Variation in concentrations of organochlorines and brominated flame retardants among eggs in abandoned clutches of a terrestrial raptor Jan O. Bustnes a,⇑ , Georg Bangjord b , Nigel G. Yoccoz a,c a Norwegian Institute for Nature Research, FRAM – High North Research Centre on Climate and the Environment, NO-9296 Tromsø, Norway b Oddatunet, NO-7057 Jonsvatnet, Norway c Department of Arctic and Marine Biology, UiT The Arctic University of Norway, NO-9037 Tromsø, Norway highlights  Tawny owl clutches abandoned by the parents were collected.  Chlorinated and brominated compounds were analyzed in all eggs.  Concentrations were similar among eggs within clutches.  Abandoned eggs seem to provide a relatively reliable measurement of lipophilic pollutants. article info Article history: Received 10 June 2014 Received in revised form 3 October 2014 Accepted 5 October 2014 Available online 17 November 2014 Handling Editor: Myrto Petreas Keywords: Tawny owl PCB DDE PBDE Bird eggs abstract Bird eggs are often used to measure various pollutants in monitoring programs. In protected species, however, it might only be possible to collect eggs abandoned by the parent birds. In order to assess the appropriateness of abandoned eggs for contaminant monitoring we examined intra-clutch variation in concentrations of 24 halogenated organic pollutants (16 organochlorines [OCs] and 8 brominated flame retardants) in six abandoned tawny owl (Strix aluco) clutches from central Norway. The variation among eggs within a clutch was low for nearly all compounds (intra-class correlation >0.9 both for lipid- and wet weight). This study suggests that abandoned eggs provide a relatively reliable measurement of lipophilic pollutants in clutches of terrestrial raptors such as the tawny owl. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Bird eggs, especially from raptors and aquatic birds have been used to monitor persistent organic pollutants (POPs) for several decades (Hebert et al., 1999; Helander et al., 2002; Klein et al., 2012; Bustnes et al., 2007). However, in protected species it is often only possible to collect eggs abandoned by the parents (e.g. Helander et al., 2002; Vorkamp et al., 2005; Bustnes et al., 2007). Such eggs may be unfertilized, the embryo may have started to develop or they may be addled. In addition, embryo development potentially cause alterations in the concentration and composition of POPs in the egg (Klein et al., 2012). If abandoned eggs should be appropriate for monitoring persistent POPs, they must reflect the concentrations in the clutch as a whole. We are, however, aware of no studies that have investigated the intra-clutch variation of POPs in abandoned clutches of terrestrial raptors such as owls. In this study we analyzed intra-clutch variation in organochlorines (OCs) and polybrominated diphenyl ethers (PBDEs) in tawny owl (Strix aluco) from Central Norway, in order to document intra- clutch variability. Six whole clutches (4–5 eggs in each; 26 eggs in total) abandoned by the parent birds were collected and ana- lyzed for 24 different organic compounds (Table 1). 2. Materials and methods 2.1. Study area and sample collection The study was carried out in the area surrounding the city of Trondheim (63.42°N, 10.23°E) in Sør-Trøndelag County, Central Norway. More than 100 tawny owl nest boxes have been deployed. The boxes were visited in mid-May when the young had hatched, http://dx.doi.org/10.1016/j.chemosphere.2014.10.017 0045-6535/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +47 77 75 04 07; fax: +47 77 75 04 01. E-mail address: Jan.O.Bustnes@nina.no (J.O. Bustnes). Chemosphere 118 (2015) 357–360 Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere