Estimating the number of genome copies in a tissue sample can serve various purposes. For example, such an estimate serves as scaling variable when measuring telomeres with quantitative PCR. We describe the primer development and evaluation for the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene in the Great Tit Parus major, as a control gene to estimate genome copy number. We demonstrate specific amplification with negligible variation in 48 Great Tits and cross-amplification in 53 Blue Tits Cyanistes caeruleus. We conclude this primer set to be reliable for amplification of GAPDH as a reference gene for quantitative PCR analysis in Great and Blue Tits.