Parasites can impact the behavior of animals and alter the interplay with ecological factors in their environment. Studying the effects that parasites have on animals thus requires accurate estimates of infections in individuals. However, quantifying parasites can be challenging due to several factors. Laboratory techniques, physiological fluctuations, methodological constraints, and environmental influences can introduce measurement errors, in particular when screening individuals in the wild. These issues are pervasive in ecological studies where it is common to sample study subjects only once. Such factors should be carefully considered when choosing a sampling strategy, yet presently there is little guidance covering the major sources of error. In this study, we estimate the reliability and sensitivity of different sampling practices at detecting two internal parasites— Serratospiculoides amaculata and Isospora sp.—in a model organism, the great tit Parus major . We combine field and captive sampling to assess whether individual parasite infection status and load can be estimated from single field samples, using different laboratory techniques—McMaster and mini‐FLOTAC. We test whether they vary in their performance, and quantify how sample processing affects parasite detection rates. We found that single field samples had elevated rates of false negatives. By contrast, samples collected from captivity over 24 h were highly reliable (few false negatives) and accurate (repeatable in the intensity of infection). In terms of methods, we found that the McMaster technique provided more repeatable estimates than the mini‐FLOTAC for S. amaculata eggs, and both techniques were largely equally suitable for Isospora oocysts. Our study shows that field samples are likely to be unreliable in accurately detecting the presence of parasites and, in particular, for estimating parasite loads in songbirds. We highlight important considerations for those designing host–parasite studies in captive or wild systems giving guidance that can help select suitable methods, minimize biases, and acknowledge possible limitations.

Aims: Wildbirds interaction with poultry increases the likelihood of exchange of parasites between wild birds and poultry highlighting the need to understand wild bird endoparasites to reduce cross-infection at the wild bird-poultry interface. This study investigates the prevalence and diversity of endoparasites among wild birds in Kaduna State to provide baseline data on the wild birds' endoparasites which could be a source of infection to poultry. Study Design: Wild birds in live wild bird markets, free-flying wild birds and semi-domesticated birds were the samples for endoparasites. Place and Duration of Study: Birds were sampled in Kaduna State, Nigeria and the samples were analyzed at the helminthology laboratory of Ahmadu Bello University, Zaria between April 2012 and December 2012.  Methodology: Wild birds faecal samples were examined for endoparasites by the simple flotation method.  Results: Of the 357 birds sampled, 36.4% were infected with at least one species of endoparasite. Charadriidae (7.1%) and Meleagris gallopavo (23.5%) had the lowest family and species prevalence respectively. Free flying, live poultry markets (LPM) and live wild bird markets (LWBM) birds had a prevalence of 39.1%, 37.2% and 34% respectively. The endoparasites identified were coccidia (30.5%), Ascaridia (5.9%), nematode larvae (0.8%), Capillaria (0.6%); Syngamus, Raillietinia and Trichuris (0.3% for each). There was a significant difference between the prevalence (p = 0.00), mean intensities (p = 0.00) and abundance (p = 0.01) of coccidia and Ascaridia. The prevalence   of multiple infections was 2.0% representing 5.4% of infected birds. The study is first to report  in Kaduna State, Nigeria of Trichuris in Anas platyrhynchos and Raillietina in Laniarius  barbarous. Conclusion: Wild birds in Kaduna State, Nigeria harbours endoparasites of economic significance to poultry and there is the need for more study of these wild birds’ endoparasites at the wild bird–poultry interface.

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