Seeing in the dark: Using thermal imaging to directly observe nocturnal migration

Nocturnal migration has fascinated and puzzled ornithologists for centuries. Today, using technologies from weather surveillance radar to multi-sensor geolocators, we can study the continental magnitude of these flights and the intricate details of individual journeys. Yet, we still lack a way to directly observe migrants, hampering our ability to understand migration at the individual and species level. Combining recent advances in thermal imaging optics and digital photography, we detected, illuminated, and identified nocturnally migrating birds at low altitudes (0–300 m). We describe insights this technique has to offer using ~200 observation hours during three autumns (2020–2022) at Cape May, New Jersey, USA. Our novel approach allowed us to observe migratory behavior at night, identify thousands of nocturnally migrating birds, and begin quantifying the passage of silent individuals and silent species. Aside from a few highly vocal families—primarily thrushes, sparrows, and wood-war..., , # Data from: Seeing in the dark: Using thermal imaging to directly observe nocturnal migration

Dataset DOI: [10.5061/dryad.tmpg4f5cz](https://doi.org/10.5061/dryad.tmpg4f5cz)

## Description of the data and file structure

This dataset contains count data of nocturnal migrants from 32 well-annotated observations (eBird checklists) collected over 20 nights (65.3 hours) between 20 September and 28 October 2022. These observations were recorded from two primary vantage points in Cape May, New Jersey, USA: Cape May Point State Park (38°55'58'' N, 74°57'28'' W) and the western dunes of Cape May city (38°55'48'' N, 74°55'29'' W). Nocturnally migrating birds were identified using a combination of criteria: photographs of illuminated birds, expert visual identifications (with binoculars) of illuminated birds, and expert auditory identifications of distinctive call notes. Within this Sep-Oct 2022 dataset, 105 unique species or species complexes were identified from 26 avian families. Please see...,