'White-Faced' Terns

164 PAL:•XER,'White.faced' Terns I.[Auk April

'WHITE-FACED' TERNS

BY RALPH S. PALMER

Plate 7 DxvvEt•sTplumages of the samespecies of ternshave been given new namesso many times that the Marpies have included in their bookon 'SeaTerns' (1934:opp. p. 23) a plate labelled"Comparative Diagram of the 'Spurious'Terns." One of the birds shownis the non-breeding'white-faced' Arctic Tern, Sterna 'portlandica.' While conductinga behaviorstudy of the CommonTern (Sternahitundo) on the SugarloafIslands, at Popham Beach, Maine, the writer has collectedand observedboth breedingand non-breeding'white-faced' examplesof this species.Since the significanceand occurrenceof 'white-faced'plumages in ternsare not generallyunderstood, the writer has undertakento sum up here the available evidenceon plumage sequencein the CommonTern. While most of the factspresented refer specificallyto the CommonTern, they apply equallywell to the Arcticand, in manyrespects, to the Roseateand other terns. The writer wishesto acknowledgethe assistancehe has received from the following institutionsand individuals: the authorities in chargeof the U.S. NationalMuseum and Biological Survey collections, the authoritiesof the American Museum of Natural History, and Mr. Arthur H. Norton of the Portland (Maine) Societyof Natural History for the loan of valuablespecimens. Professor S. A. Asdell,of the Departmentof Animal Breedingat Cornell University,has kindly loanedthe writer many reprintsfrom his filesand has made helpful suggestionspertaining to the endocrineaspect of plumagesequence.

EXPLANATION OF PLATE 7

Contmon Terns--The left-hand bird is a juvenal and can be so recognizedby the markingson the back. In other respectsit is much like the next two specimens,which are summer non-breedersin fresh eclipse,i.e., 'portlandica,' plumage. The two right-handbirds are old-agebreeders. The nature of the cap and the color of the basesof the bills at oncedifferentiate them from 'portlandica' specimens. Arctic Terns--The left-hand bird is the type of Sterna portlandica Ridgway. It is badly soiled and does not show the cubital wing band very well in the plate. The next two are also summer-eclipseor 'portlandica' birds. The fourth is an old-age breeder of the 'pikei' type. The fifth may possiblyrepresent either a partial assumptionof breeding plumage by an 'immature' bird or a condition approachingold age. THE AuIq VOL. 58 PLATE 7

JUVENAI.AND '•¾}IITE-FACEI)' COhll•ION

t'•¾HITE-FACEI)' fiiRCTIC TERNS Vol.1941,58] a PALMER,'Whiteffaced' Terns 165

RELATION OF GONADS TO BREEDING AND F.CLIPSE PLUMAGES As here used,the term 'eclipse'includes all postjuvenalplumages assumedby certain'hooded' or 'capped'Laridae when the gonadsare quiescentor relativelyso. The juvenal stagemight alsobe called eclipse,but it is not socalled because this plumage is easilydistinguish- able from subsequentnon-breeding plumages. This definition of eclipsepertains to the speciesunder discussion, since the physioloõical basisfor arrivingat equivalentplumages in ducksand otherbirds is knownto differfrom that of gullsand terns. Both sexes of the Common, Arctic and Roseate Terns exhibit the followingcharacters in thejuvenal and in the eclipsestates: (1) a light foreheadand a blackishcrown; (2) purewhite under parts; (3) a dusky cubitalband on eachwing; (4) lesshighly colored bills and feet than in breedingplumage. Both sexesof the samethree specieshave the followingcharacters in breedingplumage (with an exceptionwhich will be discussedlater): (I) a black cap,which includesboth foreheadand crown; (2) under partseither •ray or white tinted with pink; (3) no duskycubital band; (4) relativelyhighly coloredbills and feet (in breedingRoseate Terns the bill at the base is bright orange-redand not all black, as is commonlybelieved). The juvenal and eclipseplumaões are assumedduring the time when the gonadsare relatively quiescent. The breeding plumage in at leastpart of the Laridae is apparentlythe one dependentupon the secretionof a sex hormonefor its development. Whereasthis is not the casein many birds, as has been explainedadequately by Domm (1939),I feel certain it is true with the ternswith which we are deal- ing becauseof evidencefrom castrationexperiments on the Black- headed Gull, Larus ridibundus (Van Oordt and Junge, 1930, 1933a, 1933b). This gull hasa plumagesequence and certainsecondary sexual charactersvery similar to thosein Common,Arctic and RoseateTerns. It has a 'hood' on the head, as well as bright-coloredbill and feet, which are presentduring the breedingseason in both sexes. Char- acters of this nature have been called 'ambosexual'characters by Champy (1930)and Champyet al. (1931). If gulls of this species are castratedin winter plumage-eitherfirst winter or succeedingones- the nuptial plumagefails to develop. At the time of the prenuptial molt the birdsagain assume the winter (eclipse)plumage. Further- more, the bill and feet remain in winter condition. Therefore, the assumptionof the nuptial plumage and bright bill and foot color appear to be influencedby a testishormone which cannotbe secreted by castratedbirds. 166 PALMER,'White.laced' Terns L[Auk April

While Van Oordt workedon male birds only, a matter commented on by Domm (1939:283), he statedthat he supposedthat ovariectomy would producethe sameresult, sincefemales and maleshave similar plumages. The fact that Common and Arctic Terns of both sexes, that have very small gonadsand do not breed, revert to the eclipse plumageat the time of the springmolt, lendssupport to his statement. As we shall soonsee, Common Terns ordinarily do not breed at an early age, nor do first-yearbirds appear on the breedinggrounds in any numbers. Those which do appear usually have minute non- breedinggonads and are found to be in fresheclipse plumage which they acquiredby a completespring molt. That 'portlandica'birds were non-breedersthat acquiredsuch a plumagein spring was well

BREEDING

ECLIPSE

NATAL

Sum. Fall Win. Spr. •u•. Fall Win. SpF. •um. F&11 Win. Spl'. Sum. TEXT-FIe. 1.--Diagrammaticrepresentation of the sequenceof plumagesin early life in the CommonTern. The probablenormal sequenceis shownby the heaviest line. Dotted spacesindicate, in a general way, times of molt.

understoodby Dwight (1901: 52). These birds are, in plumage, equivalentto Van Oordt'scastrated gulls. Just how long a tern may revert to the eclipsestage semi-annually is not definitelyknown, but it is fair to assumethat they do so aslong as they stayaway from their breedinggrounds. The matter can only be definitely settled when many banded non-breedingbirds are re- coveredat various times of the year. In general, the sequenceof plumagesof the CommonTern in early life appearsto be thus: (1) natal (acquiredbefore hatching); (2) juvenal; (3) first-wintereclipse; (4) first-summereclipse--'portlandica' (rarely a breedingplumage is acquired instead); (5) second-wintereclipse; (6) second summer, either: a, eclipseagain ('portlandica'),or b, first-nuptialplumage. Many birds require anotheryear beforeattaining their first-nuptial stage. The diagramof plumagesequence shows the probablenormal sequenceup to the fourth summer. It doesnot showduration of molt. Vol.•94• •8] a PALMER,'White-[aced' Terns 167

I havenot calledthe immaturesummer plumages 'nuptial' plumages, as Dwight (1925) has done with gulls, sincethe term is more ap- propriatefor breedingstages. The Common Tern resemblessome of the smaller gulls much more closely,both in time of beginningto breedand in time of assumption of breedingplumage, than many writers have hcrctoœorcrealized. The followingdata will make this clear.

YouNG 'WHITE-FACED' TERNS Attainment of breedingage.--No Common or Arctic Tern appears yet to have bccn recordedwith absolutecertainty as breedingin any form of immature 'portlandica'or eclipseplumage. Coloniesof Cabot'sand SandwichTerns (racesof Thalasseussandvicensis) and Royal Terns (T. maximus)have a fair shareof the breedingpopula- tion showingwhite in the œorchcads.These lighter birds appear to bc first-yearbirds and arc quite definitely known to breed in this plmnagc(H. W. Robinson,1910, 1940). One SandwichTern in "œull winter plumage"has bccn sccn to incubatean egg (Robinson,1940: 150). The Black-headedGull breedsregularly in "immature"plumage (Kirkman, 1937: 111). Havcrschmidt(1931)mentions the same fact and also statesthat the Herring Gull (L. argentatus)and the LesserBlack-backed Gull (L. fuscus)breed bcœorcattaining the fully adult stage. Tinbergen (1936)reported that immatureHerring Gulls may pair, nest and copulatc,but fail to lay eggs. Many sub-adult Larinac very commonly'play' with nestingmaterial at the season when adults arc breeding. Juvenal CommonTerns oœtcnpick up grassand twigson or near the territory where they wcrc hatched,but the reasonfor their sodoing is not clear. Whereas the Marplcs (1934: 190) stated that Common Terns normally breed when one year of age, the Austins think otherwise. O. L. Austin,Jr., (1999: 130)concluded from his very extensiveband- ing and rctrappingrecords that this speciesdoes not breedat the age of one year, that all do not breed when two yearsold, but that the third year normally sccsthem productive. Later, O. L. Austin, Jr., (1932: 137)reported capturing a singleyear-old Common Tern which was incubatingeggs. Sincenothing was said to indicate otherwise, wc may assumethat it had attained the breedingplumage and that it had a definite connectionwith the eggs. Thus it seemsthat the Common Tern may rarely breed when one year old. From the factsthat year-oldbirds arc rarely rctrappcdat nests,that œcwtwo-year-old birds arc taken, and that the birds arc usuallyin their third year when first recaptured,wc must cometo one of two 168 PALMER,'White-[aced' Terns I.[Auk April conclusions:either (1) the youngbirds do not breed,or (9) if they do, they nestin other placesrather than near the colonywhere they were bandedas nestlings.Since the Austinshave concludedfrom their data basedon a numberof Cape Cod coloniesspread over a considerable area that Common Terns tend to return to breed "in the generalvicinity" of their natal homes(O. L. Austin,Jr., 1929:128), and sinceit is well knownthat oncethey begin to breedterns tend to comeback to the samenesting site annually, we are facedwith the firstalternative, namely, that youngbirds do not breed. Furthermore, bandingreturns from moredistant colonies in no way conflictwith this conclusion. Distribution.--There are relatively few data as to where non- breedingyear-old and two-year-oldCommon Terns are to be found, althoughLincoln (1927)published a small amountof evidencebased on bandedbirds. Thousandsof juvenalsgo southwith their parents annually. Do they tend to wanderlike year-oldHerring Gulls? This seemsvery likely. This wanderingprobably takes place in the tropics or even farther south. Many writers, suchas Ticehurst (1924: 140), have stated that more southerlysummering birds were in the 'portlandica' plumage. Such wanderingmight also accountfor the fact that severalCommon Terns, which were taken in the Antarctic regions, were referredto by Murphy (1956: 1099)as "birds of the year." O. L. Austin (1958: 15) has attemptedto accountfor youngbirds by consideringthem as "drones,"or idle birdsnear breedingcolonies. My own work in relativelysmall colonies($50 to 500 pairs of birds) doesnot favor this concept,but rather showsthat the birds which gather in rows and flocksnear coloniesare breedersand that they are indulgingin what maybe calleda socialsunning reaction (Watson, 1908). Terns are social creaturesand this tendencyto becomea member of a flock manifestsitself frequently all during the breeding season. However, once a tern leaves a flock and flies to the nesting territory, it becomesstrongly territorial in its reactions.Thus these idle flocksare, in general,made up of maturebreeding birds in normal breedingplumage and not of "drones"or youngnon-breeding terns. A few exceptionswill be discussedlater. As the matingseason advances we find a sortof floatingpopulation, but this consistsof birds that have lost their eggsor chicksand sowere breederswhen they arrivedin the colonies. Gonadsand migration.--Putzig(1957) and Hann (1959)have shown that a total of five species--twogulls and three passerines-willmigrate southwardafter castration. Therefore, their urge to undertakethis migrationis not dependenton the presenceof male gonads. Of course, Vol.•941 58'1 .• PALMER,'White-laced' Terns 169

when one stopsto think about it, this doesnot seemvery unusual,for the youngof certainspecies whose gonads have never enlarged, migrate southwardsuccessfully even without accompanyingadults of the samespecies. The springmigration is another matter. it is indeed interesting that a few non-breeding'portlandica' terns,with their very minute and undevelopedgonads, should come northward at this season. Ap- parentlyterns tend to be socialall the yearround and thesefew young birdsreturn to the breedingcolonies not becauseof anyurge to migrate within themselves,but becausethey happen to associatewith normal migratingindividuals.

OLD-AGE 'WHITE-FACED' TERNS Longevity.--O. L. Austin, Jr., (1932: 139) stated that the 'average' length of a CommonTern's life was somewhatless than nine and a half years. Flower (1938: 224) reported the average life span for twenty banded ternsof three speciesas eight yearsand nine months. Consideringthe great age attained by someof their gull relatives, it is not surprisingto find that many terns live well beyond their averagespan of life. Cooke (1937: 55-56) reported twelve-year-old CommonTerns, nine-year-oldArctic Terns, and seven-year-oldRoseate Terns. The Austins find thirteen-year-oldCommon Terns quite regularly,and theseappear to showfirst the old-age'white-faced' condition. The Marples (1934: 123) quoted from Trans. Norfolk and Norwich Nat. Soc., 1922, an interestingcase where a Common Tern nestwas found on the samesite for seventeenconsecutive years, and contained"very distinctiveunspotted eggs." The bird was killed by a stoat in 1920 and similar eggshave not been found there since. If this bird did not breeduntil the secondor third year, it had attained altogetheran ageequal to doublethe averagelife spanfor the species. A banded Black Tern has been recoveredin Italy at the age of at leasteighteen years •Schenk, 1934: 69). There is little evidencethat birds past breedingage form part of a breedingcolony. There are few idle birds of any sort present. The specializedmode of life and the long migrationswhich terns undertakeinsure that lessvigorous individuals are weededout and do not survive. The caseappears somewhat different with Kirkman's Black-headedGulls, for he states (1937: 62) that there were birds too old to breedpresent in the Twigmoorgullery and that theywere easilyrecognized by their "dilapidatedplumage" and "generalair of feebleness."He further points out that thesebirds excite hostility and attackfrom more vigorousindividuals. Sincethis speciesis fed 170 PALMER,'White-faced' Terns 1[Auk April in parksand about citiesin Europe,and is not a highly migratoryone, individuals stand a better chanceof survivingto past breedingage than do any speciesof terns. Pluraage.-O. L. Austin (1938: 21) has reportedthat thirteen-year- old breedingCommon Terns showcertain plumage changes, such as a "markedwhitening of the featherson the crown,"which rendersthese birds easily recognizableto an experiencedbander. He gave no further detailsregarding the appearanceof thesebirds. The writer, however,has observedand collectedbirds in this plumageand has examinedothers in variouscollections. At the prenuptialmolt these old birds (Common,Arctic, and probablyRoseate Terns) acquirethe following characteristics:(1) white, or at least lighter, under parts; (2) a white or mottledforehead and black crown; (3) a duskycubital bandon eachwing; (4) highlycolored bills and feet. Characteristics1, 2 and 3 are shared in a general way by old-age breederswith the juvenal and all eclipsestages. In contrastto the others,however, the old birds are definitelyknown to breed (Austin, loc. cit.); they have bright bills and feet, and the precisenature of the light and dark feathersof the cap is quite distinctive. They have strikingcharacteristics of both non-breedingand breedingbirds. This plumage appearsto be comparableto the Sterna pikei of Lawrence (1853), which Ridgway (1875) separatedfrom 'portlandica'on the basisof colorsof soft parts. Both birdswere Arctic Terns. The blackishcrown of juvenal and eclipseCommon, Arctic and RoseateTerns has a rather washed-outappearance, and mergesvery gradually into the forehead. In 'white-faced'breeders it appearsas if a cap as black as that of youngerbreeding birds had been assumed, then the foreheadpart of it shedand replacedby pure-whitefeathers. This is exactlythe appearanceof the headsof youngerbreeders when they begin to assumethe eclipseplumage in September. However, with these old birds all the feathers of both forehead and crown seem tobe of anequal age in May,June and July speclmens. • ' Both sexes have this plumage,which is not merely an early onsetof the fall molt of youngerbreeders. In the case of skins of some summer individuals which I have ex- mined, that have black feathers scatteredthroughout the light foreheadand yet otherwiseresemble old-age terns, I am not certain but what this intermediateplumage may representyoung birds in a first imperfect breeding plumage. However, it might equally well representan onsetof the old-agecondition. There are no published data from bandersdealing with this matter. Possiblya sex hormone influencesplumage by its presenceor ab- Vol.,•8' I PALMER,'White-faced' Terns 171 •94• a

sence. These terns, as they approachold age, show characteristics of the non-breedingplumages. There may be a differentialthreshold of amountsof hormonenecessary for the assumptionof (1) the bright colorsin bill, legsand feet,and (2) the full normalbreeding plumage. The birdsare ableto breedwhen they do not producethe full breeding plumage. Whether or not Sandwichand Royal Terns have an old-age'white- faced'breeding plumage appears to be unknown. If differentspecies of ternsdo have this plumageand acquireit at differentages in each species,the factsmight be determinedby banders: It is well known that birds in captivityor in a half-wildstate show plumage changesof various sortswhen they becomeold. Millais (1902: 17) has recordedsuch changes in both sexesof the Mallard, but thesechanges appeared after the birdspassed breeding age. Numbers.--Neitherthe Austinsnor the Marples have reported on the numbersof 'white-faced'terns in the colonieswhich they have studied. After 'portlandica' was described,the bird was stated to be "of rare occurrence"in such lists as that of Brewer (1875: 450). Coueswrote about the bird severaltimes, but said little or nothing of its numbers. Hersey (1920: 203) statedthat many Arctic Tern colonies had no so-called Portland Terns, while other colonies contained a "considerablenumber." Dwight reported one 'portlandica' bird to a thousandnormal breedersin the large Sable Island, Nova Scotia,colony. Upon examinationof his series! find that one of his Sable Island 'white-faced'terns is in the old-ageand not the 'portlandica'plumage. At the SugarloafIslands ! have noticedabout one 'white-faced'bird (includingboth sub-adultand old-ageterns) to 150 pairsof ordinary- plumagedbreeding Common Terns during the summersof 1938 and 1939. Immature and old-agebirds were about equal in number in these small colonies. ! rather suspectthat the latter would pre- dominateif the colonieswere older, but they have had an interrupted existence,and the presentpopulation began to colonizethe islands about 1923. SomeMaine gunnersof a pastgeneration were familiar with birds with light foreheads,and referredto them as 'White-faced Medricks'. By the time that the banding of nestlingsand the trapping of banded adults has progressedbeyond the extremelife probability of ternsin a number of large colonies,it shouldbe possibleto construct a histogramshowing the relative numbersof eachage class up through the old-age'white-faced' stage. One could then ascertainwith reason- able mathematical accuracy the relative numbers of 'white-faced' 172 PALMER,'White-laced' Terns LAprilI'Auk

breedersfor a colonyof anygiven size. O.L. Austin,Jr., (1952:157) has preparedsuch a histogramcovering eight years'work, but this is not long enoughto providedata on old birds. The eclipse-plumaged birdsare not truly migratory,hence their numbersare not predictable. Behavioro[ 'white-[aced'birds.--Dwight (1901: 52-55) reportedthat attention was often drawn to the 'portlandica'Arctic Terns on Sable Island, Nova Scotia,by their "singleharsh croak seldom uttered .... " They must,indeed, have been conspicuous, for he succeededin getting eight 'white-faced'specimens. Holder and Wagstaffe(1928) reported seeinga few non-breedingCommon Terns eachsummer for several yearson the SouthLancashire coast, where the birdspossessed some of the pugnacityof adultsand occasionallywould swoopat humanson the beach. The few 'portlandica'Common Terns which I have ob- servedhave usually been silent. I have not noticed that they were unusually conspicuousin a colony insofar as they themselveswere concerned,but theywere sometimesfollowed about by severalbreed- ing adultsas Barn Swallowspursue an albinofellow member of their species.Breeding terns seem to recognizethese non-breeders in summer-eclipseplumage as not beingpart of the breedingcolony. Perhaps non-breedersfail to indulge in the formalizedposturing of sexually active individuals. Austin (1958:21) has pointedout that clutchesof eggsof 'white- faced'Common Tern breedersare of averageor larger size,and that fertility seemsto be normal. These old-agebirds are not very conspicuous, nor are they accorded different treatment by younger breeders,as can be seenfrom the followingextract from my records madefrom a blind on July 2, 1959: A white-facedbird came and stood on a commonperching rock within sight. It called to passersby;would face in one direction, then in another. Bird has orange in bill and highly-coloredfeet--much different from white-faced bird I collectedin June. No other bird paid any noticeableattention to it. Another bird standingby a nest not far away has a number of white feathers in the forehead. It is mated to a bird with an all-blackcap. Thus it seemsthat old breedingbirds with white foreheadsfind that a whiteningabout the 'brows'is no drawbackto acquiringa mate, or in participatingin any phaseof the normalbreeding cycle. They are as readily acceptedfor mates,as long as their behavioris suitable, as are the oddly plumaged first-year male American Redstarts (Setophaga). I have no field data on old-ageArctic Terns. The 'white-faced' birds known to be breedingand seenby Lord W. Percy in Siberia and by Jourdainin Spitsbergen,which were mentioned by Witherby Vol.58] PAI.M•,'White-faced' Terns 173 •94• •

(1924:713, footnote), were almost certainly of the old-agetype which I havediscussed, and not true 'portlandica'examples.

SYNOPSIS OF COMMON T• PLUMAGES Muchof the datahere presented are supplementaryto the material in Dwight'spaper (1901). Natal plumage.--Thethick natal downwhich chicks wear at hatching is replacedby a completepostnatal molt. The natal down of RoseateTerns hasa distinctivespinous character, like that of T. sand- vicensis. Natal Common and Arctic Terns show a wide variation and cannotalways be distinguishedfrom eachother. The throat of Com- mon Terns rangesfrom white to black,but is usuallyquite dark. The foreheadis generallylight. Natal Arctic Terns usuallyhave a dark throat, and this color extendsup and acrossthe forehead,but those skinsshowing a light foreheadcannot be separatedwith certaintyfrom CommonTerns. The natal down is pushedout graduallyand there are usuallyonly tracesof it left aboutthe headand flankswhen the juvenalsbegin to fly betweenthe agesof 27 and 32 days. Juvenalplumage.--The crown in juvenalsis whitish or pale buff, usuallygrading rather graduallyinto the rather dark crown. This can be seenin the juvenal CommonTern shownin the accompanying plate (Plate 7). The back exhibitsa widely varyingpattern from bird to bird. The ventral surface is white. There is a dark cubital band on the wings. When CommonTerns are a week old and still downy,the bill is usuallylight flesh-colorat the baseand blackish towardthe tip. This colorusually brightens as the birdsgrow older, and is moreor lessorange-red in flyingjuvenals. After the birdshave been flying about two weeks (i.e., about September10 in Maine), the bill beginsto darkenand in a shorttime it is practicallyblack- in first-winter condition. However, the bills of a few individuals never brightenthus in the late pre-flyingand early-flyingstages. The bill staysdark and is essentiallyin first-wintercondition when thesebirds beginto fly, or from late Augustonward. The feet of natal Common Terns are generally pale. Those of juvenalsat flyingage range from pale flesh-colorthrough a brilliant orange to nearly black. Chamberlain (1959) has reported a wide rangeof color in the legsof youngRoyal Terns. Like the bills, the feet tend to brighten,then later grow dark and are practicallyblack during the firstwinter. Also,as with the bills, somefeet are blackish long beforethe birds fly. It is importantthat bandersshould realize that dark-lootedflightless young exist, for somebanders of limited experience,who work in mixed coloniesof Commonand Roseate 174 P•,LMER,'White-[aced' Terns LApril[Auk

Terns, useleg color to distinguishjuvenals of the two species. It is not wiseto assumethat all dark-lootedyoung are RoseateTerns, since somemay be Common Terns. Natal RoseateTerns are easilyrecognized, while juvenalsof this specieshave fine markingson the back and a generallydifferent 'look' from Commonor Arctic Terns. There is a closeassociation between intensity of leg and bill color in individuals of all ages. The heaviestCommon Terns which the writer has weighedhave been Septemberjuvenals. Floyd (1927) and Heinroth (1928) have providedsome data on weight and growthrate of youngterns. First-winter eclipseplumage.--Dwight (1901: 54) stated that the first-winter(eclipse) plumage is acquiredby a partialpostjuvenal molt, limited mainly to the body feathers. Someindividuals may not molt at all (Witherby, 1924: 710) and so retain a worn juvenal plumage throughout the winter. Birds in first-wintereclipse plumage have white under parts, a dark cubital band on the wings,a whitish fore- headgrading into the blackishocciput, and dark bills and feet. There seemsto be no certainway of distinguishingbetween first and subsequenteclipse stages. Judging from museum skins, it appears that eclipsebirds having somecolor in the bills and feet are probably breedersin winter condition,and that they do not loseas much of the color then as do younger birds which had less color to begin with. One should be careful in acceptingstatements pertaining to birds seenor collectedin 'first-winterplumage' unless the birds actuallywere banded and their agesknown. Tern skins retain the colorsof soft parts very well, but after ageingfor a few decadesin museumcases there is a noticeabledeterioration, perhaps caused by greasein the skins. First-summereclipse plumage.-The first spring molt, which is a completeone, is thought to start later and end later than succeeding ones. This molt may be followed by a nuptial plumage in a few individuals. Usually the birds assumethe eclipse again, both in feathersand in soft parts, and apparentlycannot be separatedwith certaintyfrom eclipsebirds of any age. I have alreadypointed out that O. L. Austin,Jr., (1932)recorded capturinga year-oldbird on a nest, also that it is possiblethat an imperfect breeding plumage may sometimesbe assumedby some youngbirds. Second-wintereclipse plumage.--After a completefall molt the birds repeatthe eclipseagain. We may be certainthat this molt takesplace because(1) older birds have a completefall molt, and (2) because available 'white-faced' birds do not show the extreme amount of wear VoL58' ! PALMEg,'Whitedaced' Terns 175 •941 .• exhibitedby late-winterexamples that failed to shedtheir juvenal feathers. In regardto Herring Gulls of this age,Dwight (1925: 188)reported that an "unknownproportion" of second-winterbirds reverts to the "first year plumageor a type resemblingit," which partly accounts for the largenumber of "youngbirds" which are seenor collected. Second-summerplumage.--Since a few Common Terns breed at this age,it is certainthat somethen acquirethe adult characteristics which! havealready listed earlier in this paper. The prenuptialmolt, which takesplace normallybetween February and late April, is a completeone, and breedershave fresh feathersin wingsand tails as well as new body-feathers.Non-breeders go into the eclipsestage again. Third-wintereclipse plumage.--Presumably like othereclipse stages. Third-summerplumage.--All Common Terns appearto breed at this age. The succeedingfall molt beginsto be in evidenceby early August,when featherscan be seenon the brood-spots.In Maine the tail 'streamers'are shed and the winter cubital bands begin to appear in the majorityof individualsbefore they start southward. 'White-faced'breeding plumage.--If a bird has survivedabout ten yearsof breedinglife, whichtakes it well pastaverage age, it acquires the 'white-faced'breeding plumage, which I have alreadydescribed in somedetail. It hasalso been pointed out how thisplumage differs from eclipsebirds. Collectorshave frequentlywritten "sterile" or "gonadsminute" on labelsof 'portlandica'skins, but we do not find thison tagsof old-agebreeders. They appearto havebeen considered as normal breederswhich were molting unusuallyearly, but I have alreadyshown that anotherexplanation for this'white-faced' condition is morein keepingwith the knownfacts. It is not yet known for how many summersthe old-ageplumage may be worn,nor whetherit is acquiredat differentages in different species. Skinsof Arctic Terns having the old-agetype of cap some- timeshave rather grayishunder parts and so,unlike CommonTerns, are not aspale as eclipsebirds. AlthoughI haveseen summer-eclipse RoseateTerns, ! have never seena skin or live bird of this species which ! could refer with absolutecertainty to the old-agecategory. All the plumageswhich I have listed are acquiredby Common Terns of both sexes. This is probably true of other speciesalso.

SUMMARY (1) CommonTerns usually start breeding when two or threeyears old. Evidenceindicates that non-breedershaving small gonadswear onlythe eclipse type and never the nuptial type of plumage. 176 P,•MER,'White-laced' Terns LI'Auk April

(2) Data are lackingas to where the majority of non-breedersare to be found, but probably they are on the winter range of breeders, or even farther south. (3) Assumptionof breedingplumage appears to be influencedby a sex hormone, as is the case with the Black-headed Gull. Some of the smallergulls and certainterns parallel one anotherin manyrespects. (4) Old birds show intermediatecharacters between eclipse and nuptial stages,while still being able to breed. (5) Terns have a long life span,but birds past breedingage have not yet been recordeddefinitely as occurringin breedingcolonies. (6) Eclipse-plumagedterns in nestingcolonies are not treated like breedersby fellowmembers of their species. (7) The springmigration is undertakenby a few eclipse-plumaged birdswith verysmall gonads, probably not becauseof anyurge within themselvesto migrate,but becausethey tend to associatewith normal migrantsand arereacting socially with them. (8) Both sexesof the Common Tern acquire the summer-eclipse ('portlandica')and old-agebreeding ('pikei') plumagewhich I have discussed.

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DWICHT,JONATHAN, JR. 1901. The sequenceof moultsand plumagesof the Laridae (gullsand terns). Auk, 18: 49-63. 1925. The gulls (Laridae)of the world; their plumages,moults, variations, re- lationshipsand distribution. Bull. Amer. Mus. Nat. Hist., 52: 63-401. FLOWER, S. S. 1938. Further notes on the duration of life in animals.--IV. Birds. Proc. Zool. Soc. London, A, 108: 195-235. FLOYD, C. B. 1927. Noteson the developmentof youngCommon and RoseateTerns. Bull. NortheasternBird-banding Assn., 3: 95-101. HANN, H. W. 1939. The relation of castrationto migrationin birds. Bird-banding,10: 122- 124. HAVERSCHM1DT,F. 1931. On the breedingof the Black-headedGull (Larusr. ridibundus)in first summerplumage. Ardea, 20: 147-150. HE1NROTH, O. AND M. 1928. Die V/•gel Mitteleuropas,vol. 3. Berlin. HERSEY, F. S. 1920. The probablebreeding of the Aleutian Tern in southeasternAlaska--a query. Condor,22: 203-204. HOOPla, F. W., AND WAGSTAFFE,R. 1928. Notes from the South Lancashire coast. British Birds, 21: 190-194. KIRKMAN, F. B. 1937. Bird behaviour. London. LAWRENCE, G. N. 1853. Descriptionsof new speciesof birds of the genera Ortyx Stephens,Sterna Linn., and Icteria Vieillot. Ann. Lyceum Nat. Hist. New York, 6: I-4. LINCOLN, F. C. 1927. Notes on the migration of young Common Terns. Bull. Northeastern Bird-banding Assn.,3: 2•-28. 5fARPLES,G. AND A. 1934. Sea terns or sea swallows. London. MILLAIS,J. G. 1902. The natural history of the British surface-feedingducks, vol. I. London. MURPHY, R. C. 1936. Oceanic birds of South America, vol. 2. New York. PUTZlC, P. 1937. Von der Beziehungder Zugablaufszum Inkretdriisensystem.Der Vogelzug, 8: 116-130. RIDGWAY, R, 1874. Notice of a speciesof tern new to the Atlantic coastof North America. Amer. Naturalist, 8: 433. 1875. Note on Sterna longipennisNordmann. Amer. Naturalist, 9: 54-55. ROBINSON, It. W. 1910. Marked SandwichTern apparentlynesting in its first year. British Birds, 4: 88. 1940. The SandwichTern breeding in winter plumage and in immature plumage. Ibis, (14) 4: 150-151. 178 PALMER,'White-faced' Terns LI-Auk April

SCHENK,J. 1934. A m. kir. MadJrtani Int6zet 1931-32 6vi madJrje151•sei.Aquila, 38-41: 32-90. TICEHURST, C. B. 1924. The birds of Sind, part 8. Ibis, (11) 6: 110-158. TINBERGEN,N. 1936. Zur Soziologicdcr Silbcrm6wc,Larus a. argentatusPont. Bcitr. z. Fort- pfianzungsbiol.d. V6gcl, 12: 89-96. VAN OORDT,G. J., ANDJ•JNCE, G. C. A. 1930. Die hormonale Wirkung des Hodens auf Federkleid und Farbe des Schnabelsund der Fiissebei der Lachm6we (Larus ridibundus L.). Zool. Anzeiger, 91: 1-7. 1933a.The influence of the testishormone on the developmentof ambosexual charactersin Black-headedGulls (Larus ridibundus). Acta Brevia Neer- landica, 3: 1-3. 1933b.Die hormonale Wirkung der Gonadenauf Sommer-und Prachtkleid. 1. Der Einflussder Kastrationbei m•nnlichenLachmfwen (Larusridibundus L.). Roux' Archiv f. Entwicklungsmechanikder Organismen,128: 166-180. WATSON,J. Bo 1908. The behavior of Noddy and Sooty Terns. Papers from Tortugas Lab., Carnegie Inst., 103: 189-255. WITHERBY, H. F. [EDITOR]. 1924. A practical handbookof British birds, vol. 2. London. Cornell University Ithaca, New York