SHORT COMMUNICATIONS 179 The Condor89: 179-182 0 The CooperOrnithological Society 1987 EXTRA ADULTS AT THE NEST IN BARN SWALLOWS’ MANDY M. MEDVIN, MICHAEL D. BEECHER, AND SANDY J. ANDELMAN Animal BehaviorProgram, Department of PsychologyUniversity of Washington, Seattle, WA 98195 Key words: Barn Swallow; Hirundo rustica; extra where we saw three birds together at a nest, however, adults;reproductive strategies; plumage dlflerences. one of them had the distinctive plumage of an extra adult. Moreover, in only one instance did we ever see Extra adults at the nest have been noted in a wide more than three adults at a nest. variety of bird species(for reviews, see Skutch 1961, The retention of juvenal plumage, as seen in our Lack 1968, Ricklefs 1974, Brown 1978, Emlen 1978). extra nest attendants, has not been reported in other We use the neutral term “extra adult” to refer to non- studiesof Barn Swallow extra adults (Mvers and Waller breeding adults that interact frequently and nonhos- 1977, Crook and Shields 1985, in press).Retention of tilely with the primary breedingpair at or near the nest, juvenal plumagefeatures has been found in Tree Swal- regardlessof whether they care for the young or later lows (Tachvcineta_ bicolor. Kuetzi 1941. Sheppard__ 1977) breed. In Barn Swallows, extra adults at the nest have and Mexican Jays (Aphelocomaultramarina; Brown been reported in two populations (Myers and Waller 1963, see also Brown 1978). 1977; Crook 1984; Crook and Shields, in press). The purpose of this note is to report our findings on extra FREQUENCY OF EXTRA ADULTS adults at the nest in a third population, and to point Extra adults were seen at 12 of the 13 nests (Table 1). out notabledifferences, in plumageand behavior,among Extra adults were seenat the nest as early as the initial the three populations. courtship of the primary pair. At two of the nests, the extra adult ultimately nestedwith the male (seebelow). METHODS At the remaining 10 nests, we compared the number In 1979 and 1980, we studied 13 solitary nests on the of days an extra adult was seen with the family group, grounds of the Woodland Park Zoo and in the sur- relative to the number of days the male and female rounding neighborhood, in Seattle, Washington. In were seen.On average,an extra bird was presentduring 1979, we monitored eight secondor late clutchesat the 24% of the observation periods, compared to 84% and nest, and for several weeks after fledging. In the latter 90% for the male and female respectively. We cannot context, we identified family groupsby color marking be sure that we always saw the same extra adult at a young; family groupstypically stayed together for one particularnest rather than one of severaldifferent birds. to two weeks (Medvin and Beecher 1986). In 1980, We favor the first alternative, however, for two reasons. we watched five nests during both first and second First, some of the extra adults had distinctive mark- clutches.Observation periods averaged 30 min, for a ings, and identification was unequivocal. Second, in total of approximately 175 hr. We sexedbreeding adults general, a breeding pair interacted with the light-col- by tail length (Samuel 1970), and song.Extra adults at ored extra adult in a tolerant fashion, suggestingfa- each nest were identified by plumage markers (see sec- miliarity, which contrasted sharply with their aggres- tion below); such identifications were independently sive reaction to the occasionaldark-colored intruder. confirmed by at least two observers. In addition, we The high proportion of nestswith extra adults in our marked the breeding pair at 4 of the 13 nests (Table study is similar to that seen in the New York popu- 1). lation studiesby Crook and Shields (in press), where 78% of the nestswere attended. The proportion differs RESULTS from that seenin the Ohio populationstudiedby Myers and Waller (1977) in which attendants were reported PLUMAGE DIFFERENCES at less than half of the nests. While the typical plumage of the adult Barn Swallow includes a reddish-brown breast, and deeply forked, HELPING BEHAVIOR OF EXTRA ADULTS long tail feathers, the extra adults all had either white The extra adults infrequently fed at nests. In 40 ob- or light colored breastsand/or short tail feathers, and servation hr during the nestling period, we saw only resembledjuveniles of the first clutch. The plumage of 12 feedingsby extra birds (distributed over three nests); the extra adults was so distinctive that we could easily parents typically feed that much in an hour. In the distinguish them from both primary adults and juve- postfledgingfamily groups,we observedan extra adult niles. There may have been extra adults who lacked feeding fledglingsin two groups. The feeding rate we these unique plumage markers. In virtually all cases observedis much lower than the 15% of the total feed- ing visits at nestswith extra adults observedby Myers I Received 20 January 1986. Final acceptance1 July and Wailer (1977), but it is much higher than the two 1986. feedings observed by Crook and Shields (in press) in 180 SHORT COMMUNICATIONS TABLE 1. Extra adult sightings. Number of days When seen?’ Nest Male Female Extras Nest CB I N PF observed seen seen seen Aur/79 - Y Y Y 33 31 32 12 Cam/79 - - - Y 3 2 3 2 Comm/79 - Y Y 44 41 41 16 Day/79b Y - - - 15 11 9 Duck/79 Y Y Y Y 29 25 29 ii Pony/79 - - Y 12 11 12 2 Zeb N/79” - - Y Y 15 15 15 11 Zeb F/79 n n n n 6 6 6 0 Zeb/lO Y n n - 23 16 19 2 Comm/8@,e Y Y - - 16 14 14 2 DucW8@ Y Y Y - 67 52 55 10 Ele/80 Y Y - 64 52 59 11 Pony/80Q Y Y - - 21 11 13 8 aWhen an extraadult wasseen. CB = courtship/nestbuilding, I = incubation,N = nestling,PF = postfledging,y = yes,n = no, - = no observations during this phase. bObservations during secondclutch; courtship seen, but no eggslaid. cFemale marked. dMale and primary female marked. c Pony/X0was a caseof polygyny;&mm/80 a replacementfemale. The numberof times the extra femalewas seenis tabulatedonly to the point whereshe nested. 2,000 to 5,000 observation hr. Crook and Shields (in as well. At the end of the normal incubation period of press) also describe eight instances of infanticide by 15 days, however the eggshad failed to hatch. On 3 extra adults, whereasneither we nor Myers and Waller June, the third adult and the male were building a new (1977) observed any such instances. nest, approximately 10 m from the old one. The male assistedthe third bird with nest building on that day EXTRA ADULTS SOMETIMES NEST only; she completed the nest by herself. On 8 June, the At 2 of the 12 nests with extra adults, the extra adults male and primary female copulated and engaged in mated with the primary male. At one of these nests, renesting activities. The primary female completed a the primary female died, and the third adult became clutch of six eggson 16 June, and the third adult, now a replacementfemale. At the other, the male and third the secondarymate of the male, completed a clutch of adult mated shortly after the primary female’s nest five eggson 18 June.The primary female’s eggshatched failed. Subsequently,the primary female renestedwith on 1 July; the secondaryfemale ’s eggson 3 July. During the same male, thus forming a polygynous trio. We the nestlingstage, each female fed only at her own nest. describe these two casesin some detail here. The male fed once at the secondaryfemale ’s nest, but The extra adult (second female) at nest Comm/lO otherwise fed only at the primary female’s nest, and becamea replacementnester. This bird was easilyiden- spent most of his time with her. The primary female’s tified becauseof a light-colored band on her breast. young fledged on 23 July; the secondary female’s on The bird was first seen at this nest on 6 Mav 1980. 29 July. We did not see the secondarv female again. during the nest building stage.The primary fe-maleof The primary female completed a second clutch-that this nest completed a clutch of four eggson 18 May. hatched on 13 August; these birds fledged 11 Septem- We found her dead of unknown causestwo weekslater, ber. with only two eggs remaining in the nest. The next evening, the male was found sleepingby the nest with DISCUSSION the third bird; the following day the nest had fresh mud and new feathers. Within another week, the former A REPRODUCTIVE STRATEGY? third bird laid her first egg,and she completed a clutch In Tree Swallows,yearling females retain juvenile-like of four eggson 12 June. The pair stopped incubating plumage (brown versus blue-green) (Kuerzi 1941, on 19 June for unknown reasons, and subsequently Sheppard1977, De Steven 1978). Sinceour extra adults begana replacementclutch of six eggs,which was com- also retained juvenile-like plumage,perhaps they were pleted on 4 July. Four of the six eggshatched on 19 yearlings. In support of this idea, the lighter plumage July, and the young fledged by 9 August. and shorter tail feathers seen in the extra adults may The extra adult (second female) at Ponv/PO even- indicatean incompletepostjuvenile molt (Rohwer, pers. tually nested polygynously. All three birds were first comm.; Palmer 1972). In addition, Crook and Shields seen on 3 May 1980. From the start, the three birds (in press)reported that a high proportion of their extra interacted frequently (e.g., vocalized antiphonally, for- adults were yearlings. aged together).