Courtship and Territorial Behavior of Hairy Woodpeckers
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THE AUK A QUARTERLY JOURNAL OF ORNITHOLOGY VoL. 77 JULY,1960 No. 3 COURTSHIP AND TERRITORIAL BEHAVIOR OF HAIRY WOODPECKERS LAWRENCE I,[ILHAM THE presentstudy of a pair of Hairy Woodpeckers(Dendrocopos villosus),made in a swampnear Seneca,Maryland, indicatesthat this specieshas a lively courtshipin which the femalemay attract a mate to her fall and winter territory by drumming and then join him in display flights. I observedthis behavior in the pair HF-HM from mid-October1958, until nest excavationin April 1959, in all a total of 130 hours. The phenomenadescribed are not readilyobservable in any one year, and I have encounteredthe prolongedtype of pair formation in only one of the yearsfrom 1951 to 1960 in which I havebeen study- ing Hairy Woodpeckersin the sameswamp. Thesebirds appear to be moreor lesspaired the year aroundunder usual circumstances. Hairy Woodpeckersare not easy to study in woodedcountry, and this may explain why publishedaccounts of their life histories,such as thoseof Bent (1939), are far from complete. Hailman (1959), for example, has pointedout that the drummingof female Hairy Woodpeckersis not mentioned in most accounts. As describedbelow, the female HF did an extraordinaryamount of drumming. Individual recognitionof the woodpeckersstudied became possible with closeand prolongedobservation. Figure 1 givesthe headmark- ings by which I distinguishedHF and HM as well as of two other Hairy Woodpeckerswith whichthey had occasionalcontacts. Certain featuresof habitand territory,given below, further aidedin the recog- nition of individual birds. TERRAIN AND TERRITORY Territory and drum trees. Observationswere centralized in the terri- 259 260 K•n_x.•t,Courtship ofHairy - •[%odpeckers [ Vol.Auk 77 M.LE$ FEMALES Figure 1. Variations in the black and white markings on the heads of four Hairy •Voodpeckers,which aided in recognitionof individuals. The male HM and the female HF are represented by the two central figures. tory of the femaleHF, wheremost of the courtshipand the later nest excavationtook place. The terrain consistedof a rim of trees sur- roundingthree to four acresof open swamp. Sincethe openarea was dry duringthe fall and was frozenduring muchof the winter, I was able to walk aboutthe centerof I-IF's territory and adequatelyview her activities. There were severalindications that the territory of I-IF had fairly definiteboundaries. One was that shecontinually made rounds of certaindrumming trees, of which three were visitedon many occa- sionsand five otherswith lessfrequency. She wouldalight at particu- lar spotswhere she could obtainthe greatestreverberation. The farthestdistance between regular drum trees was 450 yards(Figure 2). The width of HF's territory was in the vicinity of 250 yards,as esti- mated by the locationsof conflictsand distancesbetxveen two of the main drummingtrees. The male HM had an adjacentterritory, ap- proximately400 yards long, but I had less completeobservations on its dimensionssince •nost of the activitiesconcerned xvith pair formation took placein the territory of his mate. Territory and conflicts. A secondcircumstance that servedto estab- lish the boundariesof HF's territory consistedof sevenconflicts with intrudingHairy Woodpeckersthat I observedin boundaryzones (Fig- ure 2) in the courseof nine months. Five of theseconflicts were be- tween females,and two were betweenrival males. There was a ten- dencyfor conflictsto be repeatedin the samezones, for two of the female conflictswere in one zone and two took place in another. Con- flicts in a third zone were of a differentpattern. On 14 March HM fought another male, and on 21 March 1959, his mate HF fought a rival femalealong the sameboundary, which was not far removedfrom the tree where HF excavateda nest hole in late April. Nest sites of three different years bunched. The territory of HF July19601] KILI-IAM,Courtship ofHairy I•oodpeckers 261 TERRITORY OF b ß " ß DRUMTREES OF 9 I •O YARO5 I O •T HOLES • CONFL•TSWITH RIVALS Fibre 2. D•am of •e fall and win•r territo• of the female Hai• W•ker HF, show•g the l•tions of her main d• wees, the zones of •da• conflicts,and •e ncst sitesof th• su•essive years. was not only the site of nest excavationin 1959, but also of nest holes whereI hadobserved parent Hairy Woodpeckersfeeding their young in 1957 and 1958 (Figure 2). The three nestholes were within a distance of 100 feet. PAIR FORMATIONIN FALL ANDWINTER Drumming.I hearddrumming from HF's maindrum tree during Septemberand October 1958, but it was18 October before the swamp becamedry enoughfor me to start consistentobservations. The female HF drummedhundreds of timeson favorable days. Sucha daywas 8 November.HF begandrumming at 7:45A.•., whenthe swamp was coveredwith frost and skim ice. She drummed 54 times in five minutes on what I called her China Tree becausek had a reverberationand tone,due to its hardness,which I couldrecognize at 800 yards. Her drummingrate of 11 burstsa minuterepresented an intenselevel of behavior.This intensitywas also reflected in anothertype of drum- mhlg. At about8 A.M.,On the samemorning, I foundHF feeding 262 KH•H^•.r,Courtship ofHairy Woodpeckers [ Vol.Auk 77 amonglow willows,but pausinghere and there to drum one or two burstsin placesof no particularresonance. She drummed19 bursts on eight differentspots within 10 minutes. It appearedas if shehad a great urge to drum even when feeding. I watchedher drumming from 2:35 P.vt. until sunsetof the sameday, and by dusk I had heard her drum at least 400-500 times. The drummingof HF was particularlystriking becauseno other speciesof woodpeckerin the swampdid muchdrumming during the fall, and because,with continuedobservation, it becameobvious that HF was trying in a persistentfashion to attractthe male HM. This situationwas clearly seen on 9 November. On this day, HF drummed a total of 98 bursts in 20 minutes as she moved from her main China Tree to a dead willow closeby the territory of her mate HM. She stoppeddrumming as soonas he flewacross to join her. The pair were togetherfor about15 minutes. HF did not alwayscome close to HM's territory when trying to attract him by her drumming,for she often drummedon her Low Tree, which was nearly450 yardsaway, and he wouldfly to her there. On 26 December,for example,HF's drumming rangout clearlyfrom a hollowportion of the Low Tree. I watchedas sheflew to the top of an adjacenttree as if expectant,then flew to join HM in the top of a deadelm right abovewhere I stood. Suchmeetings were alwaysof muchthe sameform. The two birdsabove me rested within aboutfive inchesof eachother withoutdisplay of any kind and exchangeda rapid jeek, jeek vocalization. Figure 3. Duet flight of the pair of Hairy Woodpeckers HF-HM, whleh took place above the treetops, usually over the territory of HF. July1960 ]1 KXL•XAM,Courtship of Hairy Woodpeckers 263 Displayflights. HF and HM usuallylaunched themselves off on a displayflight after their ]eek,]eek greetings.I termedthese perform- ancesduet flights. When standingin the centerof the swamp,I could watch the two Hairy Woodpeckers,one rising and one falling as they swunggreat bounds and loops above the treetopsof HF's territory,now one and now the other in the lead as if withoutapparent aim. These flightswere not pursuits; HF and HM wouldalight peacefully,fairly closetogether, in pausesbetween flights. The duet flightscentered, primarily,over the woodswhere the 1957,1958, and 1959nest excava- tions were all located(Figure 2). HF performeda secondtype of display. I termed it the Floating Flight, and I had viewsof HF in theseflights on six occasionsbetween 1 Novemberand 28 December1958. A floatingflight on 8 November was of specialinterest. HF had done much drumming,as described above, and had participatedin many duet flights with her mate. At sunset,which was about4:30 P.M., I was standingin the openswamp when HF, flying toward me in boundingflight, suddenlybroke into a batlikeflutter with alternationsof floatingwith wingsheld motionless, at an angleof 45 degrees. She made tweeck,tweeck notes at the same time. I have not heardthese notes from a Hairy Woodpeckeron any other occasion. HF alit on a dead oak, drummed five or six bursts, Figure 4. The female Hairy WoodpeckerltF in a floating display flight. then went off on a longflight up swamp,as I presumed,to roostfor the night. Thesefloating flights of HF alwaystook place when she was flyingto or awayfrom a meetingwith her mate. If maleHairy Wood- peckershave a similardisplay flight, I havenot observedit. 264 K•Lu^•,Courtship ofHairy Woodpeckers [ Vol.Auk 77 Tapping. The tappingof the Hairy Woodpeckerscame as a surprise, for it was doneunder different circumstances than thosethat I (1958) had observedfor Red-belliedWoodpeckers (Centuru,r carolinua). The tappingof both speciesis at a countablerate of two to three taps a second. HF had drummedalmost incessantlyduring the morning of 22 Novemberwhen, at 11:30 A.•., she alightedon a small tree 30 feet from me. She now tapped9 or 10 times,loud and clearly,paused, then tappedeight more seriesfor a total of about80 taps. I heard HF tap on four occasions between 9 November and 7 December. None of this tappingwas associatedwith any obviousnest hole, but on 1 February 1959,I sawHM fly to a freshexcavation and tap threebursts just below it. I believedthat HF wasnearby for I heardjeeks. The excavation belongedto a pair of Red-belliedWoodpeckers, which nestedin it the followingMay. Conflicts. HF was facinga rival femaleat one of her territorial boundaries in each of the five conflicts that I observed between Novem- ber 1958and March 1959. A conflicton 17 Januarywas representative. HF alit on a tree trunk abovethe intruder, pointingher bill upward and almost backwardas she did a bill-waving dance,which involved jerking of her head and body as well as half-startingmotions with her wings. Her rival posedas if frozen with her bill pointedstraight for- ward. HF droppedto a lower position,then pursuedher adversaryup the trunk. Suchdance displays are carriedout by both sexes,but all conflictsI haveobserved have been between Hairy Woodpeckersof the samesex.