Occurrence of Birds on a Great Basin- Mohave Desert Ecotone in Southwestern Utah

Merrill Webb

Abstract—During four 1998 breeding season visits to a Great spp.), hopsage (Grayia), winterfat (Ceratoides), and grease- Basin-Mohave Desert ecotone in southwestern Utah, a total of 29 wood (Sarcobatus). The plant communities of the Great different bird species were observed. Five species were determined Basin are simple, often consisting of similar uniform gray to be migratory, and two additional species were foraging as they and gray-green shrub stands over large areas (Smith 1974; flew over the transects, reducing the number of meaningful resident Mozingo 1987). I followed Welsh and others (1993) for species to 22. Ash-throated Flycatcher, House Finch, and Common taxonomic treatment of plant species. Raven were the three species with highest numbers in the ecotonal Hot deserts are dominated mostly by creosote bush (Larrea area. Transects through the Mohave Desert and the Great Basin tridentata) accompanied by bursage (Ambrosia dumosa) or Desert to the south and north, respectively, provided species num- burrobush (Hymenoclea salsola). Of the hot deserts, the bers for comparison. Mohave, transitional between the Great Basin and the Sonoran, is the poorest in species, has the simplest vegeta- tional composition, and contains some species in common with the Great Basin. Mostly it is a rolling plain covered with The zone where two or more different communities meet creosote bush and sagebrush, its monotony broken by volca- and integrate is an ecotone. This zone of intergradation may nic mountains and the curious Joshua trees (Yucca brevifo- be narrow or wide, local or regional. Three types of ecotones lia), a Mohave Desert endemic (Smith 1974). are recognizable. One is an abrupt transition, the result of a The purpose of this study was to determine bird species dramatic change in such environmental conditions as soil composition and numbers in the Mohave Desert-Great Ba- type or soil drainage. The second is a sharp transition sin Desert ecotonal area, and to compare these numbers brought about by plant interactions such as competition. with bird species in the Mohave Desert to the south and the The third type is a blending of two or more adjacent vegeta- Great Basin Desert to the north. The hypothesis was that the tional types. In the second and third types the superior plant highest number of bird species should occur at the junction competitors on one side of the ecotone extend as far out as of the two Deserts. Common and scientific bird names are their ability to maintain themselves allows. The ecotone listed in the appendix (American Ornithologists’ Union contains not only species common to the communities on 1997). both sides; it also may include a number of highly adaptable species that tend to colonize such transitional areas. Be- cause of this the variety and density of life is often the Location, Materials, and greatest in such areas. This phenomenon has been called the edge effect (Smith 1974). Methods ______Juniper-pinyon (Juniperis-Pinus) woodlands dominate A transect was selected in southwestern Utah’s Washing- almost 30 percent of Utah’s land area, and are estimated to ton County where the vegetation of the Great Basin Desert cover from 43 to 80.2 million acres of the Western United merges with that of the Mohave Desert. This transect was States. In Utah, this type occurs primarily between 5,000 selected on the basis of (1) being as representative of an and 7,000 feet in elevation, but it is not uncommon for these ecotonal community as was accessibly possible by car, and limits to be transgressed. For example, the woodlands occur (2) having a limited amount of vehicular traffic noise, which as low as 3,200 feet near St. George (Davis and Harper 1990). would affect the ability to adequately hear the birds. Using Basically, the North American desert can be divided into the same criteria as mentioned above, two other transects two parts, the northern cool desert—the Great Basin—and were selected for comparative purposes, one in the Mohave the hot deserts of the Southwest—the Mohave, the Sonoran, Desert to the south and one in the Great Basin Desert to the and the Chihuahuan. The cool and warm deserts, however, north. grade one into the other at ecotonal sites like the one I The Mohave Desert transect veered south on a road examine here. toward Beaver Dam Wells from the Eardly Road on the Sagebrush (Artemisia) is the dominant plant of the cool Beaver Dam Slope at an elevation of 3,833 feet. This road desert. Other important shrubs include saltbushes (Atriplex traversed typical Mohave Desert vegetation dominated by creosote bush, Joshua tree, black brush, blue yucca (Yucca baccata), and cholla cactus (Opuntia sp.). The ecotonal transect was 20 miles to the north of the In: McArthur, E. Durant; Ostler, W. Kent; Wambolt, Carl L., comps. 1999. Eardly Road just off the Motoqua Road at an elevation of Proceedings: shrubland ecotones; 1998 August 12–14; Ephraim, UT. Proc. RMRS-P-11. Ogden, UT: U.S. Department of Agriculture, Forest Service, 3,835 feet (transect ran north-south bisecting the Motoqua Rocky Mountain Research Station. Road). The vegetation was characterized by both single-leaf Merrill Webb is a Science Teacher, Provo High School, Provo, UT 84604.

USDA Forest Service Proceedings RMRS-P-11. 1999 35 and two-leaf pinyon pine (Pinus edulis and P. monophylla), fasciculata), indicator species of the Mohave Desert, were Utah and western juniper (Juniperus osteosperma and J. each present on seven transects though not in large numbers. scopulorum), Joshua trees, black brush (Coleogyne The Mohave Desert transect was conducted May 27, 1998. ramossima), blue yucca, and big sagebrush (Artemisia tri- Thirteen species of birds were identified with the Black- dentata). throated Sparrow being the most abundant. This sparrow The Great Basin transect was approximately 30 miles to and the Ash-throated Flycatcher occurred on eight of the 10 the north of the Motoqua road. This transect started ap- stops (table 2). proximately 15 miles west of the town of Enterprise where The Great Basin Desert transect west of Enterprise was it entered the Dixie National Forest at the southernmost conducted June 17, 1998. Twenty species of birds were edge of the Great Basin (transect ran east-west). Vegetation identified, with the Juniper (Plain) Titmouse being the most was pinyon pine, juniper, big sagebrush, and scattered abundant in terms of numbers (table 3). The Common Raven patches of rabbitbrush (Chrysothamnus ssp.) and bitter- was the only species present at all 10 stops. brush (Prushia tridentata). The transect through the Mohave Desert-Great Basin Four sampling trips to coincide with optimal songbird ecotone was sampled four times during 1998: April 11, April breeding were conducted through the ecotonal transect— 24, May 28, and June 16. A total of 29 species were identified two in April, one in May, and one in June. One sampling during the four visits covering the three month period attempt in March was aborted due to rain, snow, and muddy (table 4). However, 11 bird species were recorded only once, road conditions. The Mohave Desert was sampled in May either as flyovers or probable migrants, and all were initially and the Great Basin Desert was sampled in June. eliminated from consideration as permanent ecotonal in- Each transect was 2 miles long and consisted of 10 stops, habitants. Subsequently, upon further examination only each 0.2 miles apart. Observations at each stop lasted for five of the 11 bird species were eliminated as probable 10 minutes and consisted of listening for bird calls within migrants. Three species probably moved into the area as a hearing range and watching for bird activity using result of post-breeding dispersal. The remaining two species 8 x 30 binoculars. All counts were started at 7:00 a.m. (Webb, (Red-tailed Hawk and Violet-green Swallow) were probably in press). Identification of bird species was made by using just foraging as they passed over the ecotonal area. So, in the “Field Guide to the Birds of North America” (National terms of breeding purposes I believe the ecotone was impor- Geographic Society 1983). tant to a total of 22 different species of birds. Plant species numbers were determined through the eco- Of the 29 bird species recorded on the transect through the tone study area with help from students in my Provo High ecotone, 10 species were present during all four visits. School Zoology Class during my second trip on April 24, These were Ladder-backed Woodpecker, Ash-throated Fly- 1998. Each of the 10 quadrats was 0.2 miles apart and catcher, Common Raven, Juniper Titmouse, Bushtit, corresponded with the location of the birding stop. Each Bewick’s Wren, Blue-gray Gnatcatcher, Chipping Sparrow, rectangular quadrat (100 x 30 m) paralleled the road, ordi- Black-throated Sparrow, and House Finch. Seven species narily on the right hand (or passenger’s side of the car) occurred three of the four times. situated 30 m out from the edge of the road. Five bird species (Mourning Dove, Ash-throated Flycatcher, Common Raven, Bewick’s Wren, and House Finch) occurred on all three transects. These five species could be regarded Results and Discussion ______as generalists (table 5). Three species, Mourning Dove, Bewick’s Wren, and House Finch, were more common on the Blackbrush was the most abundant species in the ecotonal ecotonal transect than in either of the other two transects. study area (table 1). It occurred on all 10 transects, most of Four species occurred only in the ecotonal area: Common the time with large numbers of individual plants. Juniper Bushtit, Brewer’s Sparrow, Black-chinned Sparrow, and trees were present on nine of the transects, but pinyon pine Brown-headed Cowbird. Comments about each of these four occurred on only one transect. Big sagebrush, the main species is warranted here. The Common Bushtit occurs over indicator of the Great Basin Desert, was present on only four a wide range of habitats. My observations do not imply of the transects. Joshua trees and desert peach (Prunus specificity, only one breeding pair and scattered individuals

Table 1—Woody plants of a Mohave Desert-Great Basin Desert ecotone.

Number of plants occurring in each transect Plant species 1 2 3 4 5 678910

Blackbrush (Coleogyne ramosissima) 13 3 149 141 88 198 103 34 62 85 Big sagebrush (Artemisia tridentata)495000200700 Juniper (Juniperus spp.) 6 4 0 1 5 2 11 17 5 7 Pinyon pine (Pinus spp.) 0 0 0 0 0 0 0 0 0 2 Brigham tea (Ephedra spp.) 4 0 3 0 0 7 1 0 6 0 Desert peach (Prunus fasciculata)30012600024 Joshua tree (Yucca brevifolia) 0420121065 Cholla cactus (Opuntia spp.) 0 2 2 6 0 0 0 0 1 0 Cliffrose (Cowania stansburiana) 0004000000

36 USDA Forest Service Proceedings RMRS-P-11. 1999 Table 2—Birds of the Mohave Desert Transect (Beaver Dam Well Table 4—Number of bird species by date at the ecotone study site. Road). 1998 Number of stops Speciesa 04-11 04-24 05-28 06-16 out of 10 transects 1 Red-tailed Hawk 1 Speciesa Number bird occurred on 2 Mourning Dove 1 14 3 3 Black-chinned Hummingbird 1 1 Gambel’s Quail 7 5 4 Broad-tailed Hummingbird 3 2 Mourning Dove 2 2 5 Ladder-backed Woodpecker 3121 3 Ladder-backed Woodpecker 1 1 6 Gray Flycatcher 1 3 1 4 Ash-throated Flycatcher 12 8 7 Ash-throated Flycatcher 3 7 12 15 5 Common Raven 3 2 8 No. Rough-winged Swallow 2 6 Cactus Wren 11 7 9 Western Scrub Jay 2 3 1 7 Rock Wren 3 3 10 Pinyon Jay 9 5 8 Bewick’s Wren 2 2 11 Common Raven 4634 9 Northern Mockingbird 8 6 12 Juniper (Plain) Titmouse 11 4 4 9 10 Loggerhead Shrike 5 4 13 Bushtit 2215 11 Black-throated Sparrow 22 8 14 Cactus Wren 3 12 Scott’s Oriole 5 4 15 Rock Wren 1 1 6 13 House Finch 3 3 16 Bewick’s Wren 9 11 8 11 17 Ruby-crowned Kinglet 1 Total Species 13 18 Blue-gray Gnatcatcher 1333 aCommon names given, see appendix for scientific names. 19 Gray Vireo 10 13 20 20 Black-throated Gray Warbler 2 21 Green-tailed Towhee 1 22 Spotted (Rufous-sided) Towhee 1 23 Chipping Sparrow 3 29 2 1 Table 3—Birds of the Great Basin Transect (Dixie National Forest, 24 Brewer’s Sparrow 2 6 1 west of Enterprise, Utah). 25 Black-chinned Sparrow 2 26 Lark Sparrow 3 Number of stops 27 Black-throated Sparrow 3 10 16 16 out of 10 transects 28 Brown-headed Cowbird 1 2 Speciesa Number bird occurred on 29 House Finch 11 12 10 15 Total Species Each Visit 16 20 17 20 1 Mourning Dove 2 2 2 Northern Flicker 8 6 aCommon names given, see appendix for scientific names. 3 Gray Flycatcher 10 8 4 Ash-throated Flycatcher 5 5 5 Western Scrub Jay 9 7 6 Common Raven 11 10 Table 5—Number of birds observed for the five most common species 7 Juniper (Plain) Titmouse 16 6 in all communities. 8 Bewick’s Wren 7 7 a 9 Blue-gray Gnatcatcher 3 3 Species Mohave Ecotone Great Basin 10 Western Bluebird 1 1 Mourning Dove 2 4 2 11 Mountain Bluebird 2 2 Ash-throated Flycatcher 12 9 5 12 Gray Vireo 15 9 Common Raven 3 11 2 13 Black-throated Gray Warbler 5 3 Bewick’s Wren 2 10 7 14 Western Tanager 1 1 House Finch 3 12 1 15 Black-headed Grosbeak 1 1 16 Spotted (Rufous-sided) Towhee 11 6 aCommon names given, see appendix for scientific names. 17 Chipping Sparrow 11 8 18 Lark Sparrow 5 3 19 House Finch 1 1 20 Lesser Goldfinch 2 1 Dam Mountains. I believe that these two birds were in the study area as a result of post-breeding dispersal from their Total Number of Species 20 usual chaparral habitat. The Brown-headed Cowbird occur- aCommon names given, see appendix for scientific names. rence on only the ecotonal transect is probably an anomaly of later sampling dates rather than being absent from the other two desert communities, especially the Great Basin Desert where it is a known nest parasite. were observed and they could have been in any of my studied I detected Cactus Wren, Spotted Towhee, and Black- habitats. I was surprised that Brewer’s Sparrows were only chinned Sparrow on the ecotone transect on June 16, the last observed in the ecotonal area; ordinarily this species is date of my four visits. This could be due to post-breeding common in the sagebrush habitats of the Great Basin. In dispersal where the Cactus Wren moved in from the Mohave Utah, the Black-chinned Sparrow is usually found in the Desert to the south, and the Spotted Towhee and Black- chaparral community (Rising 1996). A chaparral commu- chinned Sparrow (see previous paragraph) came in from the nity occurs southeast of the transect in the nearby Beaver chaparral plant community to the east.

USDA Forest Service Proceedings RMRS-P-11. 1999 37 The most abundant birds in the ecotonal transect were the edges in order to provide habitat for many species (Yoakum House Finch (48 birds), Black-throated Sparrow (45), Gray and Dasmann 1971). Ecotones may also serve as sources or Vireo (43), Bewick’s Wren (39), and Ash-throated Flycatcher sinks for species. A source for a species is a place where (37) (table 4). These species are widespread throughout individuals can live and reproduce while individuals in other western habitats, so it is not surprising that they were locations are dying or are stressed to the point where they abundantly represented in the ecotone. The Gray Vireo was are unable to reproduce. Species may expand into sinks after absent from the first sampling date in April because, based reaching the carrying capacity of the original environment on my experience with breeding birds in that area, it had not (Pulliam 1988). yet arrived on the breeding grounds. It is likely that num- bers increased for the Ash-throated Flycatcher, Gray Vireo, and Black-throated Sparrow, with each succeeding visit due Acknowledgment ______to recruitment into the population of young of the year birds. I would like to express thanks to students in my zoology I observed sparrow and vireo fledglings exhibiting begging class at Provo High School for helping me on one of the behaviors on my last trip on June 16. survey dates. I would also like to thank Durant McArthur of Four species associated with the Mohave Desert that were the Shrubland Biology and Restoration Research Work Unit also present in the ecotonal area were Ladderback Wood- for providing financial assistance to cover travel expenses to pecker, Cactus Wren, Rock Wren, and Black-throated Spar- and from the study sites and for providing valuable technical row. Even though the Ladderback Woodpecker occurred in assistance. both the Mohave Desert and on the ecotone, I never observed it on a pinyon tree or on a juniper tree in the ecotone. It was always foraging or perched on a Joshua tree. References ______Nine species from the Great Basin Desert were also recorded in the ecotone. These included: Gray Flycatcher, American Ornithologists’ Union. 1997. Forty-first supplement to Scrub Jay, Juniper Titmouse, Blue-gray Gnatcatcher, Gray the American Ornithologists’ Union checklist of North American Vireo, Black-throated Gray Warbler, Spotted (Rufous-sided) birds. Auk. 114: 542-552. Davis, J. N.; Harper, K. T. 1990. Weedy annuals and establishment Towhee, and Chipping Sparrow. of seeded species on a chained juniper-pinyon woodland in central The unusually high numbers of Chipping Sparrows ob- Utah. In: McArthur, E. D.; Romney, E. M.; Smith, S. D.; Tueller, served on April 24 was due to a mixed flock of sparrows, P. T., comps. Proceedings—symposium on cheatgrass invasion, including Lark Sparrows, migrating through the area on shrub die-off and other aspects of shrub biology and management; 1989 April 5-7; Las Vegas, NV. Gen. Tech. Rep. INT-276. Ogden, that particular date (table 4). UT: U.S. Department of Agriculture, Forest Service, Intermoun- tain Research Station: 72-79. Mozingo, H. N. 1987. Shrubs of the Great Basin. Reno, NV: Univer- Conclusion______sity of Nevada Press. 342 p. National Geographic Society. 1983. Field guide to the birds of North In conclusion, an ecotone is an area between two or more America. Washington, DC: National Geographic Society. 464 p. different kinds of plant communities that contains some of Pulliam, H. R. 1988. Sources, sinks, and population regulation. American Naturalist. 132: 652-661. the vegetation and animal life (in this study, bird life) Rising, J. D.; Beadle, D. D. 1996. The sparrows of the United States present in the surrounding communities. Ecotones gener- and Canada. San Diego, CA: Harcourt Brace and Company. 365 p. ally have more species than that of the surrounding areas. Smith, R. L. 1974. Ecology and field biology, 2nd edition. New York Ecotones are not only places that species from neighboring City, NY: Harper and Row Publishers. 850 p. habitats may find attractive, but species from places other Webb, M. 1999. Importance of pinyon-juniper habitats to birds. In: Monsen, S. B.; Stevens, R.; Tausch, R. J.; Miller, R.; Goodrich, S., than the immediate surroundings may consider ecotones comps. Proceedings: ecology and management of pinyon-juniper more suitable than the habitats that combined to create it. communities within the Interior West; 1997 September 15-18; This seems to be the case for the Bushtit which was present Provo, UT. Proc. RMRS-P-9. Ogden, UT: U. S. Department of on all four sampling dates and only in the ecotone on this Agriculture, Forest Service, Rocky Mountain Research Station. 244-248. particular study. The House Finch was the most abundant Welsh, S. L.; Atwood, N. D.; Goodrich, S.; Higgins, L. C. 1993. A Utah species on the ecotone during the transect followed by the flora, 2nd edition. Provo, UT: Brigham Young University Print Ash-throated Flycatcher, Black-throated Sparrow, and Gray Services. 986 p. Yoakum J.; Dasmann, W. 1971. Habitat manipulation practices. In: Vireo. rd The higher biodiversity present in ecotones is important Giles, R., ed. Wildlife Management Techniques, 3 ed. Washing- ton, DC: The Wildlife Society: 173-231. for many reasons. Ecotones may serve as places for species preservation. Many wildlife managers purposefully create

38 USDA Forest Service Proceedings RMRS-P-11. 1999 Appendix ______

Common name Scientific name 1. Red-tailed Hawk Buteo jamaicensis 2. Gambel’s Quail Callipepla gambelii 3. Mourning Dove Zenaida macroura 3. Black-chinned Hummingbird Archilochus alexandri 4. Broad-tailed Hummingbird Selasphorus platycercus 5. Ladder-backed Woodpecker Picoides scalaris 6. Northern Flicker Colaptes auratus 7. Gray Flycatcher Empidonax wrightii 8. Ash-throated Flycatcher Myiarchus cinerascens 9. Loggerhead Shrike Lanius ludovicianus 10. Gray Vireo Vireo vicinior 11. Western Scrub Jay Aphelocoma californica 12. Pinyon Jay Gymnorhinus cyanocephalus 13. Common Raven Corvus corax 14. Northern Rough-winged Stelgidopteryx serripennis Swallow 15. Juniper Titmouse Baeolophus griseus 16. Bushtit Psaltriparus minimus 17. Cactus Wren Campylorhynchus brunneicapillus 18. Rock Wren Salpinctes obsoletus 19. Bewick’s Wren Thryomanes bewickii 20. Ruby-crowned Kinglet Regulus calendula 21. Blue-gray Gnatcatcher Polioptila caerulea 22. Western Bluebird Sialia mexicana 23. Mountain Bluebird Sialia currucoides 24. Northern Mockingbird Mimus polyglottos 25. Black-throated Gray Warbler Dendroica nigrescens 26. Western Tanager Piranga ludoviciana 28. Green-tailed Towhee Pipilo chlorurus 29. Spotted Towhee Pipilo maculatus 30. Chipping Sparrow Spizella passerina 31. Brewer’s Sparrow Spizella breweri 32. Black-chinned Sparrow Spizella atrogularis 33. Lark Sparrow Chondestes grammacus 34. Black-throated Sparrow Amphispiza bilineata 35. Black-headed Grosbeak Pheucticus melanocephalus 36. Brown-headed Cowbird Molothrus ater 37. Scott’s Oriole Icterus parisorum 38. House Finch Carpodacus mexicanus 39. Lesser Goldfinch Carduelis psaltria

USDA Forest Service Proceedings RMRS-P-11. 1999 39