%0 Journal Article
%T Dead Embryos despite Low Contaminant Loads in Eggs of Eleonora's Falcon
%A Marion Gschweng
%A Frieda Tataruch
%A Otmar Fr£¿hlich
%A Elisabeth K. V. Kalko
%J ISRN Zoology
%D 2011
%R 10.5402/2011/510202
%X 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¡ä-dichlorodiphenyltrichloroethane), PCB (polychlorinated biphenyl), and heavy metals. Although infertile eggs seem to be correlated with the highest values of ¡Æ 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
%U http://www.hindawi.com/journals/isrn.zoology/2011/510202/