WESTERN BIRDS

Volume 19, Number 1, 1988

PASSERINE MIGRATION ALONG THE INNER COAST RANGE OF CENTRAL CALIFORNIA

L. RICHARD MEWALDT, Arian BiologyLaboratory, San JoseState University, San Jose, California 95192 SUSAN KAISER, 521 46th Street, Sacramento, California 95819

With mistnets and groundtraps we sampledthe springand fall flowsof land birdsmigrating along Mission Ridge, just southeastof the southtip of San FranciscoBay. Few suchstudies have been made of land-birdmigration along the Pacific coast of North America. In northern California, the broadest-basedof theseis the annotatedfield list prepared by McCaskieet al. (1979), whichpresents graphically the relativeabundance by months,hence the timingof migration,of all speciesknown from that area. It was basedon many years of recordsfrom the Middle PacificCoast Region reportsin AmericanBirds and theirback-up files. These files were initiatedby Howard L. Cogswellin 1954 and are now maintainedby the regionaleditors of the quarterly reports. Severalstudies have reportedthe timingof migrationat specificlocations. Weston (1948) reported spring arrival dates of 15 speciesat Berkeley, California, for the years 1911 to 1947. Littlefieldand McLaury (1973) reported on springmigration and arrival dates at Malheur National Wildlife Refuge in easternOregon. Stewart (1972) dealt with the timing of peak migrationof several passerinesin central coastalCalifornia, while Ralph (1971) and Stewartet al. (1974) demonstratedthat unusuallyhigh numbers of youngpasserines of somespecies appear along the centralCalifornia coast in fall migration.The mostcomprehensive of thesespecific location studies is the monographof DeSanteand Ainley (1980), whichanalyzed the originsof the transient avifauna of Southeast Farallon Island, California. For this tran- sientavifauna they providespring and fall datesof occurrence,numbers en- countered on daily censuses,and numbers captured in mist nets and a Heligolandtrap for 331 speciesfor the years 1968 to 1976. Other studies, such as Wolfsoh'S(1945) pioneeringwork on the ex- perimentalmanipulation of migrationin juncos(Junco byemalls), have dealt with singlespecies. Johnson (1965, 1970, 1973) studiedthe migratorypat- terns of Hammond'sFlycatcher (Empidonax hammondii) and the Western Flycatcher(E. difficilis).There is alsothe broadspectrum of studiesdealing Western Birds 19:1-23, 1988 1 PASSERINE MIGRATION with the migratory biology of the White-crownedSparrow (Zonotrichia leucophrys),such as thoseof Farner (1955), Mewaldtet al. (1964), Cor- topassiand Mewaldt (1965), King et al. (1965), DeWolfeet al. (1973), and King and Mewaldt (1981a,b). Several workers have discussedapparent differencesbetween passerine migrationin the easternand westernparts of the continent (e. g., Paxton 1965, Lowery and Newman 1966, DeBenedictis1967). In westernNorth America the movements of the fewer migratory land-bird species are obscuredby a morerugged topography and by morecomplex weather pat- terns. Westernobservers do not often see the massivelandfalls of grounded migrantsthat are seen in the mid-westernand easternparts of North America. These are usuallycorrelated with certain weather conditions. Especiallyin centralCalifornia there are few strictlypassage migrants. Here alongthe PacificCoast the presenceof residentcomponents (winter, sum- mer, permanent)of manyspecies tends to obscuremigratory movements by the migratorycomponents of thosesame species. We reporton a two-yearstudy of the abundanceand timing of passageof migrantland birdsalong the innerCoast Range of centralCalifornia. Using mistnets and trapswe captured,banded, and recapturedmore than 14,000 individualbirds in two springand two fall seasonsfrom Augustof 1970 to May of 1972. We havecompared these findings with those reported for the nearbyFarallon Island station of PointReyes Bird Observatory (DeSante and Ainley 1980).

STUDY AREA

Our studieswere on the E. O. Wool Ranch on MissionRidge, a northwest extensionof the Diablo Range lying 55 km east of the PacificOcean and overlookingthe southend of San FranciscoBay (Figure1). Our operations were centeredin a valley615 m abovesea level, just eastof the 800-meter crestof MissionRidge and astridethe boundarybetween Santa Clara and Alameda counties.The surroundingphysiography consists of grassyrolling hills,interspersed to the eastwith steepcanyons, wooded on theirnorth- and east-facingslopes, and to the westwith the grassyuplands of MissionRidge. The westslope of MissionRidge drops abruptly to South San FranciscoBay nearthe cityof Fremont.Land eastof the Wool Ranchdrops off to Calaveras Reservoir(water surface elevation 233 m), beyondwhich additional ridges of the Diablo Range rise to more than 1000 m. The studyarea is characterizedby warm, dry summersand cool, rainy winters.Although the PacificOcean and San FranciscoBay exerta moderating influenceon temperature,the effectis somewhatdiminished at highereleva- tions.In our studyarea temperatureswere from 3 to 6øC higherin summer and lower in winterthan thoserecorded in nearbyMilpitas (elevation 33 m). Thermographrecords maintained during operations showed a high of 41øC (10 Aug 1971) and a low of - 2øC (2 Feb 1972). Especiallyin springand ear- ly summer,thermal inversions prevent ocean fog flowing inland from reaching highground. Mission Ridge then standsout at dawn, as thoughan islandor peninsula,above the surroundingfog, whichoften totally obscures areas below 500 m elevation. PASSERINE MIGRATION

Rainfallrecords, maintained by the Woolfamily from 1942 to 1972, reveal a yearlymean of 66 cm (range35 to 102 cm). Thisamount is approximately doublethat fallingon the southend of San FranciscoBay 10 km to the west. Virtuallyall precipitationfalls from Octoberto April, with mean highsof 13 cm in both Decemberand January.Precipitation, including some snow, was substantiallyhigher than averagein the 1970-71 winterseason and substan- tially lower than averagein the 1971-72 winter season. The uplandsof the studyarea supportopen grassland,oak woodland,and chaparral.Grassland, occupying the ridgesand the moreexposed south- and west-facingslopes, is composedprimarily of annualgrasses and herbs,with wild oats (Auena fatua) predominating.Oak woodland occupiesthe north- and east-facingslopes. This woodland consists principally of CoastLive Oak (Quercus agri•:olia)and Valley Oak (Q. Iobata), with California Bay

Pablo Bay

Point Reyea rd Obaervatery

FARALLON (•Oaklond ISLANDS SanFran½11 •'C•O PACIFIC

WOOL RANCH o

•San Joao

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Figure1. GreaterSan FranciscoBay area,showing the locationof the WoolRanch on MissionRidge and the FarallonIslands. PASSERINE MIGRATION

(Umbe!iulariacalifornica) and CaliforniaBuckeye (Aesculuscalifornicus) as associates.California Sycamores(Platanus racemosa) and Bigleaf Maples (Acer macrophyilum)grow at springsand along resultingstreams. Isolated areas of chaparral, some composed mostly of Chamise (Adenostoma fasciculatum),occur on the dry, rocky slopesfacing CalaverasReservoir. These and most other areas of chaparral contain substantialamounts of PoisonOak (Toxicodendrondiversiiobum), Toyon (Heteromelesarbutifolia), Coyote Bush (Baccharispilularis), Coffeeberry (Rhamnus californicus), StickyMonkey Flower (Mimulusguttatus), ceanothus (Ceanothus sp.), and small Coast Live Oaks. Most of the ranch (about 530 ha), as well as the surrounding3500 ha of undevelopedregional park and watershedlands, were grazedby cattle.The immediatestudy area (Figure2) was dominatedby a 20-ha irrigated(well water) orchard of prunes (Prunussp.) and walnuts (Juglanssp.). A usually dry gully, drainingfrom northto souththrough the easternportion of the or- chard, containedintermittent patches of willows (Salix sp.), smallCoast Live Oaks, Coyote Bushes,and PoisonOak (Figure3). This gully, terminatingin a 0.1-ha permanentstock pond with willowson two sides,proved a substan- tial attractantto residentsand groundedmigrants. Another important attrac- tant was a large wooden water tank, continuallyseeping, at the southwest corner of the orchard and at the base of a hill wooded with Coast Live Oak, CaliforniaBay, and understoryclumps of Coffeeberry.Surface water on the higher portions of Mission Ridge was usually restrictedto the immediate vicinityof the orchardand ranch buildings,except for a few springsusually associatedwith a stock-wateringdevice or pond. In the wet springof 1971 there were scatteredvernal pools on the higher portionsof the ridge.

METHODS

Capture Methods and Data Collection Birds were capturedwith Japanesemist nets and Pottertraps. The basic nettingunit, a net-hour,consisted of a 4-panelnylon mistnet 12 m longand 2 m high set with the bottomtrammel line about0.15 m abovethe ground and operatedfor 1 hour. At severalsites a secondnet was joined to and mountedabove the ground-levelnet and elevatedwith lanyardsand pulleys on guyed 5-m polesto a heightof about4.15 m. Such an arrangement, althoughprobably not twiceas efficientas a singlenet run for 1 hour, was countedas 2 net-hours.Nets were made of 70-denierblack nylon yarn with stretched36-mm mesh or occasionallywith 30-mm mesh. Nets were placed in lanes cut acrossthe willow-dominateddraw, in the prune orchard,and at strategiclocations under trees adjacent to the leaking water tank (Figure2). The netsin the willow draw and at the water tank, con- sistingof 20 nets at 7 sites,were operatednearly constantlyfrom seasonto season.The nets in the orchardand nets set occasionallyat sitesup to 300-400 m from the orchard were run opportunistically.Opened 20 minutesbefore sunrise and closedshortly before noon, nets were operated daily during the springand fall periodsof migrationand intermittentlyin otherseasons -- exceptduring June and July when none wasoperated. Net hoursand numbersof birdscaught at each site were logged.

4 PASSERINE MIGRATION

Four-celledwelded-wire Potter traps (eachcell 20 x 25 x 20 cm high) were baitedwith chickscratch and placedin nearbybrushy areas associated with oak woodlandand alongthe edgebetween grassland and chaparral.A trap-hourwas a four-celledtrap openfor ! hour. Trap lines,consisting of 10 to 40 trapsat 4 to 15 stations,were run irregularly,but mostoften in early

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Figure 2. The main study area on the Wool Ranch. Mist net locationson the several sitesare indicatedby heavy solid lines. PASSERINE MIGRATION springand late fall, when they were operated2 to 4 daysa week. Trap hours and the numbersof birdscaught at each site were logged. All birds except hummingbirds(tail-clipped to detect recaptures)were banded with U.S. Fish and Wildlife Service aluminum bands. Data recorded on each capture and recaptureincluded species, age, sex when possible, hour of capture,site of net or trap, wingchord (ram), weight(g), and, in ap- propriate season, reproductive condition (brood patch, cloacal pro- tuberance,etc.), conditionof molt, amountof fat, skullpneumatization, and standardnotes related to determinationof age and sex. Photographswere taken of rare and unusualspecies. Project Personnel Nets and traps were operated and most of the bandingand data collection were done by advanced undergraduateand graduate studentsenrolled in Field Studiesin Bird Migrationat San •JoseState University.All had either takenOrnithology or weretaking it concurrently.Several participated during all four migratoryseasons. Four to six studentseach day, in rotationfrom a rosterof •14to •16,worked sevendays of each week duringspring and fall migration.When heavy waves of migrantsappeared or specialproblems arose, additionalhelp was summonedby telephone.Daily crew chiefswere selectedfrom among thosewith greaterexperience.

RESULTS AND DISCUSSION

The •14,•159birds of •109 taxa (•107 speciesincluding 2 with 2 races distinguishedin each) were capturedand recaptured22,67! timesin two fall and two springseasons from August•1970 to May •1972 (Table •1).Only six species(two hummingbirds,two flycatchers,and two warblers)are strictly passagemigrants through the San FranciscoBay region. The rest are residentsof one kind or anotherin the greaterSan FranciscoBay region.Our determination of the migratory status of central California residentswas based in part on whether or not the speciesin questionappears on the FarallonIslands as a migrant(DeSante and Ainley •1980). Supplemental data, includingthe captureof four additionalspecies, were obtainedin the springof •1970and from sporadicfield work from the fall of •1972to •1979 (Appendix). The data are biased in two ways that limit effectiveapplication of biometricalanalyses. (•1) Many net lanesand trap lineswere changedfrom seasonto seasonto maximizecapture efficiency.(2) Operationscould not be continuedbeyond 3! May in the springsof eitheryear. Thuswe had no data for •Juneand coverageof •Julyand Augustwas weak. Nonetheless,the data providea valuablesample of •andbird migration through the southSan Fran- ciscoBay regionin the early •1970s.Kaiser (1976) reportedfurther detailed informationon the subjectswe coverand otheritems such as medianmigra- tion dates, age ratios,fat deposition,and correlationswith weather. Capturesin Nets Of •14,338captures in mistnets, 9392 werefirst encounters with migrants, 2108 were firstencounters with resident species, and 2838 wererecaptures

PASSERINE MIGRATION

Table 1 Status and Number of First Captures of the 109 Taxa of Birds Captured in Mist Nets and Pottertraps on the Wool Ranch from August 1970 through May 1972

Species Number

Residentwith no apparent migratorycomponent: California Quail Callipepla cali]ornica 199 Western Screech-Owl Otus kennicottii 2 Nuttall'sWoodpecker Picoidesnuttallii 20 Downy Woodpecker Picoidespubescens 2 Hairy Woodpecker Picoidesvillosus 6 Steller'sJay Cyanocittastelleri 64 Scrub Jay Aphelocomacoerulescens 49 Yellow-billedMagpie Pica nuttalli 7 Chestnut-backedChickadee Parus ru]escens 55 Plain Titmouse Parus inornatus 105 Bushtit Psaltriparusminimus 136 White-breasted Nuthatch $itta carolinensis 24 Bewick'sWren Thryomanesbewickii 65 Western Bluebird $ialia mexicana 30 Wrentit Chamaea [asciata 6 California Thrasher Toxostoma redivivum 17 Brown Towhee Pipilo [uscus 147 Rufous-crownedSparrow Aimophila ruficeps 10

Residentwith a migratorycomponent: Cooper's Hawk Accipiter cooperil American Kestrel Falco sparverius 5 Mourning Dove Zenaida macroura 83 Loog-earedOwl Asio otus 1 Anna's Hummingbird Calypte anna 42 Acorn Woodpecker Melanerpes[ormicivorus 5 Northern Flicker Colaptesauratus 48 BlackPhoebe $ayornisnigricans 17 Horned Lark Eremophila alpestris 118 Red-breasted Nuthatch $itta carolinensis 1 Brown Creeper Certhia americana 1 Rock Wren $alpinctesobsoletus Winter Wren Troglodytestroglodytes 8 Golden-crownedKinglet Regulussatrapa 4 Hermit Thrush Catharusguttatus 994 AmericanRobin Turdusmigratorius 95 Northern Mockingbird Mimus polyglottos 27 Phainopepla Phainopepla nitens 1 LoggerheadShrike Lanius ludovicianus 5 EuropeanStarling Sturnusvulgaris 47 Hutton's Vireo Vireo huttoni 30 Orange-crownedWarbler Vermivoracelata 387 Audubon's Warbler Dendroica coronata audubonf 149 Common Yellowthroat Geothlypistrichas 4 Rufous-sidedTowbee Pipilo erythrophthalmus 177 Lark Sparrow Chondestesgrammacus 713 Sage Sparrow Amphispizabelli 1 PASSERINE MIGRATION

Table 1 (Continued)

Species Number

Savannah Sparrow Passerculussandwichensis 1:30 Song Sparrow Melospiza melodia 2 Oregon Junco Junco hyemalissspp. 1516 Red-wingedBlackbird Agelaiusphoeniceus 184 WesternMeadowlark $turnellaneglecta 12 Yellow-headedBlackbird Xanthocephalusxanthocephalus 1 Brewer'sBlackbird Euphaguscyanocephalus 53 Brown-headed Cowbird Molothrus ater 1 Purple Finch Carpodacuspurpureus 280 House Finch Carpodacusmexicanus 1088 Pine Siskin Carduelispinus 1 LesserGoldfinch Cardveilspsaltria 256 Lawrence's Goldfinch Carduelis lawrencei 12 American Goldfinch Cardveils tristis 61

Summer resident: Allen's Hummingbird $elasphorussasin 10 Olive-sidedFlycatcher Contopusborealis 3 WesternWood-Pewee Contopussordidulus 33 WesternFlycatcher Empidonax difficilis 701 Ash-throatedFlycatcher Myiarchuscinerascens 14 WesternKingbird Tyrannusverticalis 1 Violet-greenSwallow Tachycinetathalassina 1 House Wren Troglodytesaedon 27 Swainsoh's Thrush Catharus ustulatus 850 SolitaryVireo Vireo solitarius 10 WarblingVireo Vireo gilvus 210 Yellow Warbler Dendroicapetechia 148 Black-throatedGray Warbler Dendroicanigrescens 8 MacGillivray'sWarbler Oporornistolmiei 74 Wilson'sWarbler Wilsoniapusilla 461 Yellow-breasted Chat lcteria virens 5 WesternTanager Piranga ludoviciana 66 Black-headedGrosbeak Pheucticusmelanocephalus 118 Lazuli Bunting Passerinaamoena 43 ChippingSparrow $pizellapasserina 494 Black-chinnedSparrow Spizellaatrogularis 1 GrasshopperSparrow Ammodramus savannarum 1 Bullock'sOriole lcterusgalbula bullockii 55 Winter resident: Sharp-shinnedHawk Accipiterstriatus 12 Red-breastedSapsucker $phyrapicustuber 22 Ruby-crownedKinglet Reguluscalendula 259 Varied Thrush 1xoreus naevius 12 Water Pipit Antbus spinoletta 1 Cedar Waxwing Bombycillacedrorum 43 Myrtle Warbler Dendroicacoronata coronata 21 Townsend's Warbler Dendroica townsendi 4 Fox Sparrow Passerellailiaca 236 Lincoln'sSparrow Melospizalincolnii 41 PASSERINE MIGRATION

T&ble I (Continued)

Species Number

White-throatedSparrow Zonotrichiaalbicollis 3 Golden-crownedSparrow Zonotrichiaatricapilla 1753 Puget Sound White-crowned Sparrow Z. leucophryspugetensis 203 Gambel's White-crowned Sparrow Z. I. gambelii 344 Migratorywith no residentcomponent: CalliopeHummingbird $tellula calliope 10 RufousHummingbird $elasphorusrufus 168 Willow Flycatcher Empidonaxtraillii 72 Hammond'sFlycatcher Empidonaxhammondii 8 NashvilleWarbler Vermivoraruficapilla 25 Hermit Warbler Dendroica occidentalis 8 Vagrant, no residentor migratorycomponent: Gray Flycatcher Empidonax wrightii 11 Bell's Vireo Vireo bellii 1 BlackburnJan Warbler Dendroica fusca 1 American Redstart Setophaga ruticilla 1 Green-tailed Towhee Pipilo chlorurus 1 Black-throatedSparrow Amphispiza bilineata 2 Slate-colored Junco Junco hyemalisbyemalls 3 Additionalspecies captured in the supplementalperiods (see Appendix) Killdeer (resident) Charadriusvociferus 3 Say's Phoebe (winter resident) Sayornissaya 1 Canyon Wren (resident) Catherpes mexicanus 1 TennesseeWarbler (vagrant) Vermivora peregrina 1

(Table2). Most of the recaptureswere of residentspecies. The 3664 spring migrantswere caughtin mistnets at a rate of 24 per 100 net hours (15,116 net hours),whereas fall migrants,numbering 5728, were caughtat a rate of 38 per 100 net hours (14,877 net hours). This 56% increasein numbersof fall migrantsover springmigrants, resulting from approximatelyequal spring and fall efforts,is consistentwith an expectationof greaternumbers following summerreproduction. Similarly, the 153% increasein late summerand fall nonmigrantsor residents(597 Jan-May versus 1511 Aug-Dec) roughly fulfillsour expectationof encounterswith dispersingjuveniles of resident species. Captures in Traps Of 8333 capturesin Potter traps, 2659 were first encountersand 5674 were recaptures(Table 2). Traps capturedmostly granivorous species, in- cludingboth migratorywinter residentssuch as Golden-crownedSparrows and residentssuch as Lark Sparrows.The trend seen in mistnet captures toward more capturesin the latesummer and fall waseven greaterwith trap- caughtbirds. The 749 springcaptures (9 per 100 trap hours)were much less

10 • A A A • A A

A • • A A A A

A A A A A A A

• A • A • A A

l! PASSERINE MIGRATION than half the 1910 late summerand fall captures(30 per 100 trap hours). Part of thissubstantial difference was due to dispersingjuveniles of residents suchas Lark Sparrowsand BrownTowhees. Another component adding to fall numberswas the banding of newly arrived winter residents,such as Golden-crownedSparrows, including substantial numbers of juvenilesraised in Canada and Alaska.Because these wintering birds were stillpresent in the spring,they did not contributeto springcounts of newly bandedbirds. Althoughmost species were caughtalmost exclusively in nets (e. g., fly- catchers,thrushes, and warblers)or traps (e. g., CaliforniaQuail, Horned Larks, and Lark Sparrows),a few, such as Golden-crownedand White- crownedSparrows, Oregon Juncos, Fox Sparrows,towhees, and jays were caughtin both nets and traps. Post-breedingDispersal Experience(Mewaldt unpublished, DeSante and Geupel 1987) makesit clear that dispersalby juvenilesand post-breedingwandering by adultsof local breedingspecies begins as early as late May (e. g., Orange-crowned Warbler, see below) and increasesin volume through June, July, and August. These post-breedingmovements were evident on MissionRidge (Table3) in Augustand Septemberfor residentspecies such as Steller'sand Scrubjays, Chestnut-backedChickadees, and BrownTowhees, which prob- ably lack a migratorycomponent. Numbers of dispersingRufous-sided Towheesand Oregon Juncoscaptured were supplementedby migrantsof each speciesbeginning in September.Dispersal of juvenilesand localwinter wanderingby Lark Sparrowsand HouseFinches certainly blended and may prove difficultto distinguish.The lack of data from June, July, and early August makesfurther discussionof dispersalunrewarding. Springand Fall Migration The arrival,approximate duration, and peak of passageof springmigrants capturedin significantnumbers are displayedfor both I971 and 1972 in Table4. It is evidentfrom the numberscaptured in the finalsix days of May, however, that somespecies must have continuedas birdsof passageon Mis- sion Ridge into the first week or two of June. Noteworthyin this category were WesternFlycatchers, Swainson's Thrushes, Warbling Vireos, Orange- crownedWarblers, Yellow Warblers,Townsend's Warblers, MacGillivray's Warblers,Wilson's Warblers, Western Tanagers, Black-headed Grosbeaks, and Lazuli Buntings.Clearly, some northern or mountainpopulations of these specieswere still migratingin late May and early June while local populationswere alreadynesting. These 11 specieshave centralCalifornia populationsthat regularlybegin nesting in April or early May (e. g., Grinnell and Wythe 1927, Sibley 1952, Stewart 1972, Verner and Boss 1980). Noteworthyis the Orange-crownedWarbler, of whichno fewerthan 30% of the 88 captured11-31 May were recentlyfledged birds. The timing, approximateduration, and peak of passageof thesesame speciesare displayedin Table 5 for the fall seasonsof both 1970 and 1971. Coverageof the month of Augustwas weak, and the Augustdata are com- plicatedby probablyincluding locally raised, pre-migratory,dispersing juveniles.Species probably subject to this complicationare the Northern 12

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17 PASSERINE MIGRATION

Table 6 Comparisonof Numbersof SelectedSpring and Fall Migrants BandedFall 1970 to Spring1972 on MissionRidge and Spring1968 (part) to Spring(part) 1976 on the South FarallonIslands (DeSante and Ainley 1980)

Spring Fall

Mission Farallon Mission Farallon Species Ridge Islands Ridge Islands

CalliopeHummingbird 10 3 0 0 RufousHummingbird 168 32 0 0 Red-shafted Flicker 4 6 44 22 WillowFlycatcher 5 64 67 57 WesternFlycatcher 122 106 579 224 Ruby-crownedKinglet 26 164 231 188 Swainsoh's Thrush 721 89 129 114 Hermit Thrush 66 98 928 186 NorthernMockingbird 11 13 16 31 WarblingVireo 143 45 67 124 Orange-crownedWarbler 335 440 52 101 Nashville Warbler 23 21 2 27 Yellow Warbler 94 116 54 357 Audubon's Warbler 59 268 84 192 Black-throatedGray Warbler 4 5 4 60 Townsend's Warbler 41 280 3 169 Hermit Warbler 8 13 0 56 MacGillivray'sWarbler 65 33 9 77 Wilson's Warbler 409 1245 52 289 WesternTanager 15 70 51 91 Black-headed Grosbeak 64 38 54 24 Lazuli Bunting 10 16 33 71 ChippingSparrow 94 45 400 355 SavannahSparrow 27 7 61 518 Fox Sparrow 18 10 216 146 Lincoln'sSparrow 17 90 24 144 Golden-crownedSparrow 223 81 1486 1207 Gambel's White- crownedSparrow 67 106 277 496 Puget Sound White-crownedSparrow 71 53 132 461 Bullock's Oriole 51 5 4 5 PurpleFinch 161 23 89 142 Lesser Goldfinch 75 7 178 63 Lawrence's Goldfinch 0 1 12 3 American Goldfinch 50 8 11 2 Degree of correlationof Coefficientof Coefficientof numbersof springand of correlation= correlation= fall migrants + 0.469712 + 0.74201 Probabilityof positive correlation P = 0.9880 P = 0.9997

18 PASSERINE MIGRATION

Mockingbird,Warbling Vireo, Orange-crownedWarbler, Black-headed Grosbeak,Lazuli Bunting, Chipping Sparrow, and LesserGoldfinch. Species-by-speciescomparisons from Tables4 and ;5with the accountsin DeSante and Ainley (1980) reveal closeparallels in many speciesbetween passageperiods and peaksof passageon SoutheastFarallon Island and on MissionRidge--except that at MissionRidge we lackJune-July records.Ob- viousexamples of closeagreement include peak migrationperiods for Her- mit Thrushesin the lastfew daysof April, comparedto Swainsoh'SThrushes in the lastfew days of May, and Puget Sound White-crownedSparrows in earlyApril, comparedto GainhersWhite-crowned Sparrows in late April. Patternsof numberscaptured and banded of 34 of the more commonly capturedspecies on SoutheastFarallon Island and MissionRidge (Table6) are very well correlated.The actual numbersbanded, treated as profiles, show bett.ercorrelation for the fall period than for the springperiod. Most specieswere capturedin largernumbers in the fall migrationthan in springin both places. However, a few species, including Orange-crowned, Townsend's,and Wilson'swarblers, were more abundant in the spring on both SoutheastFarallon and MissionRidge.

SUMMARY

Mist nets and Potter traps were used to capture and band 14,159 land birdsof 109 taxa on MissionRidge, overlookingthe southend of San Fran- ciscoBay, on the westernedge of the innerCoast Range of centralCalifornia from August1970 to May of 1972. Numbersof eachspecies are tabulatedby 5-day periodsfor March, April, May, August, September,and Octoberand by monthsfor January,February, November, and December.There were no operationsduring June and July. Definitionof the timing of migratory passagevaries from excellentto obscureas a functionof suchfactors as type of residenceand juveniledispersal. Numbers of migrantsand timingclosely parellelsimilarly taken data from SoutheastFarallon Island.

ACKNOWLEDGMENTS

We extendsincere thanks to the 55 peoplewho participatedin field work, mostof them studentsenrolled in Biology190, FieldStudies in Biology,at San JoseState University.Their participationtime and personalexpense were far in excessof normal classrequirements. Robert M. Stewart,then Land Bird Biologistat PointReyes Bird Observatory,stimulated the initiationof the study.We thank WilliamG. Bousman, HowardL. Cogswell,Alan M. Craig,David F. DeSante,Thomas W. Keeney,John S. Luther, C. dohn Ralph, and Ralph d. Raitt for their very helpfulcomments on the manuscript.We thank MichaelRighey for preparationof Figure 1. Personnelof the U.S. Bird BandingLaboratory, Laurel, Maryland, were most cooperative.We are very gratefulto the E.O. Wool Ranch, Inc., and to Mr. ErnestO. Wool, Jr. in par- ticular, for accessto the ranch lands and useful ranch facilities.

LITERATURE CITED

Cortopassi,A. J., and Mewaldt, L. R. 1965. The circumannualdislribution of White- crowned Sparrows.Bird-Banding 36:141-169.

19 PASSERINE MIGRATION

DeBenedictis,P. 1967. The changingseasons. Am. Birds 21:4-6. DeSante, D. F., and Ainley, D. G. 1980. The avifaunaof the South FarallonIslands, California. Studies Avian Biol. 4. DeSante, D. F., and Geupel, G. R. 1987. Landbirdproductivity in centralcoastal California:The relationshipto annualrainfall and a reproductivefailure in 1986. Condor 68:636-653. DeWolfe,B. B., West,G.C., andPeyton, L. J. 1973. The springmigration of Gambers Sparrowsthrough southern Yukon Territory.Condor 75:43-59. Farner, D. S. 1955. The annualstimulus for migration:Experimental and physio- logical aspects,in Recent Studiesin Avian Biology. (A. Wolfson, ed.), pp. 198-237. Univ. IllinoisPress, Urbana. Grinnell, J., and Wythe, M. W. 1927. Directoryto the bird-lifeof the San Francisco Bay Region. Pac. Coast Avifauna 15. Johnson, N. K. 1965. Differentialtiming and routes of the springmigration in the Hammond Flycatcher.Condor 67:423-437. Johnson,N. K. 1970. Fall migrationand winter distributionof the HammondFly- catcher. Bird-Banding41:169-190. Johnson,N. K. 1973. Spring migrationof the WesternFlycatcher with noteson seasonalchanges in sex and age ratios.Bird-Banding 44:205-220. Kaiser, S. 1976. Passerinemigration through the inner coast range of central California.M. A. Thesis,San Jose State University. King, J. R., Farher, D. S., and Mewaldt, L. R. 1965. Seasonalsex and age ratios in populationsof the White-crownedSparrows of the race gambelii.Condor 67:489-,504. King, J. R., and Mewaldt, L. R. 1981a. The averagerate of travelby migratingWhite- crowned Sparrows, Zonotrichia leucophrysgambelii. N. Am. Bird Bander 6:98-100. King, J. R., and Mewaldt, L. R. 1981b. Variationof body weightin Gambel'sWhite- crowned Sparrows in winter and spring: Latitudinal and photoperiodiccor- relates. Auk 98:752-764. Littlefield,C. D., and McLaury, E. L. 1973. Bird arrivaldates on Malheur National Wildlife Refuge, Oregon. W. Birds4:83-88. Lowery, G. H., Jr., and Newman, R. J. 1966. A continent-wideview of bird migra- tion on four nightsin October. Auk 83:547-586. McCaskie, G., DeBenedictis,P., Erickson,R., and Morlan, J. 1979. Birds of North- ern California. Golden Gate Audubon Society, Berkeley. Mewaldt, L. R., Morton, M. L., and Brown, I. L. 1964. Orientationof migratory restlessness in Zonotrichia. Condor 66:377-417. Paxton, R. O. 1965. The changingseasons. Am. Birds 19:4-7. Ralph, C. J. 1971. An age differentialof migrantsin coastalCalifornia. Condor 73:243-246. Sibley,C. G. 1952. The birdsof the SouthSan FranciscoBay Region.Santa Clara Valley AudubonSociety, San Jose, California. Stewart, R. M. 1972. Fall migrationof common passerinesat Bolinas,California. Calif. Birds 3:9-12. Stewart,R. M., Mewaldt, L. R., and Kaiser,S. 1974. Age ratiosof coastaland inland fall migrantpasserines in centralCalifornia. Bird-Banding 45:46-57.

2O PASSERINE MIGRATION

Verner, J., and Boss, A. S. 1980. California wildlife and their habitats:Western Sierra Nevada. Gen. Tech. Rep. PSW-37, U.S. ForestService, Berkeley. Weston, H. G., Jr. 1948. Spring arrival of summerresidents in the Berkeley area, California. Condor 50:81-82. Wolfson,A. 1945. The role of the pituitary,fat deposition,and body weightin bird migration. Condor 47:95-127. Accepted 27 February 1988

APPENDIX

In shorterperiods of operationin the springof 1970, in late 1972, and in the years 1973 to 1979 another2142 birdsof 83 specieswere captured 2873 timesin netsand traps (Table A). These included four speciesnot captured during the main study: Killdeer, a resident (3), Say's Phoebe, a winter resident (1), TennesseeWarbler, a vagrant (1), and Canyon Wren, a resident(1). Severalresident passerines first encountered 1970-72 were stillbeing recaptured as late as 1979. These includedpermanent residents as well as migratorysummer and migratorywinter residents. We receivednotice from the U.S. Bird BandingLaboratory of four recoveries: 1. Swainsoh'SThrush banded 4 May 1970, recovered 17 May 1973 at Salem, Oregon. 2. Starlingbanded 24 November 1971, recoveredin July 1972 at Port Townsend, Washington. 3. Black-headedGrosbeak banded 22 September1971, recovered12 April 1974 at Taretan, Michoacan, Mexico. 4. Puget Sound White-crownedSparrow banded 7 October1970, recovered25 April 1972 at Duncan, British Columbia.

Table A Birds Captured in Mist Nets and Potter Traps in the Spring of 1970 and from the Fall of 1972 to the Fall of 1979

Species Jan Feb Mar Apr May -- Sep Oct Nov Dec Total

Sharp-shinnedHawk 1 1 2 Cooper'sHawk 1 1 California Quail 1 1 Killdeer 3 3 Mourning Dove 4 4 Western Screech Owl 1 1 Anna's Hummingbird 3 3 RufousHummingbird 1 9 10 Allen's Hummingbird 1 1 Nuttall'sWoodpecker 3 3 Hairy Woodpecker 1 1 Red-shafted Flicker 3 3 Olive-sidedFlycatcher 1 1 Willow Flycatcher 5 5 Hammond's Flycatcher 4 4 Gray Flycatcher 1 10 11

21 PASSERINE MIGRATION

Table A (Continued) Species ,JanFeb Mar AprMay -- Sep OctNov Dec Total

WesternFlycatcher 4 64 68 BlackPhoebe 1 1 1 3 Say'sPhoebe 1 1 Ash-throatedFlycatcher 1 6 7 WesternKingbird 3 3 HornedLark 2 3 14 5 1 25 Steller'sJay 10 4 14 ScrubJay 3 2 3 5 13 Yellow-billedMagpie 1 2 1 2 6 Chestnut-backedChickadee 2 2 Plain Titmouse 8 10 18 6 42 Common Bushtit 1 1 Red-breasted Nuthatch 1 1 White-breastedNuthatch 1 1 2 BrownCreeper 1 1 CanyonWren 1 1 Bewick'sWren 1 1 1 1 1 5 House Wren 1 1 2 Ruby-crownedKinglet 1 5 1 7 Western Bluebird 5 7 1 13 Swainsoh'sThrush 113 113 Hermit Thrush 2 3 8 36 3 23 75 American Robin 1 12 13 Wrentit 1 1 NorthernMockingbird 5 5 California Thrasher 1 1 CedarWaxwing 2 2 LoggerheadShrike 2 1 3 EuropeanStarling 2 1 3 SolitaryVireo 1 1 WarblingVireo 1 11 12 Tennessee Warbler 1 1 Orange-crownedWarbler 8 38 46 Nashville Warbler 1 7 8 Yellow Warbler 7 7 MyrtleWarbler 1 2 3 Audubon'sWarbler 1 2 1 4 Black-throatedGray Warbler 3 3 Townsend'sWarbler 4 4 Hermit Warbler 2 2 MacGillivray'sWarbler 1 19 20 Wilson'sWarbler 5 53 58 Yellow-breastedChat 3 3 WesternTanager 9 9 Black-headedGrosbeak 4 30 34 Rufous-sidedTow bee 1 1 1 5 1 9 Brown Towbee 2 4 6 8 7 3 4 1 35 Rufous-crownedSparrow 1 1 ChippingSparrow 7 60 1 68 LarkSparrow 5 2 9 3 29 27 1 3 79

22 PASSERINE MIGRATION

Table A (Continued)

Species Jan Feb Mar Apr May -- Sep Oct Nov Dec Total

Savannah Sparrow 20 1 2 7 1 31 Fox Sparrow 4 1 5 2 2 14 Song Sparrow 1 1 Lincoln'sSparrow 1 6 1 8 Golden-crownedSparrow 100 180 61 43 33 15 103 29 8 572 Puget Sound White-crownedSparrow 2 6 2 15 2 4 10 41 Gambel's White-crowned Sparrow 1 29 10 7 6 12 65 Oregon Junco 1 56 57 20 9 5 42 17 207 Red-wingedBlackbird 3 24 10 37 Western Meadowlark 7 1 8 Brewer's Blackbird 2 15 12 32 6 67 Bullock's Oriole 5 27 32 Purple Finch 1 1 House Finch 6 45 16 33 100 Lesser Goldfinch 5 29 34 Lawrence's Goldfinch 2 9 11 American Goldfinch 2 3 5 Total new captures 113 303 183 203 901 122 251 57 9 2142 Recaptures 28 83 161 183 220 2 44 8 2 731 Net hours 0 44 86 357 3997 ø 59 101 13 0 4657 Trap hours 132 90 239 261 33 19 106 91 12 983 a In May1970 nets were run 3,847 net hours -- fromdawn to dusk.

23 Sage Sparrows Sketchby Narca Moore-Craig

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