Butll. GCA 14: 69-72,1997 Notes on the social status of the Coal aferand the Crested Tit IParus cristafusin the Pvrenees L. BROTONS

Social interactions between Coal and Crested Tits of known age and residence status were investigated at a feeder in the Pyrenees. In accordance with previous studies, the relation between these two was not clear-cut, since at the feeder an adult male was able to dominate a yearling female Crested Tit. Site-related dominance was probably the main cause for the detected deviation from the generally recognised size-related hierarchy in these two species

Key words: Coal Tit, Parus ater, Crested Tit, Parus cristatus, hierarchy, dominance, Pyrenees.

Lluís Brotons. Dept. Biologia (Vertebrats). Facultat de Biologia. Univ. de Barcelona. Av. Diagonal, 645. 08028 Barcelona. E-mail: [email protected] Rebut: 09.1 2.97; Acceptat: 31.03.98

Species of smaller size have typically ( Tit was found to be dominant over the been considered subordinate in social larger Willow Tit in most cases. Due to the hierarchy to larger . It is commonly importance of dominance in interspecific accepted that the Coal Tit Parus ater (mean: competition for food and foraging sites 9.3 g), due to its small size, is subordinate among the tit guild (Dhondt 1989), data to both the Crested Tit Parus cristatus (mean: on this topic are of great interest. The 1 1.2 g) and the Willow Tit Parus montanus observations of Kallander (1997) on a Coal (mean: 11.5 g), as well as to the other tit Tit that dominated both Blue Parus caeruleus species (Dhondt 1989, Suhonen et al. and Great Tits Parus major also suggest that 1992). However, as pointed out by Haftorn dominance relationships may not always (1 993), few data exit on the issue, and the be related to body size. results of his study suggest that the social In this paper, I present data on status of the Coal Tit requires further interspecific interactions between Coal and consideration. In Haftorn's study, the Coal ( Crested Tits at an artificial feeder. Birds were Butll. GCA 14. 1997 of known sex, age and size, which, it was actions between a young female Crested felt, might help to elucidate the nature of Tit (the smallest of the four, tarsus length the interspecific interactions observed. 17.7 mm vs. x= 19.0 mm, mean for the Data were collected at on artificial tem- other three) and an adult male Coal Tit porary feeder provided with fat, located in (tarsus length 17.2 mm), the latter won four the "Parc Natural Cadi-Moixeró", Pyrenees (sign test= 0.60, N.S.). It also made (46" 83' N, 4" 08' E) in an urea 1950 m significantly more attacks on its opponent above seu-level and surrounded bv than did the Crested Tit (6 vs O, sign test= Mountain Pine Pinus uncinata mixed 2.04, p<0.05), although in some cases the secondarily with Scots Pine Pinus sylvestris. Crested Tit continued feeding on the fat. Observations were collected during the The adult male Crested Tit which visited the winter 1995-96, from November to feeder won seven out of eight interactions January. Only Crested and Coal Tits visited over the adult female Coal Tit (7 vs 1, sign- the feeder; these are the only tit species test= 1.76, p=0.07). The other interadions regularly present in the urea during winter. between Coal and Crested Tits were, All birds were colour-ringed, and the usual unfortunately, few and ambiguous. morphometrical measurements were taken These observations support the idea that each time they were captured. Birds were the Crested Tit is generally dominant over sexed according to their behaviour during the Coal Tit. Also recorded were mixed the breeding season and on size winter flocks, where Crested Tits won all of differences, and aged according to the eleven recorded conflicts (1 1 vs. O). Svensson (1992). Observations were However, the data presented show that on collected during four sessions of 1 hour, some occasions Coal Tits can defeat with the observer situated 10 m from the Crested Tits at especially rich food sources. feeder. Haftorn (1993) raised the possibility that During the sessions, visits by birds were factors other than size were related to recorded, especially those which involved dominance in the hierarchy of tits he both species. In 70 visits were recorded (26 studied. Different experiments on tits have by Coal Tits and 44 by Crested Tits). When shown that when checking for factors such two birds visited the feeder simultaneously, as size or age, prior residence determines a was considered to be dominant if: dominance (Koivula et al. 1993, Sandell & (1) it chased the other away; (2) it Smith 1989). These experiments, carried supplanted the other; (3) the other withdrew out with both Willow and Great Tits Parus on its approach; or (4) the other waited major, suggest that pay-off asymmetries nearby until the dominant bird left. Only dependent on previous experience rather interactions with a clear and unequivocal than theoretical fighting potential (¡.e. size outcome were included in the analyses. or age) determine rank within these species, Four Crested Tits and two Coal Tits were and that prior residence often overrides observed during the sessions. A total of 15 advantages of size and age (Koivula et al. intraspecific (which served to establish the 1993). The two Coal Tits in my study had hierarchy within species) and 16 been ringed four years earlier as juveniles interspecific interactions between Coal and a few metres from where the feeder was Crested Tits were recorded. The Crested Tits placed, whereas all but one of the Crested were not clearly dominant over the Coal Tits were juveniles. Tits, although most Crested Tits won the Therefore, it seems feasible that the interactions with Coal Tits (1 1 vs. 5 times, adult male Coal Tit had a higher position sign-test= 1.55, N.S.). However, of six inter- in the hierarchy, as an effect of prior Social status of Tits in the Pyrenees residence, which compensated for the bird's manuscript. The fieldwork received financial smaller size and enabled it to win most of support from the Parc Natural del Cadi- the interactions with one of the Crested Tits, Moixeró. During the study I was supported a juvenile female. The fact that the Coal by a gran.t from the Comissionat per a Tits used attacks (more costly to individuals, Universitats i Recerca de la Generalitat de Lemel & Wallin 1993), causing juvenile Catalunya. Crested Tits to retreat from the feeding pla- ce, seems to reinforce the view of a higher position of the adult Coal Tits in the RESUM hierarchy. In this way, Coal Tits may occasionally gain access to important Notes sobre I'estatus social de la resources, which compensate for the energy Mallerenga Petita Parus ater i la Malle- invested in making the attacks. Differences renga Emplomallada Parus cristatus als in motivation due to differences in food Pirineus deprivation may occasionally lead to En una menjadora situada als Pirineus switches in a linear hierarchy, potentially es varen investigar les interaccions socials resulting in observations similar to mine entre mallerengues petites i emplomallades (Lemel & Wallin 1993). d'edat i estatus coneguts previament. De Bearing in mind that most Crested Tits manera similar a estudis anteriors, la relació were dominant over Coal Tits, the fact that de dominancia entre les dues especies no adult Coal Tits may be able to defeat young va ser clara, ien determinades ocasions un Crested Tits in agonistic interactions ut a mascle adult de Mallerenga Petita va concentrated food source is of great desplacar una femella jove de Mallerenga interest, because it raises the issue that site- Emplomallada d'una menjadora. Es related dominance or differences in discuteixen els factors que poden estar al motivation might switch positions in size- darrere de les desviacions detectades res- related hierarchies within, but also between, pecte d'una jerarquia basada en la mida species. de les dues especies. During winter, Coal and Crested Tits use pine cones as an important food source, and cones rich in ~ineseeds could be a location REFERENCES where the kin'd of interactions referred to in this paper may become important. As stated DHONDT, A. 1989. Ecological and by Haftorn, more experimental data on evolutionary effects of interspecific interspecific encounters between tits are competition in tits. Wilson Bull. 101 (2): needed to determine the inters~ecificrank 198-216. order of tits, because this hierarchy is likely to depend on several factors and thus may HAFTORN, S. 1993. Is the Coal Tit, not always be the same: Parus ater, the most subordinate of the Scandinavian tits? Ornis Scand. 24 (4): 335-338. ACKNOWLEDGEMENTS GLLANDER,H. 1997. En dominant I am grateful to the staff of the "Parc svartmes Parus ater. Ornis Svecica 7: 37. Natural del Cadi-Moixeró" for their help in the field. 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