Bart Hoekstra

@barthoekstra.bsky.social

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Postdoc @ Copernicus Institute of Sustainable Development | Movement Ecology | Radar Aeroecology | Birds | Energy | Climate | Monitoring & Comms. @batumiraptorcount.org | Remote Sensing | Open Science | He/Him | barthoekstra.com

An animated gif of a time series of radar measurements during NYE in the Netherlands. The radar measures comparatively little reflectivity before 00:00 and then a massive take-off of birds everywhere from midnight onwards. Look for the emerging ‘bloom’ of birds starting from midnight, not the pattern of rain moving left to right (west to east) with the wind prior to midnight. The black lines show the outlines of terrestrial parts of the Netherlands. After midnight, birds clearly move towards the large water bodies, the Wadden Sea and IJsselmeer. The stationary red spots are wind turbines. To the left of the radar (center cross) we see a large swath of sea clutter.
An animated gif of a time series of radar measurements during NYE in the Netherlands. The radar measures comparatively little reflectivity before 00:00 and then a massive take-off of birds everywhere from midnight onwards.
Fig. 2. Maps of nocturnal bird migration across the Netherlands in spring and autumn, with the 100 km radius circles of the weather radars enclosing the onshore study area. Colors represent seasonal migration passage, converted from the original bird densities. Shaded areas mark grid cells for which over 25% of the input data, prior to filtering, were impacted by ground clutter. Migration passage in these regions may be compromised in either direction: overestimated due to remaining clutter artifacts or underestimated where terrain features partially obstruct the radar’s lower scanning angles.
Team photo of the Shuamta team which counted 145k of the 170k raptors yesterday. I’m on the right.
The opening slide of the presentation titled ‘Large-scale radar-based mapping of nocturnal bird migration for avoidance and minimisation of wind energy impacts’.
Visitors at Het Grote Amsterdamse Vogel Spel, or ‘The Big Amsterdam Bird Game’
A juvenile Peregrine falcon flying in golden hour light.
A visualisation of the crown diameter of (one of) the largest tree(s) of the Amazon, showing the tree crown with a similar diameter as 5 school buses and the total length of the NASA Space Shuttle and launch vehicle.
A screenshot of the website titled ‘Monitoring the reaction of birds to fireworks’.
A picture of a person photographing Studio Roosegaarde's Spark project, a sustainable ‘fireworks’, which appears like lights slowly floating in the sky, like fireflies.
A picture showing a mass mortality event of Starlings in Rome, Italy, with many dead birds scattered on a road.
A figure showing the marginal effect of habitat model predictors and bird community compositions across six habitat types: agricultural, semi-open, forests, wetlands and waterbodies.
Densities of birds in flight during New Year's Eve (NYE; red) and on five regular nights (blue) as a function of distance to fireworks. The lines show the highest response close to fireworks, the response declining when approaching 5km, but then staying fairly stable at ~10X the flight activity compared to normal up to 10km from fireworks.
The two weather radars detect the mass take-off of birds following the lighting of fireworks just after midnight on January 1st, 2018. In the study area (surrounded by the red arcs), no less than 384,000 birds immediately flee from fireworks. This video is part of a publication in Frontiers in Ecology and the Environment titled ‘Fireworks disturbance across bird communities’.
The figure has three parts. (a) Vertically integrated reflectivity (VIR) derived from measurements by two operational weather radar installations in the Netherlands, showing clear spatial structures as birds are taking flight. (b) Total radar cross-section (RCS), a measure of the number and size of birds on the ground, as estimated from nationwide systematic winter bird counts. Dark gray areas within the region of analysis represent areas without bird counts. (c) Habitat types from which habitat proportions were calculated. The shaded areas beyond 66 km (red arcs) from the nearest radar installation (solid red circles) were excluded from the analysis.
A composite image of birds flying in front of fireworks, meant to depict fleeing birds.
A male Bearded Reedling holding on to a single reed stem. Because of thick fog the morning this bird was photographed, the background is entirely white, giving the impression this bird was photographed in a studio.
A male Pallid Harrier giving impeccable views as it rapidly passed the count station. The bird shows its characteristic almost black-and-white plumage with the thin black wedge at the wingtips, and stands out clearly against the dark backdrop of the Batumi bottleneck.
A Hobby (the species of falcon) beautifully lit against a dark background, carrying a prey — likely a Short-toed Lark.
A crowd of protesters gathered on the Malieplein in The Hague, while they are being addressed by labor unionists, students, politicians. Most protesters are staff from universities and students.
Beautiful weather at the heathlands. An image showing some trees surrounding the heathlands under light blue skies
An inquisitive but then startled juvenile Short-toed Eagle
A juvenile Honey Buzzard
A dark morph male Marsh Harrier
Screenshot of the eBird gallery discussed in the post, showing photos of raptors in flight
A photo composite of wind turbines, weather radar imagery and birds flying past