284 HARDY,'s Book Cliffs and Bird Migration L['Auk April

The specimenis much blacker than most breedingbirds from Nova Scotia to Ontario, and comparedwith worn Newfoundlandbirds, loaned through Dr. H. C. Oberholser by the Cleveland Museum of Natural History, appearsreferable to nigrideus. Hitherto the specieshas been recorded three times in Greenland: Qornoq near Godthaab;Sukkertoppen and Graedefjord. H•rring and Salomonsen,1941, p. 74, refer'the earlier recordsto T. m. migratorinsLinnaeus, apparently without consider- ing the then newly describedrace nigrideus. It is probablethat all the recordsbelong under the heading Turdus migratorins nigrideusAldrich and Nutt. I am aware that occasionaldark birds, as dark as nigrideus,occur in the populations of T. m. migratorins,as far west as the Mackenzie delta, and the Greenland speci- men might be a dark example of migratorins, but it seems advisable to refer it to nigrideus on probability.

OLDENDOW,•. 1933. Fugleliv Grinland. Der Gronlandske Selskabs Aarsskrift, 1952-1933: 17-224. SCHI6LER,]•. L. 1926. Danmarks fugle. Med Henblik paa de i Grinland, etc., 2. (KCbenhavn.) SALoMONSEN,FINN 1935. Some records on birds, new or rare to Greenland. Meddelelser om Gron- land, 93 (no. 6). H•tRRINO,RICH., ANDSALOnrONSON, F•NN 1941. Further records of rare or new Greenland birds. Meddelelser om Grin- land, 131 (no. 5). PHILLIPS, 3OI-IN C. 1923. A natural history of the ducks, 2. National Museum of Canada Ottawa, Canada

UTAH'S BOOK CLIFFS AND BIRD MIGRATION

BY ROSS HARDY THE majority of the mountain rangesof westernNorth America have their main axesrunning in a north-southdirection. One of the most important exceptionsto this is the of north- eastern Utah which extend about two hundred miles eastward from the northern Wasatch Mountains into . The West and East tavaputs plateaus,located about 100 miles southof the Uintas and running in a paralleldirection, are not sowell known. The southern faceof the WestPlateau is mucheroded, forming many vertical cliffs varyingfrom 300 to 1500feet in height. Thesesouthern supporting rampartsof theseplateaus, known as the Book Cliffs, form the north- ern boundaryof CastleValley in Carbon, Emery, and Grand coun- ties and the southernboundary of the'. The Greenand Pricerivers pass through these mountains in narrow,winding canyons. Vol.x94764] -• HAgl)¾,Utah's Book Cliffs and Bird Migration 285

Price, in CastleValley (altitude: 5567 feet), is at the southernedge of thesecliffs. The summitof the West Tavaputs,less than ten miles north, varies from 9000 feet to 10,050 feet. The cliffs north of Price, in the Kenilworth area, rise very abruptly, having a vertical south- ern exposure. Springbird migrationinto thisregion seems to comedirectly from the south,passing over the low-lyingmesas and foothillsof the ex- tensiveCastle Valley or comingalong the Green-PriceRiver system from the southeast.After passingthrough these low areas,the birds encou/qtera mountainrange standing across their pathwaywhich providesan almostmile-high change in elevation. Perhapsthis acts as a temporaryobstacle to many birds, especiallyif there is a dense cloudbankrising another mile or so higher and hiding the upper parts of the mountains. The sheerledges below the cloudsrising hundreds of feet into the thick mists would appear as a barrier. This is believedto retard temporarilythe migration of birds in the spring. While the proof for thesestatements is by no meanscon- clusive,it is believedthe idea may be of value to future investiga- tors who may be interestedin this problem; at least certain data are best explainedon the basisof this hypothesis. Observationswere made by the writer from September, 1933, to May, 1935,at Spring Canyon,in the westernpart of the Book Cliffs; during 1935-1936at Sunnysidein the easternpart of Carbon County's Book Cliffs; and from September,1936, to May, 1938, at Price, on the Price River betweenthe two first-namedpoints. Usually many more migrantsare seen in the spring than in the autumn in spite of the fact that the total populationof a species traveling southwardafter the nestingseason is undoubtedlygreater than the northward-movingspring population. Somespringtime mi- gratingbirds delay to feed in this area while waiting for the higher snow-covered areas to the north to become warmer. But not all these birds nest in thesemountains, for someof them migrate farther and are not found in the areasimmediately to the north. The Northern Sage Sparrow (,4mphispizabelli nevadensis)is commonin the sagebrushareas of the pigmy conifersand in the greasewoodin spring. These sparrowswere especiallynumerous after the beginningof a springstorm. In spiteof almostdaily visits to the areasaround Price, only one autumnrecord has been obtained-- that of a singleindividual collected on October10, 1936,in the pig- my conifers. This specieswas abundant in the same areas from March 17 until April 7, 1937. 286 HAdtoy,Utah's Book Cliffs and Bird Migration I.[Auk April

Likely when stormsare present,the sheercliffs delay the north- ward migration and the birds remain at Price and near by. The northern slopesof thesemountains are without cliffs and have a more gentle slope,and birds approachingfrom the north would travel over this gently rising incline for about thirty miles before comingto the abrupt edgeof thesecliffs that drop to the valleybe- low. Also, thunderstormsof the type which causehigh cloudbanks to rest upon the tops of thesepeaks were observedless often in the autumn than during the spring and summer. Birds such as Sage Sparrowsmigrating through the area in the autumn, once they reachedthe summit of the plateau, would no longer be impededin their flight and would not linger near Price as they did in the spring. Many cloudsrested on the mountainsummit north of Price just before sunseton March 16, 1937. A rather heavy rain had ceased and cloudbankshung east, west, and north. The sun occasionally shone for a few minutes from the west. The mountains and the heavy cloudbanksnorthward seemedto act as a barrier to further migration,for more Mountain Bluebirds (Sialia currucoides)and WesternRobins (Turdus raigratorius propinquus) were in the pigmy forest area on this night than on any other night observed. Flocks numberingfrom four to twentyindividuals were seenin numerous juniperand pition trees. It wasimpossible to gomore than fifty feet in any directionwithout encounteringthese bir•ls. As dusk cameon, a few flewnorth, but their placeswere filled by arrivalswinging their way in from the south. When last seenat dark, the treeswere lit- erally filled with Bluebirdsand Robins. The last of the northward- passingMontana Juncos (Juncooreganus raontanus) twittered as they settleddown in near-bybranches for the night. The next morn- ing, when it was clear weather,these birds had all gone. On other evenings,when the horizonwas clear or nearlyso, only a very small fraction of this number of Bluebirds and Robins were in these trees, althoughfully as many were seenwinging their way northward. A weekof stormyweather often keepsmany waterfowl along the PriceRiver, but immediatelyupon the clearingof the weather,the waterfowldisappear. During clearweather, far fewermigrants are observedalong the river than duringstormy weather. So oftendid thisoccur that many of thezoology students at CarbonHigh School commentedupon the factthat waterfowland wading birds, usually rare alongPrice River, wereabundant during stormy weather but wererarely found when the stormended. Someof the speciesso affectedwere the White-faced Glossy Ibis, Brewster's Egret, Treganza's Vol.194764 .••] HOWARD,.4 Question in Taxonomy 287

Heron, ducks,and smallershore birds. Likely during clear weather thesewater birds follow the Price River northward through the nar- row winding Price Canyon. During stormyperiods, the fog in this area would discouragesuch movement. During stormsalong other streamsmuch farther south in Castle Valley, as well as elsewherein Utah, the writer has not found con- centrationsof migratingbirds to the sameextent as that which seems to be causedby the combinationof cloudbanksand a long east-west range of mountainsin the Book Cliffs region. Weber College Ogden, Utah

AN ANCESTRAL GOLDEN EAGLE RAISES A QUESTION IN TAXONOMY BY HILDEGARDE HOWARD I• studyingthe eaglesof the Rancho La Brea Pleistoceneseveral yearsago (1932), I noted certain sizediscrepancies between the limb bonesof the fossiland the modern Golden Eagle. However, as there were available for study, at that time, only a very few skeletonsof modern Golden Eagle for comparisonwith the great seriesof fossils, no conclusions were drawn on the basis of these observations. After Harvey Fisher'sdiscovery (1944) of the small but important differencesbetween the fossil and living California Condor, it ap- pearedwise to review the subjectof the Golden Eagle in more detail. A considerablygreater number of modern bones are now available for comparison,numbering from 20 to 30 for all important limb elements, and about 18 skulls. The available fossil bones, however, still far exceed the modern, in most instances. With regard to limb elements,the most outstandingdistinction between fossil and Recent bones lies in the fact that, whereas the fossil humeri and ulnae averagelarger than the modern, and attain a maximum of 10 min. greater length, the tarsometatarsiaverage shorter,and none of the 660 bonesequals the maximum for the Re- cent eagle. Unfortunately, in no instancein the fossilseries are wing and leg elementsof individual birds associated.It is hardly proper, therefore,to statedefinitely that the Pleistoceneeagle had relatively shorterlegs and longer wings than the living bird, although the evi- dencefrom disassociatedbones points in that direction. Examination of individual bones in series of each limb element does not show any proportional or structural differencesbetween fossil and modern bones.