TheCondor88:156-159 0 The CooperOrnithological Society 1986 THE SINGING BEHAVIOR OF FEMALE NORTHERN CARDINALS’ GARY RITCHISON Department of BiologicalSciences, Eastern Kentucky University,Richmond, KY 40475 Abstract. Observationswere made and playback experiments were performed in central Ken- tucky in an attempt to determine the function(s)of singingby female Northern Cardinals(Cardinalis cardinalis).Singing by female cardinalswas uncommon and was noted primarily during the period after males had establishedterritories and before nesting had begun (early March to mid-May). When singing,females were generallyjoined by singingmates. Experiments revealed that females rarely sangin responseto playback of male or female songs.Such evidence suggeststhat singing by female Northern Cardinals is important in pair bonding and, perhaps, in reproductive syn- chronization. Key words: Northern Cardinals; Cardinalis cardinalis; singing:pair-bond maintenance. INTRODUCTION Although females sing less than males, or not fledging of the young, it would suggestthat at all, in most oscine species,singing does ap- singing might play some role in family-group pear to be a regular feature of female behavior maintenance and might not be important in in severalspecies (Ritchison 1983a). Among the the formation of pair-bonds or in territorial speciesin which singing by females has been defense.Playback experiments were used in an reported is the Northern Cardinal (Cardinalis attempt to further clarify function. For ex- cardinalis).For example, Bent (1968: 11) in- ample, an increasedrate of singingin response dicated that in the Northern Cardinal “both to playback of conspecificsong within the ter- sexes sing, and the song of the female is but ritory might indicate that female song serves little inferior to that ofthe male.” Lemon (1965) a territorial function (Beletsky 1983). Further, noted that both male and female Northern if males, whose singing is known to serve in Cardinals possesseda repertoire of several dis- territorial defense,sing in responseto playback tinctive songs. and females do not, this would suggestthat Only a few possiblefunctions have been sug- singingmight serve different functions in males gestedfor singingby females. Beletsky (1982) and in females. suggestedthat singingby female Northern Ori- oles (Zcterusgalbulu) plays some role in pair- METHODS AND MATERIALS bond maintenance. Ritchison (1983a) pro- Field work was undertaken from January posed that singing by female Black-headed through Septemberin 1983 and 1984 and from Grosbeaks (Pheucticusmelanocephalus) was mid-February through early Septemberin 1985 of importance in family-group maintenance. at the Central Kentucky Wildlife Management Beletsky (1983) reported that female Red- Area, located 17 km southeastof Richmond, winged Blackbirds (Agelaiusphoeniceus) pos- Madison County, Kentucky. Observations sessedtwo song types, one of which probably were made at least three times weekly. Obser- functions in pair-bond maintenance and the vation periods were at least two hr in duration other in territorial defense.In a review of avian and began shortly after sunrise.I attempted to vocal behavior, Nottebohm (1975) suggested record on tape all observed bouts of female that singingby females may play some role in song. Whether recorded or not, for each bout pair formation or may aid in territorial de- I noted the identity and location of the female, fense. The objective of the present study was the number of songsuttered during the bout, to ascertain the possible function(s) of female and the location (if known) and behavior (sing- song in the Northern Cardinal. ing or not singing)of the nearest male. I define I used both field observations and playback a “bout” as a seriesof songsseparated in time experiments in an effort to determine the func- from each other by intervals that were signif- tion of female song in the Northern Cardinal. icantly longer than the intervals between songs Observations were undertaken to determine within a bout (Farabaugh 1982). During the when and in what situations female cardinals three years of the study I monitored fifteen sang. Such information could provide some pairs of cardinals. All cardinals under obser- insight into function. For example, if singing vation were captured in mist nets and marked were limited to the period just before and after with colored leg bandsand colored plastic tape attached to the rectrices (Ritchison 1984). Re- I Received 10 December 1984. Final acceptance2 1 Oc- cordingswere made with a Uher Report Mon- tober 1985. itor tape recorder with a Dan Gibson parabolic D561 SINGING OF FEMALE NORTHERN CARDINALS 157 reflector and microphone. Playback tapeswere 60-t l-150 subsequentlymade from these recordings. Playback experiments with six females were conducted from 11 April to 20 May 1983 and with six more females from 23 April to 1 May 1985. Each playback experiment consisted of three 5-min segments(pre-test, test, post-test). In 1983 each bird was tested twice with the songsof a neighboringmale and twice with the songsof a neighboring female. In 1985 each female was tested twice with the songs of a 25 non-neighboring female; in addition, a study skin of a female Northern Cardinal was placed within 1 m of the loudspeaker.Birds with com- 27 13 27 10 24 8 22 5 19 3 17 31 14 28 mon territorial boundaries were designated MAR APR MAY JUN JUL AUG neighbors. For each test a loudspeaker was FIGURE 1. Singing rates of male and female Northern placed 2 to 3 m above the ground in a bush Cardinals. (Values are averagesfor seven-day periods be- or tree near the center of the territory. Different ginning on the dates indicated. Six females were observed testswith individual females were at least two in 1983, four in 1984, and five in 1985. Five males were days apart. All experiments were conducted observed in 1985.) between 0700 and 1200. The following features of responsewere used almost all singingby females occurred before to ascertain a bird’s reaction to playback: (1) nestinghad begun.Finally, singingfemales were Numberof songsand notesper song.Songs of usually accompanied by singing mates. The Northern Cardinals may vary considerably in fifteen females under observation sang for a the number of notes per song and previous total of 207 min and were joined by “duetting” studies suggesta possible correlation between mates for 162 min, or 78% of the time. This the number of notes per songand a bird’s level value increasesto 87% if one exceptional sing- of aggression(Gottfried and Gottfried 1978). ing bout is removed from the analysis. On 20 Notes were uttered by test birds at a rate that April 1985 an unbanded female was sighted allowed accuratecounting. (2) Distanceof clos- near the territorial boundary of the pair under est approachto the speaker.(3) Number of observation. After this female began to sing, flights. Flights of less than 50 cm were not the territorial male flew to a perch near the counted. (4) Number of chip calls. Northern center of the territory and also began to sing. Cardinals utter these calls in various situa- After nearly two minutes the unbanded female tions, and they may indicate excitement. Lem- flew acrossthe boundary and was chased,first on (1968a) reported that territorial males ut- by the male and then by the female. Shortly tered chipcalls in responseto trespassingmales thereafter, the two females began to sing from and females. The Wilcoxon signed-rankstest perches about 35 m apart and continued, un- was used for all statistical comparisons (Sokal accompaniedby any males, for nearly 22 min. and Rohlf 1969). PLAYBACK EXPERIMENTS RESULTS The playback experiments performed in 1983 revealed that females responded similarly to FIELD OBSERVATIONS the songsof males and females (Tables 1 and The singingbehavior of female Northern Car- 2). Typically, females responded to playback dinals differed from that of males in several of both male and female songsby moving a respects.First, femalessang less frequently than few meters closer to the speaker and uttering males. I spent over 45,000 min in the field and a significantlygreater number of chipcalls (P < noted only 207 min of female song (less than 0.05). Only two females sang in response to 0.5% of the time). In addition, male and female male songs(Table 2), and no singingwas noted Northern Cardinals differed in the timing of in responseto female songs(Table 1). In sim- their singing. Whereas males begin singing in ilar experiments with males, all individuals January or February (Laskey 1944) females tested (n = 6) responded to playback of male did not begin singinguntil March (Fig. 1). Fur- and female songswith a significant increasein ther, whereasmales continued singinguntil late number of songs(P < 0.05). Augustor early September(Fig. 1; Laskey 1944, The observation of 20 April 1985 noted Lemon 1967) I rarely heard singingby female above appeared to indicate that female song cardinals after mid-May (Fig. 1). Most pairs may be important in certain female-female in- of cardinals began nestingby late April. Thus, teractions. Tests were conducted in 1985 in an 158 GARY RITCHISON TABLE 1. Responsesof females to the songsof neigh- TABLE 3. Responsesof females to the songs of non- boring females. neighboringfemales and a female model.= Closest Closest approach No. approach No. Notes/ (ml songs Flights Chips (m) son.& song Fbghts Chips Pre-test period (PTP) 32.5a 0 1.4 3.2 Pre-test period (PTP) 23.0 0 - 0.5 1.1 Test period (P) 18.1 0 5.9 28.9 Test period (P) 7.1 2.3 6.3 5.6 32.6 Post-test period (PP) 26.2 0 4.2 15.0 Post-test period (PP) 12.2 0 - 0.6 12.8 PTP vs. P NSb - NS 0.05 PTP vs. P 0.05 NS - NS 0.05 PTP vs. PP NS - NS NS PTP vs. PP NS NS - NS NS P vs.