Geese_movements

Geese survival

The detection of death reason is a combination of field observation when I went to pick up loggers from died individuals and inference after I left NL.

For example, the predation_day_terrestrial event: the incident happened in the afternoon on a pasture with uneven terrain for predators to ambush. Activity was detected from ODBA, and after the predation, the GPS data became immediately unavailable (failed localization), most like the died individual was dragged into a den. After 1 day, the logger might be brought out by the predator so I could find it with the available new locations.

Detection of aerial predations was from sudden stop during a flight with high ODBA values.

Detection of human hunting was from sudden stop during a flight and afterwards the logger sent locations from hunter houses.

The natural death: individuals became more and more inactive (gradually decreased ODBA from day to day). Individual 0849 and 0848 were travelling together and became unwell temporally close to each other, which might be due to infectious disease (early winter).

(Female 068d is still alive, the short bar is due to lack of data from Druid server. I will ask them to get all data from this individual)

Landuse

Using Corine Land Cover 2018 dataset (land use status of Europe), 100m resolution;

summarized monthly landuse percentages of each individual.

Might be useful for management?

Flight height

The base ground height was from google earth, R can directly read data from the google api (charge a small amount of fee if you ask for more data from their service). And the trackers we used on barnacle geese have good accuracy of horizontal and vertical accuracy (SD of vertical accuracy about 10m). I haven’t filtered these data yet, that’s why there are minus 0 above ground level readings.

The median flight height of all individuals across the past year was about 15m, pretty low, maybe just to conserve energy. There were several dispersers such as 068b, who flew higher during long distance flights (0851 just travelled to north of NL, no further).

There are places in South Holland where wind turbines could be found. We did have several individuals flew very close to the turbines.

Flight height of residential geese might be a potential topic?

Other potentials

Family bond.

The 6-individual family story: they were tightly together until 27th Dec 2024, when the adult female 069c was possibly ambushed and eaten by a fox at night (this logger was later sent back to Henk and the initial guess was an eagle, but since it was predated at night, so most likely a fox or other nocturnal predator). The father of the family flew away from their night site and separated with the rest juvs for more than 10 days. They reunited with each other later, but the family bond was weak and the father separated with the juvs generally early. Compared to the 4 individual family, the 2 juvs hanged around until the next breeding round. In addition, the adult male of the early separated 6-individual family found another partner, but did not have enough time in incubation (failed breeding).

So family bond and separation might be an interesting topic.