Non-destructive sampling of maternal DNA from the external shell of bird eggs Gregory Schmaltz 1 Christopher M. Somers 1,2 Priya Sharma 1 & James S. Quinn 1, * 1 Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4K1, Canada; 2 Department of Biology, University of Regina, 3737 Wascana Parkway, Regina, SK, S4S OA2, Canada (*Corresponding author: Phone: +1-905-525-9140; ext: 23194; Fax: +1-905-522-6066; E-mail: quinn@mcmaster.ca) Received 16 June 2005; accepted 7 October 2005 Key words: avian maternal DNA, Caspian terns, egg swabbing, herring gulls, non-destructive genotyping Abstract The use of non-destructive sampling methods to collect genetic material from wildlife allows researchers to minimize disturbance. Most avian studies employ capturing and handling of young and parents to draw blood for DNA analysis. In some cases adult female birds are difficult to catch, so maternal genotyping has required collection of contour feathers from nests, or destructive sampling of eggs. Many species do not leave contour feathers in the nest, and destructive sampling has been unreliable due to contamination with embryonic DNA. Alternative field sampling techniques for collection of maternal DNA from birds are therefore desirable. Here we demonstrate that avian maternal DNA can be isolated in a non-invasive and non-destructive way from the external surface of eggs. We used cotton swabs to collect maternal DNA from the external shells of herring gull (Larus argentatus) and Caspian tern (Sterna caspia) eggs. DNA was then amplified by the polymerase chain reaction (PCR) for microsatellite genotyping. We verified that the DNA samples were maternal by comparing microsatellite profiles to those obtained from adults and chicks from the same nests. In 100% of Caspian tern (n=16) and herring gull families (n=12), the egg swabs that amplified matched the maternal microsatellite genotype. In a screening of many nests of both species, we successfully amplified microsatellite markers from 101/115 (88%) egg swabs. Swabs from eggs with blood stains on the shell were more likely to amplify successfully than those from clean eggs. The advantages of this new method include increased parentage assignment/exclusion power, and increased availability of maternal DNA for genotyping of species that do not deposit contour feathers in nests. Introduction Genetic markers have vastly improved our under- standing of different aspects of avian ecology such as phylogeography and population genetics, mat- ing systems, kinship and conservation biology (Queller et al. 1993; Jarne and Ladoga 1996; Avise 2004). Obtaining DNA for genetic analysis often involves long hours in the field spent trapping birds, finding nests, and collecting blood or feather samples. In studies of parentage and kinship, obtaining DNA from every individual of a given family is often challenging. Capturing birds may increase risks of injuries or nest desertions and may lead to abnormal behavior (Go¨tmark 1992; Cri- scuolo 2001). As well, catching females is fre- quently more difficult because they generally tend to be less aggressive than males and therefore do not respond well to playbacks, which are typically used to lure birds into mist-nets (Stouffer 1997). In some avian taxa, the period of association between the female and the nest and/or territory is very brief making female-capture difficult or impossible. For instance, in polyandrous species such as coucals or Conservation Genetics (2006) 7:543–549 Ó Springer 2006 DOI 10.1007/s10592-005-9065-x