennia, pampas hawks (Buteo swainsoni)* have lived geographically symmetrical lives, wintering in mid-latitude grasslands of Argentina and nesting in mid-latitude grasslands and desert shrublands of western North America. Traveling in flocks of up to 200, they fly as far as 7000 miles during spring and fall migration.

With their long, tapered wings and relatively light bodies, pampas hawks can soar for miles on fall thermals, completing a more than 5000-mile migration to grasslands in southern South America. Photo by Stephen Jones.

We once saw a flock of more than 100 individuals riding a thermal over the southern Wyoming prairie in early October and were astonished to see a golden eagle dive down and snatch a hawk out of the sky. One autumn, Ruth Carol Cushman, Larry Crowley, and other local naturalists saw an equally large flock circling over a plowed field east of Lafayette, where a subdivision now spreads across the land. Other Boulder County observers have seen dozens following tractors across fields in late summer, presumably catching grasshoppers stirred up by the plowing.

Pampas hawks typically begin arriving in Boulder County around the first week of April, but in recent years sightings have been reported as early as March 20. We wondered if climate change might be affecting their long-distance migration.

Surprisingly, neither the Boulder County Audubon 1978-2014 wildlife inventory nor eBird 1900-2020 data show a trend toward earlier first arrivals. The vast majority of these long-distance migrants continue to arrive in Boulder County in April, with only a few trickling in toward the end of March.

This handsome youngster fledged from a nest in a large cottonwood in Ruth Carol and Glenn Cushman’s front yard. Photo by Glenn Cushman.

However, we’ve observed another trend that may implicate climate change. These open country specialists have begun nesting on the urban fringe. Seven pairs nested within the Broomfield city limits during a recent spring, and a pair has begun nesting in downtown Louisville across the street from the public library. 

Ruth Carol and Glenn Cushman enjoyed watching a nesting pair in a large cottonwood along their driveway near Teller Lakes Open Space from 2005-2009. This nest fledged 1-3 young per year, and the adults had no compunction about divebombing Ruth Carol and Glenn when they walked down the driveway to pick up their mail.

This handsome youngster fledged from a nest in a large cottonwood in Ruth Carol and Glenn Cushman’s front yard. Photo by Glenn Cushman.

Meanwhile, red-tailed hawks seem to be taking over historic pampas hawk nesting territories in remnant grasslands of Boulder County. Red-tails reside here year-round and have increased in number. They typically begin incubating eggs as soon as deciduous trees leaf out, which now begins as early as mid-March. So when most of the pampas hawks arrive in April, the aggressive red-tails have already claimed the best rural nesting territories.

Is this shift in nesting habitat limiting pampas hawk numbers? The 1987-1992 and 2007-2012 Colorado Breeding Bird Atlas data indicate no decline statewide, nor do North American Breeding Bird Survey data.

All birds gravitate toward easy food sources, and pampas hawks have long nested around agricultural fields, where they hunt grasshoppers and small rodents. During late spring and early summer, when small mammals tend to dominate their diets, semi-urban life may suit them just fine, since rodents typically thrive around human settlements. For what it’s worth, the nest in downtown Louisville fledged two young last July. 

However, urban nesting can have its perils. In the San Francisco Bay Area, burrowing owls have nested in rodent burrows near airports and landfills for decades, but productivity in these areas remains low due to predation on the young by urban-adapted carnivores.

Either way, we would hate to live in a world where most birds face the choice of adopting an urban lifestyle or vanishing, as have long-billed curlews, mountain plovers, and other grassland-nesting birds of Boulder County. That’s one powerful incentive for continuing to lobby for conservation of native grasslands here and throughout Colorado.

*For this article, we’ve used a descriptive name derived from the term for South American grasslands. One Arapaho name is heeyei biitei, denoting “hawk ghost,” and the American Ornithological Society (AOS) moniker remains Swainson’s Hawk. Ruth Carol deferred to Steve on this issue but prefers using the AOS name believing that a standardized name facilitates communication and lessens the possibility of misunderstanding. For more about the growing controversy over patronymic naming of other beings, see Ted Floyd’s recent article in Birding magazine. 

Additional March events:

• Listen for chorus frogs chirrup in wetlands throughout the plains.

• Look for early emerging hoary comma and mourning cloak butterflies in foothill canyons and on the plains. They are among a half-dozen Boulder County butterflies that overwinter as adults.

• Watch flocks of migrating greater sandhill cranes fly over on their way to the North Platte River near Lewellen, Nebraska, where they will spend the month fattening up on corn and invertebrates before continuing north.

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Nature Almanac is a series by Stephen R. Jones and R. Carol Cushman. For many years, Boulder-area readers have enjoyed the wonderful perspectives of our local natural world that Steve and Carol so beautifully portrayed.  We thank Steve and Carol for agreeing to continue inspiring us.  Stephen Jones and Ruth Carol Cushman are authors of Wild Boulder County and The North American Prairie. 

Teen Naturalists Uncover Tallgrass Treasures

When international documentary filmmaker Yan Chun Su offered to lead a filmmaking workshop for our Boulder County Audubon Teen Naturalists, we had no idea what they would come up with. None of the students had ever attempted videography, and many were just beginning to experiment with close-up photography.

Yan led us out into the South Boulder Creek and Boulder Tallgrass state designated natural areas during too late-summer mornings in 2019, and we returned for more photography during September, 2020. She spent a half hour going over camera mechanics, then turned the students loose. As is typically the case with this group, they got right to it, capturing some sublime footage and still photos.

Boulder County Audubon started the Teen Naturalist Program in 2013, when two home-schooled brothers, Marcel and Joel Such, asked me why Boulder County Audubon didn’t have a program for teens. I thought, “why not,” and the three of us began organizing monthly outings. The program is open to students in grades 6 -12.

Since then, three dozen students have passed through the program. Several, including Joel and Marcel, have gone on to work as field ecologists and pursue graduate degrees.

Among current teen participants, some publish nature blogs or bird profiles online. Several help conservation organizations with field research and bird banding. Others have given public programs on subjects ranging from Ferruginous Hawk conservation to Wild Patagonia.

One student recently received grants from Boulder County Parks and Open Space and Boulder County Nature Association to study impacts of cheatgrass infestation on local wildlife. Another created a stunning video showing hummingbirds feeding and caring for their nestlings in a backyard ponderosa pine.

A dozen students have received scholarships to attend the National Audubon summer birding camp in Maine, where they photograph nesting puffins from cliff-top blinds and participate in bird banding sessions led by some of North America’s most respected ornithologists.

Eva Getman, 14, says the program has helped her feel more at home in the natural world while sharing her passion for nature with new friends.

“As a teenager, it sometimes feels like I can’t make a difference, no matter how much I care. However, being a teen naturalist means I’m regularly asked to take part in conservation activities, like bird surveys, and then provided information about what I can do to protect areas around my home and in the wilderness I love.”

Below are a few of the students’ still photos from our sessions in the Boulder tallgrass prairie preserves. Yan is helping the group edit their video footage, and we plan to have a short film ready to show by spring 2021.

The South Boulder Creek and Boulder Tallgrass State Designated Natural Areas protect the largest remnants of Colorado’s native tallgrass prairies, including rare habitat for nesting bobolinks and Ute ladies-addresses orchids. To visit these areas, park at the South Boulder Creek West trailhead along SH 93, one mile south of Boulder; or the South Boulder Creek East trailhead at the intersection of SH 93 and Marshall Road.

To experience Yan Chun Su’s quiet, heartfelt documentaries about traditional peoples and the richness of their lives, visit www.waterdropfilms.com.

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Stephen R. Jones is the author of The Last Prairie, a Sandhills Journal and co-author of Peterson Field Guide to the North American Prairie, Wild Boulder County, and Butterflies of the Colorado Front Range. He taught in the Boulder Valley Schools for 33 years and currently works as a wildlife consultant. To find out more or register for the Boulder County Audubon Teen Naturalist program, e-mail Steve at curlewsj@comcast.net.

How to Attract Birds to Your Garden

Birds are fascinating to watch, and birding is the fastest-growing recreational activity in the U.S. Boulder County is no exception! Birds are also necessary components of balanced ecosystems, no matter if you live in the mountains or on the plains, in a suburban neighborhood, or in the foothills. More and more gardeners are realizing the importance of attracting birds to their gardens.

Boulder County hosts more than 300 species of birds in its various habitats, including the migratory birds who call it home only in the spring and summer, such as the Western and Mountain Bluebird and the Green-tailed Towhee. The most common birds that thrive here are: chickadees, robins, magpies, Northern Flickers, sparrows, nuthatches, finches, House Wrens, grackles, jays, Red-winged Blackbirds, Mourning Doves, crows and ravens, some owls, hawks, falcons, eagles, and our resident geese and ducks.

Many birds species are insect or invertebrate-eaters, from flies, aphids and mosquitoes to caterpillars and worms. So the smart organic gardener will want to attract birds who will help keep the insect population down during the growing season. You will also enjoy being in your garden much more if flying insects are not “bugging” you! Birds are natural insect repellants.

If you want to make your garden attractive to birds, there are four resources that are essential that any habitat must supply for them: food, water, shelter and cover, and nesting sites.

Food

You will want plants, flowers, and trees and shrubs that will supply the widest array of foods for the greatest diversity of birds. Grow plants that supply berries (sand cherry, currants, gooseberry, chokecherry), fruits (crabapple, cherry), nuts (acorns, pine nuts), nectar for hummingbirds (hyssop, penstemon, delphinium–particularly wildflowers with the red blossoms), and seeds (native grasses, native sunflowers) for the seed eaters such as sparrows and finches. Try to plant the widest variety of plants for the different things they produce at different seasons of the year, as some birds will eat different parts of a plant at different times, and they depend on good food sources especially when they are building nests, producing eggs, and feeding their young, and migrating.

Note: Bird feeders and grocery/hardware-bought bird feed are okay, but consult a specialty bird retailer about the best products to buy. Supplemental feeding is most helpful to our resident birds in the winter and for the migratory birds that are passing through our area in the fall.

Water

If you can provide a source of water for drinking and bathing, you will see an increase in the number of birds in your garden. A birdbath is the easiest way to provide water, and it doesn’t have to be fancy. A simple terra cotta or plastic plant saucer will do the trick—just be sure to place it sheltered from strong winds, where it will not get too warm at midday, and near shrubbery that will provide shelter from predators. Birds like the water depth at no more than 3”, and need a slightly rough surface to get a foothold when they land and wade. You can heat your birdbath during the winter with an electric, submersible rubber heater, and during the summer, change the water daily to avoid molds and bacteria build-up. Birds also love moving water, such as sprinklers, dripping faucets, and bubbling and re-circulating streams and fountains. Geese and ducks tend to like large bodies of water, but if you are lucky enough to have a pond or stream on your property, you may have them visit once in a while.

Shelter and Cover

Birds need plants to provide shelter from wind, sun, and precipitation, and foliage cover can protect them from predators such as free-roaming cats and hawks. Birds also need places to roost and sleep. A tall canopy, mid-height shrubs, and smaller bushes and plants provide those things, depending on the birds’ needs at the time they visit your garden. It is also a good idea to leave snags and uprooted trees, wind-blown leaves, and brush piles in your yard or around the garden, as they provide good shelter from sun and predators, and insects for food. If you feel that bare limbs and piles of pruned brush are unsightly, consider planting vines to grow on them, such as Virginia creeper or clematis.

Nesting Sites

Different birds need different nesting places, and by providing a variety of locales in your garden, you will attract a bigger variety of birds. You can provide grasses and low foliage for ground nesters; some build their nests in shrubbery, others in tall tree limbs and cavities, and still others prefer tree trunks, ledges on buildings, walls, fence posts, and hedgerows. The wider variety of plants you have, the easier it is for birds to find natural materials for building nests.

Note: Only birds who normally use holes in trees for nesting, including chickadees, nuthatches, wrens, bluebirds and some swallows will utilize a birdhouse if you choose to erect one in your garden. Consult your local bird specialty retailer for the best kind for different species. Keep it away from the feeder, face it away from the prevailing wind, and hang it so that it is protected from predators. Keep the hanger short to prevent too much swinging.

So, think about attracting birds as you plan and plant your garden. You will reap the benefits as you enjoy their singing, their antics as they feed and bathe, their beauty as they fly in and out of your yard, their dedication as they sing for a mate, nest and raise their young, and you will share their joy in the return of spring each year!

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Authored by Mary Balzer, 25 August 2015

References

Attracting Birds, Sunset Books, Menlo Park, CA, 2000.

Colorado Wildscapes, Bringing Conservation Home. Audubon Colorado, Westcliffe Publishers, 2005