As a long-distance migrant which crosses more than 20 African countries, Eleonora's Falcons might have experienced a substantial accumulation of contaminants when returning to their breeding grounds. In 2004 and 2005, we collected 21 failed eggs from two colonies on Sardinia, Italy. We found a high percentage of dead embryos and suspected this was due to a high contaminant load. Despite this, the overall values for the contaminants analysed were rather low and lay within the range found in other raptor species. We analysed the eggs for residues of DDT (p,p′-dichlorodiphenyltrichloroethane), PCB (polychlorinated biphenyl), and heavy metals. Although infertile eggs seem to be correlated with the highest values of ∑ D D T , we did not find substantial values of any of the contaminants investigated. Because of the low world population of the species and varying reproduction rates in the colonies ranging from Cyprus to the Canaries, we highly recommend further censuses of the reproductive success of Eleonora's Falcon, including the examination of failed eggs. 1. Introduction Eleonora’s Falcon (Falco eleonorae) has a restricted breeding range across the Mediterranean Sea and the adjoining part of the Atlantic. This rare, colonially breeding falcon has an estimated world population of only 15,300 breeding pairs [1]. Censuses have revealed that the breeding population of Eleonora’s Falcon has undergone a moderate decline of more than 10% since the 1990s [1]. This rate might be well within the range of a natural flux, but, regarding the overall small population, this decline should be carefully monitored in the coming years. According to studies in previous years, the reproduction rate of Eleonora’s Falcon varies substantially across its range. The highest rate has been measured in Morocco, where each breeding pair produced on average 2.6 offspring per year [2]. The lowest reproduction rate was documented in a colony on Cyprus with only 0.8 offspring per breeding pair per year [3]. Interestingly, this rate has remained stable at this low level over the years (Ristow, personal communication). Without incoming new breeding pairs, that is, offspring from other colonies, a reproduction rate as low as that on Cyprus is likely to further accelerate the present population decline [1]. During fieldwork at the breeding sites of Eleonora’s Falcon from 2003 to 2005 [4], we found a high number of dead eggs left in the eyries. Because of the use of pesticides in African countries [5, 6], the spraying of DDT in the wintering area of Eleonora’s Falcon in Madagascar between
References
[1]
A. Dimalexis, S. Xirouchakis, D. Portolou et al., “The status of Eleonora's Falcon (Falco eleonorae) in Greece,” Journal of Ornithology, vol. 149, no. 1, pp. 23–30, 2008.
[2]
A. L. Clark and D. B. Peakall, “Organochlorine residues in Eleonora's Falcon Falco eleonorae, its eggs and its prey,” Ibis, vol. 119, pp. 353–358, 1976.
[3]
H. Walter, Eleonora's Falcon. Adaptations to Prey and Habitat in a Social Raptor, The University of Chicago Press, Chicago, Ill, USA, 1979.
[4]
M. Gschweng, E. K. V. Kalko, U. Querner, W. Fiedler, and P. Berthold, “All across Africa: highly individual migration routes of Eleonora's falcon,” Proceedings of the Royal Society B, vol. 275, no. 1653, pp. 2887–2896, 2008.
[5]
S. Hollamby, J. Afema-Azikuru, J. G. Sikarskie et al., “Mercury and persistent organic pollutant concentrations in African fish eagles, Marabou storks, and Nile tilapia in Uganda,” Journal of Wildlife Diseases, vol. 40, no. 3, pp. 501–514, 2004.
[6]
R. Peveling, A. N. McWilliam, P. Nagel et al., “Impact of locust control on harvester termites and endemic vertebrate predators in Madagascar,” Journal of Applied Ecology, vol. 40, no. 4, pp. 729–741, 2003.
[7]
A. Fadda and M. Medda, “The colony of Eleonora's Falcon Falco eleonorae in Toro Islet, Sardinia,” Aves Ichnusae, vol. 7, pp. 3–21, 2005.
[8]
D. Ristow, “International Species Action Plan Eleonora's Falcon Falco eleonorae,” European Commission (BirdLife International), 1999.
[9]
B. Conrad, “Zur Situation der Pestizidbelastung bei Greifv？geln und Eulen in der Bundesrepublik Deutschland,” ？kologie der V？gel, vol. 3, pp. 161–167, 1981.
[10]
D. Ristow and M. Wink, “Breeding success and conservation management of Eleonora's Falcon,” ICTP Technical Publication, vol. 5, pp. 147–152, 1985.
[11]
G. Prinzinger, Ed., Pestizide und Brutbiologie der V？gel, Kilda, Greven, Germany, 1980.
[12]
G. Dell'Omo, D. Costantini, J. Wright, S. Casagrande, and R. F. Shore, “PCBs in the eggs of eurasian kestrels indicate exposure to local pollution,” Ambio, vol. 37, no. 6, pp. 452–456, 2008.
[13]
V. M. Mendenhall, E. E. Klaas, and M. A. R. McLane, “Breeding success of barn owls (Tyto alba) fed low levels of DDE and dieldrin,” Archives of Environmental Contamination and Toxicology, vol. 12, no. 2, pp. 235–240, 1983.
[14]
D. Ristow, B. Conrad, C. Wink, and M. Wink, “Pesticide residues of failed eggs of Eleonora's falcon Falco eleonorae from an Aegean colony,” Ibis, vol. 122, no. 1, pp. 74–76, 1980.
[15]
M. Wink, H. Biebach, F. Feldmann, et al., “Contribution to the breeding biology of Eleonora's Falcon (Falco eleonorae),” in Proceedings of the Hawk and Trust Conference, pp. 59–72, 1993.
[16]
N. Bianchi, C. Leonzio, S. Casini, M. C. Fossi, and S. Focardi, Valutazione dello Stato di Contaminazione nel Falco eleonorae Attraverso l'Utilizzo di Metodologie non Distruttive, Dipartimento di Scienze Ambientali, Università di Siena, Italy, 2003.
[17]
M. Weber, W. Fieber, and M. Stubbe, “Persistente chlororganische Verbindungen, Quecksilber und radioaktive Nuklide in Eiern von Rotmilanen (Milvus milvus) aus Sachsen-Anhalt,” Journal fur Ornithologie, vol. 139, no. 2, pp. 141–147, 1998.
[18]
R. S. Boumphrey, S. J. Harrad, K. C. Jones, and D. Osborn, “Polychlorinated biphenyl congener patterns in tissues from a selection of British birds,” Archives of Environmental Contamination and Toxicology, vol. 25, no. 3, pp. 346–352, 1993.
[19]
E. Denker, A. Buthe, H. Knuwer, T. Langgemach, P. Lepom, and I. Ruhling, “Comparison between the burden of xenobiotics in eggs of the Sparrowhawk (Accipiter nisus) from Brandenburg and North-Rhine-Westphalia, Germany,” Journal of Ornithology, vol. 142, no. 1, pp. 46–62, 2001.
[20]
E. Denker, A. Büthe, D. Glimm, M. H？lker, W. Prünte, and T. Trendelkamp, “Changes in the DDT and PCB burden in life stages of Montagu's (Circus pygargus) and Marsh Harriers (Circus aeruginosus) from North-Rhine Westfalia, Germany,” Journal fur Ornithologie, vol. 144, no. 4, pp. 411–417, 2003.
[21]
N. Kenntner, Chlororganische Pestizide, polychlorierte Biphenyle und potentiell toxische Schwermetalle in Organproben von Seeadlern und Habichten, Thesis, Humboldt Universit？t zu Berlin, Institut für Zoo- und Wildtierforschung, Berlin, Germany, 2002.
[22]
T. Wiesmüller, P. S？mmer, M. Volland, and B. Schlatterer, “PCDDs/PCDFs, PCBs, and organochlorine pesticides in eggs of Eurasian sparrowhawks (Accipiter nisus), hobbies (Falco subbuteo), and northern goshawks (Accipiter gentilis) collected in the area of Berlin-Brandenburg, Germany,” Archives of Environmental Contamination and Toxicology, vol. 42, no. 4, pp. 486–496, 2002.
[23]
M. R. Driss, L. Mahmoud, L. Bhari, and M. L. Bouguerra, “Etude préliminaire de la contamination des oeufs de Faucon Pélerin (Falco peregrinus) et Lanier (Falco biarmicus) par les produits organochlorés en Tunisie,” Ecological Bulletin, vol. 19, pp. 43–49, 1988.
[24]
P. Wegner, G. Kleinst？uber, F. Baum, and F. Schilling, “Long-term investigation of the degree of exposure of German peregrine falcons (Falco peregrinus) to damaging chemicals from the environment,” Journal of Ornithology, vol. 146, no. 1, pp. 34–54, 2005.
[25]
A. J. García-Fernéndez, J. F. Calvo, E. Martínez-López, P. Maria-Mojica, and J. E. Martínez, “Raptor ecotoxicology in Spain: a review on persistent environmental contaminants,” Ambio, vol. 37, no. 6, pp. 432–439, 2008.
[26]
J. A. Gervais and D. H. Catlin, “Temporal patterns of DDE in burrowing owl eggs from the Imperial Valley, California,” Southwestern Naturalist, vol. 49, no. 4, pp. 509–512, 2004.
