Data from: Vehicle-mounted cameras reveal negative impact of the Fukushima Daiichi nuclear power plant accident on large-bodied bird abundance via paddy field abandonment

Populations of birds utilizing farmlands are declining due to farmland
abandonment and agricultural intensification. Effective conservation
strategies require appropriate monitoring approaches, including efficient
and scalable survey methods. In this study, we developed a large-scale
monitoring method for herons and egrets (family Ardeidae, hereafter
referred to as herons) using vehicle-mounted video cameras and distance
sampling models that incorporate location uncertainty. The survey was
conducted in and around the evacuation zone of the Fukushima Daiichi
nuclear power plant accident. A total of 7031 km of roadside
video footage was recorded, covering 24.41 km² of farmland.
Herons were observed only outside the evacuation zone and were entirely
absent within it. Predicted abundance differed greatly between areas
inside (0.0279 ± 0.0307/km2) and outside
(4.57 ± 5.36/km2) the evacuation zone. Incorporating
location uncertainty into the distance sampling model had little effect on
the estimates (4.57 ± 5.36 vs.
4.51 ± 5.29/km2 with and without integrating location
uncertainty, respectively). This finding suggests that our video-based
roadside survey method is robust to location uncertainty in structured
landscapes such as Japanese paddy fields. The accuracy may be attributed
to the study system, where levees and roads divide paddy fields, limiting
potential error in observer-target distances. Our method can be applied to
other open habitats, including natural grasslands and wetlands, especially
in areas lacking artificial markers, by incorporating measurement
uncertainty into the model. This combination of roadside surveys with
vehicle-mounted cameras and distance sampling provides a practical and
transferable approach for monitoring large-bodied species in open
landscapes, enhancing both the efficiency and spatial coverage of
biodiversity assessments.