Biology subjects

de Margerie, E.

Publications and source records attributed to de Margerie, E..

2 recordsLinked to original sources

bioRxiv2025

Conserving a urban habitat: Enhanced detection of common swift nests in buildings using a video fusion method.

O_LICommon swifts (Apus apus) nest in cavities and cracks in building facades and roofs. It is a declining species in Europe, partly due to the loss of suitable breeding habitat caused by urban building renovation (e.g. thermal insulation). In several countries, building renovation projects imply quantifying the amount of habitat occupied by swifts that will be destructed, and proposing compensatory measures, such as installing nest boxes in the renovated building. A difficulty is that nesting swifts are uneasy to detect visually. C_LIO_LIHere we report a new video method we used to improve swift nest detection. It is based on continuous filming of a buildings facade (for 1-2 hours), and later video-frame fusion to reveal swift flying in and out of cavities in the facade. C_LIO_LIWe succesfully used this method on two large building renovation projects, revealing larger than expected breeding populations (78 nests), and resulting in the implementation of ambitious compensation measures (212 nestboxes), commensurate with the habitat actually destroyed. C_LIO_LIBased on a continuous dataset of swift passages during a full breeding season, we discuss favorable period in the season and day hours to efficiently detect nesting activity and assess building occupancy. C_LIO_LISolution. A video method is proposed to survey bird populations nesting in walls or cliffs. Video frame fusion reveals the fleeting movements of birds to their hidden nests. We provide software to use this tool in conservation projects, in particular ecological inventories prior to building renovation work. C_LI

ecology↗

bioRxiv2024

Recording butterfly movements from a UAV

Tracking and understanding the movements of animals in the wild is a fast-growing area of research, known as movement ecology. However, tracking small animals such as flying insects, which cannot easily carry an electronic tag, remains challenging as existing field methods are costly either in terms of equipment or tracking effort (e.g. VHF radio-tracking, scanning harmonic radar). Here we attempted to record the movements of free-flying butterflies from an unmanned aerial vehicle (UAV), maintaining a static position in the sky and recording video vertically downwards. With an appropriate flight height and image filtering algorithm, we recorded 166 flight tracks of Pieris butterflies (P. brassicae and P. rapae), with a median tracking length of 40 m (median flight duration 13 s), and a high temporal resolution of 30 positions per second. Average flight direction varied significantly over the course of the flying season, from a northward azimuth in June and early July, to a southward azimuth in September, congruent with a trans-generational migratory behaviour that has previously been documented by field observations or experiments in flight cages. In addition, UAV imagery unlocks the possibility to measure high-resolution flight movement patterns (e.g. path tortuosity and transverse oscillations), which will possibly help understand perceptual and locomotor mechanisms underlying spatial behaviour. We explore the technical details associated with UAV tracking methodology, and discuss its limitations, in particular the biases associated with a 2D projection of 3D flight movements, the limited spatial scale, and the difficulty to distinguish between visually similar species, such as P. brassicae and P. rapae.

animal behavior and cognition↗