Bua. GCA 9: 43-46, 1992 Bill abnormalities in a pair of IBlack Oenanthe leucura

G. BLANC0 & J.L. TELLA

Both members of o pair of Black Wheatears captured in central Spain showed an appreciable elongation of both mandibles. The male had an extraordinary elongation and curvature of its upper mandible, which later broke and took on the normal form.

Key words: Black , Oenanthe leucura, bill abnormalities.

Guillermo Blanco. Dep. de Biologia (Vertebrados). Facultad de Biologia. Universidad de Alcala de Henares. Alcalá de Henares, 28871 Madrid. Jose Luis Tella. Dep. de Biologia Animal (Vertebrados). Facultad de Biologia. Universidad de Barcelona. 08028 Barcelona. Rebut: 02.02.93; Acceptat: 23.03 93

Among the many morphological defor- rnations which have been described in , those affecting the bill are the most varied (Pomeroy 1962, Santos 1 98 1 ). They may be of genetic origin, or caused by accidents, food deficiencies, parasites or due to the action of mutagenic and theratogenic agents present in the environment (Porneroy 1962, Gilbertson et al. 1976, Threlfall & Roy 1988). The frequency of occurrence of such abnormalities in birds' bills is always low, although there is a great deal of variation between &ferent species and areas, de. pending on the presence and/or operation of the factors causing these abnormalities Fig. 1. Aspecto inicial del pico del macho de (Pomeroy 1 962, Gilbertson et al. 1976). Collalba negra. A male Black Wheatear Oenanthe leu- cura was captured while roosting with a conspecific- female inside an old gypsum rharn~hothecain its upper rnandible, with mine near San Martin de la Vega, Madrid an estimated curvature in the distal third of (40.17N 3.32W), on August 23, 1992. It the bill of about 180'. The lower mandible showed extraordinary elongation of the was normal in both lenght and curvature,

43 Butll. GCA 9,1992

Sex Male Female Male Weight 37 35 37 Wing 98 95 99 Tai1 68 71 Bill length 32.80 25.20 Bill depth - 4.50 Bill width 3.90 Head lengthl 46.90 Lower mandible ~arsus*

1. From back of head to tip of biii. 2. Method of Potti & Montalvo (1991).

Table 1. Biometries (mm; weight in grammes) of a pair of Black Wheatears with bill abnormalities. Tabla 1. Biometná (mm; peso en gramod de una pareja de Collalbas negras con malfmaciones en el pico.

although its end was blunt (Fig. 1 ). This sarne were within the normal range for the species. individual was again captured, and ringed, Only on this last visit did we find ectopara- in the sarne site on 1 1 Novernber 1992; sites (Acarina)around one of the male's eyes. this tirne we rneasured several characteristics No plurnage alterations caused by the puta- (Table 1 ), following Svensson (1984), except tive inability to maintain it correctly (Pomeroy for tarsus length which followed Potti and 1962) were noted during any of the visits. Montalvo (1991 ). On a later visit (21 No- Hence, the basic abnorrnaliíy in both indi- vernber 1992) airned at capturing the fe viduals consisted of a abnorrnal elongation rnale wheatear, we ascertained that the in both mandibles, with a later breakage in male's bill was again close to "normal", as the male's lower rnandible, which was prob- a consequence of the fragrnentation of the ably the cause of the excessive elongation rhamphotheca at the level of the beginning in the upper mandible (see Pomeroy 1962 of the curvature. The upper and lower man- for several similar exarnples). dible ends were both blunt in this occasion. Arnong bill deforrnations in birds, ex- On 1 8 December 1992 both individuals cessive growth and subsequent arching of were captured and measured in the same one or both mandibles is observed quite roosting site (Table 1). The female showed frequently in many species. However, pro- on appreciable elongation in both rnandi- nounced curvature is rare in birds bles (see Svensson 1984, Cramp 1988, (Pomeroy 1962). The duration and evolution and Zamora 1988, for the normal rneasure- of these abnormalities is unknown for most ments of the bill), while the male's upper observed cases in wild birds as these are rnandible now showed its normal pointed usually based on circurnstantial observations forrn. The rest of the rneasurements (Table 1) which are not subsequently monitored. The Biíi abnormalities in Black Wheatears

exam~leof the male Black Wheatear here RESUMEN docukented shows that the structure of the deforrned bill may be temporary in nature Malformaciones en el pico de una and very plastic, as a probable conse pareja de Collalbas negras Oenanthe leu- quence of accidental events. Also, behaviou- cura. ral idiosyncrasies may also be irnplied (He 10s componentes de una pareia de col- ward 195 1, Cutthill et al 1992). The fact lalbas negras capturados en España Central that both rnembers of the pair showed the mostraron una irregularidad en el pico con- same abnorrnality, albeit a; different stages, sistente en la elongación anormal de ambas suggests that factors enhancing the malfor- mandibulas. El macho presentaba una cur- rnation had been acting in the same way vatura desmesurada en la mandibula supe- on both individuals and were probably of rior, que posteriormente se rompió adquirien- environmental origin (Threlfall & Roy 1988). do una forma y longitud normal. Foraging behaviour and survival may be affected bv bill deformations and the 's mass rnay be indicative of overall physical REFERENCES condition (Porneroy 1962). The male's weight before and after recovering its normal CRAMP, S. (ed.) 1 988. The Birds of the bill forrn was the same, and higher than that Western Palearctic. Vol. V. Oxford: Oxford of the female ITable 1 I which showed a less Universiíy Press. advanced stage of deformation. It seerns logical to conclude that the rnale's bill rnal- CUTHILL, I., WITTER, M. & CLARKE, L. formation did not affect his physical condi- 1992. The function of billwhipping. Anim. tion. On the other hand, the male did not Behav. 43: 103-1 15. carry stones to the base of the nest, as cornmonly occurs in this species: 87.00 %, GILBERTSON, M., MORRIS, R.D. & 90.48 % and 9 1.95 % of nests had stones HUNTER, R.A. 1976. Abnormal chicks and in study areas in Almeria (n=37), Granada PCB residue levels in eggs of colonial birds (n=57) and the Valle del Ebro (n=87) respec- on the lower Great Lakes (1971-73).Auk tively (Richardson 1965, Soler et al. 1983 93: 434-442. and pers. obs.1. This could be due to the malei inability 'to carry stones because of HOWARD, L. 195 1 . Abnorrnal bill of his deforrned bill, combined with other fac- Great Tit. Brit. Birds 46: 254. tors, such as the distance of the nest frorn the rnine entrance 138 ml, or the total ab- POMEROY, D.E. 1962. Birds with ab sence of light in ;he su;oundings of the normal bilis. Brit. Birds 55: 48-72. nest. POTTI, J. & MONTALBO, S. 1 99 1 . Male arrival and female mate choice in Pied Flycatchers (Ficedula hypoleuca) in Central ACKNOWLEDGEMENTS Spain. Ornis Scand. 22: 45-54.

We thank S.Merino, M.C. Blonco, J.A. RICHARDSON, F. 1965. Breeding and Fargallo, R. lopez and J.A. Cuevas for help feeding habits of the Black Wheatear in capturing and measuring wheatears, and (Oenanthe leucura) in Southern Spain. Ibis J. Potti for translating the manuscript. 107: 1-16. Butll. GCA 9, 1992

SANTOS, T. 198 1 . Variantes de plu- to European Paserines. Svensson: Stoc!&olrn. maie y malformaciones en Turdus spp. Arde- o10 28: 133-138. THRELFALL, W. & ROY, N.A. 1988. Skull deformity in a Herring Gull chick (Larus SOLER, M., ZUNIGA, J.M. & CAMA- argentotus).Journal of Wildlife Diseases 24 CHO, 1. 1983. Alimentación y reproduc- (1): 133-136. ción de algunas aves de la Hoya de Guadix (sur de España). Trab. Monogr. Dep. Zool. ZAMORA, R. 1988. Estructura morfo- Univ. Granada (N.S.)6: 27-100. Iógica de una comunidad de passeriformes I de alta rnontaiia (Sierra Nevada, SE de SVENSSON, L. 1984. ldentification Guide , España). Ardeola 35: 71-95.