Influence of Agriculture on Waterbird, , and Shorebird Use Along the Lower Colorado River 1

Robert D. Ohmart2 , Be rtin W. Anderson3 , and

Wil liam C. Hunter 4

Abs t ract.--Wat er , wader, and shorebird use of the Colorado River was restricted to habitats i n or i mmediately ad j acent to t he river prior to agricultural development. ~e studied agricultural habitats systematicall y for t hree years and identified those agricultura l se t ting s t hat were most import ant for individual spe cie s and groups of wa t erbirds , , and shorebirds .

I NTRODUCTION waders are associated with open wa t er and marsh habitats which, l i ke agricult ural areas, hav e The importance of ri par i an habit ats to wild­ increased substa ntially since t he beginning of t he and t heir rapid disa ppearance in t he wes tern 20th cent ury (Ohmart et al. 1977). Many of these has received much attent ion ov e r the pa st species make use of both aquatic and agricultural Conversion of riparian habitats t o areas for roosting and f or aging, res pectively. al l and accounts fo r a major portion of Geese, cranes, and sever al species are loss of riparian habitats . Yet, a gricultural examples. In addition, shoreline and sandbars are tats have r eceived l i t t le attent ion with very local in distributi on; whereas, agricultural to wi ldlife value s, with the exception of areas have proven to be among the most productive es on i nter f acing agriculture-riparian situa­ habitats for finding and stud ying many trans ient (Ca r others e t al . 1974 , Co nine et al. 1978) and resident shor ebird species on t he lower mo r e compr ehensive study of the influence of Colorado River (Anderson and Ohmart 1984) . ure on wi ldlife in the lowe r Color ado val ley ( Anderson and Ohmart 19 82). Fr om the We descri be agr i cultural featur e s most assoc­ study, we report here on the f a ctors that iated with occur r ence of waterbi rds, waders, and nee waterbird, wader, and shorebird use of shorebirds . ~e r eport habi tat use by pre sence/ icultural area s of the lower Color ado River a bsence cr i t er ia becaus e of t he er r atic oc cur­ ley. rences of some agricultural f eatures , the f locking tendencies of s ome species vs. t he sol itar y natur e man y terrest rial riparian bird of others, and t he overal l low densiti e s of many suffered f r om heav y habitat loss in species treated here. Finall y, we exam ine the conv ersion of land to agricult ural production minimum range of agricultural features nec es sary the l owe r Colorado River valley (approximately t o maximize use of an area by wa t e rbirds, wader s, 000 ha si nce 1890) , seve ral groups of species a nd shorebirds in t he lowe r Color ado River valley. ag ricultura l habita ts have increased. rds, waders, and shorebirds are among the lpe ci es t ha t have benefitted from or a t l east make DBe of agricultural features. llist waterbirds and METHODS

1 The general s t ud y area i ncl udes agr i cultural Pa pe r present ed a t t he Ri parian Ecos ys tems land in southwe s t e rn Arizona and southeastern Their Management: Reconciling Conflicting Californi a . Fi ve localities we r e s t ud ied; these COnfe r ence . [University of Arizona, Tucson, included t he Wellton- Mo hawk and I mperia l-Coachella 16-1 8 , 1985 ]. valleys, the Mohave and Colorado River Indian Rober t D. Ohmart is an Associate Director of Reserva tions, and Cibola National Wildl i fe Ref uge :he Center for Environmental Studies at A.rizona (Anderson and Ohmart 1982) . The l a tte r three tat) Uni versity, Tempe , Ariz. s ites are directl y ad j a cent to t he l Ower Colorado Bertin W. And e rson is a Research Associate of River. :he Center for Environmental Studies at Arizona ta t ~ Universit y, Tempe, Ariz. we re censused along 23 4. 8-km transects Ia William C. Hunter is a Graduate Re search three times pe r mo nth . Agricultural land along Bistant in the Center for Env i ronmental St udi e s each transect wa s subdivided i nto 0.2- or O.4-km It Ari zona Sta t e University, Tempe, Ar i z . s ections; each secti on usuall y repr esented a dis­

117 Table 1.--Numbe r of times each fi t inct unit containing only one field t ype . Sam­ (4 eld ty pling included the area wi t hin 0 . 2 km l ateral to ha or more) on agricultural c pe occurr wa terbirds and waders ( full h ensuses f ed each side of the transect , and t he t otal numbe r of h t ree or hectares censused was calculated . In additi on, we s orebirds (migration periods onl years) alld times cr op/fea t ure censused' P y) . 1/ .. mea sured the extent of inhabi ted areas, margins, ' r op. '" pr canals , and feedlots. tion. °por_

Major crop types included cotton , alf alfa, grass, wheat , and milo . In ad diti on , f ields gr ow­ Waders and Wa ter birds ing lettuce , squash, t omatoes, onions , a nd melons ----­Shorebirds were grouped under the cat egory of truck crops because they are structurally similar , and -:------. cultivation and harvesting techniques are simil ar. Crop/ Prop. feature Irrigated N of t otal Prop. When a field was be i ng changed from one crop type N of tOt al to another, it often was cleared; such f ields were ref e r red to a s plowed. Each field t ype wa s cate­ Plowed Yes 73 0 .017 gorized as to whether or not i t was irrigated and 54 --­0.032 No 46 8 whether t he crop was > or <25 cm tall. 0 .109 308 Alfalfa 0. 185 Yes Waterbirds and waders were censused monthly >25 cm 55 0 .013 34 No 0.02 0 from March 19 78 through Octo ber 1980. The number >25 cm 432 0 ~101 162 cm Yes 49 0.097 of times each crop /feature type was censused and <25 0.011 21 <2 5 cm No 39 3 O.Ol l the numb er of t imes each species was present in 0 .092 95 Cot ton 0.057 t he field type was t abulated . A significant num­ >2 5 cm Ye s 75 be r of occurrences i n a given situation was deter­ 0 .018 57 0.034 cm No 388 mined by finding t he proportion of that feature >25 0 .091 220 0.132 Ye s 23 among the total crop/feature occurrences. This <25 cm 0 .005 12 0.007 No 177 proportion was t he number of times a species would <25 cm 0 .041 99 0.059 Milo be expected to have been recorded in t hat situa­ Ye s 11 tion if its occurrence was purely random. A sig­ >25 cm 0.003 No 48 nificant as sociation between the species and the >25 cm 0 . 011 Ye s 0 crop/feature was defined a s t hose cases where the <25 cm 0 .000 number of occurrences within a pa rticular situa­ <25 cm No 16 0.004 ,\. tion was significantly larger than expected at Whea t PiO .05 . The number expected was the proportion of >25 cm Yes 22 0 . 005 25 0. 015 >2 5 cm No 163 0 . 038 121 0.072 '.~ the crop/feature occurrences in the total pool of 15 i crops and features multipl ed by the total number <25 cm Ye s 0.004 18 0.01 0 148 of occurrences of the speci e s . This approach <25 cm No 0.035 51 O.Oll ide ntified important crops and feature s fo r each Truck crop s pecies, and general t rends amo ng spe cies groups >2 5 cm Ye s 6 0.001 3 0.002 were defined to maximize agricultural use by >25 cm No 51 0.012 29 0.017 0 .002 2 bi r ds • <25 cm Ye s 9 0.001 <2 5 cm No 82 0 . 019 23 0.015 Sho rebird occurrences were t a bula ted for Grass 0 . 002 7 0.0 04 Ma rch-May (vernal migration) and July-Octo ber >25 cm Yes 10 0 . 025 70 0.041 ( autumn al migration) during 197 8, 1979 , and 1980. >25 cm No 107 1 0.003 14 0.008 These months were periods of peak occurrence f or <25 cm Ye s 14 <25 cm No 132 0.031 62 0.037 mos t s pe c ies~ Shorebi rd associations wi th crop/ 0.039 182 0.1 09 feature type s were identified f o r each species as Canal 165 0.116 de termined for waterbirds and waders. Addi t ional Margins 496 0.021 a nal ys is was used to determine overall use of Inhabited 88 crop/fea tures by shorebirds. We determined if the number of fields with shorebirds was significantly l arger or smaller t han would be expected by cha nce Perce ntage of irrigated field types for the entire (PiO .05) for each crop/feature type. Lastly , we census period was 8.4% , and during the period of determined if there was a greater use of either s horebird censusing the percentage was 14.6% . i rrigated or noni r riga ted f ields acr oss all crop Mi lo, marg ins, and inhabited areas were not used types f rom a rand om distribution (PiO.05 ) for ea ch by any shorebirds so were not included in anal ysis shorebird s pecies. for this species group .

RESULTS Wading Birds The (Ca smerodius albus) , Great Crop/Feature Types Blue Heron (Ardea he rodias), Gree~ked Heron The mo st often encountered crop/feature types (Butorides str iatus) , and Snowy Egret (~ thula ) were ass oci a t ed with canals far more than i nclude, in order of highest-to-lowe st frequency Oi with a ny other agricultural fea ture (table 2). 1 of occurrence , margins, nonirrigated plowed, non­ t he se spec ies, the Green-backed Heron was the irrigated alfalfa >25 em , non1rrigated alfalfa o~ ,; heron to be largely restricted to canals with t 1 <25 cm , and nonirri gated cot ton >25 cm ( t able 1). 2.--Fields i n wh ich use by wading birds was signif icant ly ( P<0.05) grea ter than expected wi th a random distr i bution . IR = i r r igated ; NI = no t irrigated ; ) = height greater than 25 cm; < = height l ess t ha n 25 cm; + i nd i c ates pr e s ence in crop/feature but not significantl y associated with i t . Not all fiel d types are r epresented, only those are shown t hat had at l eas t one species s i gnif ica ntly associated with i t.

Percent of total occurrences

Alfalfa Plowed Milo Grass To t al % Total sign. oc currences Canals

109 55 + 15 + + 70 64 56 + 17 + + 73 37 81 81 Egret 26 19 8 + 4 + + 4 35 Eg ret cus ibi s) 109 + + 4 6 + 6 + 4 6 15 41 \ ~:.:.:--....,. Ibis \~;><-_ chi hi) 15 + 33 7 20 + 7 67

74 + 20 + 24 + 19 8 4 + 75

f or 81% of its t otal occurrence important to puddle ducks and ge e s e , given the t ural area s . Snowy and Cattle egret num ber of occurrence s compared with other species i ons were closest to a random distri bu­ within this group. ac ros s available agricultural features among Shorebirds

Cattle Egr et, Wh ite-fa ced Ibis, and Sa nd­ Fifteen of 17 species of shore birds were were not signific an tly associated with significa ntly associated wi th irrigated plowed (table 2). The Ca t tle Egre t was signifi­ f ields (tabl e 4) . In addit i on, four species each plowed, alfalfa, and gras s were significantly associated wi t h nonirrigat ed matter wh e t her the fields plowed, i rrigated and nonir rigated grass <25 cm; In contrast, t he wint e ring t hree species with i rrigated wheat )25 cm; two Cr ane occurred almost exclusively in non­ specie s each wi th nonirrigated alfalfa <25 cm, alfalfa , plowed, a nd milo f i elds; where­ i rrigated and nonir rigated grass )25 cm, and the other extreme, t he migratory Whi te­ canals. Significant associations with f i eld types s occurred only in i rrigated alfalfa, we r e r estricted to plowed fiel ds for nine s pecies I and grass fields. with all but t wo of these only wi t h irr i gated plowed fie lds ( t he exceptions were Bl a ck-bellied Wat erbirds Plover and Mountain Plover). Common Snipe and Spotted Sandpi per were associated mos t signifi­ bes , cormorants , coots, and diving ducks cantly with cana l s over all other crop/fe atures. rds and mergansers) were overwhelmingly with canals (table 3). Gee se were Eight specie s occurred significantly more exclus ively with plowed, alfa lfa, milo, oft en in irriga ted than in nonirrigated fields and grass fie lds , wi th all but the Snow (table 4). Four s pe cies occur r ed signi f i cantl y Occurring l argel y in nonirrigated fields. mo re often i n nonirrigated than in i rri gated ducks we re associated both with canals and fields. Ove r a l l, ther e were 26 signifi cant ted crop s wi t h t wo s pecies (Ame rican Wigeon associati ons between shore birds and irr i gated tn Pintai l) occuring only in irrigated f i elds and 12 with nonirrigated fields, wi th e i ght species signif icantly associated wi t h at least one each i rriga ted and nonir r igated crop/feature type. 1i1ne teen of the 25 species t reated under t his have 100% of their occur rences associated All shor e bi r d oc cur rences t05ether ind i cated y wi th one or more agricultur al crop/ that they were f ound more of t en t han expected by types. Ho wever, t hree species (Snow chance alone i n irrigated and nonirrigated plowed, 6 0~l1 a rd , a nd Northern Pintail) have less irrigated grass )25 cm and <25 cm, irri gated wheat of their occurrences associated signifi­ )25 cm, and canals (table 5) . Shorebirds occurred h ~t h some agricultural crop/f eatur e and less often t han expect ed by chance alone i n non­ ~ve a mor e r and om distribut ion in agricul­ irriga ted alfal fa )25 cm, i rriga ted and nonirri­ abitat s. Ag ricultural situations were mos t gated cotton )25 cm, and non i r rigated cotton

1 19 --

Tabh 3 .--Agricultural c rops and f eatures with ~hich , cormo rants, coots, ducks . a nd geese 'Were associat ed ~ith a frequency g reater t han expec ted with a random dist r ibution . Abbre viat ions, symbols, and notes as i n t a hIe 2.

Percent of tot al occurrenc es

Plowed Alfa lfa Milo Wh e at Grass To t al % To tal sign. Spe c ies occurrences Cana ls l R Nl >IR >Nl IR >Nl (IR ( N1 ) IR

Pied-billed (Podilym bu s podiceps) 100 100 Eared Grebe (Pod1ceps nl gri collis) 100 100 Double- c res ted Cormo rant (Pha lac roc orax aurl t us) 100 100 Amer i can Coo t ( Fu lica ame ricana ) 100 100 Common Me rgans e r Cr (Mergus mer ganser ) 12 100 100 fe Red-breasted Me rga nse r (M. serratod 3 100 100 Bufflehead (Bucephala albeola ) 2 100 100 Commo n Gol deneye (!. c langula ) 15 80 80 Total Me rgi ni 32 91 91 P: Grea t er Scaup eAy thya marUa) I 100 100 Lesser Sc aup ( ~. ~) 4 100 100 Redhead (A . americana) 4 25 50 25 100 Ring-necked Duck (~.' c011aris) 3 100 100 To t al pochards 12 7S 17 100 Wood Duck ( Aix sponsa) I 100 100 Cinnamon Teal ( Anas cyanoptera ) 63 S6 16 5 86 Blue -winged Teal (A . discors) 5 60 20 80 Green-winged Teal (A.~) I S 47 40 100 Nor the r n Shoveler (:! . clypeata) .3 33 67 100 Malla rd (.! . pla t yrhynchos) 12 25 33 + + + 58 Ame rican Wige on (A . amer icana) 6 83 17 100 Nor t he r n Pinta il TA .~ 27 48 + + + S9 Total pud d le du cks­ - - 131 38 31 78 Canada Goos e (Brant a canadens is) 30 30 23 27 90 Bran t (8. bern1cla ) I 100 100 G re B te r-Wh~t ed Goo se ( Anser al b1 frons) 100 100 Ros~se (Chen ross11 ) 100 100 Snow Go ose C.£. . cae rules c e ns ) 9 II + + II + + + 22 Total ge e se 43 24 22 36 4 88

, ~

Ta ble 4 . - - Agr 1cult ural crops and fea t ures with wh ich shorebirds were associated with a f requency g reate r tha n expected with a random distribution on transects . Ab breviations I s ymbols I a nd notes as 1n t able 2 .

Percent of total occurre nces

All c ropl Plowed Al fal fa Grass Whe a t Pe rcen t feature s accounted TotCll f or by Spe c ies occurrences 1R N1 (N1 )IR ) N1

Black-bellied Plover (Pluv1al1s s quataro la) 19 42 37 + + 79 + + Killdeer (Chsradrius vociferus) 287 II + to + + + + + 25 + 68 Mounta in Plove-r --­ (C . montanus) 16 25 63 88 + 69 Black -~tUt (Himantopus mexicanus ) 28 2S + + II 11 54 + + American Avocet (Recurviros t ra americana) 67 + 67 78 + Greate r Yellowleg-.--­ (Tringa melanoleuca) 36 30 10 53 + + Lesse r Yellowlegs (!. flav1pes ) 50 + + 50 + + Wil l et ( Ca tOEtroEhorus semiealmatus) 18 39 + + + + + 39 + + Spotted Sandpiper (Aetltis macularia ) 29 + 83 100 Whimhel ---­ (.Numen 1us phaeopus ) 45 36 + + 22 75 75 + Long-billed Curlew ( N. amer icanus ) 53 II 27 13 + + 19 + 78 + 68 Western Sandpiper (Calidris mau!"i) 10 40 + + 40 70 + Least Sandpi~ (C . minu t illa ) 61 30 + + + + IS + 48 64 + Long-b~it che r (Limn od r omus scol opaceus) 27 41 + + + + 41 63 + Common Sni pe (GalUnago 8al11n8go) 17 + + 12 59 71 82 + Wi! son Pha l a rope ( PhalaroEu s t!" icolor) 38 + + 38 88 + Ring-bil led Gu-n--­ (~ delawsrensis) 37 30 46 + + + + + 76 + 65

1 2 0 __overall s ho rebi rd use of agriculture by t ion of the environment by humans . Clearing of 5~bers of s pecies and all shorebi rds com­ land for agricul tural purposes creates new habi tat • d Irr . - i rrigated; Pres . = present ; f or species t hat previously may not have occurred e bin •a ssoc. = s ignifica ntly a ssociated; Obs . i n t he area while , a t the same t ime, destroying S ig~:erved· Exp . = expe c t ed ; NS = not sign i f ­ habi tat that may cause t he origi nal fauna to dis­ . o ~ , a ppear unle ss these latte r specie s are a ble to take advantage of t he new s i tuation. All of the s pecies treated here have i ncreased i n t heir occurrence in Number of Fields with the valley since the 1800' s due l a rgely to t he species shorebirds a ctivities of man, including agricultural prac­ tices, s torage of wa t e r i n large reservoir s ( pri­ marily for irriga tion), and creation of stable Sign . Binomial marshlands. I rr. Pres. assoc. Obs . Exp. P Grinnell (1914) described t he lower Colorado River's aqua tic and semiaquatic avifauna as depaup­ e r ate; he recorded few s pe cies and low numbers of Yes 17 15 32 12 .5 +<0.001 herons, waterfowl, and shorebirds north of the No 13 4 130 72 .3 +<0.001 Gila-Colorado river conf luence. Presently, all of these species occur in rather stable numbe rs re­ Yes 5 0 8 7.8 NS sponding to the food resources provided by agricul­ No 7 0 18 37.9 -<0 .001 tural a reas, roosting and foraging sites of open Yes 8 0 9 5.1 NS water areas, and/or a comtinati on of these . The No 8 2 23 22.3 NS vast majority of species treated here are transient and winter visitors and do not depend on agricul­ Yes 5 0 7 13 .3 -<0.05 tural areas for nesting. Exce pti ons are Killdeer No 4 0 9 51.6 -<0.001 and a few Cinnamon Teal. Ye s 4 0 3 2.7 NS No 2 0 6 23 .1 - <0.001 Cranes and geese are almost totally dependent on agricultural areas for forag ing . On t he three Yes 9 2 3 1.2 NS lower Colorado River national wi ldlif e refuges, No 9 2 12 16 . 8 NS recent increases i n abundance for both cranes and Yes 11 4 10 2 .4 +<0.001 geese a re a t tributed to managing aquatic or semi­ No 8 4 21 16.8 +<0.025 aquatic roosting sites with adjac ent agricul t ural f oraging sites ( mo stly alf alfa and milo f ields). Yes 1 0 2 0 NS Shore bird , wa terbird, and wading species associated No 1 0 6 7.4 NS with irrigated fields mus t t r a ck this resource as Yes 1 0 1 0 NS f looded f ields a re infrequent a nd ephemeral. No 3 0 4 5.9 NS Flooding of fields attracts not only spec ies t r eated here, but also swallows, water pipits, and Yes 6 3 12 5.9 +<0 . 01 blackbirds, which flock to f eed on inve r-t ebr ates No 7 0 12 28 . 2 - <0.001 d ispla ced by irrigation water. Wa terbird and some Ye s 4 0 2 3.9 NS wading s pe cies (especially Green- backed He r ons) No 2 0 7 12.1 NS find more stable foraging sites in the extensive canal systems, e speci ally along large r dirt-banked 7 2 59 42 .6 +<0.01 c anals that usually have a constant flow of wa t e r. Spotted Sandpipers and some wa terbirds use the more sterile cement-l ined canals to a greater extent. The most abundant f i eld type s were no t the places where shor ebirds occurred Several species trea ted here have undoubtedly equently. Although cotton f ields were undergone range extensions directly associated with largely by shorebi r ds , these f i e lds the expansion of agricultural practices. Most dra­ "'--" "'C.l ~ enhanced shorebird habit a t because t hey matic has been t he expansion of the Cattle Egret, ~ri odically plowed and attracted significant origi nally i n troduced fr om the Old World into t he of shorebirds . Overall, shorebird New World Tropics . This s pe cies became establ i s hed , ~curr.n,'~ i n agricult ur al area s wa s related to in the southeastern United States in the 1950's and icultural pra ctices (plowi ng, has s pread north and wes t into a reas of extensive and wi th t he presence of canals. agri cultural and horticultural production. Cattle , 12 of the 17 species pref erred either Egrets we re f irst found on t he lower Colorado River ted or noni rriga t ed fields and did not ran­ i n 1970 and are on the verge of establishing sever­ occur in both situations. In order to maxi­ al breeding colonies . Mo unt ain Plovers and Wh im­ diversity of shorebirds, a mosaic of irri­ breIs were considered casual in Arizona before the and nonirrigated fields are desirable. 1940's (Monson and Phillips 1981), but both species a r e now regula r, and hundreds of i nd ividuals occa­ sional l y occur in agricultural sit uations . DISCUSS ION Most , if not all, s horebirds have benefitted As Or ians (1975 ) has stated, t here is a need to from vari ous agricultural features on t he lower organisms t hat have be en exposed to pertur ­ Colorado River, although this r egion is not a major resulting from the unprecedented modifica­ migration route for t his group . However, shorebird

121 use of agricul ture in regions where shor elines and Cali fornia and western Ar izona . US ' estuaries have been extensively developed , such as of Reclamat ion , 316 p . Lowe r COlo;a~ Buteau in Florida and California, i s in need of i mmediate Boulder City , Nev . 0 RegioQ att ention , given t he de sperate situa t ion out l i ned Anderson, B. W., and R. D. Ohmart. 1984 ' by Myers (1983) f or this group. Our paper outlines Vegetation management study for the • important agricultural features for shorebird use enha ncement of wildlife along t he 1 OWe t t ha t may be compared with data collected in othe r Colorado River. Comprehensive final reg i ons. U.S. Bureau of Re clamation, 529 p. Lrepott to Colorado Reg ion, Boulder City , Nev . OWet Of all the ha bitat changes experienced in the Carother s, S. W., R. R. J ohnson , and S. W 10wer' Colorado River valley , as we ll a s many other Aitchison . 1974. Population structu' , . f h re and major southwestern r iparian systems, the conversion socia1 organ~ z at~on 0 sout western r1 of vas t areas to agricultural production is cer­ birds. American Zoologist 14:97 -108 patian t ainly the most drama t ic. The abundant foods pro­ Conine , K. H., B. W. Anderson, R. D. O hm~ t vided by agri cultural habitats benefit a wide J. F. Drake. 1978. Responses of rip: 1and variet y of bir ds that can opportunistically use species to agr icultural habit a t conver:ian them . Si nce ne sting s ites a r e not a concern for p . 248-262. In Strategies fo r protectio~ns . ma ny of these s pe cies on the lowe r Colorado River , management of floodplain wetl ands and oth e~nd t hey may a ttain relative ly hi gh densities. If sur­ riparian ecosystems. Pr oceedi ngs of the v ival has been high i n these over wintering or s ym pos ium. [Callawa y Ga rdens, Ga • , De cetn,Ler mi grator y indi viduals, then the population biology 11 - 13~ 197 8] US DA Forest Service General of these s pecies may be changing, with effects per­ Tech~~cal Rep?rt WO-12, 41 0 p. USDA Forest haps ev i dent on their northerly breeding grounds. Serv ~ce, Wash~ng t o n , D.C. Grinnell, J. 1914 . An account of t he mammal Although a numce r of specie s are benefitting from • • 5 and the development of agriculture, t he futur e of many b~ rds , of the lower Colorado R~ ver Valley with ripa rian species in agricultural areas is not opti­ es pec ~al r eference to t he dist ributional mistic unles s a mosaic of native riparian habitats problems presented. Unive rsit y of California and devel oped lands is managed for conserving both Publ i cations in Zoology 12:51-294 . the original and new avifaunas. Monson, G. , and A. R. Phillips. 1981. Annotat ed checklis t of birds of Ar i zona, Second edition. University of Arizona Press , Tu cson, Ar iz . ACKNOWLEDGME NTS 240 p. Myers, J. P. 1983. Conservation of migratory

,~" . The developmen t of this work and t he agr i cultural s horebi rds: s taging area s, geographic study a s a whole was aided by George F . Dr ake and bott lenecks, and r egional moveme nts. Americ an Kathleen Conine. ¥~r k Kaspryzk and Camil le Romano Birds 37: 23- 25. organized and accom plished much of the original Ohmart, R. D., W. O. De ason, and C. Burke. 1977 . data analys is . We thank the many dedicated biolo­ A r iparian case his tory: the Co l or ado River. gist s ~n o assisted in data collection and analysis . p . 35- 47. In Impor t ance, preservation and Edi t or ial a s sistance was provided by J ane R. Durham management Of r i parian habitat: a symposium. and Cindy D. Zi sner . Cindy D. Zisner also t yped Pr oceedings of the symposium. [Tucson, Ariz" t he manuscript. Th is s tudy was supported by U.S. July 9 , 1977J USDA Forest Service General Bureau of Re clamation Contract No. 8-07-30-X0027. Te chnical Report RM-43, 21 7 p. Rocky Moun ta io Forest and Range Expe r iment Stat ion, Fort Collins, Colo. LITERATURE CITED Orians, G. H. 1975. Diversity, stability and ma t urity in natur al e cosystems. p. 139-151. Ander son , B. W., and R. D. Ohmart. 1982. The In W. H. van Dobber and R. H. Lowe, eds., infl uence of the inters persion of agriculture Unifying Concepts i n Ecology. W. Junk, The and natural habi t a t s on wildli fe in southe rn Hague, Holland.