A Novel Application of Structure From Motion Photogrammetry to Measuring Ephemeral Nest Structures

Abstract

ABSTRACT A wide array of fish species construct nests that serve to protect offspring from environmental conditions while they develop or incubate, thus improving offspring survival and parental fitness. As humans continue to damage environments and endanger species, we must continue to find ways to accurately assess how nesting traits affect fitness in a changing world, but many fish nests are ephemeral in nature, which can hinder researchers' capabilities to effectively study them. The purpose of this study was to assess how well Structure from Motion (SfM) photogrammetry, a method that can potentially preserve nest structure for long‐term analysis, models the shape and size of bluehead chub ( Nocomis leptocephalus ) nests. We photographed and measured 31 individual nests, six of which were modeled multiple times on different days, from three streams near Blacksburg, Virginia, USA to later construct 38 models in Agisoft Metashape. We then compared model estimates of nest morphology with those from field measurements. Although some deviations in nest height occurred between these two methods, model estimates closely matched measurements taken in the field. Furthermore, we argue that our models more accurately measured nest height, as well as better captured the complexities of nest shape, than our field measurements. Our findings suggest that SfM is a powerful tool for future studies quantifying the exterior structure of nests, and potentially other ecologically relevant formations. We provide suggestions and considerations for future research looking to use this method.