THE AUK:

A qUARTERLY JOURNAL OF

ORNITHOLOGY.

VOL. XLVII. OCTOBER,1930. NO. 4.

NOTES ON THE NESTING OF THE AFRICAN GREEN (BUTORIDES ATRICAPILLA) IN NATAL.'

BY RAYMOND B. COWLES.

Plates XIII-XIV.

JtmGXNGby the recordsin available literature, observationson this speciesof Heron are not common,especially in SouthAfrica, and it seemsadvisable to recordthe followingobservations which were .obtained about ten miles from the mouth of the Umzumbi river on the small tributary stream,Umnambite. Apparently the favorite nestingplace of this small Heron is in the mangrovesfound growing in baysand otherinlets near the sea. But they may also be found nestingon fresh water streamsa considerable .distance from salt water. Only one nest was observed.during a periodof two yearsbut youngbirds had been seennear this locality a year prior to the time when the followingobservations were made and it therefore seemsthat at least one pair customarilybreeds in this locality. The .n•st under discussionwas first observedon September20, 1926,and, a•cordingto the native who reportedit, therehad been .only.two . in th• nestthree days previously. On the 20th h(•wev&r,three. eggs'were present, indicating that incubation h•d 'prOb&blycommenced notmore than one or twodays previous. to 'thisdate, The nesting time. coincides with that observed byA.D. Millar (-Annalsof the Durban.Museum,Vol. I, part I, E. C. Chubb,

• The work here recorded was carried on under the direction of Dr. A. A. Allen of Cornell University, as part of the requtremen• for the degree of Doctor of ßPhilosophy. 465 466 CowLes,Nesting ofAfrican . [oct.Auk pp. 29 and 47). The nest was placedabout ten feet above the stream on somefairly stout branchesoverhanging the water and was rather looselycomposed of twigs,and waswithout any lining. It was so shallowas almost to show the tops of the eggswhen viewed from its own level. The eggs were pale blue, without markingsof any kind and showedconspicuously, especially so sinceat the time of laying, and during incubation,the tree was practically denudedof leaves. During the early stagesof incubation,that is, until September 28, the parent was extremelyshy and couldbe seenon the nest only by approachingwith unusual caution. By September30, the was becomingless shy and on this date was photographed from a blind placedabout fifteen feet from the nest. By October1, the parent Heron seemedto have lost most of its fear, or the incubationinstinet had becomefirmly established. At any rate photographywas more practicableand althoughit was raining the bird wasso motionless that a shorttime exposurecould be made. On October 5 the parent was extraordinarilytame and when flushedfrom the nest soon returned. Although tame, the bird showedconsiderable nervousness, principally by raising the erest until the profile was strongly serratedand the feathersalmost vertical. In addition to this habit, when alarmed or curious, nervousnesswas evidencedby snappingthe short tail rapidly up and down, a rather ludicrousperformance when practisedin conjunctionwith the erectederest. Thesehabits of displaying nervousnessseem to disappearas soon as the actual sourceof dangeris seen,for upon actually observingan enemyapproach the bird invariably lifted the bill until it pointednearly vertically and becamemotionless except for an imperceptibleturning of the head to follow the movementsof the enemy. When attempting to escapeobservation by this "freezing,"the outlinetakes on the appearanceof anythingbut a bird. The shapeof the headand neck, even of the body when held motionless,is deceivingand in addition to shapethe coloringand the markingsof the feathers fit the resemblanceto inanimate objects perfectly. In fact it seemsas though the nest is far more conspicuouswithout the incubatingparent than with it. When observingthe protective resemblanceand colorationin this speciesone is struck by the TIlE AUK, VOL. XLVII. PLATE XIII.

AFRICAN GREEN HERON. Butoridesatricapilla. UPPER: FEEDING YOUNG. LOWER; STARTING OUT FOR FOOD. vø.h•sX•oW•] COWLES, N•tina of Afrie, an Ore• Heto•. 467

similarityand adaptationto a. reed-bedenvironment yet at the same time and more remarkablestill is the way in which the bird fits into an environment which is obviously not that to which it is particularlyadapted. When the Heronis alarmedand watchingan enemy,the peculiar situationof the eyesallows it to face the dangerand yet seewell. The eyesare so placedthat when in this position,with the bill pointedalmost vertically, they peer forwardand the llne of vision passesacross the baseof the bill. This binocularvision is doubt- . lessa greataid in estimatingthe distanceof an enemyor of prey. It is interestingto note that the youngtake this positionand have the binocularvision developed long beforethey are ready to leave the nest.. Althoughof great importanceto the this habit doesnot enhancetheir beauty when viewed from the front. In fact the pugnaciousglare of the adult and youngis rather ridiculous owing to the closenessof the eyes to the baseof the bill, and, in the young,whose eyes are of the pale hue commonin youngof many species,the apparent attempt to look ferociousbecomes laughable. Angerwas displayed by the adult on only oneoccasion, and was a demonstrationagainst the repeatedappearance of the camera"boy" near the nest. It was expressedby the raisingof her crest, threateningmotions and a few raucoussquawks. The boy approachedquite closeto the nest and she remaineduntil he wasonly a few feet away. The eggshatched about October 8, thereforethe incubation period can be given as about eighteendays, four days more or lesswould probablycover the possibleerror. Unfortunatelyit was impossibleto reachthe nest and so study the birds at close range,and for this reasonno careful observationswere made of the developmentof the feathers,and other habits requiringthe handlingof the young. When first observedthe immature birds wereonly slightlyactive, just ableto lift up their heads,and were coveredwith a light greydown. The only variationin colorat this stagewas the presenceof an almostwhite streakdown the center of the throat. The bills which were short and stubby, almost conical,were yellow, while the skin aboutthe eyeswas a greenish yellow. By October.14 the young were considerablylarger, and had 468 Cow•Es,Nesting ofAfrican Green Heron. [oct.Auk becomequite active. All three were stretchingand were busily engagedin preeningwhile the two large oneswere able to stagger about the nestusing their wingsin orderto maintain their balance. Theselarger birds, and later the smallerone, habitually perched or moved about near the edge of the nest, and while stretching or preeningwere perpetually on the verge of falling to the water below. At this stage the young were fed once every twenty minutes but as they grew older it was noticeablethat feedingswere not so frequent. One of the most interestingobservations during this middleperiod of developmentwas the fact that invariably,five minutes or so before the arrival of the parent with food, the sleepingyoung would waken, stretchand preen,stagger about the nest a few times, then the parent would announceher arrival in the vicinity with a harsh call followeda moment later by her appearanceat the nest. The invariablehabit of approachwas to alight on the endsof the branchessupporting the nest and to walk up theselimbs to the nest itself. She was never observedto fly directly to the nest and alight. After lookingabout cautiously for a short time feedingwould commenceand proceedwith only slight interruptions,followed by a short rest of five minutesor morebefore flying off in searchof morefood. The feedingprocess was interestingbut apparentlya painful procedurefor both the young and parent. Just beforereaching over the nest the parent utters a cluckalmost exactly like the cluckof a settinghen, and at oncethe youngrear to their full heightand attempt to graspthe base of the parent's bill. As soonas one of them is successful the most interesting part of the feeding processcommences. The successfulfledgling grasps the parent'sentire bill at the base in sucha way as to bring her uppermandible against the part of his mouthnearest the gullet,i.e. the top of the parent'shead is presentedtoward the youngbird and the bills of the two-areat right anglesto each other. As soonas .the properposition for feedinghas been obtained, sometimes before, the parentand young bird, eachsharing in the effort, writhe about and bob and twist as thoughin great pain, the processcontinuing until feedinghas been completed. After disengaging,the youngand parent preen, stretch,rest, and the youngsettles down as thoughasleep while the adult soonleaves on another expedition. ThE ArK, VOL. XLVII. PL•TEXIV.

AFRICAN GREEN HERON. Butoridesatricapilla. UPPER: LEAVING NEST. LOWER: INCUBATING EGGS. PARTLY CONSTRUCTED WEAVER BIRD'S (Hyphanturgus) NEST, AT LOWER LEFT. Vol. XLVIII 193o J COWLES,Nesting of African•½e• Heron. 469

On October18, at 6:20 A.M. the parent was observedfeeding the youngand on this occasionwas presentinga about four incheslong to oneoi the fledglings.The youngbird seemed unableto swallowa fish of suchsize in spiteof its comparatively huge maw, and when the •h droppedinto the nest one of the other birds picked it up. After turning it about a few times until the anteriorend pointedtowards the throat, it was success- fully swallowed. The •h was shapedsomewhat like a bassor bream and was partially digested,the head being missingand the rest of the body having the pulpy appearancecommon to fish foundin the digestivetract of a bird. That the awkwardmotions carriedon duringfeeding are producedby the youngbird as well as the adult wasplainly observedupon this occasion. The parent was nervousand apparentlywas throughfeeding, yet one of the youngrepeatedly reached up, graspedthe adult'sbill andin spite of the objectionsoffered by the parentproceeded with the writhing and twisting motions. The decided differencein the motions indicatedthe lack of coSperation.The feedingoperation observed at 6:20A.M. wasthe last until 9:00A.M. at least,and was probably the last of the early morningseries of feedings. Contrary to the conditionsobserved earlier, feeding at this later datewas noticeably moreirregular and at longerintervals. The youngbirds at this ageshow some well developedfeathers, notably the primaries and wing coverts. These feathers have white or very pale marginsso that the wings have a mottled appearance. Althoughthe retricesmay havebeen developing they were still invisible at a distanceof about fifteen feet, nearer than which it was impossibleto approach. The tail, in spite of the lack of retrices,and bearingso far as couldbe seenonly the tuft of white down,is waggedup and downas industriouslyand nerv- ouslyas that of theparent. Thebill is paleyellow while the skin about the eyes, as well as the legsand feet are pea-greenwhich in direct sunlightshows a yellowishtinge. Althoughthe feathers on the rest of the bird were not well developedthey were plainly visible on the neck and breast,but the belly and rump appeared to be coveredwith down only. Althoughthe weather during this periodwas never really cold, the youngappeared to sufferfrom the lowertemperature of early 470 CowLEs,Nesting ofAfrican Green Heron. Auk morning, and before sunrisecrouched low in the nest, huddled together for warmth. As soon as the sun appeared,however, they becameexceedingly active and for a time kept busyflapping their wings,walking about the nest and nearbybranches and even managedto hop from nest to branchand from branchto branch. Later in the day, even as early as 9:00 A.M. they appearedto suffer from heat, and became less and less active, while their breathingseemed to becomemore rapid or possiblyappeared so owingto the fact that the bill washeld openand respirationwas rather gasping. In spite of their great activity and their pro- pensity for wanderingaround in the vieinky of the nest, the fledglingsstill retired to the nest to sleep. Unfortunately it was impossible to continue observations beyond October 18 and thus to determinethe exact date upon which the nest was left but judging by the great activity of the young birds it is probablethat the period during which they might be expectedto remain in the nest would not exceedtwo weeks at most. Universityof California at Los Angeles,Calif.