An inexpensive, 3D‐printable breast muscle meter for field ornithologists

The size of the pectoral muscle is an important component body condition in birds and has been linked to indices fitness migratory performance. Bauchinger et al. (2011. Journal Ornithology 152: 507–514) developed, calibrated, validated aluminum “muscle meter” device that estimates muscles noninvasively. To make this tool more widely available, we created a CAD model from 3D‐scan data meter can be 3D‐printed durable plastic for ~ $30 USD. We tested on seven species songbirds Jamaica, Bahamas, Cameroon, Equatorial Guinea, Michigan. demonstrate breast measurements are (1) repeatable among users, (2) correlated with four‐category visual scoring system, (3) scaled mass index (an condition). Muscle scores our outperformed traditional system predicting index. Finally, device, quantified increasing American Redstarts (Setophaga ruticilla) March through May as they prepared spring migration. Given precision 3D‐scanning hardware used generate 3D image printing, produced precise useful original, but cost‐effective available.