Vol. 53 No. 2 Spring 2019 olorado irds C The Colorado Field Ornithologists’B Quarterly

CFO PROJECT GRANTS

IN THE SCOPE: SEASONAL TIMING: SPARROWS

THE HUNGRY BIRD: COMMON BUCKTHORN

Colorado Birds | Spring 2019 | Vol. 53 No. 2 1 Colorado Field Ornithologists PO Box 929 Indian Hills, Colorado 80454 Cfobirds.org

Colorado Birds (USPS 0446-190) (ISSN 1094-0030) is published quarterly by the Colorado Field Ornithologists, P.O. Box 929, Indian Hills, CO 80454. Subscriptions are obtained through annual membership dues. Nonprofit postage paid at Louisville, CO. POSTMASTER: Send address changes to Colorado Birds, P.O. Box 929, Indian Hills, CO 80454. Officers and Directors of Colorado Field Ornithologists: Dates indicate end of current term. An asterisk indicates eligibility for re-election. Terms expire at the annual convention. Officers: President: David Gillilan, Denver, 2019*, [email protected]; Vice President: Christy Carello, Golden, 2019*, [email protected]; Secretary: Wendy Wibbens, 2019, [email protected]; Treasurer: Michael Kiessig, Indian Hills, 2019*, treasurer@ cobirds.org Directors: Amber Carver, Littleton, 2021*; Gloria Nikolai, Colorado Springs, 2021*; Christian Nunes, Lyons, 2019; Sue Riffe, Lyons, 2020*; Jason St. Pierre, Durango, 2019* Colorado Bird Records Committee: Dates indicate end of current term. An asterisk indicates eligibility to serve another term. Terms expire 12/31. Chair: Mark Peterson, Colorado Springs, [email protected] Committee Members: Lisa Edwards, Secretary; Peter Gent, Boulder, 2020*; Tony Leukering, Largo, Florida, 2018; Dan Maynard, Denver, 2020*; Kathy Mihm Dunning, Denver, 2018*; Christian Nunes, Longmont, 2019*; Steven Mlodinow, Longmont, 2019*, Jason St. Pierre, Durango, 2019*, David Dowell, 2021* Colorado Birds Quarterly: Editor: Christy S. Payne, [email protected] Staff: Christy Carello, Science Editor, [email protected], Monika Edgar, Layout, [email protected], George Mayfield and Jim Esten, Photo Editors; Georgia Doyle, Proofreading. Annual Membership Dues (renewable quarterly): Household membership (digital/web) - $25; Household membership (printed and mailed) - $35; Youth/student (digital/web) - $12; Institution (print) - $40; Foreign (digital) - $25. Membership dues entitle members to an online subscription to Colorado Birds, which is published quarterly. Back issues/ extra copies may be ordered for $7.50. Send requests for extra copies/back issues, change of address and membership renewals to [email protected]. Contributions are tax deductible to the extent allowed by law. COPYRIGHT ©2019 by Colorado Field Ornithologists. Reproduction of articles is permitted only under consent from the publisher. Works by U.S. and Canadian governments are not copyrighted.

50 Colorado Birds | Spring 2019 | Vol. 53 No. 2 Colorado Birds | Spring 2019 | Vol. 53 No. 2 51 The Colorado Field Ornithologists’ Quarterly | Vol. 53 No. 2 Spring 2019

President’s Message...... 52 David Gillilan

News from the Field: Spring 2018. . . . 54 David Dowell

The Hungry Bird: Common Buckthorn. . 60 David Leatherman

CFO Project Grants...... 68

CFO Project Grant: NE Colorado Raptors...... 70 James Dwyer, Melissa Landon, Angela Dwyer

CFO Project Grant: Colorado’s Cinnamon Teal...... 76 Casey Setash

CFO Project Grant: Colorado’s Barn Swallows ...... 82 Molly T. McDermott

In the Scope: Seasonal Timing: Pink-footed Goose, Broomfield County. 05 Sparrows...... 84 January 2019. Photo by Andy Bankert. Tony Leukering

Colorado Birds | Spring 2019 | Vol. 53 No. 2 51 PRESIDENT’S MESSAGE

This President’s Message is based on my gratitude for all the people who have made Colorado birding such a wonderful endeavor; in large part due to their selfless and unpaid efforts to make it that way, for both themselves and for a whole lot of us that enjoy birds and getting to know other birders. I am thinking about things like the effort to give birth to Cobirds, and all the people that have kept it (and other modes of bird communications such as the Rare Bird Alert and FaceBook and eBird) alive and vibrant. And all the people who have served on Colorado’s Bird Records Committee, and/or helped to create two breeding bird atlases. And those who put together the Colorado County Birding and other websites. And all the people that put together and run bird clubs, and bird festivals, and lead bird trips. There are way too many such people out there, so there is no point in trying to list them all. But I think you all know a bunch of those people that I am describing.

Speaking of which, one particular dedicated bunch of volunteer bird enthusiasts that I have had the pleasure to hang out with quite often the last handful of years (you may know them as “the CFO board”) certainly has been busy. The board recently met, during a blizzard, to make decisions as to what Colorado bird-related projects we will be funding this year. We on the board are grateful that the CFO membership supports these kinds of projects, for the sake of the birds, and the people studying and otherwise enjoying birds. This same dedicated bunch of volunteers are also busy putting together the upcoming convention in Montrose in June. And given that we will have some CFO board members stepping aside after the upcoming convention, as has been happening every year now for oh, over half a century or so, I am also grateful that we have continued to find competent volunteers to take their places, so that this organization will continue to achieve its goals. And of special note, I am grateful to be able to say that for the first time in well over two years we now have a complete staff for our journal, Colorado Birds. All it took was the recruitment of a layout professional, two photo editors, a proofreader, and someone to keep alive one of the journal’s most appreciated columns. All but one of those recruits are unpaid. Volunteers; you’ve gotta love ‘em. With gratitude, David

52 Colorado Birds | Spring 2019 | Vol. 53 No. 2 Colorado Birds | Spring 2019 | Vol. 53 No. 2 53 CFO MEMBERSHIP STRUCTURE

The new membership structure for those joining or renewing their membership in CFO starting January 1, 2019, is the following: Household membership (digital/web) - $25 (same price as previous household memberships Household membership (printed and mailed) - $35 Youth/student (digital/web) - $12 Institution (print) $40 Foreign (digital) - $25

Those who have paid for membership extending past January 1 will continue to receive printed journals through the term of their memberships. But anyone wanting to convert to digital/web-only access before the end of their membership can easily do so, by one of two ways: For those who have accounts on our website (free), log on to the website, which takes you to your membership profile. There you will see a blue button at the top of your profile labeled “Change Membership to Digital Journal.” Click on that button, and you will no longer receive printed editions by mail. (And while you are there, feel free to edit your profile with updated phone, address, etc.) OR, Go to the bottom of any page of our website, and on the left side you will see a place to “Contact CFO.” Click on that, then choose the subject “Membership Status or Question” from the drop-down menu, give your name, and tell us you want to convert to digital/web access only. Need help navigating the change? See the paragraph immediately above for instructions for contacting CFO regarding membership matters. CFO will alert members when new editions are posted on the website, using email, posts on CoBirds and the CFO Facebook page, and on the home page of the website. Please note that the emails are sent via Mail Chimp, so you may want to make sure your spam filter is allowing those emails into your inbox. A NOTE REGARDING THOSE WHO USE PayPal FOR AUTO PAY OF THEIR DUES: Members who use auto pay through PayPal will NOT need to change the amount of their payment if switching to web/digital memberships, because they are the same price as the former household membership ($25). But those with existing household memberships who wish to continue to receive printed and mailed editions of the journal will need to increase their payments to $35.

Colorado Birds | Spring 2019 | Vol. 53 No. 2 53 NEWS FROM THE FIELD

News from the Field: Spring 2018 (March-May)

DAVID DOWELL

News from the Field contains reports of rare birds found in Colorado. These reports are compiled from eBird (ebird.org), COBirds (groups.google.com/forum/#!forum/cobirds), and the West Slope Birding Network (birding.aba.org/maillist/CO02). The reports contained herein are largely unchecked, and the editors do not necessarily vouch for their authenticity. Species in capitals are those for which the Colorado Bird Records Committee (CBRC) requests documentation. Please submit your sightings of these “review” species through the CFO website at coloradobirdrecords.org. SPRING 2018 SEASON OVERVIEW

Spring is a time of anticipation and activity for Colorado birders. Seeing the first Cinnamon Teal of the year in February or March reminds one that longer days and a burst of flora and fauna will soon be here. The arrivals of Lincoln’s and Sagebrush Sparrows, shorebirds and herons, swifts and swallows, phoebes and hummingbirds, confirm that spring migration is indeed underway. The crescendo builds into May, when warblers and vireos make their brief but memorable stops on their way to their summer destinations. Singing birds are found statewide. In addition to offering these annual delights, Spring 2018 provided three new species to the Colorado state list. On March 22, Kaye Lafreniere photographed a Cactus Wren in Colorado Springs. Cactus Wren’s range in the US is from western Texas to southern California, including the Albuquerque, Sante Fe, and northeast high plains areas in New Mexico. Although these northern New Mexico locations aren’t far from Colorado, the Colorado Springs sighting is still surprising because Cactus Wren doesn’t typically wander far outside its established range. On April 7 and 8, Kenny Frisch documented a California Quail at the Canyon Visitor Center of Dinosaur National Monument, just east of the town of Dinosaur. California Quail had been considered a prime candidate for the Colorado list, as it is abundant in the nearby Vernal, Utah area, and undocumented sightings in northwest Colorado had been reported previously. On May 15, Glenn Walbek discovered a Golden- crowned Warbler at Mitchek Ranch on the eastern Colorado plains, and over 100 birders had the opportunity to view this rarity during the following 9 days (see Summer 2018 issue of Colorado Birds). Native to South and Central America including Mexico, Golden- crowned Warbler is a surprise for Colorado. In mid-April, two Anna’s Hummingbirds were seen simultaneously in Larimer and Boulder counties. Colorado birders appreciate the hospitality of Rachel Hopper and Alison Sheets for providing opportunities to view these rarities. A Ruff seen on April 27 in Kiowa and a Zone-tailed Hawk seen on April 28 in Douglas are candidate fifth state records in each case. Red Crossbills were found at several locations on the eastern plains from March – May, continuing an occurrence from fall and winter. In the list of reports below, county names are italicized, and the following abbreviations are used: CFO – Colorado Field Ornithologists; CG – campground; DFO – Denver Field Ornithologists; m.ob. – many observers; NA – Natural Area; NHS – National Historic Site; NG – National Grassland; NP – National Park; NWR – National Wildlife Refuge; Res. – Reservoir; SP – State Park; STL – State Trust Lands; SWA – State Wildlife Area.

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BRANT: 1 at Ketring Park and Lake and nearby locations in Arapahoe, 15 Feb – 13 Mar (Elaine Wagner, Doug Kibbe, m.ob.). Trumpeter Swan: 21 at Browns Park NWR, Moffat, 11 Mar (David Dowell, Kathy Mihm Dunning). Tundra Swan: 13 at Browns Park NWR, Moffat, 11 Mar (David Dowell, Kathy Mihm Dunning). White-winged Scoter: 1 at Lake Beckwith, Pueblo, 21 Nov – 28 Apr (David Silverman, m.ob.); an unusually long stay for this species in Colorado. Long-tailed Duck: 1 male in breeding plumage, Rio Blanco Res., Rio Blanco, 9 May (Vic Zerbi). Northern Bobwhite x Scaled Quail (hybrid): 1 at Lower Queens Res., Kiowa, 29 May (Steven Mlodinow). CALIFORNIA QUAIL: 1 at Dinosaur NM, Moffat, 7 Apr – 8 Jun (Kenny Frisch, m.ob.). Red-throated Loon: 1 at Neenoshe Res., Kiowa, 15 – 23 Apr (Steven Mlodinow, m.ob.). YELLOW-BILLED LOON: 1 at South Platte Res. (Arapahoe / Jefferson) and Chatfield SP (Douglas / Jefferson), 4 Jan – 11 Mar (Cynthia Madsen, Joey Kellner, Tony Leukering, m.ob.). 1 at Blue Mesa Res., Gunnison, 13 Feb and 18 Mar (Kathy Mihm Dunning, Dave Hawksworth). 1 at Pueblo Res., Pueblo, 27 – 29 Mar (Brandon K. Percival, Van Truan, m.ob.). NEOTROPIC CORMORANT: 1 at Upper Queens, Neenoshe and Lower Queens Res., Kiowa, 22 Apr – 20 May (David Ely, Steven Mlodinow, m.ob.). Broad-winged Hawk: 2 at Black Canyon of the Gunnison NP, Montrose, 19 Apr (Jean Bickal, Donna Kuhn, Eric Hynes, Donna and Doug Pomeroy, Brenda Brannen, Doug Gochfeld). 1 at Nucla, Montrose, 25 Apr (Coen Dexter). 1 at Buena Vista, Chaffee, 3 May (Iván Mota). 1 near Grand Junction, Mesa, 2 May (Caleb Strand, Joshua Smith). Other reports from front range and eastern plains. ZONE-TAILED HAWK: 1 at Chatfield SP,Douglas, 28 Apr (group led by Joey Kellner).

Black-throated Green Warbler, Prowers County, 07 May 2018. Photo by David Leatherman.

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HUDSONIAN GODWIT: 1 at Neenoshe Res., Kiowa, 27 Apr – 6 May (David Tønnessen, m.ob.). RUFF: 1 at Upper Queens/Neeskah Res., Kiowa, 27 Apr (David Dowell). Dunlin: 1 at Rio Blanco Res. and XTO Retention Pond, Rio Blanco, 23 – 24 Apr (Vic Zerbi, Gregg Goodrich, Bill Maynard, Lisa Edwards, Joe Roller, John Drummond). 1 at Upper Queens/Neeskah Res., Kiowa, 28 Apr (Janeal W. Thompson, Brandon K. Percival). Buff-breasted Sandpiper: 1 at Neenoshe Res., Kiowa, 22 May (Jim Merritt, David Tønnessen). Canada Warbler, Cheyenne County, 17 May 2018. May 2018. Photo by Peter Burke. LEAST TERN: 1 at Big Bottom viewpoint, Moffat, 22 – 23 May (Jan Leonard, Forrest Luke, Vic Zerbi). 1 at Sweitzer Lake, Delta, 30 May (Betty Fenton). SNOWY OWL: 1 near Neenoshe Res., Kiowa, 4 Mar (Doug Harbour, Janeal W. Thompson). 1 at Pawnee NG, Weld, 4 Mar (Gregg Somermeyer). LESSER NIGHTHAWK: 1 at Nucla, Montrose, 28 May (Coen Dexter). RUBY-THROATED HUMMINGBIRD: 1 in Lamar, Prowers, Brant, Arapahoe County, 01 March 2018. 29 Apr and 19 May (Janeal W. Thompson). 1 east of Photo by David Leatherman. Burlington, Kit Carson, 15 May (Glenn Walbek). ANNA’S HUMMINGBIRD: 1 in Fort Collins, Larimer, 12 – 15 Apr (Rachel Hopper, m.ob.). 1 in Eldorado Springs, Boulder, 12 – 13 Apr (Alison Sheets, m.ob.). Yellow-bellied x Red-breasted Sapsucker (hybrid): 1 at Lake Hasty, Bent, 9 – 10 Apr (Brian Gibbons, Michael O’Brien, Buffie Eicher, Janeal W. Thompson). Scissor-tailed Flycatcher: 1 at Pawnee NG, Weld, Cape May Warbler, Prowers County, 07 May 2018. Photo by David Leatherman. 4 May (Pratyaydipta Rudra). 1 at Campo, Baca, 5 May (Christine Alexander, Tyler Wilson, Jesse Casias, Steve Rash, Renee Casias). 1 near Lamar, Prowers, 20 May (Jane Stulp). 1 in Mosca, Alamosa, 14 May (John Rawinski). 1 near Ninaview, Bent, 20 May (Connie Kogler). 1 at Dillon Res., Summit, 21 May (M Walt). 1 near Boulder, Boulder, 22 May (Heidi Burgess). Philadelphia Vireo: 1 at Stulp Ranch near Lamar, Prowers, 15 May (Jane Stulp, Janeal W. Thompson). Blue Jay: 1 in Pagosa Springs, Archuleta, 15 May (Byron Greco, Ben Bailey). Pygmy Nuthatch: Chestnut-collared Longspur, Kit Carson 1 northwest of Kim, Las Animas, County, 15 April 2018. Photo by David 23 Apr (Christopher Pague, Bill Romme). Dowell.

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SEDGE WREN: 1 at Bonny SWA, Yuma, 12 May (David Dowell). CACTUS WREN: 1 in Colorado Springs, El Paso, 22 Mar (Kaye Lafreniere). Varied Thrush: 1 near Franktown, Douglas, 23 Dec – 19 Mar (Karen S. Metz). Golden-winged Warbler: 1 at Melody Tempel Grove, Bent, 7 May (Tyler Wilson, Alicia Arnold, Steve Rash, Jesse and Renee Casias). 1 at Akron Golf Course, Washington, 13 May (Mark Peterson). 1 at Stulp Ranch near Lamar, Prowers, 15 – 16 May (Jane Stulp, m.ob.). 1 at Prewitt Res., Logan, 20 May (Glenn Walbek, Steve Larson). 1 near Boulder, Boulder, 20 May (Ryan Bushong). Cape May Warbler, Boulder County, 13 May 2018. Photo by Peter Burke. Blue-winged Warbler: 1 at Upper Queens/Neeskah Res., Kiowa, 10 May (David Ely, Steven Mlodinow). 1 at Neenoshe Res., Kiowa, 13 May (David Dowell). 1 at Prewitt Res., Logan, 20 May (Glenn Walbek, Steve Larson). Black-and-white Warbler: 1 at Glenwood Springs, Garfield, 14 May (John Hogan). Prothonotary Warbler: 1 at Chatfield SP,Jefferson , 8 May (Meredith McBurney, Suzy Hiskey). 1 at McElmo Creek, Montezuma, 12 May (Mark). 1 at Golden-crowned Warbler, Cheyenne Co unty, Akron Golf Course, Washington, 13 May (Mark 22 May 2018. Photo by Janeal Thompson. Peterson). 1 near Estes Park, Larimer, 15 May (Sherrie Duris). SWAINSON’S WARBLER: 1 at Riverside Cemetery in Lamar, Prowers, 6 May (Dave Leatherman, m.ob.). Tennessee Warbler: 1 near Durango, La Plata, 13 May (Jason St. Pierre). LUCY’S WARBLER: 1 in Colorado Springs, El Paso, 14 – 25 Apr (Jim Merritt, David Tønnessen, m.ob.). House Finch, Boulder County, 28 March 2018. Photo by Jane Baryames. MOURNING WARBLER: 1 at Lamar Community College, Prowers, 9 May (group led by David Suddjian). 1 at Olney Springs Res. SWA, Crowley, 11 May (Mark Peterson). 1 at Two Buttes SWA, Baca, 11 May (Glenn Walbek, Joey Kellner, Kathy Mihm Dunning). 1 at Chico Basin Ranch, El Paso, 12 May (Steven Mlodinow). 1 at Brett Gray Ranch, Lincoln, 13 May (group led by Mark Peterson). 1 at Mitchek Ranch, Cheyenne, 16 – 18 May (Joey Kellner, David Tønnessen, Scott Somershoe, Norman Erthal, Brandon K. Percival, m.ob.). Summer Tanager, Jefferson County, 01 May 2018. Photo by Rob Raker.

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Zone-tailed Hawk and Turkey Vulture, Douglas County, 28 April 2018. Photo by Rob Raker.

Kentucky Warbler: 1 in Eads, Kiowa, 20 May (Sean Walters, Steven Mlodinow). Hooded Warbler: 1 in Crestone, Saguache, 6 May (Konchog Norbu). CAPE MAY WARBLER: 1 at Chico Basin Ranch, Pueblo, 2 – 12 May (B H, Steven Mlodinow). 2 at Stulp Ranch near Lamar, Prowers, 7 – 15 May (Jane Stulp, m.ob.). 1 at University of Colorado campus, Boulder, 12 – 13 May (Katie Lehman, David Haskell, m.ob.). Bay-breasted Warbler: 2 at Sylvan Dale Guest Ranch west of Loveland, Larimer, 19 – 20 May (CFO group led by Sue Riffe). Pine Warbler: 1 in Loveland, Larimer, 26 Dec – 10 Apr (John Reichhardt, m.ob.). 1 in Cherry Hills Village, Arapahoe, 18 – 21 Mar (Jared Del Rosso, G Stacks, m.ob.). Yellow-throated Warbler: 1 in Campo, Baca, 24 Apr (Tony Leukering). 2 in Pueblo, Pueblo, 26 Apr – 26 May (Van Truan, m.ob.). 1 at Thurston Res., Prowers, 7 May (Tyler Wilson, Alicia Arnold, Renee and Jesse Casias). 1 at Akron Golf Course, Washington, 13 May (Mark Peterson). Black-throated Green Warbler: 1 at Stulp Ranch near Lamar, Prowers, 7 – 10 May (Jane Stulp, Janeal W. Thompson, Brandon K. Percival). 1 at Lamar Community College, Prowers, 8 May (Brandon K. Percival). 1 at Upper Queens/Neeskah Res., Kiowa, 8 May (group led by David Suddjian). 1 at Akron Golf Course, Washington, 13 May (Mark Peterson). 1 at Flagler Res. SWA, Kit Carson, 19 – 20 May (Dale and Joel Adams, Chris Gilbert) GOLDEN-CROWNED WARBLER: 1 at Mitchek Ranch, Cheyenne, 15 – 24 May (Glenn Walbek, m.ob.). CANADA WARBLER: 1 at Mitchek Ranch, Cheyenne, 17 – 18 May (m.ob.).

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BAIRD’S SPARROW: As many as 11 at Meadow Spring Ranch, Weld, 9 May – 10 Aug (Andy Bankert, m.ob.). As many as 8 at Soapstone Prairie NA, Larimer, 16 May – 10 Aug (Andy Bankert, m.ob.). Fox Sparrow (Red): 1 at CSU Environmental Learning Center, Larimer, 5 Jan – 2 Mar (Carl Bendorf, Andy Bankert, m.ob.). Golden-crowned Sparrow: 1 at Chatfield SP,Douglas , 12 – 13 May (group led by Joey Kellner). Sagebrush Sparrow: Reports from 13 different locations in Arapahoe, Boulder, Douglas, Jeffersonand Larimer, 3 Mar – 13 Apr. Other reports from western and southern Colorado, 28 Feb – 29 May. Summer Tanager: 1 in Mosca, Alamosa, 24 May (John Rawinski). Scarlet Tanager: 1 at Lamar Community College, Prowers, 5 – 8 May (Pablo Quezada, Gabriel Wiltse, m.ob.). 1 at Chico Basin Ranch, Pueblo, 18 May (Jim Merritt, m.ob.). 1 at Clear Spring Ranch, El Paso, 20 May (Diane Roberts, Betty Glass, m.ob.). 1 in Eads, Kiowa, 27 May (Steven Mlodinow). Painted Bunting: 1 at Clear Spring Ranch, El Paso, 23 May (Steven Brown). Baltimore Oriole: 1 near Hayden, Routt, 21 – 23 May (Nancy Merrill, Tresa Moulton, m.ob.). Scott’s Oriole: 1 near Pueblo Mountain Park, Pueblo, 30 Apr (Larry Moore). 1 in Colorado Springs, El Paso, 14 -16 May (m.ob.). Other reports from La Plata, Mesa and Montezuma. Common Redpoll: 1 in Pagosa Springs, Archuleta, 6 Mar – 9 Apr (Byron Greco). 1 at Stulp Ranch near Lamar, Prowers, 4 Mar (Jane Stulp). Other reports from Boulder, Elbert, Garfield, Jefferson, Larimer, Sedgwickand Summit, 1 Mar – 22 Apr. Red Crossbill: 9 in Burlington, Kit Carson, 20 Mar (group led by David Suddjian). 6 at Fairmount Cemetery near Lamar, Prowers, 11 Apr (Dorothy Russell). 12 at Lamar Community College, Prowers, 29 Apr – 9 May (Janeal W. Thompson, m.ob.). 4 at Purgatoire River, Las Animas, 5 May (Tony Leukering, Steven Mlodinow). 22 at Carrizo Creek, Las Animas, 7 May (Steven Mlodinow). 7 in Yuma, Yuma, 12 May (Nick Moore). 1 at Crow Valley CG, Weld, 13 May (Ric Olson). 1 near Sheridan Lake, Kiowa, 15 May (Tony Leukering). ACKNOWLEDGMENTS

The sightings reported by contributing observers to eBird, COBirds, and the West Slope Birding Network are greatly appreciated. Volunteer compilers contributed significantly to this report: Joyce Takamine (COBirds), Coen Dexter (west), Forrest Luke (northwest), John Rawinski (San Luis Valley) and David Silverman. Much of the information in this report was obtained from the eBird Basic Dataset from the Cornell Lab of Ornithology, Ithaca, New York AUTHOR David Dowell [email protected]

Colorado Birds | Spring 2019 | Vol. 53 No. 2 59 THE HUNGRY BIRD

The Hungry Bird: Common Buckthorn

DAVID LEATHERMAN

The plots and counterplots of Nature, as played out in a life and death struggle called “evolution” never cease to amaze. Take for example, a woody plant we have all seen while birding named Common Buckthorn (Rhamnus cathartica). Other names for this plant are European Buckthorn, Hart’s-thorn, Christ’s thorn, French berries, purging buckthorn, rainberry-thorn, Rhineberry thorn, waythorn, yellow berry, cambrón (Spanish), neprun pergatif (French), purgier (German) and the one which, at least sounding it out, implies something (I’ll explain directly) harilik türnpuu (Russian) (Godwin 1943, Wyman 1971). Common Buckthorn is native to all of northern Europe east to Pakistan northeast into Russia, and also occurs in extreme northwestern Africa (CABI). It was introduced into North America, maybe as Figure 1. Common Buckthorn leaves and early as the late 1700s (Wyman 1971). Because fruit as they appear in late autumn-early of its origin and success on this continent since winter. The fruit is dark and in clusters. introduction, it is generally classified by botanists as The leaves are green long after those an “invasive exotic” (Archibold et al. 1997, Gourley of most other plants have turned color and Howell 1984, Haber 1997, Knight et al. 2007). or dropped. Leaf veination (with major Once you learn to identify it, and look for it, it is not veins branching from the midvein being hard to find in Colorado’s low elevation deciduous few, pale and arching toward the leaf tip) forests and riparian corridors. is somewhat distinctive. Photo by David Leatherman. It grows to 25 feet tall, tolerates a broad range of soil types and light conditions, but does best in deciduous forest habitats on sites that are sunny and well-drained. It leafs-out early in spring before most of its plant neighbors, and likewise, maintains its leaves in autumn an average of 58 days later than other deciduous plants (Godwin 1943, Wyman 1971). These early and late-leafing attributes give it a competitive advantage and contribute to both its carbon increase (“growth”) and reputation as “invasive”. Fodder for further condemnation, it is the alternate host to a rust disease, Puccinia coronata, impacting many important plants such as oats, barley and grasses (Munkvold 1996, Simons). In certain areas in certain years it can reduce oat crops 40% (Munkvold 1996). It also hosts the destructive soybean aphid, likewise an exotic from Asia (Ragsdale 2004). Common Buckthorn has an opposite leaf arrangement (other native buckthorns are alternate). It is dioecious, having male and female flowers born on separate plants. Its inflorescences are insect pollinated. The fruit, produced as early as a plant’s fifth growing season, is green at first, maturing to greenish-red, then purplish-black. These reproductive units are formally classified as drupes, meaning they have a fleshy exocarp (“pulp”) covering a single hard shell or pit. The pit contains up to four seeds. Spread via natural means, such as simple dropping from the parent plant, is minimal. The majority of its distribution, a key to success in the evolution game, is by birds, with a minor amount being facilitated by mammals (Haber 1997, Knight el al. 2007, Gale 2000 and 2001).

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Figure 2. Unripe, green fruits of Common Buckthorn at Grandview Cemetery, Fort Collins on 8 September 2010 (note, other fruits on this same plant were beginning to turn reddish, while a very few were mature (purplish-black). Photo by David Leatherman.

OK, so what about the purported ominous consequences of consuming this plant, specifically its fruit, as implied by its various names “cathartica”, “purging”, “purgier”, “pergatif” and, yes, “turnpuu” (like I said, not sure what this truly means but I’m hooked on phonics)? True, Common Buckthorn contains a secondary compound, emodin, which can have strong laxative effect on some animals. But the story is complicated. Secondary compounds are those which an organism, in this case a plant, does not absolutely need for its most important life processes: growth, development and reproduction. It can live without them. But such compounds usually do have a specialized purpose that in most cases enhances said organism’s survivability, fecundity or aesthetics (Cipollini and Levey 1997). Emodin affects if and when the fruits are consumed and how quickly they pass through the gut of an animal that consumes them (Izhaki 2002, Levey et al. 2007). The soybean aphid excepted, emodin prevents consumption of all buckthorn parts by almost all insects (Trial 1979). It does the same for mammals, or if they eat the fruits, causes diarrhea. Take heed all you Euell Gibbons wannabes: humans are mammals. The outright deterrence and/or extra quick passage of the fruit through mammals is a nifty evolutionary twist preventing damage to the all-important germ of future buckthorn life, the seeds. As for its effects on birds, the primary group facilitating buckthorn seed dispersal, emodin influences the proceedings in various ways. Most of these are largely beneficial to both the birds and the plant, not so much the rest of the local environment. Emodin is present in high concentrations in immature, green fruits. Birds normally detect this as noxious and avoid them (Sherburne 1972). Green fruits are present from mid-summer through early autumn (Figure 2). However, as the fruit matures and the seeds ripen, emodin levels decline. This enables safe consumption by birds at a time when many species are migrating and, thus, most likely to disperse seeds. In stark contrast to its effect on mammals, emodin in certain bird species actually slows down its digestive tract passage (Tsahar et al. 2003, Cipollini and Levey 1997). This allows better assimilation of pulp nutrients, nitrogen and other materials and may also enhance germination of seeds by stratifying the excreted pits (Tsahar et al. 2003, Wahaj et al. 1998).

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Figure 3. Live Common Buckthorn bush with green leaves next to a dead one about the same size. This illustrates both the green leaf retention of live buckthorns in comparison to willows and cottonwoods in the background, and the relative lack of woody vegetation in the immediate perimeter of the buckthorns. 24 November 2013, Centennial Park, Littleton, CO. Photo by David Leatherman. Thus, contrary to popular belief, birds do not suffer diarrhea, or death by overdose, from eating buckthorn berries any more than they do from any watery fruits. Yes, buckthorn birds make a mess, but so do all fleshy-fruit-eating birds (Craves 2011). One study calculated the number of mature fruits (with low emodin levels, remember) a bird would have to eat to be fatal. The figures for most species were so high as to be very unlikely in the wild (Schafer et al. 1983).

Figure 4. Western Tanager male at Grandview Cemetery in Fort Collins eating Common Buckthorn fruits on 30 September 2018. Note, most fruits have been removed, with only their stalks remaining. Photo by David Leatherman.

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Ecologically speaking, something spread by birds is described as “ornithochorous”. While birds may be the distributors, Common Buckthorn further enhances it chances of establishing on the drop site by restricting the growth of neighboring plants via endowment of certain compounds to the soil. This “allelopathy”, a distinct negative associated with the introduction of Common Buckthorn, reduces the existence of other plant species under them, changes soil chemistry and enhances exotic earthworm populations, among other things (CABI, Haber 1997, Knight et al. 2007). The relative lack of vegetation near buckthorns has been reported on occasion to increase erosion and, thus, lower water quality (Schwie 2014). One method considered for reducing exotic buckthorns in areas where they are detrimental to native ecology is prescribed fire (Gale 2000 and 2001, Gourley 1984). However, the lack of leaf litter (i.e., fuel) resulting from their plant-restrictive presence generally precludes successful application of this method.

Figure 5. Prothonotary Warbler male on 24 November 2013 at Centennial Park in Littleton, Colorado consuming Common Buckthorn fruits. Photo by David Leatherman.

Their early leafing entices nesting by certain native songbirds like American Robins. But when birds take the bait, studies show they then face greater predation losses due to nests being placed lower than they would be in native shrubs like viburnums or dogwood, by the general lack of protective thorns and by a branching structure that allows freer movement of predators (Schmidt and Whelan 1999). Considering all this, then, like other widely established non-native plants (Russian-olive comes to mind), Common Buckthorn has its pros and cons. Bird groups commonly reported to eat Common Buckthorn fruits are thrushes, waxwings, starlings and jays (Godwin 1943). The morsels are high in water, sugar, nitrogen and other nutrients. Sugar intake equates to high energy for migrants.

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Figure 6. The Prothonotary Warbler at Centennial Park in Littleton, CO consumed large quantities of Common Buckthorn berries over its multi-day stay. Photo taken 24 November 2013 by David Leatherman.

Since coming to Colorado in 1974, I have seen the following species consume Common Buckthorn fruits: Northern Flicker, Yellow-bellied Sapsucker, Tropical Kingbird, Red-naped Sapsucker, Cedar Waxwing, Hermit Thrush, Swainson’s Thrush, American Robin, Varied Thrush (Figure 7), Townsend’s Solitaire, Gray Catbird, European Starling, White-crowned Sparrow, White-throated Sparrow, Lincoln’s Sparrow, Dark-eyed Junco, Western Tanager (Figure 4), Prothonotary Warbler (Figures 5 and 6) and House Finch (Leatherman 2019). These probably constitute but a fraction of the species that at least sample the fruits. Perhaps Colorado’s most famous consumer of buckthorn fruits was the late November 2013 Prothonotary Warbler found by Art Hudak in Littleton’s Centennial Park (Figures 5 and 6). Another celebrated buckthorn bird was the male Varied Thrush seen by dozens, if not hundreds, or admiring birders a few miles west of Colorado Springs’ famous Broadmoor Hotel along South Cheyenne Creek in Cheyenne Canyon during the winter of 2018- 2019. The riparian habitat which held this bird and made it so predictable (“gettable” in lister lingo) contained overtopping ponderosa pines and Douglas-firs, with an understory dominated by Gambel oak and introduced Common Buckthorn. The Tropical Kingbird surprising finder and verifier Frank Ferrell and Mike Lester, respectively, and all of us near South Platte Reservoir in southwest Denver in autumn 2018, along with insects, ate a considerable amount of woody plant fruit. This individual far from its normal southern haunts ate the following tree fruits: Russian-olive, Chokecherry, Virginia Creeper (or Woodbine) and, yes, Common Buckthorn. A Carolina Wren that wintered in 2018-2019 along a section of the Goodnight Trail paralleling the Arkansas River west of the Nature Center in Pueblo was in a thicket heavily infused with Common Buckthorn. While I did not observe this individual consume buckthorn fruits during a visit on 17 January 2019, I suspect it might have done so on occasion, perhaps often. Vegetable matter is reported to only amount to about 6% of this species’ annual diet but likely constitutes a higher percentage during winter. Among the materials discovered in Carolina Wren stomach contents are seeds of bayberry, sweet

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Figure 7. Varied Thrush west of Colorado Spring near Starsmore Discovery Center, 14 January 2018. This individual was reported by birders feeding on area buckthorn berries for weeks. Photo by David Leatherman. gum, poison ivy, sumac, smartweed and other “weeds”. Acorn material and pulp from an unidentified fruit have also been found (Beal 1916). Colorado only has one native buckthorn, Smith’s Buckthorn (Rhamnus smithii). It is found on dry hillsides and areas of shale along the western tier of counties (Ackerfield 2015). Another species, Birchleaf-Buckthorn (R. betulifolia) may occur in the Four Corners region. Glossy Buckthorn (R. frangula), an introduced species, occurs along the central Front Range (Ackerfield 2015). I have no experience with these species and their utility to birds. Needless to say, Common Buckthorn is worth learning to identify by field birders. Woody draws and other habitats harboring it warrant investigation, particularly when fruit is present. Like many exotics that undeniably provide “environmental services”, it is neither all bad nor all good. Despite seeing a rare bird because of buckthorn, I would think it best to avoid the fleeting temptation to intentionally plant it. The birds will take care of putting it just about everywhere it will grow. Regardless of which way the scale tips when all aspects of Common Buckthorn are considered, I will never forget the incongruous elements of that scene in Littleton’s Centennial Park many years ago: snow; a streaking, legally off-leash greyhound flanked by its wingman wiener dog; green-leafed bushes laden with low hanging buckthorn fruit; and a hungry little warbler with molten gold head that missed the last call for Columbia.

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LITERATURE CITED

Ackerfield, Jennifer. 2015. Flora of Colorado. Botanical Miscellany No. 41. Bot. Inst. Of TX, Fort Worth. Archibold, O.W., D. Brooks and L. Delanoy. 1997. An investigation of the invasive shrub European buckthorn Rhamnus cathartica, near Saskatoon, Saskatchewan. Canadian Field Naturalist 111(4):617-621. Beal, F.E.L., W.L. McAtee and E.P. Kalmbach. 1916. Common birds of southeastern United States in relation to agriculture. USDA Farmers’ Bulletin 755. CABI. Rhamnus cathartica (buckthorn). https://www.cabi.org/isc/datasheet/46996 Cipollini, M. L., and D .J. Levey. 1997. Secondary metabolites of fleshy vertebrate-dispersed fruits: adaptive hypotheses and implications for seed dispersal. American Naturalist 150:346-372. Craves, Julie. 2011. http://net-results.blogspot.com/2011/11/myth-busting-birds- buckthron-and.ftml. Gale, S.W. 2001. Control of the invasive exotic Rhamnus cathartica in termperate North American forests. http://www.hort.agri.edu/00papers/gale.htm. Gale, Samuel. 2000. Control of the invasive exotic Rhamnus cathartica in temperate North American forests. Restoration and Reclamation Review 6:1-13. Godwin, J. 1943. Rhamnaceae. J. of Ecology 31:66-92. Gourley, L. C. and E. Howell. 1984. Factors in buckthorn invasion documented; control measure checked. Restoration and Management Notes 2:87. Haber, Erich. 1997. Invasive plants of Canada Project: common buckthorn. http://infoweb. magi.com/~ehaber-factbck.htm/>NationalBotanicServices, Ottawa,ON, Canada. Izhaki, I. 2002. Emodin – a secondary metabolite with multiple ecological functions in higher plants. New Phytologist 155:205-217. Knight, Kathleen S., Jessica S. Kurylo, Anton G. Endress, J. Ryan Stewert, Peter B. Reich. 2007. Ecology and ecosystem impacts of common buckthorn (Rhamnus cathartica): a review. Biological Invasions 9(8):925-937. Leatherman, David. 2019. The hungry bird: Observed Diet of a Tropical Kingbird in Jefferson County Colorado. Colorado Birds 53(1): 38 – 46. Levey, D. J., J. J. Tewksbury, I. Izhaki, E. Tsahar, and D. C. Haak. 2007. Evolutionary ecology of secondary compounds in ripe fruit: case studies with capsaicin and emodin. Pages 37-58 in A. J. Dennis, E. W. Schupp, R. J. Green and D. A. Westcott, eds, Seed Dispersal: Theory and its Application in a Changing World. CAB International, Cambridge, MA. Munkvold, Gary. 1996. Planting date important for oat disease. Dept. of Entomology, Iowa State Univ., Ames, Iowa. http://www.ipm.iastate.edu/ipm/icm/1996/3-25-1996/ oatdisdate.html

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Ragsdale, D., D. Voegtlin, R. O’Neil. 2004. Soybean aphid biology in North America. Annals of the Entomological Society of America 97(2):204-208. Schafer, E. W. Jr., W. A. Bowles, Jr., and J. Hurlbut. 1983. The acute oral toxicity, repellency and hazard potential of 998 chemicals to one or more species of wild and domestic birds. Arch. Environ. Contam. Toxicol. 12:355-382. Schmidt, K. A., C. J. Whelan. 1999. Conservation Biology, Wiley Online Library. Effects of exoticLonicera and Rhamnus on songbird nest predation, https://doi. org/10.1046/j.1523-1739.1999. Schwie, Cindy. 2014. https://friendsoftheparks.org/about-the-mississippi-river-bluff- restoration-project/ Sherburne, J. A. 1972. Effects of seasonal changes in the abundance and chemistry of the fleshy fruits of northeastern woody shrubs on patterns of exploitation by frugivorous birds. PhD Dissertation, Cornell University, Ithaca, NY. Simons, M. D., P. G. Rothman, L. J. Michel. 1979. Pathogenicity of Puccinia coronata from buckthorn and from oats adjacent to distant buckthorn. Phytopathology 69(2):156-158. Trial, H., Jr., J. B. Diamond. 1979. Emodin in buckthorn: a feeding deterrent to phytophagous insects. Canadian Entomologist 111(2):207-212. Tsahar, E., J Friedman, and I. Izhaki. 2003. Secondary metabolite emodin increases food assimilation efficiency of Yellow-vented bulbulsPycnonotus ( xanthogygos). Auk 120: 411- 417. Wahaj, S. A., D. J. Levey, A. K. Sanders, and M. L. Cipollini. 1998. Control of gut retention time by secondary metabolites in ripe Solanum fruits. Ecology 79:2309-2319. Wyman, D. 1971. Shrubs and vines for American gardens. New York, USA. MacMillan Co.

AUTHOR David Leatherman [email protected]

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NE Colorado Raptors Colorado’s Cinnamon Teal Colorado Barn Swallows

Golden Eagle and Common Raven, El Paso County, 11 February 2014. Photo by Bill Maynard. Golden Eagle and Common Raven, El Paso County, 11 February 2014. Photo by Bill Maynard

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YOUR DONATIONS HELP SUPPORT RESEARCH ON COLORADO BIRDS!

The Colorado Field Ornithologists Project Grants program provides small grants ($1,500 or less) for field ornithologists that are working on projects specific to Colorado birds. High priority for funding is awarded to those projects that best meet our mission of conserving and understanding Colorado birds. Every submitted proposal undergoes a thorough review by 2-3 reviewers that score each proposal using a comprehensive rubric. The proposals are then presented to the Board of Directors and voted on. Each year CFO funds 4-8 projects. Funding recipients are required to write a report for Colorado Birds and/or present during the paper session at the annual conventions. Many recipients do both. Following, you will find three articles by grant recipients from 2018. As a member of Colorado Field Ornithologists, we hope you feel proud to be a part of such an important endeavor for the conservation of birds that call Colorado home for at least part of the year.

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Swainson’s Hawk. Douglas County. 29 April 2018. Photo by Jim Esten.

Assessing Relationships between the Presence of Cattle and the Abundance and Productivity of Northeastern Colorado Raptors

JAMES F. DWYER (EDM INTERNATIONAL), MELISSA A. LANDON (EDM INTERNATIONAL), AND ANGELA M. DWYER (BIRD CONSERVANCY OF THE ROCKIES)

Raptors nesting in North America must cope with landscapes increasingly dominated by human activities and human impacts (Dwyer and DallaRosa 2015, Boal and Dykstra 2018, Dwyer et al. 2018). These activities can be obvious in urban areas, where high volumes of traffic and infrastructure are apparent even to human residents, but may be less obvious in non-urban areas where activities such as high-speed vehicle traffic, renewable and non- renewable energy infrastructure, agricultural production, and climatic impacts may not be as apparent to human observers. Understanding how ecological communities respond to human impacts is important to their management. Research to further that understanding was conducted by James F. Dwyer and Angela M. Dwyer. The work was funded in part by DFO’s Research, Conservation, and Education Grants Fund in 2018. In the 1930s, the U.S. Department of Agriculture established Central Plains Experimental Range (CPER) to research range management strategies, and to evaluate the long-term impacts of livestock on grassland communities (USDA 2017). Since 1939, CPER in northeastern Colorado has conducted research in rangeland ecology to study the effects of various biotic and abiotic responses to grazing and other management strategies on grassland communities (USDA 2017). Because CPER is viewed as a leader in range management, CPER’s research directly affects agricultural practices throughout the grasslands of eastern Colorado and beyond, impacting the management of wildlife populations well beyond CPER’s 63 square kilometer footprint. CPER has investigated the response of numerous species to management strategies over many decades and is home to three raptor species listed as Tier-1 species of greatest conservation need (CPW 2015) by Colorado Parks and Wildlife: Ferruginous Hawk, Golden Eagle, and Swainson’s Hawk. Research on CPER’s raptor community began in 2015 when Dwyer and Dwyer (2017) initiated a long-term study of the richness, abundance, and productivity of raptors at CPER.

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Ferruginous Hawk. RMNWR, Denver County. 14 December 2018. Photo by Jim Esten.

In this study, because the presence of grazing cattle is one of the primary human impacts in undeveloped areas, we compared raptor nest success (defined as any fledged young) and productivity (the number of fledged young) to the presence of cattle in the pastures within which raptor nesting occurs on CPER. STUDY AREA AND METHODS We conducted this study throughout CPER, a 15,500 acre agricultural research station composed of more than 70 fenced shortgrass prairie pastures at the western edge of the Pawnee National Grassland. CPER is used primarily to explore impacts of adaptive grazing (e.g., Augustine et al. 2010, Derner and Hart 2010, Dijkstra et al. 2012), but also contributes important information on relationships between grazing and native wildlife (Rebollo et al. 2013, Augustine et al. 2014, Newbold et al. 2014). For example, grassland avian ecology in general (Derner et al. 2009, Augustine and Baker 2013, Augustine and Derner 2015), and Mountain Plovers in particular, have been the focus of substantial research over the past decade (Augustine et al. 2008, Augustine and Derner 2012, Augustine and Skagen 2014).

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From 2015 through 2018, we used an existing road network to search for and monitor raptor nests throughout CPER. These roads provided access to all potential nesting substrates for raptors within CPER, allowing us to observe every nest, every one to four weeks from March through August. Cattle were present from May through October annually. During each observation, we used binoculars to quantify the presence of an incubating adult or hatched young in each nest. We used a Fisher’s exact test to evaluate nest success and a t-test to evaluate productivity, with both tests comparing nesting in pastures with cattle to nesting in pastures without cattle. We considered each test significant at = 0.05 and, for this report, we considered each nest independently each year even though some nests occurred in the same locations across years.

Golden Eagle. El Paso County. 01 February 2015. Photo by Bill Maynard.

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RESULTS From 2015 through 2018, we monitored 38 nests of four raptor species, Golden Eagle, Great Horned Owl, Red-tailed Hawk, and Swainson’s Hawk, on CPER. Nest numbers and densities varied from a high of 11 nests (0.17 nests/km2) in 2015 to a low of 7 nests (0.11 nests/km2) in 2016, though the proportion of nests producing young each year remained relatively stable ( = 60.8, SE = 4.3; Figure 1). Cattle were present in the pastures of 18 nests, 12 of which were successful. Cattle were not present in the pastures of 17 nests, 9 of which were successful. There was no difference in nest success as a function of cattle present in the pasture supporting the nest (Fisher’s exact test two-tailed P = 0.499). Nests in pastures with cattle fledged a total of 22 young. Nests in pastures without cattle fledged a total of 10 young. More young raptors were produced from nests in pastures with cattle (t = 2.78, df = 6, p = 0.032).

Figure 1. Number of nests and percent success of raptors nesting at the Central Plains Experimental Range (CPER).

DISCUSSION Though our sample size is small, our data suggest that raptors produce more offspring per nest on CPER when nesting in pastures occupied by cattle than in pastures without cattle. We hypothesize that if our long-term study continues to indicate this result, it may reflect the increased availability of small mammal prey in pastures containing cattle. Following an additional year of study, we will undertake more in-depth analyses. We will compare success and productivity to the presence of cattle as we have done here. We also intend to compare these response variables to the presence of cattle in the previous year, to the presence of cattle in the surrounding pastures, and to the number of cattle present. Based on our observations of nest failures following late spring storms, particularly hail storms, we also intend to compare our response variables to climatic factors and to consider the potential for non- independence between years when nests are present in the same locations over time.

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Research scientists working at the CPER aim to study range management strategies, and to evaluate the long-term impacts of livestock on grassland communities (USDA 2017). The analyses of a long-term dataset that we have planned will build on CPER’s program in general, and on our existing program investigating the abundance, fidelity, productivity, richness, and survival of raptors on CPER in particular. The accumulating work will contribute basic knowledge of Colorado’s raptor populations, with important implications to raptor populations throughout eastern Colorado where lessons learned at CPER are widely applied, particularly with respect to the number of cattle per acre stocked at CPER.

ACKNOWLEDGMENTS

We thank Colorado Field Ornithologists and Denver Field Ornithologists for partially funding this work. We thank Sharon Tinianow for comments which improved this writing. LITERATURE CITED

Augustine, D. J., S. J. Dinsmore, M. B. Wunder, V. J. Dreitz, and F. L. Knopf. 2008. Response of mountain plovers to plague-driven dynamics of black-tailed prairie dog colonies. Landscape Ecology 23:689-697. Augustine, D. J., J. D. Derner, and D. G. Milchunas. 2010. Prescribed fire, grazing, and herbaceous plant production in shortgrass steppe. Rangeland Ecology & Management 63:317–323 Augustine, D. J., and J. D. Derner. 2012. Disturbance regimes and mountain plover habitat in shortgrass steppe: large herbivore grazing does not substitute for prairie dog grazing or fire. The Journal of Wildlife Management 76:721–728. Augustine, D. J., and B. W. Baker. 2013 Associations of grassland bird communities with black-tailed prairie dogs in the North American Great Plains. Conservation Biology 27:324- 334, DOI: 10.1111/cobi.12013 Augustine, D.J., J. D. Derner, and J. K. Detling. 2014. Testing for Thresholds in a Semiarid Grassland: The Influence of Prairie Dogs and Plague. Rangeland Ecology & Management, 67:701-709. Augustine, D.J., and S.K. Skagen. 2014. Mountain Plover nest survival in relation to prairie dog and fire dynamics in shortgrass steppe. The Journal of Wildlife Management 78:595– 602; DOI: 10.1002/jwmg.700. Augustine, D. J., J. D. Derner. 2015. Patch-burn grazing management, vegetation heterogeneity, and avian responses in a semi-arid grassland. The Journal of Wildlife Management; DOI: 10.1002/jwmg.909. Boal, C.W, and C.R. Dykstra. 2018. Urban raptors: ecology and conservation of birds of prey in an urbanizing world. Island Press, Washington D.C. Colorado Parks and Wildlife (CPW). 2015. State Wildlife Action Plan: A strategy for conserving wildlife in Colorado. Available online at: http://cpw.state.co.us/aboutus/Pages/ StateWildlifeActionPlan.aspx

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Derner, J. D., W. K. Lauenroth, P. Stapp and D.J. Augustine. 2009. Livestock as ecosystem engineers for grassland bird habitat in the western Great Plains of North America. Rangeland Ecology & Management 62:111-118. Derner, J. D. and R. H. Hart. 2010. Livestock responses to complementary forages in shortgrass steppe. Great Plains Research 20:223-28. Dijkstra, F. A., D. J. Augustine, P. Brewer, and J. C. von Fischer. 2012. Nitrogen cycling and water pulses in semiarid grasslands: are microbial and plant processes temporally asynchronous? Oecologia 170:799-808. Dwyer, J.F., and J.P. Dalla Rosa. 2015. Use of anthropogenic nest substrates by Crested Caracaras. Southeastern Naturalist 14:N10-N15. Dwyer, J.F., and A.M. Dwyer. 2017. Raptor nesting on northeast Colorado’s Central Plains Experimental Range. Lark Bunting; Denver Field Ornithologists 53:7-8. Dwyer, J.F., S. Hindmarch, and G.E. Kratz. 2018. Chapter 14: Raptor Mortality in Urban Landscapes. In Boal, C.W, and C.R. Dykstra, Editors, Urban Raptors; Ecology and Conservation of Birds of Prey in an Urbanizing World. Island Press, Washington D.C. Newbold, T. A. S., P. Stapp, K. E. Levensailor, J. D. Derner and W. K. Lauenroth. 2014. Community Responses of arthropods to a range of traditional and manipulated grazing in shortgrass steppe. Environmental Entomology 43:556-568; DOI: http://dx.doi. org/10.1603/EN12333. Rebollo, S., D. G. Milchunas, P. Stapp, D. J. Augustine, and J. D. Derner. 2013. Disproportionate effects of non-colonial small herbivores on structure and diversity of grassland dominated by large herbivores. Oikos 122: 1757-1767. United States Department of Agriculture (USDA). 2017. Agricultural Research Service Rangeland Resources & Systems Research: Fort Collins, CO. Central Plains Experimental Range. Available online at: https://www.ars.usda.gov/plains-area/fort-collins-co/center- for-agricultural-resources-research/rangeland-resources-systems-research/docs/rrsr/central- plains-experimental-research-location/.

AUTHORS James F. Dwyer EDM International Melissa A. Landon EDM International Angela M. Dwyer Bird Conservancy of the Rockies

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CASEY SETASH

The collective noun for a group of Cinnamon Teal (Spatula cyanoptera) is a “seasoning.” Under a San Luis Valley (SLV) sunrise, various hues of pink and purple erupting from behind the Sangre de Cristo Mountains and illuminating clusters of awakening Cinnamon Teal, the moniker seems utterly fitting. This unique ecosystem in southern Colorado holds one of the densest breeding populations of Cinnamon Teal across their North American range, and at one point provided enough suitable wetland habitat to support the densest breeding population of waterfowl in North America (Gilbert et al. 1996). For this and many other reasons, I spent the summers of 2015- 2017 studying Cinnamon Teal for my master’s research under the watchful eye of Mount Blanca (and my advisor at Colorado State University, Dr. Bill Kendall). I had this amazing opportunity, in part, due to funding from the Project Funds offered by the Colorado Field Ornithologists. Although we try to capture hens to monitor their nests, the occasional drake Cinnamon In 2009, it was brought to the attention of the agency Teal swims into one of our traps. that manages our migratory birds, the U.S. Fish and Wildlife Service, that not enough information existed on Cinnamon Teal to set appropriately-informed harvest regulations. They are, after all, a game species, and it is imperative to evaluate how many birds survive, breed, and exist to allow for a sustainable harvest. This instigated a nationwide banding effort focused specifically on Cinnamon Teal. Banding, also known as ringing to our European counterparts, entails placing a small aluminum band on a bird’s leg inscribed with a unique numeric code. These codes are recorded and entered into a central database managed by the National Bird Banding Laboratory so that when banded birds are recaptured or harvested in the future, researchers can glean information about their location, survival, and movement. Cinnamon Teal provide a unique identification challenge during banding efforts. Banding is often conducted at the end of the summer once ducklings have fledged and before the hunting season begins. At this stage of the year, Cinnamon Teal look nearly identical to the closely-related Blue-winged Teal (Spatula discors), making a conclusive identification especially difficult. This means that banding in locations where Cinnamon Teal are known to breed in high densities relative to Blue-winged Teal is particularly important to sampling the correct populations. Enter: The San Luis Valley. In addition to banding, my project was initiated to assess nesting habits of the Cinnamon Teal, including the probability that a nest hatches at least one egg (i.e., nest survival), the habitat in which hens choose to nest, and the behavior of the birds on the nest throughout incubation. Breeding information was meant to augment the survival information being assessed via banding to provide a more robust picture of this understudied species.

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Cinnamon Teal hens can be (theoretically) distinguished from Blue-winged Teal by their more spatulate-shaped bill, buffier hues across their bodies, and the lack of a bright white patch under their bills.

In order to effectively explore the nesting habits of the Cinnamon Teal, I spent the summers of 2015-2017 traipsing through the wetlands of Monte Vista National Wildlife Refuge in search of nests. I, along with several cohorts of field technicians, conducted weekly counts, searched for nests on foot, and trapped birds in the hopes that we might attach radio transmitters to hens whose nests we could subsequently monitor.

Technicians search through stands of bulrush, sedges, rushes, and grasses for Cinnamon Teal nests on Monte Vista National Wildlife Refuge.

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Once we located nests, we had to ensure our monitoring efforts did not influence the birds’ reproductive effort in any way. We mitigated any effects we might have had by placing cameras at the nest site that allowed us to record videos of the birds and check that the nest was still active without having to flush them. We also limited the frequency with which we checked nests to reduce the probability that a hen would abandon it. We were able to estimate the approximate date ducklings would hatch using a technique called “candling” (Figure 1). If you’ve ever raised chickens, you might be familiar with how this is done. Essentially, we placed a small tube up to one of the eggs in a nest and held that egg up to a light (in our case, the sun) which allowed us to see the developing embryo and estimate its age.

Figure 1. A technician candles a Cinnamon Teal egg to see what developmental stage the ducklings have reached.

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We then returned to the nest on the hatch date and marked ducklings using a method called “webtagging” (Figure 2). This involved attaching a small, numbered tag to the webbing of each duckling’s foot as it was hatching, which allowed us to estimate how many ducklings survived to fledging by recapturing webtagged birds during banding operations on the refuge.

Figure 2. A numbered webtag is placed on the foot of hatching Cinnamon Teal ducklings to estimate survival.

So how many Cinnamon Teal are successful in their nesting attempts? Approximately 20% of nests hatch at least one egg according to our estimate. This may seem shockingly low, but perhaps explains their life history strategy of breeding at a relatively young age, having a short life span, frequently re-nesting, and having a large brood size in order to improve their chances of bringing one offspring to reproductive age. The nests of individual hens vary in their probabilities of success for a multitude of reasons. Vegetation characteristics might make them more susceptible to depredation, the condition of the hen might influence how attentive she is to her eggs, or particularly bad weather might wipe out all the nests across a region in some extreme cases. We evaluated many characteristics with the potential to affect nest survival and found that nests surrounded by a higher proportion of native grasses and a lower proportion of forbs (e.g., small, leafy plants like clovers, vetch, and yarrow) relative to what was available had a higher probability of success. This information is especially important in an area where habitat is actively managed to support migratory waterfowl. We think many of the forbs contributing to lower nest survival were likely invasive species like Perennial Pepperweed (Lepidium latifolium). The SLV Refuge Complex upholds a strict regimen of invasive plant removal to prevent low-quality habitat from running rampant, and will continue to do so given these recent findings.

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Technicians record vegetation measurements at a Cinnamon Teal nest on Monte Vista National Wildlife Refuge.

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We also used the cameras placed at the nest site to assess how behaviors during incubation affected nest survival and found that birds taking longer, less frequent recesses from their nests during incubation were more likely to hatch eggs. We believe this may be related to the increased likelihood of attracting predators caused by frequent comings and goings. We also found that hens spent less time on the nest overall when the ambient temperature was higher, and that they spent a greater proportion of the day incubating the closer the eggs were to hatching.

A Cinnamon Teal leaves her nest with her newly-hatched ducklings. This photo was captured using a trail camera located at the nest site.

Once ducklings hatch, they have a tough couple of months ahead of them before they are ready to migrate south. Roughly 50% of ducklings survived to fledging during our study period. We still do not have a thorough understanding of what drives duckling survival, although quite a bit of research exists assessing duckling survival of other waterfowl species. This research will go on to inform wildlife management agencies from the local level (e.g., Monte Vista National Wildlife Refuge) to the national level (The U.S. Fish and Wildlife Service’s Division of Migratory Birds) about appropriate management decisions. In the meantime, I will continue to appreciate Cinnamon Teal and the fact that I live in a place where, on any given summer day, they might spice up my life! LITERATURE CITED

Gilbert, D. W., D. R. Anderson, J. K. Ringelman, M. R. Szymczak. 1996. Response of nesting ducks to habitat and management on the Monte Vista National Wildlife Refuge, Colorado. Wildlife Monographs, 131:3-44. AUTHOR Casey Setash

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MOLLY T. MCDERMOTT, DEPARTMENT OF ECOLOGY & EVOLUTIONARY BIOLOGY, UNIVERSITY OF COLORADO BOULDER

INTRODUCTION Many songbirds that breed in North America, including Colorado, are long-distance migrants smaller than a fist (Pyle 1997). Due to their size, these birds are extremely difficult to track throughout the year. We lack information about migratory routes and the non- breeding portion of their life cycle (Marra et al. 2015). Where do migratory songbirds go in the winter, and how does their non-breeding environment impact breeding success the following year? Answering these questions will help us to conserve Colorado’s existing bird species and contribute to our understanding of their natural history. Barn Swallows are a migratory bird species found throughout the northern hemisphere, including all of Colorado, that nest almost exclusively on human infrastructure in both cities and rural agricultural areas. Due to loss of infrastructure, pesticide use, and other factors, Barn Swallow populations in North America declined 46% from 1966 to 2011 (Sauer et al. 2013). Swallows are important to humans ecologically and culturally. Farmers have long protected birds on their property, recognizing their value in reducing mosquitoes, flies, pests, and other undesirable insects (Brown and Brown 1999). Well-fed birds are more likely to complete migration and successfully attract a mate upon returning to their breeding grounds. However, we lack specific information about the migratory routes and non-breeding locations used by North American Barn Swallows, and how this might affect their breeding activities. We set out to fill this gap in knowledge by addressing the following questions: Question 1. Do Colorado’s Barn Swallows co-occur during the breeding season (i.e., how strong is migratory connectivity)? Question 2. How does food availability in non-breeding environments affect reproductive success? METHODS We are using two methods to link individual birds to specific non-breeding locations: geolocator tags and feather isotopes. Just prior to fall migration, we tagged 72 adult birds and took feather samples. In spring 2019 we will collect tags, take feather samples, and monitor nests of returning birds. Adult Barn Swallows are highly site-faithful, often returning to the same barn or even the same nest, increasing chances of tag recovery. Feather isotope analysis takes advantage of the unique isotopic signatures of different parts of the world encoded in feathers to get a rough estimate of non-breeding location. Collecting feather isotopes is less invasive and cheaper than tags, allowing us to survey additional birds. To characterize migratory connectivity (Question 1), I will map the locations occupied by Barn Swallows from Colorado in the non-breeding season, and use distance metrics to quantify connectivity. To address how reproductive success is affected by non-breeding conditions (Question 2), I will model the number of offspring fledged as predicted by several metrics of body condition (estimates of food availability from environmental parameters in non-breeding areas, stress hormones, feather condition, and feather color).

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PROGRESS SO FAR During summer 2018, other lab members and I monitored 286 adult Barn Swallows at 15 breeding colonies around Boulder County that vary in size from 2-100 birds. We banded and measured adults, observed nesting chronology, and banded and measured all nestlings. With the support of Colorado Field Ornithologists and others, I was able to purchase geolocator tags that track a bird’s movements during migration and the non-breeding season. In August we deployed 72 geolocators on adult Barn Swallows (Figure 1). When they return in spring 2019, we will collect the tags and I will report on their migratory routes and likely wintering range.

Figure 1. CU Boulder graduate students Molly McDermott (left) and Sheela Turbek (right) fit a Barn Swallow with a geolocator tag at a colony in Hygiene, CO. LITERATURE CITED

Brown, C. R., & Brown, M. B. (1999). Barn Swallow (Hirundo rustica). In The Birds of North America (A. F. Poole and F. B. Gill, Editors). Ithaca, NY, USA: Cornell Lab of Ornithology. Retrieved from https://doi.org/10.2173/bna.452 Marra, P. P., Cohen, E. B., Loss, S. R., Rutter, J. E., and Tonra, C. M. (2015). A call for full annual cycle research in animal ecology. Biology Letters, 11(8), 20150552. https://doi. org/10.1098/rsbl.2015.0552 Pyle, P. (1997). Identification guide to North American birds: a compendium of information on identifying, ageing, and sexing “near-passerines” and passerines in the hand. Slate Creek Press. Sauer, J. R., Link, W. A., Fallon, J. E., Pardieck, K. L., and Ziolkowski Jr., D. J. (2013). The North American breeding bird survey 1966–2011: summary analysis and species accounts. North American Fauna, 79(79), 1–32. AUTHOR Molly T. McDermott Department of Ecology & Evolutionary Biology, University of Colorado Boulder

Colorado Birds | Spring 2019 | Vol. 53 No. 2 83 CFO PROJECT GRANTIN THE– COLORADO’S SCOPE CINNAMON TEAL Seasonal timing: Sparrows

TONY LEUKERING

Some five years ago, I published a piece in this column on the use of seasonal timing as an aid to bird identification (Leukering 2014). That piece was focused on a suite of Colorado species – small, green flycatchers -- that presents among the most-difficult identification challenges in Colorado birding. While the reader can find that piece on the Colorado Field Ornithologists’ website (see link provided in the Literature Cited section, below), some of the introductory material deserves repetition here (with some slight editing). Amongst the most-used criteria brought to bear on bird identification by expert birders is likelihood. Not just likelihood as to whether one finds Species X swimming on lakes or Species Y occurring in the Northern Hemisphere, but the likelihood of occurrence of Species Z at this place, and ON. THIS. DATE. Though many birders seem to think that migration is migration is migration, that is far from the case. Even in spring migration, which is a phenomenon much more compressed in time than is fall migration for most bird species, different species move at different times, and the details – arrival, peak, completion – have been refined over and over through the millennia, with most of the outliers being culled from the breeding population. So, while individual birds do show up outside the typical migration seasons of their respective species, the percentage of individuals that do so is miniscule. The penalty for a bird that arrives too early in spring may well be dying of starvation – death of the individual. A migrant arriving too late may find all of the good territories and/or good mate choices taken – death of those genes that do not get passed on. It is a well-known aphorism that any book that includes information on spatial or temporal occurrence of birds is out-of-date even before it is published. One of the driving forces in making that statement true is that organisms are constantly pushing the occurrence envelope, typically via variation in genetics; it is an evolutionary safeguard against changing conditions. Oh, such efforts do not always work – species do go extinct, but it can allow for alteration in any number of aspects of bird occurrence (e.g., habitat, wintering area, spring- migration timing), and there is a large body of published works on just such. Though bird books, perforce, present out-of-date temporal-occurrence summations, as noted by Leukering (2014), eBird (www.ebird.org) presents up-to-date knowledge of spatial and temporal bird occurrence and I feel that it is greatly under-utilized by Colorado’s – and the rest of the world’s – birders, particularly as that facet that can inform on bird identification. The back cover of this issue presents temporal-occurrence graphs taken from eBird. These graphs point out how typical occurrence timing might inform on one’s field- identification skills.In fact, at least some skilled, experienced Colorado birders could figure the species involved solely from the occurrence parameters! ––Nota Bene–– For those that are interested in developing their own data comparisons in eBird but that do not know how to go about it, I have written a post on the Colorado-Wyoming eBird blog (Leukering 2019). This post – Getting Information From eBird – uses a step-by-step process to obtain occurrence graphs such as those presented in this essay. The post can be accessed by entering this web address – https://tinyurl.com/gettingeBirddata – into your Internet browser.

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THE USEFULNESS OF SEASONAL TIMING First, a caveat: I do not encourage identification solely on likelihood, just as I do not encourage using a single plumage character or other appearance feature, as the basis of identifications. However, incorporating knowledge of what is typically found when will greatly assist in elevating the percentage of correct identifications. Histograms (graphs): In the histograms used in this paper’s figures, the x axis (horizontal) represents the calendar, with each month divided into four weeks beginning on the 1st, 8th, 15th, and 22nd, with the last “week” varying from 7.25 to 9 days long. The y axis is frequency – that is, the percentage of eBird checklists from that region during that time period that reported the presence of that species. When looking at larger regions (such as counties or Colorado’s plains), even common species rarely see frequencies in these presentations much above 20% (that is, occurrence on 1 in every 5 checklists). All histograms used here use all relevant public eBird data as of 15 February 2019. Some histograms refer to the entire state of Colorado, while others refer to individual West Slope and eastern-plains subsets of counties. I selected a set of five counties to represent the West Slope: Delta, La Plata, Mesa, Montrose, and Routt. All five counties host a large elevational gradient (unlike counties such as San Juan that are strictly, or nearly so, montane) and cover the latitudinal breadth of the state. They are also, possibly, the five most-heavily birded counties on Brewer’s Sparrow. North Park. 30 August 2009. the West Slope with that large elevational Photo by Peter Burke. gradient (thus ruling out Summit), resulting in a more-robust data set to analyze. I selected nine counties to represent the eastern plains: Adams, Arapahoe, Logan, Morgan, Prowers, Sedgwick, Washington, Weld, and Yuma. I chose these counties primarily to exclude foothill and montane areas from consideration, as areas of topographic relief and the plains have quite different suites of breeding birds. I surmise that these are also the most heavily birded plains counties that lack even foothills. In construction of the data filters that are the backbone of eBird data quality, I used the frequency value of 1% as a guideline indicating “rarity” -- that is, less than 1 of 100 eBird checklists recording that species in that area in that week. Here I use that same guideline to suggest that particular care should be made in identifying that species at that time and at that location.

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I present, in two sets of four species each, the occurrence parameters in Colorado of eight sparrow species, seven of which breed in the state: Chipping and Brewer’s (Spizella passerina and breweri, respectively), Vesper (Pooecetes gramineus), Savannah (Passerculus sandwichensis), Song and Lincoln’s (Melospiza melodia and lincolnii, respectively), and White-crowned (Zonotrichia leucophrys). The first of these sets is those lacking significant streaking on the underparts (here termed “unstreaked”), though I divide it into two subsets: Chipping and American Tree (Spizelloides arborea) sparrows and Brewer’s and White- crowned sparrows. I make that further split of species to highlight the very strong differences in occurrence parameters between the two species of the first subset, as birders frequently confuse the two. The second set houses sparrows that are generally more or less heavily streaked below (“streaked”): Savannah, Vesper, Song, and Lincoln’s sparrows. With the above, though, there are further caveats. All Colorado-occurring sparrows are streaked below as juveniles (including juncos and towhees). However, with one important exception, virtually all individuals of all eight species molt out of most of their juvenile plumage before migrating. While there are partial exceptions to this “rule” among species not discussed here (e.g., White-throated and Swamp sparrows), juvenile Chipping Sparrows breeding in western North America usually move long distances in post-breeding dispersal and migration wearing all or much of their juvenile plumage (Pyle 1997 pg. 557, Floyd 2011). In fact, some are still sporting obviously streaked underparts into October! For those with even a little interest in learning more about molt in birds, I suggest (and cannot praise more highly) Steve Howell’s very accessible treatment of the subject (Howell 2010). Sparrow Occurrence Patterns – The Passerellidae (New World sparrows; formerly considered part of the mostly Old World family, Emberizidae) houses many species, the predominant color of most being brown, and these species cause many birders identification consternation. While this essay is not the venue for detailed discussion of differentiating the various Colorado species, gross aspects of size; shape; relative tail length; and extent, color, and definition of any streaking below can quickly winnow the choices. Do not forget leg color; most sparrows have pink legs (Leukering 2015), but some have dark legs. Throw in location and date, and one is often left with only one or two options. I present histograms of temporal occurrence for eight sparrow species of relatively common and widespread occurrence in Colorado; Figures 1-3 on this issue’s back cover and Figures 4-8 placed in the body of the text. Of these, all but one breed in the state: Note that the occurrence parameters of White-crowned Sparrow are complicated by the fact that the breeding subspecies, oriantha (called Mountain White-crowned Sparrow), is replaced in winter by the taiga-breeding gambelii (Gambel’s White-crowned Sparrow). I do not here treat the two subspecies’ differences in occurrence in the state (though see Leukering and Mlodinow 2017), instead, presenting parameters at the species level. American Tree Sparrow is the eighth species and differs from all the others in that it occurs in Colorado only in the colder months.

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UNSTREAKED SPARROWS, SUBSET 1: CHIPPING SPARROW VS. AMERICAN TREE SPARROW While Chipping and American Tree sparrows share quite a few plumage features (including gray rump and upper-tail coverts), there are many differentiating factors in color of soft parts (Leukering 2015) and plumage parts (bill, eyeline, upper sides, and legs are just a few). However, perhaps the most distinctive difference between the two is that there is, essentially, very little overlap in the two species’ temporal occurrence in Colorado (Figures 1-3 on back cover). Figures 1, 2 (Back Cover). Frequency of detection on Colorado eBird checklists of Chipping and American Tree sparrows presented in two fashions. See Histogram text for explanation of “weeks.”

Figure 3 (Back Cover). Frequency of detection on eBird checklists of Chipping and American Tree sparrows in nine eastern-plains Colorado counties (see text for enumeration of counties). See Histogram text for explanation of “weeks.” The line graph in Figure 1 (back cover) presents eBird data from Colorado and indicate that the only time in the year in which neither species is rare (rare defined as <1% frequency)at the same time is the last two weeks of October. More specifically, American Tree Sparrow Colorado- occurrence frequency drops below 1% in spring before Chipping Sparrow frequency rises to or above 1%, so there is essentially no spring overlap of the two species. In fact, in the first week of April – where the two species’ frequency curves cross heading in opposite directions, those frequency values represent totals of only 185 Chipping and Song Sparrow. Morrison County. 25 February 111 American Tree sparrows… in all of Colorado 2013. Photo by Peter Burke. and in all years combined (eBird 2019). Compare those values to the individual peaks of abundance – 58,572 Chipping Sparrows in the second week of May and 15,113 American Tree Sparrows in the last week of December – and one can readily see the insignificance of those first-week-of-April totals. Additionally, note that the respective peak-number weeks are only two weeks from being exactly six months apart! I have included the bar graph of Figure 2 (back cover) as another representation of the data set involved in Figure 1 (back cover); some readers may understand the difference in seasonal-occurrence timing of the two species better in this histogram (the top bar graph represents Chipping Sparrow). Figure 3 (back cover) presents a comparison of frequency histograms of these same two species, but only in eastern-plains counties. Note that the Chipping Sparrow histogram is more complex than the one using data from the whole state. The difference is that Chipping Sparrow is essentially absent from the plains as a breeding species; note the two confirmed breeding reports from Weld Co. (Ortega 2016). Thus, except for the much-lower frequency of Chipping in June and early July, the parameters of the graph in Figure 3 (back cover) are essentially the same as those of the statewide graph, with frequency curves crossing in the same weeks and with both species’ frequency values being ≥1% at the same time only in the last two weeks of October.

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UNSTREAKED SPARROWS, SUBSET 2: BREWER’S AND WHITE-CROWNED SPARROWS Unlike the two species in the first subset of unstreaked sparrows, birders probably only rarely confuse Brewer’s and White-crowned sparrows each for the other; highlighting the two species in the first subset results in this dichotomy. Two features are obvious in Figure 4, the first being the higher detection rate of White-crowned Sparrow over nearly the entire year and the second that Brewer’s Sparrow is not present during the colder months (contra White-crowned Sparrow). One confounding aspect of the first feature is probably birders’ preference for visiting the generally higher-elevation habitats of White-crowned Sparrow in summer, rather than Brewer’s Sparrow’s favored sagebrush flats. There are certainly other confounding factors, as I believe that Brewer’s Sparrow has a higher (much higher?) overall breeding abundance in Colorado than does White-crowned Sparrow, considering the huge swaths of the state that host breeding Brewer’s Sparrow, while White-crowned Sparrow has a relatively narrow (figuratively and literally) choice of breeding habitats. In fact, the most- recent Colorado Breeding Bird Atlas (CBAP 2016) found Brewer’s Sparrow in 484 atlas blocks and White-crowned Sparrow in just 348 (Magee 2016, Opler 2016).

Figure 4. Frequency of detection on Colorado eBird checklists of Brewer’s and White-crowned sparrows. See Histogram text concerning explanation of “weeks.” The only time during the year that Brewer’s Sparrow detection rate climbs higher than that of White-crowned Sparrow in the state is in the four weeks from the second week of August through the first week of September. I believe that a cause of this shift in relative detection rates of the two species is a change in birder focus. In early fall, a large percentage of eastern Colorado birders (which greatly outnumber western Colorado birders) moves from a stronger-than-usual focus on foothill and montane birding to a strong focus on migration on the plains, particularly the migration of shorebirds (pers. obs.). The lack of White-crowned Sparrows among the hordes of migrant sparrows on the plains in that period (Figure 5) probably accounts for at least some of the change in statewide relative detection rates (Figure 4). However, looking at West Slope data (Figure 6), we can see that Brewer’s Sparrow detection frequency is also higher there during early fall, but with only three weeks in that period (as compared to the state-level four-week period). So, either White-crowned Sparrows get really secretive in early fall (possibly due to molting at that time; see discussion below) or West Slope birders also concentrate on low-elevation habitats in early fall; perhaps both are true.

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Figure 5. Frequency of detection on eBird checklists of Brewer’s and White-crowned sparrows in nine eastern-plains Colorado counties (see text for enumeration of counties). See Histogram text for explanation of “weeks.”

Figure 6. Frequency of detection on eBird checklists of Brewer’s and White-crowned sparrows in five West Slope Colorado counties (see text for enumeration of counties). See Histogram text for explanation of “weeks.”

STREAKED SPARROWS These four sparrow species – Savannah, Vesper, Song, and Lincoln’s -- are the cause of many identification headaches, with all being confused with each other by many birders at various times. Lincoln’s is something of the odd-man-out species here, though, as its underparts streaking is always laid over buff coloration; the streaking of the other three is mostly or entirely laid over white or whitish on non-juvenile-plumaged individuals. Though various structure differences (e.g., bill shape, head shape, tail length and shape) are quite useful identification cues, these differentiating features require fairly extensive experience with all species in order to use them reliably.

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During the breeding season, habitat is a powerful identification predictor, though where preferred habitats abut, one can encounter more than one species in proximity. Additionally, Song and Lincoln’s sparrows occupy similar riparian habitat (though Lincoln’s also breeds on brushy hillsides with seeps; pers. obs.), but are, for the most part, elevational replacements of each other, with Song Sparrow being found at lower elevations. That Song Sparrows are very strongly tied to shrubby riparian habitat as breeders in Colorado (and throughout the West) causes Eastern birders problems, as the species is nearly ubiquitous in shrubby habitat within the core of the eastern breeding range. Song Sparrow does not typically breed in Colorado in drier shrub-dominated habitats (e.g., Four-winged Saltbush, Gambel Oak, or Mountain Mahogany) (Henwood 2016). Seasonal timing can also inform on these species’ identification. Figure 7 presents Colorado- wide eBird frequency data for these four sparrow species; some aspects of the various species curves differ in obvious ways. One is that Song Sparrow weekly frequency values are all higher than all Savannah Sparrow frequency values (though, again, beware of the local habitat during the breeding season). In fact, except for a small number of weeks of the year, Song Sparrow is consistently the most frequently detected sparrow of this species suite. The other obvious take-home message is that Song Sparrow is found commonly throughout the year (that is, frequency values are always >1%). Savannah, Vesper, and Lincoln’s are all rare in the state in winter, with Vesper being particularly rare. Interestingly, and also obvious in Figure 7, by the time that Song Sparrow has reached its fall frequency peak in Colorado (in the last week of October), the other species have, essentially, left the state.

Figure 7. Frequency of detection on Colorado eBird checklists of Savannah, Vesper, Song, and Lincoln’s sparrows. See Histogram text for explanation of “weeks.”

Another interesting aspect of Figure 7 is the strong August dip in frequency of detection of Song Sparrow, similar to that of White-crowned Sparrow (Figures 4, 6) and Vesper and Lincoln’s sparrows (Figure 7). One’s first reaction to that dip might be that there are, for some reason, many fewer Song Sparrows in the state in August. However, detection frequency is not necessarily equal to actual presence. In fact, that equivalency is virtually never true, for a large variety of reasons, some having to do with the birds, themselves (e.g., vocalization rate, behavior, habitat selection), and some with the observers (e.g., hearing and vision capability, skill and experience levels). In fact, this “post-breeding frequency dip” is a feature of detection curves of many bird species (Best 1981, eBird 2019) and is partly due to the cessation of or decline in singing activity (pers. obs.). Molt, also, probably

90 Colorado Birds | Spring 2019 | Vol. 53 No. 2 Colorado Birds | Spring 2019 | Vol. 53 No. 2 91 CFO PROJECT GRANTIN THE– COLORADO’S SCOPE CINNAMON TEAL plays into this detection dip, as adults of many bird species (but nowhere near all) initiate replacement of their plumage around the time that any progeny achieve independence. Especially when such birds are replacing flight feathers (primaries, secondaries, rectrices), their flight capabilities are somewhat reduced, hence birds may become more secretive during the process (Vega Rivera et al. 1998). Additionally, birds may move into or spend a higher proportion of time in denser habitats than earlier in the breeding season, again reducing the chance that birders detect their presence (McClure and Hill 2012). However, changing focus of eBirders in late summer and early fall may also have some impact on this frequency dip. The result of the departure of Savannah, Vesper, Lincoln’s – and of Lark Bunting and Fox Sparrow – means that Song Sparrow is the default streaked sparrow in the state during most of the colder portion of the year. As summary, Table 1 provides various parameters of seasonal occurrence of seven of the eight species treated in this essay. Finally, Figure 8 provides the weekly sample sizes of public eBird checklists for the state of Colorado (as of 22 February 2019). TABLE 1. Temporal occurrence parameters in Colorado of seven breeding sparrow species, as presented by public data at eBird (2019).

Figure 8. Weekly sample size of Colorado eBird checklists (as of 22 February 2019). See Histogram text for explanation of “weeks.”

ACKNOWLEDGMENTS

I greatly appreciate Ted Floyd’s thorough review of an earlier draft of this essay. Any remaining mistakes are certainly mine.

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LITERATURE CITED

Best, L. B. 1981. Seasonal changes in detection of individual bird species. Studies in Avian Biology No. 6:252-261. https://tinyurl.com/Best1981 Colorado Bird Atlas Partnership [CBAP]. 2016. The Second Colorado Breeding Bird Atlas (L. Wickersham, Ed.). Colorado Bird Atlas Partnership, Denver. eBird. 2019. eBird: An online database of bird distribution and abundance [web application]. eBird, Ithaca, New York. Available: http://www.ebird.org. (Accessed: 22 February 2019). Floyd, T. 2011. Mid-summer dispersal, nocturnal movements, and molt migration of Chipping Sparrows in Colorado: Taxonomic implications and conservation applications. Colorado Birds 45:181-197. Henwood, M. 2016. Song Sparrow. In The Second Colorado Breeding Bird Atlas (L. Wickersham, Ed.). Colorado Bird Atlas Partnership, Denver, CO. Howell, S. N. G. 2010. Molt in North American Birds. Houghton Mifflin Harcourt, New York. Leukering, T. 2014. Seasonal timing: Small, green flycatchers. Colorado Birds 48:249-254. [https://cobirds.org/CFO/ColoradoBirds/InTheScope/54.pdf] Leukering, T. 2015. Soft parts: Leg color in passerines. Colorado Birds 49:117-118. [https://cobirds.org/CFO/ColoradoBirds/InTheScope/59.pdf] Leukering, T. 2019. Getting information from eBird. Colorado-Wyoming eBird blog. [https://tinyurl.com/gettingeBirddata (Accessed: 2 March 2019)] Leukering, T. and S. G. Mlodinow. 2017. Selected bird subspecies of interest in Colorado: Part I. [https://cobirds.org/CFO/ColoradoBirds/InTheScope/78.pdf] Magee, P. 2016. Brewer’s Sparrow. In The Second Colorado Breeding Bird Atlas (L. Wickersham, Ed.). Colorado Bird Atlas Partnership, Denver, CO. McClure, C. J. W. and G. E. Hill. 2012. Dynamic versus static occupancy: How stable are habitat associations through a breeding season? Ecosphere 3:1-13. [https://tinyurl.com/ McClureHill2012] Opler, P. A. 2016. White-crowned Sparrow. In The Second Colorado Breeding Bird Atlas (L. Wickersham, Ed.). Colorado Bird Atlas Partnership, Denver, CO. Ortega, J. C. 2016. In The Second Colorado Breeding Bird Atlas (L. Wickersham, Ed.). Colorado Bird Atlas Partnership, Denver, CO. Pyle, P. 1997. Identification Guide to North American Birds, Part I. Slate Creek Press, Bolinas, CA. Vega Rivera, J. H., W. J. McShea, J. H. Rappole, and C. A. Haas. 1998. Pattern and chronology of prebasic molt for the Wood Thrush and its relation to reproduction and migration departure. Wilson Bulletin 110:384-392. [https://tinyurl.com/VegaRivera1998]

AUTHOR Tony Leukering PO Box 52, Wiley, CO 81092 ([email protected])

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Instructions for contributors to Colorado Birds Colorado Birds is devoted to the field study of birds in Colorado. We invite you to submit articles of general or scientific interest for publication. Authors are encouraged to submit materials that contribute to the enjoyment and understanding of birds in Colorado. The preferred submission method is via email attachment to the Colorado Birds editor, [email protected]. Submissions may be edited for length and content. Photos or other art may be submitted in black and white or color. Files should be saved as high-resolution jpeg or similar format and must be a minimum of 900 x 750 pixels. Potential cover images must be at least 2625 (vertically) x 1725 (horizontally) pixels. For cover photos, it is also important to remember that there needs to be space at the top of the image for the journal title, etc. Please DO NOT save photos in MS Word or otherwise embed within a document. Include photo captions along with the photographer’s name, where and when taken, and other relevant information. All photos should be sent to the Colorado Birds editor, [email protected]. Contributors who are not members of CFO will, upon request, receive a complimentary copy of the issue of Colorado Birds in which their articles appear. The articles in this journal reflect the research and opinions of the individual authors. As such, the articles do not necessarily reflect the opinions or positions of the Officers, Directors, or other representatives of CFO.

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Colorado Birds │ Summer 2018 │ Vol. 52 No. 3 155 Three presentations of all public Colorado eBird data for two species of sparrows (as of 22 Feb 2019). Do you know which species are represented? See page 87 for the individual figure captions (Figures 1-3).

Figure 1

Figure 2

Figure 3

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