cooK•, Effect of Altitude on Bird Mt•ratt'on. [.July the good wish of that man, the
hurry he was in, and the vast many heresay accounts he depended on. _Nov.
338
cooK•,Effect ofAltitude onBirdMt•ratt'on.
[.July
the goodwish of that man,the hurry he was in, and the vast many heresayaccountshe dependedon. _Nov.2.5'th,•r82L Since I left Cincinnati I have finished 62 drawings of birds and plants,3 quadrupeds,2 snakes,fifty portraits of all sorts,and the large one of Father Antonio,besides giving many lessonsand I have made out to send moneyto my wife sufficientfor her and my Kentuckylads,and to live in humble comfortwith only my talentsand industry,without onecent to begin on.
THE
EFFECT
OF
ALTITUDE BY
WELLS
ON W.
BIRD
MIGRATION.
COOKE.
SURROUNDED by mountains,Asheville,North Carolina,is situated in the valley of the FrenchBroadRiver, at an altitudeof two thousandfeet. Directly eastis Raleigh, at about three hundred feet aboveoceanlevel. This differencein altitudecausesquite a differencein the climate of the two places; the averagetemperature at Raleighis about6oø F., whileat Ashevilleit is five degrees colder. The formeris in the Austro-riparianlife zone,the latter at the extremeupperlimit of the Carolinian. A differencein the avifaunanaturallyfollowsthesevariationsin climate. The higher altitudeof Ashevillepreventssomebirdsfrom occurringthere that are foundin summerat Raleigh. Amongthesemaybe mentioned the Chuck-will's-widow, Blue Grosbeak,and the ProthonotaryWarbler. In a largernumberof cases,birdsremainthroughthe winter at Raleighthat are seldomif ever foundat Ashevilleduringthis season. Examplesof thisclassare the SwampSparrow,Chewink• Brown Thrasher,and Ruby-crownedKinglet. These all appear at Ashevilleas springmigrants. A few mountain-loving speciesare regular visitorsat Asheville, but occur as rare stragglersonly at Raleigh. The Baltimore Oriole is a strikingexample,and the samepreferenceis shownby the Olive-sidedFlycatcherand the BlackburnianWarbler.
Vol. XXI-] COOKE, E•bclofAllilude onBirdAlt•'ralt'on. 339 x9o4
As would be expected,spring migration is, on the whole,later at Asheville than at Raleigh, and the voluminousrecordsof the
BiologicalSurveyfurnish data for a quite exact statementof the amount of variation in the times of arrival at the two places. The late J. S. Cairns sentmigrationnotes for the years i89o to x894, inclusive, from the town of Weaverville, ten miles distant from Asheville; Minor Davis recorded the dates of arrival of the
birds at Asheville in i899 , and W. M. Rackerr the samedata for i9o2 at Weaverville. These sevenyearsof observationfurnisha satisfactorybasisfor estimatingthe averagedates of arrival in this district. From C. S. Brimley, at Raleigh, the Biological Surveyhas receiveda very full report on migration for eighteen years,from •885, the whole forming,probably,the largestamount
of migrationdataever recordedby onepersonat any onelocality in the United States.
With this amount of material at command,
the movementsof the birds at Raleigh can be ascertainedwith great accuracy.
Twenty-one species of common birds arrive in the spring at
Raleigh,on the average,3.6 daysearlierthan at Asheville,or one day earlierfor each x.4øF. that Raleighis warmerthanAsheville. Most of these birds were migrating during April, and for this month the temperatureof the two localitiesdiffers scarcelyfour degrees. Therefore, it can be said that with reference to these
two localitiesspringmigrationis delayedone day for eachdegree of cold. This relation, of course,wouldnot hold goodfor other localities,thoughthe migration between Raleigh and Washington is not muchdifferent. During April Raleigh averagessix degrees
warmer than Washington,and the birds averageeight days in making the journeyof the two hundred miles betweenthe two places,or one and a third days for each degreeof temperature. The trip from St. Louis to St. Paul is performedat a rate of about a day and a half for each degreeof differencein temperature. These statementsare the averagesof such widely differing quantitiesthat they cannotbe used to ascertaineven approximately the time that any particular speciesrequiresin its passage from one locality to another.
The followingdatesshowhowgreatlythe differentspeciesvary in the time ot5their arrival at the two places, Raleigh and Asheville.
34ø
i_July CooKE, Effbcg ofAltigude onBird Mriffration. ['Auk
Averageof the first seen.
Difference.
Days.
Species.
R aleigh. Black and White
Warbler
March 26 "
Blue Gray Gnatcatcher Parula
Warbler
.
Rough-wingedSwallow Summer
26
April 9 • II
Asheville.
April
2
March 28
A•p•ril •6 14
Warbler
Whip-poor-will Ovenbird
Red-eyed Vireo Yellow-throated
Kingbird Wood
.
14
"
20
"
15
"
26
"
17
"
24
"
I8
•t
20
"
24
"
29
"
24
"
26
Vireo
.
Thrush
Ruby-throatedHammer Great Crested Flycatcher Hooded
"
Warbler
Summer Tanager Catbird Wood Pewee Chat .
Indigo Bird
Black-poll Warbler Yellow-billed
Cuckoo
Average
3 3 April •7
4
April 2•
3.6
In addition there are three speciesthat move much more
slowly;the Yellow-throated Warblerappearsat RaleighMarch 26 and is not seenat Ashevilleuntil April 2x, a differenceof 26
days. The corresponding datesfor the MarylandYellow-throat are March3ø andApril x8, a difference of x9 'days. For the White-eyed Vireothetimesof arrivalareApril2 andApril •5, a difference of x3days. Thesethreeare all earlymigrants, andit is truein generalthat the earliera species movesnorthward in thespringtheslowerwill be itsaverage dailyadvance.All three findnearAsheville theirhighestextension intothe mountains, and it is possible that this fact mayaccount fortheirdelayed arrival. Thoughwhenbirdsare migrating in a levelcountrytheopposite is true,-- theymigratemorerapidlyastheyapproach the northern limit of their range.
The mostinterestingphaseof the comparison of migration at the two localities is connectedwith the time of arrival of the followingspecies:
Vol. XXI'] s9o4 ..I
EATON-, SpriagBirdM•'gratioa, zclo?. Average of the first seen.
Difference.
Species.
Days.
Raleigh.
SolitaryVireo .
.
Worm-eating Warbler Scarlet Tanager.... Black-throated Rose-breasted
$4 I
Blue Warbler Grosbeak .
Asheville.
March 26
March
Ap,,u24 28
Ap,,il2o 2o
"
28
May 2
IO
i6 4
8
"
24
4
•l
23
9
Each of these species appears at Asheville, in the mountains, before being seen at Raleigh, on the plains. The probable expla-
nation of this anomalyis that each of these speciesbreeds commonly at Asheville, and rarely or never at Raleigh. There is here a striking and unexpectedexemplificationof the rule that the southernmostbreedtingbir•ts constitutethe van in spring migration. While the presentsum of knowledge is not sufficientto warrant
the statementthat this rule is universal,and very likely further investigationwill showsomeexceptions,yet the abovefactsfurnish strong evidence in its favor.
SPRING BIRD MIGRATIONS BY
ELON
HOWARD
OF i9o3 .
EATON.
B•RD migration is a very elusive subject. At least we have
found it so in westernNew York, after tryingfor years to determine its times and seasons, bird routesand isopiptoses, causesand results. Even if onecouldbe everywhereall the while at the same time, it would be difficult to run down the last factor in this com-
plex problem. Meanwhile we are after facts.
The writer has beengreatlydisappointed to find howimperfect are the recordsof observersin determining the presenceof a bird at any given station, rendering it almost impossible to draw cor-
rectlythe linesof simultaneous arrival. Consequently at Roches-
