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The aim of this study is to evaluate how drone surveys compare to other potential methods for monitoring seabird populations in Zeeland. This study will quantify to advantages and shortcomings of using drones with the aid of an experiment. After this evaluation, the drone method will be compared to two established methods: wildlife cameras and traditional ground surveys.
The aim of this study is to evaluate how drone surveys compare to other potential methods for monitoring seabird populations in Zeeland. This study will quantify to advantages and shortcomings of using drones with the aid of an experiment. After this evaluation, the drone method will be compared to two established methods: wildlife cameras and traditional ground surveys.
== Introduction ==
Many seabird populations face existential challenges as their natural breeding and foraging areas shrink in the face of human activity. {{Cite|resource=Resource Hyperlink 00825|name=BirdLife International (2010)|dialog=process-linkwebsite-dialog}} reports that 5% of seabird species are ''critically endangered'', while 28% are ''threatened''. To face this problem the European Commission has put in place the Natura 2000 network. This network consists of “core breeding and resting sites for rare and threatened species” ({{Cite|resource=Resource Hyperlink 00826|name=European Commission, 2019|dialog=process-linkwebsite-dialog}}). The monitoring and censusing of seabird species populations in the Natura 2000 areas will help evaluate the initiative’s effect on restoring seabird populations in Europe. More generally, the bird population counts also provide a proxy measure of ecosystem health, as their high mobility allows them to move from disturbed habitat to more attractive locations ({{Cite|resource=Resource Hyperlink 00827|name=Gelinas, 2018|dialog=process-linkwebsite-dialog}}).


The task of monitoring and inventorying seabird populations, however, can be difficult as traditional bird censusing methods involve sending an experienced surveyor to count, from the ground, the number of individuals and/or nests in a flock. Such methods are time-consuming, costly, and have been noted to be disruptive to birds ({{Cite|resource=Resource Hyperlink 00828|name=Borrelle & Fletcher, 2017|dialog=process-linkwebsite-dialog}}).  
== Scope ==
To help evaluate the viability of using drones for seabird censusing and monitoring, this work makes use of the results of an experiment carried out during the summer of 2019. It must be noted, however, that only one drone model was considered in this study. Moreover, the drone used was an off-the-shelf model on which no attempt of improvement was made. Further, due to flight license restrictions, the drone could only be flown at a maximum of 50 meters.


There is increasing interest in the field of bird population ecology to leverage new technologies to obtain better, cheaper, and/or more frequent data. Specifically, the use of drones as a means of estimating population counts has been explored by many authors (e.g. {{Cite|resource=Resource Hyperlink 00832|name=Sardà-Palomera et al., 2017|dialog=process-linkwebsite-dialog}}, {{Cite|resource=Resource Hyperlink 00831|name=2012|dialog=process-linkwebsite-dialog}}; {{Cite|resource=Resource Hyperlink 00833|name=Chabot, Craik & Bird, 2015|dialog=process-linkwebsite-dialog}}; {{Cite|resource=Resource Hyperlink 00834|name=Dulava, Bean & Richmond, 2015|dialog=process-linkwebsite-dialog}}''';''' {{Cite|resource=Resource Hyperlink 00835|name=Goebel et al., 2015|dialog=process-linkwebsite-dialog}};{{Cite|resource=Resource Hyperlink 00836|name=Ratcliffe et al., 2015|dialog=process-linkwebsite-dialog}}; {{Cite|resource=Resource Hyperlink 00837|name=Rümmler et al., 2015|dialog=process-linkwebsite-dialog}}; {{Cite|resource=Resource Hyperlink 00838|name=Chabot & Bird, 2012|dialog=process-linkwebsite-dialog}}).
Finally, the experiment performed to help quantify the performance of the drone as a censusing method only used a small selection of stuffed birds (taxidermy birds) as its subjects. The species of the specimens used only represent a small subset of all the seabird species which forage on the tidal flats of Zeeland. However a range of size and colors was used to select the species in question. 
 
Questions remain as to whether drone surveys cause less disturbance to bird populations than do traditional ground surveys. There is evidence that, for certain applications, drones can have little to no disturbance when compared to ground surveys (e.g. {{Cite|resource=Resource Hyperlink 00832|name=Sardà-Palomera et al., 2017|dialog=process-linkwebsite-dialog}}, {{Cite|resource=Resource Hyperlink 00831|name=2012|dialog=process-linkwebsite-dialog}}).
 
Other studies, however, have shown that the use of drones can cause subjects to become disturbed and vigilant (Rümmler et al., 2015).
 
The question of whether drones cause significant disturbance to birds is also complicated by the fact that most of the available insight on the question has come from studies on nesting bird colonies (e.g. {{Cite|resource=Resource Hyperlink 00833|name=Chabot, Craik & Bird, 2015|dialog=process-linkwebsite-dialog}}; {{Cite|resource=Resource Hyperlink 00836|name=Ratcliffe et al., 2015|dialog=process-linkwebsite-dialog}}; {{Cite|resource=Resource Hyperlink 00831|name=Sardà-Palomera et al., 2012|dialog=process-linkwebsite-dialog}}). Nesting birds have less of a tendency to flee or to flush because they have a vested interest in protecting their nests and eggs. This fact is important because flushing behaviour is the primary outward signs of disturbance and the one most often used to measure disturbance. This protective behaviour of breeding birds may bias the results of studies attempting to answer the question of whether drones cause significant disturbance to birds.
 
Intertidal flats are important feeding grounds for migratory and permanent seabird populations. The southern Dutch province of Zeeland has the particularity of having the entirety of its intertidal zones included in the Natura 2000 network. The monitoring and censusing of permanent and migratory seabird population in the Zeeland intertidal flats therefore represent an important step in the assessment of seabird health throughout the Natura 2000 network.
 
Further, most studies (e.g. {{Cite|resource=Resource Hyperlink 00832|name=Sardà-Palomera et al., 2017|dialog=process-linkwebsite-dialog}}, {{Cite|resource=Resource Hyperlink 00831|name=2012|dialog=process-linkwebsite-dialog}}; {{Cite|resource=Resource Hyperlink 00833|name=Chabot, Craik & Bird, 2015|dialog=process-linkwebsite-dialog}}; {{Cite|resource=Resource Hyperlink 00835|name=Goebel et al., 2015|dialog=process-linkwebsite-dialog}}; {{Cite|resource=Resource Hyperlink 00836|name=Ratcliffe et al., 2015|dialog=process-linkwebsite-dialog}}; Rümmler et al., 2015; Chabot & Bird, 2012) in this area have focused on counting individuals in flocks or colonies of a single species. Intertidal flats, however, often host multiple species of seabirds (e.g. sandpipers, oystercatchers, spoonbills). Therefore, when monitoring seabirds feeding on intertidal flats, it is necessary to not only count the birds, but also to identify their species. {{Cite|resource=Resource Hyperlink 00834|name=Dulava, Bean and Richmond (2015)|dialog=process-linkwebsite-dialog}} explored the possibility of using drones to distinguish between waterfowl species. They concluded that image resolutions could be no coarser than about 5 mm if the waterfowl species were to be distinguished. Such a resolution requirement for species identification in drone surveys is quite high and would require lower flight altitudes than single-species drone surveys.
 
The viability of using drones to monitor seabird populations on intertidal flats is then hinged on the question of whether it is possible to obtain imagery of sufficiently fine resolution to identify the species of seabirds at a flight altitude which does not disturb the subjects.


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Huidige versie van 12 nov 2020 om 16:31

The aim of this study is to evaluate how drone surveys compare to other potential methods for monitoring seabird populations in Zeeland. This study will quantify to advantages and shortcomings of using drones with the aid of an experiment. After this evaluation, the drone method will be compared to two established methods: wildlife cameras and traditional ground surveys.

Scope

To help evaluate the viability of using drones for seabird censusing and monitoring, this work makes use of the results of an experiment carried out during the summer of 2019. It must be noted, however, that only one drone model was considered in this study. Moreover, the drone used was an off-the-shelf model on which no attempt of improvement was made. Further, due to flight license restrictions, the drone could only be flown at a maximum of 50 meters.

Finally, the experiment performed to help quantify the performance of the drone as a censusing method only used a small selection of stuffed birds (taxidermy birds) as its subjects. The species of the specimens used only represent a small subset of all the seabird species which forage on the tidal flats of Zeeland. However a range of size and colors was used to select the species in question.