Åòòîëîã³ÿ Á3åðêó 12Â4èï. 2100 258 - 26 CALL FUNCTION AND VOCAL ACTIVITY IN THE SOUTHERN BALD IBIS AT A BREEDING SITE Grzegorz Kopij Abstract. Studies were carried out in a breeding colony at Welgelegen, eastern Free State, South Africa in 1994. Seven different calls in the Southern Bald Ibis were distinguished and their function has been determined: clangor, alarm, barking, copulation, snoring, greeting and begging. In the pre-laying phase, breeding and non- breeding pairs were equally vocal. Among breeding birds females were more (60.0 %) vocal than males (40.0 % of 402 calls recorded), while among non-breeding paired birds the reverse was true (males: 57.5 %, females: 42.5 %; n = 134 calls recorded). At the nest, breeding birds were more vocal during the incubation than during the pre-laying and nestling phases, while non-breeding paired birds are more vocal at the beginning of the breeding season than latter. During the day, breeding birds are more vocal in the morning (7001000; 40.5 %), while non- breeding paired birds are more vocal around the noon (10001400; 50.6 %) and in the evening (16001800; 23.4 %). Key words: Southern Bald Ibis, Geronticus calvus, South Africa, vocalization, vocal activity. Address: Department of Zoology & Ecology, Agricultural University of Wroc³aw, ul. Ko¿uchowska 5b, 51- 631 Wroc³aw, Poland. Ôóíêöèè êðèêîâ è âîêàëüíàÿ àêòèâíîñòü ó ëûñîãî èáèñà â ìåñòàõ ãíåçäîâàíèÿ. - Ã. Êîïèé. - Áåðêóò. 13 (2). 2004. - Èññëåäîâàíèÿ ïðîâîäèëèñü íà îäíîé èç ãíåçäîâûõ êîëîíèé â Âåëãåëåãåíå íà âîñ- òîêå Îðàíæåâîãî Ñâîáîäíîãî Ãîñóäàðñòâà â ÞÀÐ â 1994 ã. Áûëî âûäåëåíî 7 ðàçëè÷íûõ êðèêîâ è îïðåäå- ëåíà èõ ôóíêöèÿ: òðåâîãà, êîïóëÿöèÿ, ïðèâåòñòâèå, âûïðàøèâàíèå è äð. Ïåðåä îòêëàäêîé ÿèö âîêàëüíàÿ àêòèâíîñòü ãíåçäÿùèõñÿ è íåãíåçäÿùèõñÿ ïòèö ïðèìåðíî îäèíàêîâà. Ñðåäè ãíåçäÿùèõñÿ ïòèö áîëåå àê- òèâíî âîêàëèçèðóþò ñàìêè (60,0 %), ÷åì ñàìöû (40,0 %, n = 402), ñðåäè íåãíåçäÿùèõñÿ ñàìöû (57,5 %, ñàìêè: 42,5 %; n = 134). Íà ãíåçäå ãíåçäÿùèåñÿ ïòèöû áîëåå êðèêëèâû âî âðåìÿ íàñèæèâàíèÿ, ÷åì äî îòêëàäêè ÿèö èëè ïðè âûêàðìëèâàíèè ïòåíöîâ. Íåðàçìíîæàþùèåñÿ ïàðû áîëåå àêòèâíî âîêàëèçèðóþò â íà÷àëå ãíåçäîâîãî ñåçîíà, ÷åì ïîçæå. Íà ïðîòÿæåíèè äíÿ ãíåçäÿùèåñÿ ïòèöû áîëüøå êðè÷àò óòðîì (700 1000; 40,5 %), íåãíåçäÿùèåñÿ îêîëî ïîëóäíÿ (10001400; 50,6 %) è âå÷åðîì (16001800; 23,4 %). INTRODUCTION monospecific colonies, not on trees but on sandstone cliffs. Unlike other members of the Ibises (Threskiornithinae) are a cosmopoli- order it is also not directly associated with tan ciconiifrom subfamily of 32 species found wetlands and it inhabits mountain grasslands mainly in the tropics (Del Hoyo et al., 1992). and farmlands. It is silent while feeding, but In the Afrotropical region, there occur eight vocal in breeding sites. ibis species (Dowsett, Forbes-Watson, 1993) Behaviour of this species in breeding sites associated usually with lowland wetlands. has been thoroughly investigated in its strong- Most of these species are gregarious both while hold in the eastern Free State (Kopij, 1998b; feeding and at nesting sites. The extend of so- Kopij et al., 2000). Its breeding display, ago- cial tendency varies, however, from species to nistic, anti-predator, comfort and parental be- species. Threskiornis is strictly colonial, Ge- haviour were found to be highly developed and ronticus and Plegadis are less so, and Bostri- complex, and it is often accompanied by spe- chia is actually a solitary breeder (Brown et cific vocalization (Kopij 1998a). Although, the al., 1982). Because of gregariuos habits, most Southern Bald Ibis behaviour is well documen- ibis species should be vocal, but they are in ted, little is known about vocalization in this fact rather silent as their vocal apparatus is not species. Brown et al. (1982) listed seven dif- well developed. ferent calls, but these calls are not fully de- Among ibises occurring in Africa, the scribed and their function is not always well Southern Bald Ibis (Geronticus calvus) is es- explicit. The purpose of this study was to pecially interesting. Unlike most other mem- analyse at breeding sites, the function of the bers of the order Ciconiiformes it breeds in Southern Bald Ibis calls, daily and seasonal © G. Kopij, 2004 Âèï. 2. 2004.Call function and vocal activity in the Southern Bald Ibis 259 vocal activities between male and female, be- tions; the first one was occupied by a breeding tween parents and offspring and between non- pair, while the other one by a non-breeding breeding and breeding pairs. pair. Observations, using 10 x 50 binoculars and a Panasonic TTL 200 mm video camera, STUDY SITE were made from a shelter built on a rocky out- crop on the opposite cliff at a distance of 15 m Studies were carried out at a colony situ- from the first and 20 m from the second nest. ated in a gorge, 7 km north of Clarens in the The shelter was entered without any distur- eastern Free State (28°30' S, 28°20' E), South bance to the birds. Africa. The gorge is narrow (c. 1020 m), but Observations at the two nests were stan- deep (c. 80 m), with a small stream flowing dardised and were carried out on a weekly basis through it. As the gorge is closed on three sides, from 21 July until 4 October 1994; i. e. 21 and the stream flowing into it forms a narrow wa- 27 July (pre-laying phase); 4, 11, 18, 25 and terfall. There is a small (c. 30 m2) but quite 30/31 August (incubation phase), 6/7, 13/14, deep (2 m) pool at the point where the gorge 20/21, 27/28 September and 4 October (nest- broadens. Further on the gorge is much ling phase). On 27 July and 4, 11 and 18 Au- broader, forming a valley vegetated with trees gust both nests were under detailed observa- (mainly Grewia occidentalis, Leucosidea tion. Since the nest of the non-breeding pair sericea, Populus tremula and Salix babylo- was occupied only occasionally after 30 Au- nica). The gorge is bordered on one side by gust, observations on it were stopped. From mountainous highveld grassland utilised as 21 July to 25 August, studies were conducted pastures for cattle and sheep, and on the other throughout the day (6001800), whereas latter by cultivated fields with maize as the main on, observations in the morning (6001200) and crop. A dam is situated 3 km north of the gorge. afternoon sessions (12001800) were carried out The Southern Bald Ibis colony was occu- on alternate days (vide Kopij et al., 2000). pied by 23 breeding and seven non-breeding Most call notes were kept in the form of pairs, and later in the season (after 5 Septem- time-scores (for each 15 minute period). There ber), seven immature birds remained in the is no sexual dimorphism in the Southern Bald colony. Five other nests, built on sandy rock Ibis. Sexes were distinguished in the nests by ledges, were located out of the gorge 100, 200, behaviour and by individual characters, e. g. 400 and 500 m away from the main colony. marks on their foreheads or cheeks. The nest under detailed observation was al- ready occupied by a pair on the first day of the RESULTS AND DISCUSSION study. The first egg was laid on 4 August, the second on 8 August and the third on 10 Au- Call function gust, while the first nestling hatched on 1 Sep- Seven different calls were distinguished in tember, the second on 3 September and the last this study: clangor, alarm, barking, copula- on 5 September. The youngest chick died at tion, snoring, greeting and begging. age 5 days and the next one at age 12 days; the The Clangor: whee-okh, whee-okh, whee- oldest (when 35 days old) was killed by a Black okh ... A prelonged, flute-like call, somewhat Eagle (Aquila verreauxii) (Kopij, 1995). resonant, usually given by birds arriving or de- parting the breeding colony. This call most MATERIAL AND METHODS probably encourages other birds to leave the colony. Studies on the behaviour of the Southern The alarm call: peeokh. It sounds like a Bald Ibis were conducted at the Welgelegen short version of the clangor. At breeding site, colony during the breeding season, from 2.07 it was heard most often at the beginning of the until 4.10.1994 (Kopij et al., 2000). Two nests incubation phase (i. e. 1118 August; 77 % of were under detailed week-to-week observa- all records of this call; Fig. 1). During the day, 260 G. Kopij Áåðêóò 13. 20 35 SEASONAL DAILY 30 15 25 20 10 15 10 PERCENTAGE 5 5 PERCENTAGE 0 0 1234 123456789101112 DAY TIME DAILY 30 SEASONAL 20 25 20 15 15 10 10 5 PERCENTAGE PERCENTAGE 5 0 6H 7H 8H 9H 10H 11H 12H 13H 14H 15H 16H 17H 0 TIME 123456789101112 DAY Fig. 2. Seasonal and daily vocal activity of non- breeding Southern Bald Ibises at a nesting site. Fig. 1. Seasonal and daily vocal activity of 1 27 July, 2 4 August, 3 11 August, 4 breeding Southern Bald Ibises at a nesting site. 18 August. Black columns indicate adult birds, white chicks; 1 21 July, 2 27 July, 3 4 August, 4 11 August, 5 18 August, 6 25 August, with growls and moans was also distinguished 7 30/31 August, 8 6/7 September, 9 13/ in the invitation call. The so called croop call 14 September, 10 20/21 September, 11 27/ of the Northern Bald Ibis (Geronticus eremita) 28 September, 12 4 October (12: pre-lay- is probably homologous to this call. Pegoraro ing phase, 37: incubation phase, 812: nest- and Foger (1995) studied intraspecific varia- ling phase). tion in this call and evidenced sexual and indi- vidual distinctiveness of this call indicating its function as an expression of motivational the call was recorded mainly between 1000 and stages of the signaller.