Distribution, Status, and Origin of Water Pipits Breeding in California ’
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The Condor89:788-797 0 The CooperOrnithological Society 1987 DISTRIBUTION, STATUS, AND ORIGIN OF WATER PIPITS BREEDING IN CALIFORNIA ’ JON H. MILLER 1034 ShattuckAvenue, Berkeley, CA 94707 MICHAEL T. GREEN Department of Biology, Universityof North Carolina, Chapel Hill, NC 27514 Abstract. We investigatedthe racial identity, distribution, and abundanceof WaterPipits (Anthusspinoletta) breeding in the mountainsof California.This commonnesting species of alpinetundra was not knownto breedin Californiauntil the 1970s;a reviewof historical evidencesuggests recent colonization. Mensural and plumagecomparisons show California populationsto be A. s. alticola, the breedingrace of the Rocky Mountains. This is of biogeographicalinterest, because the abundantwintering and migratorypipit of California is A. s. pacificus,while alticola normally occurshundreds of miles to the east.Water Pipits currentlynest in mesicalpine vegetation throughout much of the southernand centralSierra Nevada.Breeding densities are highestand mostuniform in the southernmostpart of this range.The only known breedingpopulation in California outsideof the Sierra Nevada occurson San Gorgonio Mountain in southernCalifornia. We hypothesizethat the previous absenceor rarity of breeding Water Pipits in the Sierra Nevada may be attributable to the most recentpaleoclimatic xerothermic period, the Hypsithermal(ca. 5,000 to 2,900 years BP), whichimuoverished many alnine biotasof arctic-oldcordilleran affinitv. Climate and habitat differencesmay prevenipa$cus from breedingin California, and geographicbarriers may have hindered colonization by alticola. The occurrenceand timing of the present colonizationmay be fortuitous.Alternatively, it is possiblethat prior colonizationof Great Basinranges by alticola facilitatedeventual dispersal to the SierraNevada. Key words: Water Pipit; Anthus spinoletta;Sierra Nevada;historical status; colonization; biogeography;alpine. INTRODUCTION and Montana (Verbeek 1970; Miller and Green, The Water Pipit (Anthus spinoletta) is a principal pers. observ.), south to New Mexico and Arizona and widespread member of alpine avifaunas in (AOU 1957), and west to the easternGreat Basin western mountain ranges that support mesic al- ranges(Behle 1978; R. E. Johnson, unpubl.). The pine tundra. However, this specieswas not known winter range of this taxon is not well known, but to breed in the Sierra Nevada of California until appearsto be from southern Utah south to Mex- quite recently, and appears to have been rare or ico (Phillips et al. 1964, Hayward et al. 1976). absent during the first half of this century. This A small number have been collected in coastal prior absence is noteworthy, because the Sierra California during the spring migration (Swarth Nevada is among the largest mountain rangesin 1900, Grinnell and Miller 1944). Anthus s. pa- North America and contains extensive alpine cz$cus breeds in the Pacific cordillera from the habitat suitable for breeding Water Pipits. The mountains of Oregon north to the alpine and recent discovery of breeding Water Pipits in the arctic tundra of Alaska. This race winters in the southern and central Sierra raises several ques- Pacific states,east to the Rocky Mountains, and tions of biogeographical interest, including the south to western Mexico (Grinnell and Miller origin and racial identity of these birds. 1944, AOU 1957, Phillips et al. 1964). The Water Pipit is holarctic in distribution, The fact that the Sierra Nevada lies entirely with two racesbreeding in arctic and alpine tun- within the winter range and migration route of dra in western North America. Anthus s. alticola pacijicus,while alticola was not known to regu- breeds throughout the Rocky Mountains and larly approach California at any time of the year, outlying rangesfrom southern British Columbia led to a natural assumption that newly discov- ered Sierran pipits were alsopaczjicus (e.g., Parkes ’ ’ Received27 October 1986. Final acceptance31 1982). A critical determination of racial identity March 1987. was lacking, however. 17881 WATER PIPITS BREEDING IN CALIFORNIA 789 In this paper we determine the racial identity, discussthe former status,and document the cur- rent distribution and abundance of Water Pipits breeding in the mountains of California. We also discuss hypotheses regarding the dynamics of colonization. STUDY AREAS AND METHODS Alpine habitat in California occursin the Klam- ath, Cascade, Sierra Nevada, Sweetwater, and White Mountain ranges(Major and Taylor 1977) (Fig. 1). The vast majority of alpine area in the states is found in the Sierra Nevada, stretching from Olancha Peak (Tulare County, 36”16’N) in the south, north to the Lake Tahoe vicinity (El Dorado County, 38’50’N). The alpine zone oc- curs at elevations above approximately 3,350 m in the southern Sierra, dropping to 3,050 m in the northern part of the range. The largest ex- pansesof alpine vegetation in the Sierra Nevada are found in a nearly continuous band of roughly 3,000 km2 from the Great Western Divide and Sierra Crest in the south to slightly north of So- nora Pass in the north, a distance of some 260 km (Fig. 1). Additionally, the Warner Mountains Km Ok in northeastern California (Modoc County) and 120 ’ 119” D 118 San Gorgonio Mountain in southern California (San Bernardino County) include subalpine sum- FIGURE 1. Map of alpine regions of the Sierra Ne- vada, White, and Sweetwater (SW) Mountains, Cali- mits which harbor small enclaves of relict alpine fornia (redrawn from Kuchler 1977). Censusplots (MB, vegetation. DB, PB, RR, -NP) are describedin text and in Table 1. We investigated the historical status of Water Lake Tahoe (LT), Mono Lake (ML), and the cities of Pipits in California by searching published lit- Fresno and Bishop are included as reference points. erature and unpublished field notes at the Mu- OP = Olancha Peak, PP = Pyramid Peak. Inset shows location of map and additional pertinent areas:Klam- seum of Vertebrate Zoology, University of Cal- ath Mountains fKL). Mt. Shasta(SH) and Mt. Lassen ifornia, Berkeley (MVZ), and the Yosemite (LA) (CascadeRange), Warner Mountains (WA), and National Park Natural History Museum San Gorgonio Mountain (SG). (YNPNHM). We also compiled published and unpublished records of recent pipit sightings in the state. tempted to cover as much optimal habitat as We conducted fieldwork for this study from possible in 1 or 2 days. 1982 through 1986; most of our distributional, Within the Sierra Nevada we made over 25 breeding density, and racial data were collected trips during which we searchedfor pipits in most between late May and early August in 1984 and large expansesof alpine habitat throughout the 1985. We attempted to determine the current range. We devoted extra attention to areaswhich breeding distribution of Water Pipits in Califor- marked the apparent limits of this species’ dis- nia by surveying nearly every alpine region in tribution. the state, as well as the two subalpine areas men- We searchedthe following non-Sierran areas tioned above. Distribution surveys consisted of between 20 May and 20 July 1984: Eagle Peak, walking through appropriate alpine habitat Warner Mountains (Modoc County); Panther searching for pipits and recording habitat data Creek and other western drainageson Mts. Shas- (availability of mesic tundra vegetation, riparian ta and Shastina (twice) (Siskiyou County) and areas, and snowbanks). In each region we at- Mt. Lassen (twice) (Shasta County), Cascade 790 JON H. MILLER AND MICHAEL T. GREEN TABLE 1. Water Pipit censusareas and censusresults in the SierraNevada, California. 46 Total Mesic mesic Density plot area areain areain No. of (birds/ha No. of Censusarea Coordinates Elevation (m) (ha) plot (ha) plot pipits’ mesic) nestsb Mitre Basin (MB) 36”32’N 3,410-3,660 146 18 12 34 1.89 12 118”16’W Dusy Basin (DB) 37”06’N 3,440-3,600 120 17 14 21 1.24 8 118”32’W Pioneer Basin (PB) 37”28’N 3,290-3,540 383 33 9 0 0.00 0 118”48’W Ritter Range (RR) 37”43’N 2,990-3,350 139 50 36 5 0.10” 0 119”ll’W North Peak (NP) 37’=59’N 3,170-3,410 160 22 14 15 0.68 4 119”18’W aIncludes nesting pairs and unmatedterritorial maleswithin censusplot boundanesduring censusperiods. bIncludes only pipit nestslocated within censusplot boundaries. f Not strictly comparableto other densityvalues. Seetext for explanation. Mountains; Mt. Patterson vicinity, Sweetwater Miller censusedthe RR plot for four peripds (X = Mountains (Mono County); White Mountain 3.2 hr) over 3 days. Green searchedfor pipits for Peak vicinity, White Mountains (Mono County); 15.5 hr over two 2-day periods in PB. In both San Gorgonio Mountain (San Bernardino Coun- of these regions additional time spent searching ty); and San Jacinto Mountain (Riverside Coun- adjacent areas corroborated the densities found ty). We visited San Gorgonio Mountain again in in the plots. 1985. We did not visit the Klamath Mountains, Censusing involved mapping the location of where alpine communities are very limited (Ma- all pipit sightings on enlarged (4 x) USGS 15’ jor and Taylor 1977). topographicmaps. The approximate distribution In 1985 we measured breeding densities of of wet and moist tundra vegetation (mesic tun- Water Pipits in five alpine locations (Fig. 1) at dra) in each plot was mapped by visual inspec- roughly equidistant intervals along the known tion. We concentrated our censusefforts on wet pipit breeding range in the Sierra Nevada. All and moist meadows, as these are preferred nest- censusareas were located at or above tree limit ing and foraginghabitats, but all area within plots and were selected to be representative of local was thoroughly covered. Pipit density values suitable habitat. Location, size, and additional (birds/hectare mesic tundra habitat in census details of thesecensus plots are given in Table 1. plots) include breeding pairs with known nests In the Mitre Basin (MB), Dusy Basin (DB), in the plots, and pairs or individual singing males and North Peak (NP) censusareas we surveyed whose mapped activities were centered in the the available habitat and selectedcensus plots to censusplot and appearedto have territories with- include as much optimal moist and wet alpine in the plot boundaries.