Movements of Michigan Herring Gulls*

BIRD-BANDING

A JOURNXL OF ORNITHOLOGICALINYESTIGATION

Vol. XXX April, 1959 No. 2

MOVEMENTS OF MICHIGAN HERRING GULLS*

BY W. JoHN SMITH

INTRODUCTION Since July 1931 Mr. Claud C. Ludwig of 279 Durand Street, East Lansing,Michigan, and his two sons,Dr. FrederickE. and Dr. Claud A. (and sometimesa small crew of helpers), have banded a total of 37,414 juvenile Herring Gulls, Larus argentatus,in 17 Michigan colonies.Mr. Ludwig recentlyhas made his carefully kept recordsof this work availableto Dr. GeorgeJ. Wallace of the Departmentof Zoology,Michigan State University, for analysisby a student. This report is that analysis. Sincerethanks are due to Mr. Ludwig for supplyingthese data, and for his patienthelp in answeringmy queries aboutthe field work in which I had no part. The nearly 105,000 birds of many speciesbanded by the Ludwigteam standas a truly remark- able tribute to the servicethese men have done ornithology. To Dr. Wallace I should also like to expressmy gratitudefor his constant advice,suggestions, and carefulcriticism during both the analysisand literature-searchthat precededthe writing of this report and the period of writing itself. Dr. P. J. Clark, alsoof the Departmentof Zoology, has instructedme on the use of the contingencychi-square method and helpedin its applicationto the data. The banded gulls have to date yielded some 1,143 recoveries,not includingthose young birds recoveredon or within a few milesof the coloniesshortly after being banded. The high mortality of juvenile HerringGulls still in the colonyis too well knownto requirediscussion here; and the inclusion of such recoverieswould obviously tell us nothingnew concerningthe species'life history,but rather would serveonly to distortour pictureof its movements.These 1,143 recoveries,representing 3.06% of the birds banded,provide a large sample from which has emergeda clear picture of the seasonaldistribution of Michigan-bornHerring Gulls. Otherbanding studies of this speciesin North America and Europehave been publishedand will be referred to below, along with studieson closelyrelated Larus speciesfor comparison. Locationo/ Colonies The bandingwas donein 17 colonies.The nine in Lake Huron, from north to south, are as follows: St. Martin Shoals, off St. Martin Bay, UpperPeninsula, about 8 milesnorth-northeast of St. Ignace; * This paper was prep,aredin partial fulfillment of t,he requiren•entsof the degree of Master of Scienceat Michigan State University.

69 Bird-Banding 70] Sn•TH,Michigan Herring Gulls April

TABLE I Nos. of gulls banded in each colony.

Lake Huron Lake Michigan

- NO. OF

1931 •4 14

•932 9 II •0

193• I• 8 43 69 I

19• 10 4 •60 3 57 8 755

1935 107 IZ• 483 298 5 7 167 •47 •5•5

•9•6 46 149 •53 514 12 430 49 376 19Z9

1937 •40 157 ZI0 •31 4• •0 I Z•3 380 174 ZI85

•938 46 19• 39• 64G 443 16 I 545 4•5 Z40 •9• •146

19•9 •OJ Z49 •8 711 409 6 4•1 •9• •5• 401 40•7

J940 •4 248 396 575 •el 8 • 15l 252 152 131 • 155 2798

1941 260 185 229 5'8Z 482 145 I0 129 408 164 394 2988

J 942 9 z I i

1•6 •3l 4 161 231 262 169 1lse 1947•465 37• e38

i94E 51e 204 39 459 I2zo

194• 400 401

19• 1087 85 I01 •39 •81 iI1•

195J 719 J•28 1947

1952 460 18• J 16 5 • 1•6 1906

195• 8• 860

J• 478 566 15z2 2566

•55 s• 1054 I I10

195• •6l 306 •7 617 I• I I

•57 402 •o 104• , EOOI 23 92833•33• 5192236 46 822 432440 •73 I•T 1496• 155 37409 •RASS•.•.•CH.t•O j 5 5 TOT&L NO. BANDED 37414 NONE BANDED J945-194S INCLUSIVE

GooseIsland, about 10 milesto the eastoff MarquetteIsland; Thunder Bay Island,Sugar Island, Gull Island, SulphurIsland, and Scarecrow, in ThunderBay or just off North Point by Alpena; BlackRiver Island, a mile and a half off BlackRiver 17 milessouth of Alpena; and Little Charity Island in SaginawBay, 32 miles northeastof Bay City. On these nine Lake Huron colonies20,468 gulls, 54.71% of the total, werebanded. On the sevenLake MichiganIslands 16,791 gulls, 44.88% e vo•.1•..50xxx SMITH,Michigan Herring Gtdls [ 71 L/AT JAME.• BAY

zoo

FIG I FIRST YR. RECOVERIES BEFORE DEC 3•

ß SINGLE RECOVERY ß 5 RECOVERIES 18l RECOVERIES IN MICHIGAN SLANTED NU•4Et•AL$ GIVE NOS. t•' BIt•D$

X SITES OF COLONIES

of the total, were banded.Four of theseislands, Gull, Pizmire,Hatt, andShoe, are in the BeaverIsland group, Gull andPizmire lying to the westof BeaverIsland beyond High Island,and Hatt and Shoelying north and a bit east aboveGarden and Hog Islands. BellowIsland is in the mouthof Grand TraverseBay north of TraverseCity, and Green Island lies in the western Straits of Mackinac, about 6 miles northwestof MackinawCity. Thereremains Grass Island, a low island in the Beavergroup on whichonly five gullswere banded,and none of thesefive has been recovered. In Lake Superiorthe Ludwigsbanded 72] SMITH,Michigan Herring Gulls Bird-BandingApril

O 200

fiG. 2 FIRST YR. BIRDS AFTER DEC ß SINGLE RECOVERY $LANTœD NUIdœR*•œ$GIVE NOS OF BI•D$ •tHICH COULD NOT BE X SITES OF COLONIES

only on RoundIsland, just eastof Brimley at the head of St. Mary's River and only 155 birds in one year, 0.41% of the total. Table 1 showsthe numberof gullsbanded each year in eachcolony, and the total number banded in each colony in the 24 years. No banding was done from 1943 to 1945 inclusive. Fig. 1 showsthe locationsof coloniesor groups of coloniesexcept for Round Island from which there have been only nine recoveries. Vol.1959xxx S•IT}•,Michigan Herring Gulls [73

200

RECOVERIES OF BIRDS OVER I YR. OLD

NUMERALS GIVE AGES 211 RECOVERIES IN MICHIGAN 5œANTEO NUMErAlS GIVE AGES OF BIRDS WHIGH GO0œO NOT BE ß SECOND YR. BIROS X SITES OF COLONIES

MOVEMENTS Fivemaps (Figs. 1 to 5) showthe distributionof the 1,143recov- eries. In someways it mighthave beenpreferable to presentthis materialas a unit and to useonly one map for eachof the three age groupsrecognized. The largenumber of recoveries,however, could not havebeen properly represented on thesmall scale this would have required.Accordingly, these age groups are presented separately only on thosethree maps showing the UnitedStates (except Maine), On- tario and part of Quebec.All recoveriesfrom easternQuebec, the AtlanticProvinces and Maine are showntogether on onemap, and all recoveries'from south o{ the United States on another. The areas in Bird-Banding 74] SMITH,•lgichiga. Herring Gulls April

o o _

which groups of coloniesor single coloniesare located are marked on the maps of the United States,but no attempt has been made to indicate each colonyin a group as I felt the desirabilityof using a largesymbol for placeof origin outweighedany advantagethe alterna- tive might have. A centre of origin to which to relate the linear distance flown has been chosen and is indicated. Vol. XXX 1959 SMITH,Michigan Herring Gulls [75

The advisabilityof dividingthe datainto agegroups was recognized after completinga preliminaryplotting, and the groupswere chosen in accordance with their correlation with obvious distributional tendencies (seeTable 2). Thesegroups, then, are as follows: Bird-Banding 76] SMITH,Michigan Herring Gulls April

FIRSTYR. • • • ,., OVERI YR. FIRSTYR.• m-- OVERI YR. NO. % •õ .o. % .o. % •.•;-' N0. %

MICH. 214 50-3 181 33 211 49-7 ALA. 6 I 5

ONT. 177 67.8 162 15 84 :3 2.2 KEN. I

WISC. 29 46'8 19 I0 33 53.2 TENN. 7 2 • I

ILL. 12 70.6 I II 5 29,4 MISS. I I I

IND. 8 50 I 7 8 5 0 MINN. 4 I

OHIO 44 74.6 29 15 15 25.4 SO. DAK

PENN. 6 5 I 2 TœX. $3 91'7 $ 30 3 8'3

N.Y :33 56'9 16 17 P. 5 4:3.1 IOWA I I

ME. 4 4 NEBR. I I

P.Q. 44 78-6 42 2 12 21.4 KANS. 2 2

N.B. 3 3 MO. I I

RE.I. 2 2 ARI• 4

NFLD. 2 2 2 LA. 15 I00 I 14

N.J. :3 I 2 OKLA. I I

MO. 4 2 2 I CUBA VA. 3 i 2 2 MEXICO 32 88'9 I $1 4 I1'1

W.VA. I 40NDURAS I I

H.C. 2 I I NICARAGUA I I S.C. I I BAHAMA TOTALS 724 63'3 482 242 419 36.7 FLA.GA. 124- 9 2-$ I 123 I 7,7 [ ' TABLE 2 Recoveries by o9e groups

(1) birds recoveredbetween the time of bandingand December31st of their first year, except,as noted above,those recovered on or withina few milesof the coloniesshortly after beingbanded, (2) birds recoveredin the six-monthperiod between December 31st of their first year and the followingJune 30th, (3) all birds over one year old. These have been indicated on the map by figuresshowing the year of life in which each was recovered.In somecases the group of birds in their second year will be mentionedseparately.

Of the 1,143 recoveries,724 or 63.34% were of first-yearbirds. To be more specific,42.16% of the total were of birds recoveredbefore December31st of their first year, and 21.2% betweenDecember 31st and June 30th. Thus some 419 birds, or 36.6%, were recoveredsub- sequentto their first year, and of these 32.2% (135 or 11.8% of the 1,143) were second-yearbirds. The high mortality of first-year birds, particularly up to December31st, will be discussedbelow. •ol. XXX 1959 SMITH,Michigan Herring Gulls [77

Michigan Recoveries The homestate of Michiganyielded 425, or 37.18% of all recoveries. About half, 50.35%, were first-yearbirds. If we analyzethe Michigan recoveriesby monthwe seethat many Herring Gullsleave in December Month J F M A M J J A S O N D

Percent of the M,ichigan recoveries 2.9 2.7 2.2 2.8 7.6 9.3 9.8 20.2 13.3 11.9 11.9 5.2 and someat leastreturn at the end of April, althoughmany over-winter in the state. Certainly part of the reasonfor the larger number of summerreturns is that more peoplefrequent beaches then, and from July on we mustfurther considerthe appearanceof youngof the year, amongwhich mortality is high. This latter point may be demonstrated by dividing the percentageof the recoveriesin each monthinto two categories,percentage of first-yearbirds and percentageof olderbirds: Month J F M A M J J A ,S O N D

Percent of recoveries (lst year) 1.9 1.0 1.0 1.4 2.4 0.0 1.7 10.7 10.2 8.6 7.6 3.1 Percent of recoveries (older) 1.0 1.7 1.2 1.4 5.2 9.3 8.1 9.5 3.1 3.3 4.3 2.1 This does show a heavy mortality of young in August, September, Octoberand November,and indicateseither that this rate of mortality drops quickly by Decemberor that the young birds scatter out of Michigan. The maps show the latter to be at least partly the case, and probably both causesare operative. Considerablymore adults than first-year birds appear to winter in home waters. The increased numberof recoveriesof adultsin June,July and Augustmay largely reflectthe distributionof peoplewho find the gulls. Twenty birds bandedin the colonieswere recoveredthere in later yearsas shownbelow. Note that 13 of the returnswere of fully mature Colony W.here Recoveredin Recoveredin (Ages and colony•of Banded Same ,Colony Another Colony recoveryin brackets) Hatt 1 (1) Gull (L. Huron) 1 (7) 2 (2, B1. River; 1.0, Sulphur) Pizmire 2 (6, 9) 2 (4, 4, both .at Gull, L. Mich.) Green 1 (11) Scareer,ow 2 (1, 1, both at B1. River) Black Rver 5 (2, 1, 5, 4, 3) 1 (4, Little Charity) St. Martin Shoals 2 (12, Sugar; 15, B1. River) Bellow 1 (19)

11 9 birds, four yearsor older. If the birds recoveredwere breeding,then there is at least some exchangebetween colonies, although perhaps not muchbetween lakes. This is further shownby two birds recovered by the Ludwigsbut not bandedby them: onebanded by A.D. Trempe in 1932 at Hatt Island and found dead in 1940 on Black River Island, and one bandedby W. I. Lyon in 1932 on Big Gull Island, Lake Michigan,and recoveredin 1938 on Sugar Island, Lake Huron. The 78] SMITH,Michigan Herring Gulls Bard-BandingApril list also showssome return to the colonyof birth, and this is further substantiatedby a bird bandedby W. I. Lyon in 1935 on Green Island and recoveredthere in 1936 by the Ludwigs. Linear Distanceso/ Recoveries]rom Colonies To examine the distances at which recoveries were obtained I have drawn circles of 300, 500, 1000, and 1500 miles radii from the center point. Below are listed the numbersand percentagesof the total of recoveries within each circle.

First-Year t•irds First-Year Birds Total, First. Until Jan. 1st Jan. 1st to June 30th Year Birds No. Percent No. Percent No. Percent

Within 300 miles 359 31.4 77 6.7 436 38.1 300-500 53 4.6 26 2.3 79 6.9 500-1,000 61 5.3 43 3.8 104 9.1 1,000-1,500 7 0.6 56 4.9 69 5.5 Over 1,500 2 0.2 40 3.5 48 3.7

Second-Year Second-Year Third-Year and Older Birds and Older Grand No. Percent No. Percent No. Percent Total

Within 300 miles 345 30.2 79 6.9 266 23.3 781 300-500 43 3.8 17 1.5 26 2.3 122 500-1,000 19 1.7 14 1.2 5 0.4 123 1,000-1,500 6 0.5 3 0.3 3 0.3 69 Over 1,500 6 0.5 5 0.4 1 0.1 48 Obviouslyfirst-year birds, particularlyin the period betweenJanuary 1st and June 30th, fly farther than older birds. This is in agreement with the calculationsmade by Gross (1940) for mean distancesflown by differentage groupsof Herring Gulls from coloniesboth in the Great Lakes and at Kent Island, New Brunswick. DispersalPattern Recoverieswere mostfrequent from the shoresof the Great Lakes, in particular Michigan, Huron and Erie with a considerablenumber, however,from Lake Ontario, and relativelyfew from Lake Superior. Most Michiganrecoveries were from the lake shores,and the remainder almost all from river systems.Out-of-state recoveries fall into two categories,bot. h well represented: (1) the MississippiRiver and its tributary systemaccounting for virtually all of the inland recordswest of the easternmountains, (2) the seacoasts,including: (a) the Atlantic coastand the rivers leadingto it, as well as the coastsof Cuba and the Bahamas, and (b) alongthe costof the Gulf of Mexico,including Nicaragua and Honduras. Of the 38 records, exclusive of the West Indies, from south of the United Statesonly one, from Monterrey, Mexico, was any appreciabledistance inland (although one from the West coast of Mexico represents a bird that had crossedthat country,perhaps at the Isthmus of Tehuantepecin the companyof suchother soaring coastal speciesas the MagnificentFrigate Bird, Fregata magnifi- certs,which Dalquest [1951] observedover the Isthmus). Vol.1959XXX SMITH,Michigan Herring Gulls [79

3600

150 3000

2400

90 1800

60 1200

6OO

GRAPH I rio.bonded per yeor,scole on left.

...... no.recovered peryeor,scole on right.

Exactlyhow the gulls reach the Atlantic coast cannot be determined from the recoveries,but probableroutes can be shown.Of the 57 recoveriesin this group(West Indies excluded; the St. Lawrence River belowFather Point included),five on the mainlandcould not be located from the data available. Of the other 52, 39 were on or near the coast,or on islands,such as Newfoundland,off the coast. Sixteenin the Gulf of St. Lawrencearea showthis river to be a main 80] SMITH,Michigan Herring Gulls Bird-BandingApril artery to the coast. The remaining11 were on rivers flowingto the coast south of the St. Lawrence. Four on the upper Hudson may indicate ano.therlink betweenthe Great Lakes-St.Lawrence system and the coast,a possibilityconsidered below. There are six records from rivers in Georgia,the Carolinas,Virginia and Pennsylvania,and one from very near the St. JohnRiver in Maine. Thesecould represent birds that have flown overland to these rivers, as Gross (1940) believes, or birds that have been on the coast and followed these rivers upstream.In view of the fact that inland recoveriesaway from major river systemsare practicallynonexistent, and consideringthat mountainbarriers lay in the paths of theseseven gulls, the second alternativeappears more likely. The Bonaparte'sGull, Larus philadelphia,a bird perhapsmore accustomedto foreststhan the Michigan Herring Gullsof the GreatLakes, has been observed by Brooks(1952) to fly overthe Allegheniesbut he doesnot mentionthe Herring Gull. If the Herring Gull doesnot usuallycross the mountains,then access to the Atlantic coastis primarily by way of the St. Lawrenceand, perhaps,the HudsonRivers. A similar explanationmight well be valid for the five recoveriesof birds on rivers which are not tributariesof the Mississippibut which do flow into the Gulf of Mexico. In these cases, however, the head- waters of the rivers concernedare all very near tributaries of the great river, and there are no mountainousbarriers involved.

Use o! Waterwaysand Coasts That Herring Gull movementsshould be confinedto waterwaysis aot surprising,since their food (Bent, 1921, Mendall, 1939, Otterlind, 1948, Pimlott, 1952, Spark, 1951, Witherby, et al., 1941, give the most comprehensiveaccounts) is primarily found in or near water. Herring Gullsare omnivorous,however, and couldpresumably travel overland, feeding primarily on insectsand vegetablematter, and evenrefuse at garbagedumps. That they do not appearto do this may be traceable to certain other inducements that rivers and coasts hold for them. The Herring Gull is a soaringbird, in fact such an accomplished soaring bird that it has been met with by aircraft at heightsup to 3500 feet (Ingram, 1919, and further observationsby Mitchell, 1955, and Woodcock, 1942, the latter not concerned with aircraft). When travellingit prefers to make use of up-currentsof air (Tinbergen, 1953), and, indeed, will often not travel when it cannot soar-- Woodcock (1940, 1942) reports that Herring Gulls are not seen 100 miles or more at sea off the east coast until the autumn when cold continental air flows out over the warm sea and creates thermal conditions. A movementof any distanceis undoubtedlyfacilitated by up-currents,for Griffin (1943), while conductinga homingexperi. mentwith 176 MassachusettsHerring Gulls,found that rapid homing was favouredby unstableair and strongupdrafts to permit soaring. Forster (1955) has examinedthe use by birds of ascendingair currents of two origins: (1) thosedue to the effectsof wind blowingup a slopeor rise in the ground (slope currentsand wave currents), and Vol. XXX 1959 SMITH,Michigan Herring Gulls [81

(2) thosedue to the effectsof air beingheated (thermal currents). He suggeststhat "birds will tend to follow slope and thermal up- current lanes," and that "the use of up-currentspartly accountsfor the tendencyto drift with the wind during migration,"so that suitable thermal and drift conditionscould combineto be an aid to covering distance.I shall examinethe problemof drift below,but shouldfirst like to speculateon the useof up-currentsby travellingHerring Gulls. During the day a gull could find not only thermal currents over beachesand shores,but also slope currentscreated by wind on the banks or dunesand would thus have an up-currentlane besidemost large waterways.Further, due to the high thermalcapacity of water there would be, once the air was colder than the water, a thermal effect over all unfrozen rivers and lakes, as well as over the sea as mentionedby Woodcock(1940, 1942). McMillan (1938) statesthat a quarteringwind on a seacoastwill createa surf that will give both lift (Forster's"wave currents"3 and direction,and this wouldpresum- ablybe the caseon the GreatLakes as well.If, then,the HerringGull doesfollow up-currentlanes becauseit is a soaringbird, rivers and coastswould provide another inducement, besides food, to travel along them. In supportof the notionthat the gullswould follow such lanes I mightcite a few instancesof this in otherspecies. In the Suez region thermal activity in the atmosphereis marked. Goodwin(1949) tellsof from lessthan 1,000to 4,500 birds of prey a day for sevendays in Octoberall usingthermal migration. MacKintosh (1949) writes of the same phenomenonin which he says tens of thousandsof Accipiterspass over Suez in the autumn. The hawks are carefulto avoid crossingthe Gulf over whichthey would have to flap, probablybecause they have low reserves,but storks,herons, and pelicanswhich also migrate on the thermalsdo useflapping flight to cross the water. At the western end of the Mediterranean area Moreau (1953) found that soaring birds would convergeat the Straits of Gibraltar to make the water crossing (which would be without the aid of thermals)as shortas possible.He felt that the coastlineguided them to the Straits. In southernSweden Rudebeck (1951) has observeda "very close correlation"between weather conditions suitable for soaringand the migration of severalspecies of hawks, "particularly those species whichare mostinclined for soaring." In an earlier paper (Rudebeck, 1950) he stated that these hawks allow then•selvesto drift within the limits of the leading lines providedby the coastsof Swedenand Denmark.Thomson (1953) calls the tendencyto be deflectedby topographicalfeatures which act as "leadinglines" an intrinsicfactor of orientationwhich is probably a reactionto a barrier betweena favourableand an unfavourablehabitat. This,then, is an exampleof a groupwhich combines migration by soaringwith the followingof leadinglines. Broun (1939) notedthat hawkspassing over Hawk Mountain,Pennsylvania, in the autumnflight coast on the up-currents of air causedby wind striking the flanks of the mountain. 82] SMITH,-Michigan Herring Gulls Bird-BandingApril

The Factor o/ Prevailing Winds From the maps showingfirst-year birds it can be seen that recoveriesin the autumn and early winter tend to be from the east, northeastand north, whereaswinter and spring recoveriesare from the southand west. Althoughthe over-alldispersal pattern seemsto includeall pointsof the compass,few birds travel far beforeJanuary that do not go east. It is probably more than coincidencethat the prevailingwinds at this seasonare from the southwest. To be moreprecise, in Augustthe prevailingwind is westover Lake Superior and southwestdown the Great Lakes-St.Lawrence system. In Septemberand October it is similar with a north to northwest tendencydown the East coastwhich continues at leastinto February-- althoughwith frequentwesterly components. In December,however, therc is a shift to northwestacross the Great Lakes, northerly com- ponentsare frequentdown the Mississippi,while the prevailingwind on the Gulf of Mexico coastis north or northeasterlyand remainsso through February. The January winds of the southernGreat Lakes tend to be west or southwest,a condition which is common both winter and summer,but which may give way to northwesterliesparticularly in the spring. In March the windson the Gulf of Mexico, includingthe Mexican coast,become south to southeastbut remain the usual northeast over Yucatan,Central America, Cuba and the Bahamas.By April there is a good degreeof southerlyflow up the Mississippiand up the East coast (Kendrew, 1953; Baker, 1936; Bartholomew et al., 1899, and ClimatologicalData, U.S. Departmentof CommerceWeather Bureau). This pattern fits, in general,the seasonalmovements of Michigan Herring Gullsrather well. The possibleuse of the Hudsonas a lane to the coastmay be further consideredhere as recoveriesare fewer than might be expectedif it were usedto any extent.It may be that it does not get much use for the prevailingautumn winds are upstream from the south, both at the surface (Baker, 1936) and at an altitude of 500 metres (U.S. Departmentof Commerce,Weather Bureau, 1941). I have already mentionedForster's (1955) statementthat "the use of up-currentspartly accountsfor the tendencyto drift with the wind during migration." For some reason,though, early accounts.such as Cooke (1910, 1913a), and even Thomson (1936) and Allen and Peterson(1936), consideredthat wind is not important,other than accidentally,as a determiningfactor in migration. This attitudewas long lodgedin the literature. That wind is importantto birds using therm,al migrationhas been attestedto by MacKintosh(1949) who notedthat migrant Accipitersin the autumnmay find themselvescon- siderablysouth of Suez on the wrong side of the Gulf and have to turn north to Suezto avoid flappingover water. He attributedthis southwarddrift to the fact that the prevailing north wind of the autumn season carries the birds south with the thermals themselves. RegardingHerring Gulls, Grillin (1943) in his homingexperiments notedthat rapid homingwas favourednot only by strongupdrafts and good visibility, but moderateto fresh "favorable winds." That windsdo causebirds to go far out of their intendedway has beenlong known, but hasbeen thought to be a relativelyrare tragedy Vol. XXX 1959 SMITH,Michigan Herring Gulls [83 when it occurredon a large scale,as in the case,for instance,of the wind of an unseasonalanticyclonic pressure system in the springof 1948 that carried thousandsof Redwings,Turdus musicus,to Britain and to their deathsin a snowstorm (Suffern,1949). The unsuspected enormityof unintentionalwind drift has now beenrealized by William- son (1952), however,who believesthat "suchpassage migration as we enconnterover the greater part of Britain is largely due to . . . dis- placementby easterlywinds from their [the birds'] Continentalcoastal 'guiding lines' betweenSkaggerak and northern France." These migrants are so regular that they were formerly thought to be on a particular over-waterflyway in order to explain their occurrence. Williamson arguesthat anticyclonicconditions over North or Central Europe initiate southwardautumn migration on the part of large numbersof birds, and that the easterlyairstream south of the anti- cyclonecreates a certain amount of westwarddrift--enough to result regularlyin wastageon a "colossalscale" of thosebirds carried beyond the British Isles. An examplein North Americaof the effectof a shift in the prevailingwind is given by McCreary (1934). During the first half of May, 1933, in East Wyomingthe prevailingwind, normally southwest,blew almostcontinuously from the east,southeast or northeast, and pushedbirds west which normally pass further east. The birds he mentionswere all small speciesexcept for Franklin's Gulls, Larus pipixcan. From such evidenceit would appear that wind does have a very major effecton the directionof bird migration,if only to hamperthe birds in followingtheir usualcourse. Further recentpapers, however, show very definite correlationsbetween wind patternsand normal migration routesand behaviour. Landsberg(1948), for instance,has pointed out that there is a closeresemblance between certain general- ized trajectoriesof air currentsand the migration routesof the Arctic Tern, Sternaparadisaea, Wheatear, Oenanthe oenanthe, Pacific Golden Plover, Pluvialis dominica]ulva, and Greater Shearwater,Puffinus gravis (northward). This has also been noted by Allen, 1948, for two of those species,the Arctic Tern and the Golden Plover, P. d. dominica,but in this casethe claim is madefor the flight of the latter from Nova Scotia to South Ameri,ca.Landsberg further suggested that prevailing conditionswould accountfor the scatterthat occurs, that is, the deviations individual birds or flocks make. MacMillan (1938) has alsoproposed that wheneverpossible migrating birds ride the wind, and that migrationroutes are thuscorrelated with prevailing wind. Clear quantitativedemonstrations of this have been given by Loweryand Newman (1955) from their studiesof nocturnalmigration, and Devlin (1954) who also studied nocturnal migration. Dennis (1954) has observedthat southerlywinds generallyattend the northward departureof migrantsfrom the Gulf of Mexico coast, and that northerlywinds in the spring result in an arrestedwave. Dennis and Whittles(1955) have notedthat autumnmigrants reach Nantucket on northeasterlyor northwesterlywinds, and Stanford(1953) that many birds arrive from over the desertin Cyrenaicain springwith a south wind,sometimes very strong, behind them, and further migration across the Mediterraneanis held up by north or northwestwinds. Broley Bird-Banding 84] SMITH,Michigan Herring GitIls Aprn

(1947) usuallyfound that his Bald Eagles,Haliaeetus leucocephalus, migratednorth from Florida up the Atlanticcoast after the breeding season.In April, 1945,however, the prevailingwind, which normally is from the southup the Floridacoast in April andMay, shiftedand blew acrossFlorida and then swungnorth up the Mississippivalley. That year he got four inland recoveries. Not all observationscorrelating the arrival of birds with tail-winds can be used to supportthe notion that birds deliberatelymigrate with the wind, of course. Some are casesof drift out of preferred migratorypaths, and it couldbe that the birds involvedwere not using the windsas tail-winds but were (as Williamsonhas postulated) actually headingacross the winds. Suchis likely the casein the hawk migrations at Cape May Point describedby Allen and Peterson(1936). Here birds which normallypass southwestward somewhat inland are crowdedinto the narrowcape by a northwestwind. The flightsobserved by Fergusonand Ferguson(1922) for five fall seasonson Fishers Island,New York, showa goodcorrelation with northwestwind for the partly-soaringSharp-shinned Hawk, Accipiterstriatus, but not for the strongerflying falcons which could fly into opposingwinds. The Sharp-shinsflew "slightlysideways" because of the wind. Smith's (1908) observationof over 10,000 Purple Martins, Progne subis, migratingsouth down a quarter-milewide strip alongthe east shore of Lake Michiganwould indicate by virtue of sheernumbers that the birds were migratingwith the northeastwind and were beingturned acrossit to follow the guidingline of the shoreby the water barrier. Had they not begunby flying with the wind couldsuch a concentration have occurred,that is could drift alone,acting on birds flying with a southerlyheading, be responsible?Bennett (1952), on the basisof five years'study of migrationat Chicagoduring which every important autumnwave was associatedwith an advancingcold front followedby northwestwinds, concluded that birds migratewith the wind. A clear caseof migratingwith the windis recordedby Broun(1939, 1951) for the hawkssoaring on the slope-currentsof Hawk Mountain,Pennsyl- vania. Of thosecounted in Septemberand Octoberfrom 1934 to 1938, 61.9% passedon a northwestto northeastwind, and manymore hawks were aloft on days with northerlywinds than on any other days. WhetherMichigan Herring Gulls seekwesterly winds with which to fly, or are simplyput adrift by them,it doesnot appearunlikely to me that the eastwardtendency of their autumn dispersalis to a large degreecorrelated with the prevailingwind. The situationis complex, though,and the influenceof the Great Lakes-St.Lawrence system as a guiding-linemight be even more important. If it were, however, I shouldexpect more birds to scatterwest along the shoresof Lake Superior than are indicatedby the recoveries. There is perhapsa further consideration.Deelder and Tinbergen (1947) cite Lorenz'sobservation that crows,geese and gulls migrate low againstthe wind but high with a tail-wind. The reasonfor the latterLorenz supposes to be that a gustfrom behindwould cause these largebirds to loserelative airspeed temporarily and descend,hence they must be well aboveobstructions. Now Dobben (1953) adds that since birdsreact less to topographicalfeatures as theyfly highera following Vol. XXX 1959 SMITH,Michigan Herring Gulls [85

TABLE

M I C H. 425 56 • 38 49 38 I 13 I 28 • 45 24 39 5

ONT 261 32 I 24 53 WISC. 62 ILL. 17 3 I I 5 3 2

IND. 16 4 2 2 5

ONI 0 59

PENN. 8 2 I • I 2

NY • 4 7

ME. 4 2 I I

PQ. 56 II I I0 16 5 I 2 2 4 4

N.B. 3 2 I

PEA. 2 2

NFLD. 4 2 I I

N.J. 3

MD. 5 I I 2 I

VA. 5 2 I I

W. VA. I

N.C. 2 I I

S.C. I I

GA, 5 2 I I I FLA. 13 2 I 4 I • 3 I ALA. 6 I I I I I I

KEN. I I

TENN. 8 I I • I I I I

MISS. I I

MINN. 9 I I 2 2 I I I SO. DAK. 2

IOWA I I

NEBR. I I

KANS. 2 I I _ MO. I I

ARK. 5 I I 2 I LA. 15 5 I OKLA. I I TEX. •6 I

CUBA 4 MEXICO •6 5

•NOURA• I

NICARAGUA I

BAHAMA• 2 I I TOTALS 1,143 141 I B6 155 173 2 96 2 17 I 94 119 99 5T 91 9 TABLE 3 Recoveries by colonies of ,bandincj. wind servesto weakenthe guiding-lineeffect. If this is the case, then the guiding-linescould here be drawing the gulls either east or west, but the prevailing wind would tend to send them east, and would actuallyweaken the effectof the guiding-lineon dayswhen it reacheda high velocity. 86] SMITH,Michigan Herring Gulls Bird-BandingApril

Dispersaland Colony o] Birth In order to see if there was any relationshipbetween the colony of birth and the directionof dispersal(see Table 3) the contingency chi-squaremethod was appliedto a table listing numbersof recoveries by areaswith the colonieswhere the birds had beenbanded. To have numericalvalues sufficiently large for the use of this methoda certain amount of grouping was necessary,so that coloniesgeographically closetogether were grouped,and the placesof recoverywere lumped into five areaswith Michigan and Ontario consideredseparately. Since the probability of a chi-squaregreater than that obtainedwas less than 0.5%, there is apparentlysome relationship. This appearsto be largelythat more birds bandedin Lake Michigantend to be recovered in Wisconsin, Illinois or Indiana than in Ontario, while birds from Lake Huron showthe oppositetendency. This might be expectedsince the birds commence to wander on the lake of their birth. Birds from the St. Martin Shoals colony on the Lake Huron side of the Straits of Mackinac show no relationshipwhich would support this idea, althoughbirds from the Beavergroup of coloniesin Lake Michigan showa markedtendency not to go to Ontario. There is variationfrom colony to colony significantat the 5% level for the Lake Michigan coloniesand at the 10% for Lake Huron, either to show the tendency characterisic of the colonies as a whole in that lake, or to show no tendencyat all. It is difficultto know whetherthese tendencies indicate a slight geneticdifference between some of the colonies(recall, however, that nine birds bandedin one colonywere recoveredin another) or are merelyan imperfectreflection of the geographicalinfluence. A less marked tendencyfor more Lake Huron gulls to go to the East coastrather than the Gulf of Mexico, the Lake Michigan birds again showingthe oppositetendency, is probablya reflectionof their original dispersalon the later southwardmovement. It would follow if birds which have wandered to the lake shores of Ontario continue to drift down the Great Lakes-St. Lawrence system with the winds, while birds which have reachedsouthern Lake Michigan would have to let the wind carry them awayfrom the shoresand acrossthe southernpart of the state of Michigan.

Southward Movement Figure 2, graphs2 and 3, and Table 4, reveal that most recoveries from southernstates and Mexico occurin the period from January 1st to June30th, the graphsshowing that birds actuallybegin to appearat least in the southern states in December. The southward movement (characteristiconly of first-yearbirds) is probablydue to a number of factorssuch as the prevailingnorth windsof Decemberand January, the freezing of northern rivers and the new difficultiesshore ice bringsto findingfood, and perhapsa simplemovement in the direction of greatestwarmth as proposedfor many Europeanspecies by Drost (1929). Lincoln (1950) has suggestedthat this southwardmovement is the productof a "directivemigratory impulse," but I shouldlike to point out that (a) the movementbegins very late in the year, and, more important, (b) only the first-yearbirds take part to any extent. As sexualmaturity is approachedand attained,wandering of morethan 'Vol.1959XXX SMITH,Michigan Herring Gulls

28 O F M A M d d A

o j F M A M J J A $ 0 N D

GRAPH Sum of recoveries from Md.,Va.,W.Va.,N.C,,S.C.,Ga.,Fla., Ala., Ken.,Tenn., Miss., Kans .,Mo,,A rk., Okla,,La,,Tex., by month.

GRAPH Mexican recoveries by month.

two to threehundred miles is largelygiven up (seeFigure 3). It is noteworthythat the two southernmost recoveries, a bird from Honduras on February2, 1935,and onefrom Nicaraguaon February8, 1938, are bothfirst-year birds. Ratherthan a migratoryimpulse it would appearthat sexually immature gulls may simply experience less of an attractionto the breedinggrounds than do adults,and are thusmore free to wander as weather and comfort direct. 88] SMITH,Michigan Herring Gulls Bird-BandingApril

TABLE 4 Totel recoveries by month for those in which d•te

of recovery wos reported.

J F M A M J d A S 0 N J F M A M d d A S D N

12 II 9 12 33, 39 41 85 56 50 50 ?-2 ALA

II 6 5 7 8 7 I0 ?,1 59 58 39 26 KEN.

4 ?, 3 7 4 ?, 4 6 7 610 7 TENN

MISS.

;3 •1. i I ;3 I MINN.

5 3 6 4 2 2 I0 9 7 4 SO. DAK

?, I ? I I I TEX

7 5 3 6 5 2 6 7 7 3 7 IOWA

2 I I NEBR.

? 2 i 6 21 I? 8 KANS

I I MO.

ARK.

I I LA.

I i OKLA.

CUBA

MEXICO

VA. I HONDURAS

C. I NICARAGUA

BAHAMAS

GA. •' I FLA.5.C. 6I 4 I 2 TOTALSJ• Western Recoveries The mostwesterly inland recoveries (except one from Monterrey, Mexico)are 11 first-yearbirds recovered west of 95ø westlongitude in Minnesota,South Dakota, Iowa, Nebraskaand northernTexas. All are fromtributaries of the Mississippiand ten are recoveriesin April, Mayor June(one in Januaryin Texas)and probably represent birds attemptingto returnto the GreatLakes but led astrayby mistaken guiding-lines,their tendency to returnto the coloniesnot yet fully developed. Coastal Recoveries Discussionof coastalrecoveries will start with the Gulf statesand Mexico.On graph 4 areplotted recoveries from the coastal regions of Texasand Louisiana, and these are summed in graph5. First-year birdsaccount for 90.80%of the87 recoveries.Of these87, 74 or 85.06%were first-year birds taken after January lst--there are only fivefrom December: one in Mexico,one in Louisiana,and three in Texas.The remaining eight birds were older than one year: two fromTexas were in theirsecond year and one in itsfifth, four from Mexicowere in their secondand one in its sixteenth. Vol. XX• 1959 SMITH,Michigan Herri. g Gulls [89

GRAPH 4 Gulf of Mexico recoveries by year.

Texas, 36 recoveries

m--m Louisiana, l,5

...... Mexico, 36

GRAPH5 Sum of the above recoveries by year.

Correspondencebetween these two graphs and graph 1 showingthe t,otals banded per year is onlysuperficial. On graph5 a recoverypeak in the year 1936 is prominent. This consistedof 25 recoveriesof birdsbanded in 1935,a year when1,535 were banded. A banding peakof 4,027 individualswas attained in 1939,but 1940 sawonly four recoveriesfrom the Gulf region, and only one of these (Mexico, January) was bandedin 1939. 90] SMITH,Michigan Herring Gulls Bird-Banding.&Dill

Groups of Eosf coost recoveries by yeor

• Quebec, 5b recoveries m___ Aflontic Provinces & Moine ,13 ...... Georgio & Florido (except 2 • i PH6 Pensocolo),16

\/ \\\

GRAPH 7 Sum of fhl obove recoveries by yeor

Since some9,277 birds had been bandedby 1938 and not recovered by 1940, as comparedwith 853 bandedby 1934 and not recoveredby 1936, there was ample opportunityfor three ,morerecoveries of older birds in 1940. If, then, we do not considerthese three older gulls we find a ratio of about1/65, that is 1/25 as many recoveriesof first-year birdsfrom 2 2/3 morebanded (a significantdifference). Thus, placed in perspective,it is obvious that these recoveriesindicate that a 'Vol. XXX 1959 SMITH,Michigan Herring Gulls [91 much larger proportionof first-year birds (not necessarilyas great as 65:1, of course) reachedthese southerly regions in 1936 than in 1940. This is consistentwith the recoveriesof CaspianTerns, Hydro- progne caspia,banded in the Great Lakes in 1935 (Ludwig, 1942). In contrast to recoveriesfrom other years, great distanceswere covered by the terns in short times as shown by four recoveries: one in Alabama (September14, 1935), one in Cuba (November 5, 1935), one in Colombia (December 15, 1935), and a final one in Colombia(April 1, 1936). It is worthyof notethat of the total of 36 Mexicanrecoveries of Herring Gulls in this studyten are from 1936. I have been unable to discoverany environmentalcauses for this phenomenon,the exceptionalcold of late Januaryand early February in the southernGreat Lakes region that winter being unlikely as an influenceon avian movementswhich precededit. Note that only very minor recoverypeaks follow the postwarbanding peaks and that total recoveriesfor the region are fewer. For somereasoa, however, total recoveriesfrom all birds are lower after the three-yeargap in banding. Turning to the East coastrecoveries, I have plotted those from Quebec,the AtlanticProvinces and Maine, and Georgiaand Florida on graph 6, and summedon graph 7. Closein numberto the previous group,there are 85 recoveries.so comparison can be direct. Seventy-one or 82.4% are of first-yearbirds: 15 out of the 16 from Florida and Georgia,44 out of the 56 from Quebec,and 11 of the 13 from the Atlanticprovinces and Maine. In this casea major recoverypeak in 1940-1941does follow the major bandingpeak of 1939, indicatingthat different unknown factors affected the birds which went to the Gulf of Mexico. However,the secondhighest banding peak (3,206 in 1950) is not followedby a recoverypeak, and there is a low percentageof recoveries]rom all areas (seegraph 1) thereafter. Briefly we may say that there are numerousrecoveries from both the East coastand the Gulf of Mexico, and that they are primarily, beingfar from the colonies,birds in their first winter (seeTable 2). RecoveriesNorth o! Breeding Colonies From the mapsit is obviousthat dispersalcarries a number of MichiganHerring Gulls to the northof the breedingcolonies. Along the lower St. LawrenceRiver and in Newfoundlandthis can probably be explainedby a combinationof the prevailingwinds and leading-Kine effect,but many of the northernOntario records, especially the one from JamesBay, and a few of the Quebecrecords do not fit suchan hypothesis.Probably, too, thereare manymore Michigan birds that strayinto theseareas than the mapswould suggest, for the human populationis thin and largelylocalized, leaving vast lake and river areasvirtually uninhabited. Dispersal including northward directions is knownfor otherHerring Gull coloniesboth in North Americaand Europe,and for variousother Larus gulls, a,s will be mentionedlater in this paper. Heronsare notablefor a northwardpost-breeding dispersal(Cooke, 1913b, Coffey, 1954, and many other papers) which may be somewhatdifferent, however, in that in heronsthe trend seemsquite pronounced.Lowe (1954), however,noted no directionaltendency for the dispersalof Britishherons Ardea cinerea. The dispersalof at least 92] SMITH,Michigan Herring Gulls Bird-BandingApril part of the northern populationof Barn Owl, Tyto alba, in North America is also in all directions (Wallace, 1948, and Stewart, 1952). Lincoln (1950) calls the northward movement both of the herons and of the Herring Gull "vagrantmigration," "governed only by the avail- ability of food" which seemsto me to be supposinga great deal. AnotherNorth American bird whichgoes north after breeding (appar- ently both adultsand young) is the Bald Eagle of Florida (Broley, 1947) which, as I mentionedabove, seems to rely for the direction of this movementupon the prevailingwinds. Regardingthe northwardcomponent of the dispersalof Michigan Herring Gulls, then, I can only say that we do not know sufficient aboutthe numbersof individualsinvolved to characterizeit properly. It may be simplya functionof the influenceof goodhabitat on erratic dispersal,or there may be a variably inherenttendency to go north.

COMPARISON WITH OTHER AMERICAN HERRING GULL STUDIES The movementsof MichiganHerring Gullsas revealedby this study cannow be statedbriefly. In late summerand earlyautumn there begins a dispersalwith great individual variation in the time of leaving the coloniesand in the distancestraversed. Second-yearand older birds with a few exceptionstend to remain within 300 miles of the colonies, althoughsome move up to abouta hundredmiles farther alongLake Ontario. First-year birds, however, show much greater variation. Althoughsome 60.2% are recoveredwithin 300 miles the remainder wander widely. During the autumn this dispersalshows a decided eastwardtendency (perhaps a function of the prevailingwinds) and possiblya slight degreeof northwardtendency. With the advent of winter, however,many first-yearbirds, includingmany of thosestill in the Great Lakesarea, movesouthward along the East coastor the Mississippiand its tributaries. Somestop in Florida and a few get to Cuba or the Bahamas,but a concentrationoccurs on the Gulf coast of Louisianaand Texas, from which a number straggleinto Mexico or, occasionally,even farther. These birds gradually drift northward in the early spring,a few wanderingoff to the westalong tributaries of the Mississippi,and many probably reach the Great Lakes or even the breedingcolonies, although they are, of course,immature and do not breed. Very few spendthe summeras far south as the Gulf of Mexico. The most valuablestudy for comparisonis work done by Gross (1940) on 1,409 recoveriesof Herring Gullsbanded in the Great Lakes by H. C. Wilsonand William A. Lyon. Most of the gullswere banded by Wilson on the Sister Islands,Wisconsin; Lyon bandedin 50 comparativelysmall colonies in LakesMichigan, Superior and Huron. The different coloniesshowed much similarity of dispersalpattern. As notedabove, the younger,non-breeding birds as a wholeflew farther fro,mthe colonythan did the older birds. Dispersalwas erratic but Grossnoted a "distincttendency for them to concentrateon the shores of the Great Lakes and the river courses such as the St. Lawrence, Mississippi,Ohio and their tributaries." Thosewhich go down the Mississippito the Gulf of Mexicofan out alongthe coastforming a concentration--asdo the Ludwigs'birds--along the Texas coast. A 'Vol. XXX 1959 SMITH,Michigan Herring Gulls [93

"di'stinctmovement up [down] the St. Lawrenceto La:bradorand New- foundland"is explainedby Grossas a "tendencyto clingto the shore lines of the lakes and to follow the river course." As I have indicated above,I feel that this is only part of the explanationand that prevailingwinds play a major role. He alsonoticed a certainnorthward tendencywhich he felt to be merelypart of a "preliminaryexplosive dispersal"followed later by a southwardmovement. He felt this to be the samesituation as in other.species such as the Black-crowned Night Heron,Nycticorax nycticorax, a subjectupon whi.chI have commentedabove. The map on which these 1,409 recoveries are plotted revealsa closecorrespondence with the dispersal pattern of theLudwigs' birds,although the SisterIslands are somewhatmore westerly than any uponwhich the Ludwigsbanded. Gross showed that fourth-year birds do breed,and that youngerbirds usuallydo not. Lincoln (1928), on the basis of fifty somerecoveries from the BeaverIslands, was able to discernthe autumndispersal with its northwardtendency, the later, often extensivesouthward movement, andthe erratic first spring return which leaves some of theyoung birds in the south.From sucha smallsample, however, he couldnot give a moreprecise picture. These recoveries again fit the patternpresented here,but I find Lincoln'smap (Figure3 in hispaper) showing recoveries betweenJanuary 1st and the followingmidsummer to be rather misleadingas presented. This is dueto the useof arrowsrunning from the colonyto the point of each recovery.Arrows tend to give the impressionof direct flight and I stronglysuspect that many of the birdsinvolved were returning north. The westernrecoveries in particular probablyrepresent, as I havealready suggested for similarrecov- eriesof the Ludwigs'birds, casesin whichthe returninggull took the wrongtributary while comingup the Mississippi. Eaton(1933) dividedthe HerringGulls of the EasternUnited States and adjacentCanada into three populationson the basisof what he consideredto be their migratorypatterns. In mostcases he wasworking with very few recoveriesand his conclusions,as he recognized,are highlyspeculative. These proposed populations are: (1) the Atlantic which migrates down the coast, (2) the Laurentian (St. Lawrence River) whichhe felt didn't migrate,but which,according to color- bandingwork (Poor,1943) apparentlydoes pass through the Gulf of St. Lawrencethen southdown the East coast,and (3) the Lacustrine. The latter he describedas showingwide dispersalwith the first-year birds tendingto winter whereverthere is openwater on the southern GreatLakes drainage system, a lesserfraction following the Mississippi to the Gulf of Mexico,and a few winteringon the Atlantic seaboard. His Lacustrinepopulation is basedon recoveriesfrom birds banded in the followingcolonies: Red Bay (Bruce Peninsula),Ontario (9), GreenBay, Wisconsin(33), and the BeaverIslands, Michigan (89). He suggestsseveral interpretations of the "wide dispersal" of thisgroup. The first is that the coloniespossess "no fixed habit of migration" but individualsmerely "wanderindiscriminately in searchof a food supplyand open water." With thiswandering I shouldagree, whatever the reasonwhy the gullswander, as I feel that the patternwhich is more-or-lessrecurrent annually is largelyforced on the gulls'move- 94] SMITH,Michigan Herring Gulls Bird-BandingApril mentsby suchenvironmental factors as the directionof the prevailing winds and the location of thermal lanes. Individual recoveries from the West Indies, Central America, and the western tributaries of the Mississippiare frequent enoughto suggestthat if there is a "fixed habit" it is not well-fixed. The tendencyto disperse,however, is perhapsinherent. Eaton'ssecond interpretation is that the coloniesmay be a "mixture of two or more strains possessingdifferent migratory traits." He derivedthis notionfrom his analysisof the "Atlantic population"in which, on the basis of very few recoveries,he believed he could detectfairly distinctwintering grounds for birds of differentcolonies. The work of Gross(1940) at Kent Island suggeststhat this is true for the Atlantic colonies at least to the extent that birds from northern colonieswinter in the vicinity of more southern colonieswhile the occupantsof the latter are farther south. I fail to see much indication, however,of two or moreinherent tendencies toward "different migratory traits" in the dispersalpattern of the Michigan Herring Gulls. That some birds from certain Lake Huron colonies tend to go to the Atlantic while somefrom the more southerlyLake Michigan colonies tend to go to the Gulf of Mexico is likely traceableto their original dispersalon the shoresof the lakesof their birth, althoughthis itself may be geneticallygoverned. His third suggestion,namely that the Lacustrinepopulation might be divisibleon the basisof migratorytendencies into an "eastern"and a "westernelement" is probablyunnecessary if the tendencyfor more birds from certainLake Huron coloniesto go to the East coastthan to the Gulf of Mexico,or the oppositein the caseof certainLake Michigan colonies,is dependentupon their original dispersalon their home lakes. Environmentalfactors provide a much more likely explanationof the eastward,northeastward, and southwardmovements, and the straying of birds into the west on tributaries of the Mississippiis a function of their tendencyto follow water courses.Eaton's maps of this dispersal introduceno tendenciesnew to the mapspresented herewith. Gross(1940) analyzed773 recoveries(3.29%) from 23,434 Herring Gulls banded on Kent Island, New Brunswick. He found a dispersal at the end of the breedingseason, but of a lesserratic naturethan that of the Great Lakes birds. The Kent Island Gulls tend to cling to the Atlanticcoastline. Fewer go northwardthan southward,and the northward migration is followedlater by a generalsoutherly flight. A large numberreturn to the natal colonyto breed,but he found nonebanded as young in other colonies,nor any Kent Island birds breedingelse- where. There was alwaysa numberof non-breedersof all agesat the colony in summer. Although few Kent Island birds winter on their breedinggrounds, color-banding studies (Poor, 1944) indicatethat many go no farther than the New York region and reproductively- active individuals leave there in January to be back at the colony by the last week in February.

MOVEMENTS OF THE EUROPEAN HERRING GULLS Banding studiesof North Europeancolonies, such as those of Mortensen (1950) and Paludan (1953) in Denmark, indicate erratic Vol. XXX 1959 SMITH,Michigan Herring Gulls [95

dispersalbut quite restrictedmovement. In the caseof Paludan'stwo coloniesthe averagedistances of dispersalwere only 90 and 217 km., andthe farthestof the426 recoverieswas only about 800 km. Tinbergen (1953) states that neither the Dutch nor the German North Sea populationis really migratory--i.e.,there is "no shift in population area from north (east) to south (west) in winter"--but that there is massmovement along the coast.This movementis to find a safehabitat. High tidesin combinationwith strongwesterly winds completely cover the beachand the gulls'food, and the gullsshift to broadbeaches where they can rest and wait for the stormto pass. Southwesterlywinds are most frequent,and the gulls sail to the southwestusing the rising air abovethe seawardslope of the coastaldunes, "and sail for hours and hours, practically without a single wing-beat." Tinbergen believes that the reasonthe wholepopulation does not movesouthwest is that thereis considerableback migration in calmweather out over the open sea--perhapsthey use the soaring methodsdescribed by Woodcock (1940, 1942). When the wind is at right anglesto the coast, two streamsof gullstravel alongthe dunesin oppositedirections. Herring Gulls of the British Isles showat most only a "very mod- erate dispersal"(Matthews, 1952). Witherby et al. (1941) remark that they are "more or lesssedentary, a few seemto be completelyso, but [the] majoritymove away, though movement is almostentirely one of dispersalin any directionand [the] majority do not travel more than 200-300 miles." A distinct tendencyfor more extensivemove- ments,especially of birds from the more northerlycolonies, toward the south or southwest has carried a few birds to North France and the Biscaycoast (Witherby et al., 1941), butaccording to Matthews(1952), doesn'talter the generalpicture of moderatedispersal. Fisher (1954) creditsthe British subspecies,L. a. argentatus,which also breedsin Iceland,the Faeroes,N.W. Franceand the ContinentalNorth Sea coast to S. Norway, with reachingthe Mediterranean.None of the few recoveries of Irish birds show movement "other than short distance dispersal"(Witherby et al., 1941). Matthews(1952) reportsa "strongsoutherly bias" for the British birds, and notesthat recoveriesare largely restrictedto the coaston whichthe colonyis situated.Although the mostsedentary birds may scarcelyleave the colony--Lockley(1942) statesthat on Skokholm HerringGulls may be feedingyoung as late as October, and are "back at the nestingterraces on the first fine day in November"--dispersal from the coloniescommonly takes place between the end of July and mid-Augustwith returnfrom the end of Februaryor early Marchto mid-May. Duringthe autumnand wintertheir movementsin British watersare greatlyinfluenced by migrationsof the herring(Witherby et al., 1941). Immature birds often passthe summersouth of the home colonies.Some continentalbirds from Norway, Holland, Den- mark, Frisian Islands,South Sweden and North Germanycome to the British East coastin the autumn (Witherby et al., 1941), but the incidenceof this is not knownas the iramaturesof the subspeciescannot bedistinguished in the field (Leach,1944) andringing recoveries have not as yet been numerous. It wouldappear, then, that the HerringGulls of northernEurope 96] SMITH,Michigan Herring Gulls Bird-BandingApril and North America have essentiallysimilar habits of wandering,although the former may make fewer flights and show less southward tendency.Even thoughthe spatialpatterns vary from one region to anotherall appearto includea dispersalfrom the breedingcolonies, particularlyby the youngbirds, the directionsand distancesof which are largely controlledby environmentalfactors. Return to the colonies is for many individualsdependent mainly upon degreeof maturity, and for thosethat return in their first year may .be simply a function of a gregarioustendency.

COMPARISON WITH RELATED LARUS SPECIES In a numberof relatedspecies many of the samedispersal tendencies are evident. In the ,closelyrelated Ringsbilled Gull, Larus delawarensis, for instance,banding recoveries from Great Lakescolonies (Ludwig, 1943) indicatethat many of the birds go southto Florida and the Gulf of Mexico,largely by way of the Mississippior GreatLakes-St. Lawrence systems.Some winter in the Great Lakes but most immature birds at least (recoveriesof adults were few) remain south of the c.oloniesfor one or two years. Florida appearsto be the site of the chief concentration. Color-bandingstudies of gulls on the Pacific coast of the United States(Woodbury and Knight, 1951) showno real migrationpattern, but a wanderingback and forth alongthe coast. Recoveriesfrom the WesternGull, Larus o. occidentalis,for example,show a dispersalnorth and southfrom the Oregoncolonies (Ferris, 1940) in which individuals may becomeresident where they spendtheir first winter, but probably return as adultsto the generalregion of their birth. Woodburyand Knight recognizethat thereis "greatvariation in the distancetravelled by younggulls, not only amongmembers of the samecolony but also among colonies,populations or species." California Gulls, Larus cali- /ornicus,from KlamathFalls, Oregon,and Mono Lake, California,for instance, do not travel as far as those from Utah. The Utah birds, bandedat Great Salt Lake i Woodbury,Behle, and Sugden,1946), presentan interestingcase of longitudinalmigration. The first-year birds fan out, mostlytowards the West coast,and most of them reach the Pacific,descending to it alongvarious waterways. In their winter absencethey are replacedin Utah by Ring-billedGulls presumably (Woodburyand Knight, 1951) from Canadian breeding grounds, although why one leavesand the other comesto Utah has not been answered.Since most of the California Gulls from Utah go to the Pacificcoast, they may havea geneticallyfixed directionaltendency of the sortshown to be muchmore clearly present in someEuropean birds suchas Storks,Ciconia ciconia (work reviewedby Mayr, 1952). They would not be aided by the prevailing winds, and the authorsnoted no other environmental factors which could serve to direct them. How- ever, their original dispersalis erratic both in time of inceptionand in directionand someremain in the interior--a lack of consistencyis thus apparentlycommon to at leastseveral Larus species. The British Larus gulls, as describedby Witherby et al. (1941), alsoshow a pattern of erratic dispersalof immaturebirds and a certain amount of drifting with little actual migration. Some such as the CommonGull, Larus carats,are partially sedentaryor do not go Vol. XXX 1959 SMtTH,Michigan Herring Gulls [97

"any great distance" (Danish populationtreated by Munk, 1951), while the LesserBlack-backed Gull, Larus ]. ]uscus,shows a definite migration (Thomson,1924) in which most birds participate,and its immaturesdisperse to greater distances.Matthews (1952) experi- mentally comparedthe homing ability of Herring Gulls and Lesser Black-backed Gulls. He found both to be inefficient, but felt that there weremore able navigators among the latter. In North Americaprobably only the Franklin'sGull has a true migration. Justwhy there is a dispersaltendency in the Herring Gull, and why it is pronouncedonly in some first-year birds, is difficult to see. Lincoln (1939) thinks that the tendency,which he calls "migration," may be inheritedby the individual as a "recessivecharacter which it largely outgrowsas it reachesmaturity." He further suggeststhat it may representvestigial migration. Possiblyit shouldbe calledmigra- tion only in a very broad sensesince its direction and timing may be largely due to external environmentalfactors. Perhapsthe young birds do not really displayZugunrube (as reviewedby Farner, 1950), but simply are not stronglyattracted to the vicinity of the colonies. Perhapsnatural selectionfayours those which do simply drift with the wind and eventuallyproceed to the south,for theseavoid the harsh- ness of winter with which, in their inexperience,they might not be able to cope. Later, when more experienced,they are also more sexually mature and many feel an attraction to the vicinity of the colony, even if this be just a rather broad vicinity. Once fully adult and breedingthere may be lessincentive to wanderand moreto return to the nestingsites early in the year--a tendencyfrequently found in colonieswhere the best (i.e. central• sites are occupiedby the older birds (Fisher and Lockley, 1954).

MORTALITY Someidea of the causesof death of the bandedbirds can be gained from the detailsusually submitted with the recoveryreports, but equal significancecannot be given to all the recoveries.As Paynter (1947) has made clear, fates closelyallied with human activitieswill be amply recorded,but birds killed by predators,disease and other causeswill be recoveredonly by chance. He illustratesthis, and to repeat his illustration using the figures from this study, 3.02% of the 1,127 recoveriesfor which data were furnished were caught by fishermen. This does not mean that 3% of all Michigan Herring Gulls meet this fate, for these 34 birds probably representmost such catchesof the entire 37,414 banded. Thus the mortality rate due to this causeis more nearly 0.09%. Listed herewith are the causesof mortality recordedfor both the Michigan birds and Paynter'sKent Island birds. Of the latter group, 37,557 were bandedas young. Recoveriesof gulls which were banded as adults at Kent Island are not considered here. Most birds are reportedas "found dead." This category,and those of "found," and "killed," furnishesus with no information. Some13.84% of the Michigan birds recoveredwere capturedin one wayor anotheras compared with 14.76%of the Kent Islandrecoveries. ThoseMichigan birds reported as capturedby fishermenwere taken on a line, by a hook or in nets. A somewhathigher percentageof the 981 SMITH,Michigan Herring Gulls l•ird-l•a.April nding

Michigan Kent Isl,and No. Percent Percent Found dead 693 61.49 53.51 Captured and released 60 Captured 37 5.32• 1.99(during banding, not Captured by 3.2813.84% 9.02 -• comparable) fishermen 3½ 3.02 4.31J captured Trapped 25 2.22 captured1.43 14.76% Sh•t 85 7.54 5.35 Injured, sick, or wounded 76 6.74 7.58 Found 50 4.44 4.63 Killed 24 2.13 2.14 Band only 4 0.35 0.87 ("band recovered" perhaps Miscellaneous 39 3.46 3.17 not conaparable) 2.71 (,prolb. found dead) Total 1,127 100% 1.19 (collected) No information 16 1.83 (no information)

1,143 100% marineKent Islandbirds met this fate,but moreof the inlandMichigan birdswere taken in animal (mainlymuskrat) traps. Of the 85 Michigan birds shot, 48 (56%) were in their first year (35 wereshot before their first December31st). Probablymany of the recoveriesreported as "found dead" really representbirds shot as the personssending in the bandsmay have feared prosecution.European bandingstudies show much higher percentages of recoveriesfrom shot birds (Drost and Schilling,1940, record51.2% shotand 34.5% found dead,Paludan, 1953, 60.4% shotand 30.8% founddead), alongwith correspondinglyfewer birds recorded as found dead. The three recoveriesgiven as "band only" are instancesin which a band has beenpicked up in a field or on a shoreperhaps after being lostby the bird whichbore it. Paynter'scategory "band recovered"is probably not comparable. ! have lumped all recoveriesof birds reported as "injured," "sick" or "wounded"because of the likelihood that the personfinding the bird was unableto distinguishwhich was the case. The miscellaneousgroup is worthy of mention. Includedhere are two birdswhich were shot, one for a specimenand one,a four-year-old, at a state fish hatchery. Two were reportedas killed by owls, and one by an eagle (Paynterrecords two as killed by eagles). Lossesto animalpredators include one killed by a "fox or coyote,"one by a dog, and one killed "probably" by a mink. It is to be expectedthat the numberof recoveriesfrom suchsources will give a very incomplete r•ictureof the actualpredation rates. Three were hit by automobiles, three by trains, and one died in a collisionwith a jet aircraft at an airbase. Of Paynter's similarly sized sample eight deaths resulted from collisionswith aircraft, eight with automobiles,and one with a train. Two birds, reportedas being"tame," were "pickedup," and a first-yearbird was taken when it flew into a porch. Two birds were found exhausted,six frozen, two drowned, and one with oil on its plumage.Not all of thesediagnoses, of course,are necessarilycorrect, andsome, such as a bird found"paralyzed" and onewhich died of "lead poisoning,"leave considerable doubt as to the causeof death. Vol. XXX 1959 SMITH,Michigan Herring Gulls [99

One report of considerableinterest, however, tells of a four-year.old gull whichpecked at its leg until the band fell off. Althougha certain amountof forcibleremoval shortly after bandingmight be expected, this seems to indicate that some birds at least do not become accustomed to wearing bands. Paynter (1949), is of the opinion that loss of bandsby wearing and breakingprobably is not great in the Herring Gull, at least up to ten years of age, since many bands survive ten years in good condition. Recall, however, that in three casesbands of Michigan gullswere found lying in fieldsor on beaches,and bands found on nestingislands have not been considered.These birds had been banded one, six, and eight years before the bands were found. If the bands did not wear through and fall off, then either the birds themselvesremoved them or the bands were separatedfrom the birds' carcassesby some agency. The number of instancesin which these isolatedbands are found can certainlygive no idea of how many are lying on beachesand fields,as they are much lesslikely to be found than are dead gulls. If, then, many Herring Gulls do remove their bands,older age groupswill yield proportionatelyfewer returns than younger,but the extentof the bias thus introduced,if, indeed,such a bias doesexist, is unknown.This bias couldbe partly responsiblefor the failure to reconcileattempted calculations of mortality rates and longevitywith knownproductivity rates on the basisof North American bandingrecoveries (reviewed by Farner, 1955). The remainingrecoveries are likely unusualinstances: a bird was found "stuck in [an] asphaltbed" in Mexico, anotherflew into the cargohold of a freighter,one became caught between two timberson a dock, one broke its wing by flying into a ship's life line, while one in Chicagowas killed when it flew into a flagpole. Finally, in the courseof feedingone took poisonedcorn and one "chokedon a fish." The oldestbird yet recoveredin this groupwas a 19-year-oldfound deadby the Ludwigsin 1954 on BellowIsland, Lake Michigan,where they had bandedit in 1935. It may be the oldestHerring Gull yet recoveredin North America. A Herring Gull bandedin Denmarkin 1925 and recordedjust over 28 years later is claimedby Bergstrom (1956) to haveset a new longevityrecord for any speciesin the wild. CaptiveHerring Gulls,however, have reached considerable ages. Pear- son (1935) recordsa captivepair whichattained 49 and 45 yearsof age, and Flower (1938) one which reachedat least 41 years. I have already mentionedthat mortality is highest among first- year birds and statedthat 63.34% of the recoveriesin this studywere of that age group, 42.16% of the total being before December31st. This feature has been commonto all the banding studiesof Herring Gullsin Europeas well as in North Americareferred to previouslyin this paperand to studiesof otherspecies of gulls. Paynter (1947) has suggestedthat first-yearbirds are relativelyweak. Lack (1943) shows that the numberof first-yearBlack-headed Gulls, Larus r. ridibundus, which are shotis disproportionatelyhigher than for older birds. He suggeststhat they become"warier and harder to shootas they get older." Later i Lack, 1946) he suggestedon the basis of recoveries from a numberof speciesthat the higher mortality amongjuvenile birds is due to generalinexperience. Bird-Banding 100] SMITH,Michigan Herring Gulls April

SUMMARY AND CONCLUSIONS 1. Be;ween 1931 and 1957 Mr. Claud C. Luc•wi.gand his two son.sbanded 37,414 juvenile Herring Gulls in coloniesin the Great Lakes adjacent to Michigan. ß he 1,143 recoveriesare analyzed herein. 2. Dispersal begins in late summer and early .autumn. Most birds in their secondyear or older tend to remain on the shoresof the Great Lakes within 300 miles of the colony. 3. There is some evidence .of a nor*hward tendency in .the early autumn, but recoveries from sparsely-settlednorthern Ontario and Quebec ,are too few to characterizeit properly. 4. First-year birds, particularly in the period betweenJ,a, nuary 1st and J.une 30th, fly farther than older birds. There is great individual variation in the distances they cover, however, ,and in the time they quit the vicinities of the colonies. 5. Recoveries are most frequent from the shores of the Great Lakes. Other recoveries fall into two categories: (1) the Mississippi River and its tributaries, and (2• the Atlantic and Gulf of Mexico coasts. Access to the Atlantic coast is probably mainly via the St. Lawrence R•iver. 6. Waterways and coasts are followed becausethey provide a source of foe,& and it is suggestedthat they function further to supply lanes of u•ward air currents used in soarin,g. This .contentionfinds support in the literature at least to the degree that numerous other soaring species make use of thermal lanes during migration. 7. Prewailing winds probably are a major factor in controlling the direction taken by the gulls, that is, they superimposea direction upon the dispersal. This direction coin.cides with autumn movement down the Great Lakes- St. Lawrence system,.a wi.nter movement to the south down the Mississippi or the East coast, and spring return northward. Many other •birds are known to use tail winds extensively or exclusively on migration, t.hus it is likely that a soaring species such as the Herring Gull would follow suit. Since many Herring Gulls are relatively sedentary, though, it is quite possible that a condition of Zugunruhe is not typical of the movementsof the species. These movements, then. should perhaps not be considered a.s migratory, but merely as a wandering •overned directly by environmental factors. It is possible •that immature birds are less attracted to the ¾i•cinityof the breeding grounds t,han are sexually mature birds. 8. T,he most westerly inland recoveriesin the study .are probably cases.o.f young birds returnin,g home in the sprin• and takin,• a western tributary as th.•y move t•p the Mississippi. They do not represent a tendency to disperse to the west. 9. The southward movement of late December, char•acteristiconN of first-year birds, carries the •ulls on the East coast to Georgia and Florida and rarely into the West Indies. It also takes other birds from t.be Great Lakes down to 'the Gulf of Mexico, a cone.e•tration occurring in Texas a•d Louisiana. Quite a few reachMexico, and there is one record.from Honduras and one from Nicaragua. 10. In 1936 a much larger number of first-year birds reached the western part of the Gulf of Mexico than in any other year of the study. No reason for this movement has been offered 'herein. 11. A relation.shilo between colony •cff birth and •l-•e ,f re•overv exists t.o the extent that relatively more birds born in Lake Huron colonies ae re.cowr•d in Ontario than in Wisconsin. II.linois and Indiana, the opooait.ebei,•, the case for birds born in Lake Michigan colonies. Since dispersal is originally for short distancesand is probably largely on the lake of 'birth, and since mortality is highest among the youngest nulls, this is ,or really surorising. It is reflected to a lesser degree in the winter movement to the south, since Lake Huron gulls, of which more have drifted east, provide r•'lativelv more East coast and fewer Gulf of Mexico recoveriesthan do Lake Michigan gulls. Colonies vary individually in the degree to whi.ch they are characteristic of colonies in their lake as a whole. 12. Twenty Herring Gulls banded by the Ludw[gs and three by other banners were recovered in the breeding colonies. Thirteen of these were recovered in the colony where banded and ten in other colonies (one actually in another Vol. XXX 1959 SMITH,Michigan Herring Gulls [101

lake). %heseindicate both return to the colony of birth, and, if they were breeding birds, someexchange between ,colonies whi.ch wotfid reduce genetic isolation. 13. Other published banding studies of Herring Gu.11sbreeding in t'he Great Lakes show similar dispersals,,as ,do those of birds .banded on the East coast, although •he latter do not wander inland to any extent. European studiesreveal dispersalof sh,ort distances,usually in all directions and often con,fined to the coasts. Again, it is the young birds w,hich do most of the wandering, and enviror•men•alfactors may largely control what directional tendencies there are. 14. Many of the same dispersal tendenciesare evident ,in related Larus species. Erratic dispersal of first-year birds, with great individual variation, followed by same degree of drifting usually wit.hout•a fixed migration pattern, while the adults largely remain relatively close to the breeding colonies is appar- ently characteristic of most of the group. 15. Over half of the birds recovered were listed as "found dead." The next highest categorieswere of birds captured, usually ,by fishermenor muskrat trappers, of birds shot, .and of injured, sick, or wounded •birds. One very interesting case of a band recovery came after the person submitting the report watched the gull, a four-•ear-old, remove the band from its leg by pecking at it. This observation introduces t'he consideration that if such action is not infrequent, then a bias exists in the recoveries of older birds th,at will be difficult to calculate. 16. Mortality is greatest in first-year birds up to December, the rate declining rapidly thereafter.

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FALL MIGRATION OF HERRING GULLS FROM KNIFE ISLAND, MINNESOTA By P. B. HOFSLUND In June, 1950 the Duluth Bird Club began a banding study of a colonyof Herring Gulls (Larus argentatus).This studyhas continued eachsummer since, the summerof 1957 marking the eighthyear. The presentpaper dealswith the recoveriesof bandedgulls up to May 15, 1958.

120 - I[0 • • • c.• )00 90 McKNIGHT 6, McKNIGHT, BLOOMINGTON, ILLINOIS .Map 1. Recoveriesof Herring Gulls banded as nestlings on Knife Island, Minnesota.