WI - Cormorant Research Group The Bulletin - No. 4, June 2000 Original papers

CONGENITAL ABNORMALITIES IN A GREAT CORMNORANT
Phalacrocorax carbo sinensis
FROM PUNTE ALBERETE NATURAL RESERVE
(PO RIVER DELTA, NE ITALY)

Stefano Volponi

Department of Biology, University of Ferrara, Via Borsari 46, I-44100 Ferrara, Italy

Congenital abnormalities or birth defects are generally uncommon in wild birds. Their occurrences have been mostly reported in chicks and young of waterbirds, especially in long-lived fish-eating species (Anderson 1987, Fox 1993), and generally correlated with the contamination of the food web by planar halogenated hydrocarbons (Fox et al. 1991, Giesy et al. 1994).

Pelecaniform species have been identified as extremely sensitive to chlorinated organic chemicals (Anderson et al. 1969) and the occurrence of congenital malformations such as bill defects, club feet, supernumerary digits and eye and skeletal abnormalities is a well known widespread phenomenon in Phalacrocoracidae. At present, bill defects (crossed or deflected bills and bills in which the two mandibles are different in length) have been reported in six species from locations in North America, British Isles, continental Europe and Australia (Ball 1991, Fox et al. 1991, Volponi 1996). In this note I report the observation of a Great Cormorant (Phalacrocorax carbo sinensis) young with congenital abnormalities at the Punte Alberete colony in the southern Po River Delta.

Punte Alberete is a 186 ha swamp, variably flooded along the season and part of a more extended wetland area which also includes the Pialasse (1,410 ha brackish lagoons) and Valle Mandriole (a 271 ha freshwater marsh). In this area, Great Cormorants have regularly wintered since mid '80s and have bred since 1994 with an increasing number of pairs (97 in 1997). In the last two years almost all the breeding cormorants moved from Valle Mandriole to the close mixed heronry of Punte Alberete where 800-1,000 pairs of colonial waterbirds, including five Ardeidae species, Glossy Ibises (Plegadis falcinellus), Spoonbills (Platalea leucorodia) and Pygmy Cormorants (Phalacrocorax pygmeus), regularly nest on Willow (Salix sp.), Sloe (Prunus spinosa) and Hawthorn (Crataegus monogyna) shrubs.

On 30 June 1997, during a visit to the heronry for ringing heron and egret nestlings, a full grown young Great Cormorant, aged about 30 days, was hand caught. It was resting on a 2.5 m high hawthorn bush, just below a group of cormorant nests some of them still holding nestlings. At first glance, the young cormorant seemed healthy and struggling, but during handling it rapidly became manageable and showed two severe abnormalities: (i) the tip of its upper mandible was slightly shorter than the lower and bent leftward; (ii) it was blind in the right, completely closed, eye. The pectoral muscles were reduced and numerous Mallophaga were found among body and wing feathers. However, considering that the young cormorant was not yet independent for food, its poor body condition was more likely due to some days of starvation than to the consequences of its abnormalities.

Another abnormal chick (a Pygmy Cormorant P. pygmeus one) was found in 1995 (Volponi 1996). This is therefore the second record of young cormorants with birth defects found at Punte Alberete. Since their establishment as breeders, respectively 46 Great and 73 Pygmy Cormorants were checked during ringing operations, so prevalence of birth defects should be considered high when compared to data form other fish-eating birds born in the Punte Alberete area (no malformations were observed among more than 1,400 nestlings belonging to nine species of Ardeidae and Laridae) and comparable with those from areas known as contaminated by halogenated hydrocarbons. These observations confirm that cormorants are more sensitive to toxic contaminants than other waterbird species and suggest a some, perhaps heavy, degree of chemical contamination of the local aquatic food web.

Unlike contamination by heavy metals (Anconelli et al. 1980, Miserocchi et al. 1990), no information are available on the presence and level of halogenated compounds in the foraging ground of fish-eating birds around Punte Alberete. However, chemical industries are numerous and in the last years some illegal discharges of industrial wastes, containing mixture of polychlorinated biphenyls (PCBs) and other toxic compounds, have been reported.

Because they are long-lived, almost exclusively fish-eating birds, cormorants and mainly the Great Cormorants, which have greatly increased in the overall Po Delta, appear especially suitable for biomonitorage programs to measure concentrations and detect effects of halogenated hydrocarbons in aquatic food web.

References

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Anderson D. W., Hickey J. J., Riseborough R. W., Hughes D. E. & Christensen R.E. 1969. Significance of chlorinated hydrocarbon residues to breeding pelicans and cormorants. Canadian Field-Maturalist, 83:91-112.

Anderson I. 1987. Epidemic of bird deformities sweeps U.S. New Scientist 3 Sept. 1987, 21.

Ball D. 1991. A high incidence of bent beaks in nestling Pied Cormorants. Emu 91:257.

Fox G. A. 1993. What have biomarkers told us about the effects of contaminants on the health of fish-eating birds in the Great Lakes? The theory and a literature review. J. Great Lakes Res., 19:722-736.

Fox G. A., Collins B., Hayakawa E., Weseloh D. V., Ludwig J. P., Kubiak T. J. & Erdman T. C. 1991. Reproductive outcomes in colonial fish-eating birds: a biomarker for developmental toxicants in Great Lakes food chains. II. Spatial variation in the occurrence and prevalence of bill defects in young Double-crested Cormorants in the Great Lakes, 1979-1987. J. Great Lakes Res., 17:158-167.

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Volponi S. 1996. Bill deformity in a Pygmy Cormorant (Phalacrocorax pygmeus) chick. Colonial Waterbirds, 19:147-148.

Stefano Volponi, Department of Biology, University of Ferrara, Via Borsari 46, I-44100 Ferrara, Italy (email: svolponi@racine.ra.it)