Alternative 3- Ground Survey
This subsection will present the relevant information for evaluating ground surveys as a method for seabird censusing.
Cost: Unlike the other methods presented in this work, the ground survey method has no capital costs. Instead, the main costs are associated the pay of the ground surveyor and compensation for mileage and gas. Respectively, those rates are 10 € per kilometre surveyed and 0.21 € per kilometre travelled. Therefore, if a ground surveyor were to be sent out to cover a distance of 3 km (i.e. the distance covered by a drone in a single flight) and if the ground surveyor commuted from the nearest large urban, Rotterdam, which is 70 km away from the study site, the daily cost would be 3 x 10 € + 2 x 70 km x 0.21 €/km or 59.40 €.
Temporal frequency: Measurement frequency is limited only non-working days and extreme weather. Thus, it can be estimated that a surveyor can obtain a population count 20 times per month.
Disturbance: Due to the fact that there are no inconspicuous vantage points on a tidal flat, a human surveyor would always be in the view of the seabirds. Due to the remote location of the Viane tidal flats, the seabirds that forage there are not accustomed to humans and move away when approached. For that matter, the author could not get within about 100 metres of the birds before they moved away. That said, with the aid of binoculars, a surveyor would be able to stay well over 100 metres from the birds and thus not cause them to move away. Disturbance is expected to be small with only a few cautious birds being affected by the presence of the surveyor.
Deployability: A human surveyor can be deployed on any day so long as weather conditions do not pose a threat to the surveyor’s safety and so long as the surveyor is willing to work on that day (i.e. the surveyor may choose not to work on weekends or holidays). Due to the possibility of extreme weather, the likelihood of deployability of a surveyor is estimated to be about 90%.
Spatial Coverage: Surveyors are able to cover a few kilometers in an outing. With their binoculars, surveyors can also effectively see birds 150 metres away. Of course, as mentioned above, there would be no birds in the 100 m nearest the surveyor. Thus, an effective daily ground track for a human surveyor can be estimated to be (150 m – 100 m) x 3000 m or 150,000 m2.
Resolution: Within 150 metres, a bird surveyor can see birds very clearly and will have little trouble identifying their species. Small, medium and large seabirds are all expected to be identifiable.