MSc thesis: Are nest boxes a viable conservation method for black guillemots?
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| Black Guillemot |
Background and rationale
Provision of nest boxes is a relatively new concept for seabirds and has only being trialled for a handful of species, primarily petrals and shearwaters. Most species of seabird nest colonially on cliff faces so this method is only suitable for cavity nesting species. Black guillemots are one such species and although their population in the is UK is relatively stable, it is still amber listed as population numbers are lower than in past years (about 30 years ago).
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| Black guillemot at artificial nest cavity at Bangor Marina |
Artificial nests have been successfully utilised by this species at Bangor marina but there have been no other reports for this species. As one of the main limiting factors for this species is suitable nest sites, nest boxes have the potential to increase breeding numbers so this study aims to evaluate whether they can be used on the Isle of Arran?
Method
Nine nest boxes were put up for black guillemots on the Isle of Arran, Scotland, for the first time in February 2016. These were monitored during the breeding season (May-August) for signs of nesting. Natural black guillemot nests were also located and habitat data was collected and compared to unoccupied cavities to determine preferences. This habitat data included height of nest from ground, height of cavity, width of cavity, depth of cavity and percentage of vegetation cover at cavity entrance.
These nest boxes were not occupied. In terms of preferences, evidence suggests that depth of cavity is the most important factor and these birds prefer cavities at least 50cm deep. There was a statistically significant difference in all the habitat features between the natural nests and the nest boxes. Although this suggests these nest boxes aren't suitable, there was a large amount of variation in this habitat data with some values from the natural nests being very similar to the nest boxes. This indicates that these nest boxes can be used but were not chosen by this population. The most likely reason for this is that there were sufficient natural nests available, as demonstrated by the presence of surplus unoccupied cavities.
Conclusion
These nest boxes should continue to be monitored and additional nest boxes should be placed in areas where natural nest sites are limited, e.g. piers around the island. This method is a viable conservation method for this species, but the placement of these nest boxes should be carefully considered in order to improve the likelihood of success.
Undergraduate dissertation: What factors cause variation in flight-initiation distances in birds?
What? Human Disturbance
Human disturbance of wildlife has increased over the years, namely due to an increase in human populations, a rising interest in the natural world and easier access to habitats e.g. through the Right of Way Act. My research project focuses on the effect of human disturbance on bird species.
How? Flight-Initiation Distance
I have chosen to use 'flight-initiation distance' (FID) (the distance at which a bird flies away when approached by a human) as an indicator of disturbance and have collected data on a variety of different bird species, both personally in the field and from the literature.
FID is a simple measurement but the reasons why it may vary (i.e. you can get closer to some birds compared to others) between bird species is more complicated to answer. It may be a species specific trait (all members of a species have a similar FID) or could be affected by habitat, sociability (e.g. alone or in colonies), diet, body mass or brain size.
Why? Conservation applications
All these factors are going to be analysed and if there is a relationship then FID could potentially be predicted for birds, e.g. perhaps larger birds fly away at a larger distance. This could be applied to conservation as humans can be prevented from accessing birds at a certain distance (e.g. through the use of fences) which can help minimise disturbance. This is important as research has indicated that human disturbance can have a negative impact on species, such as reducing their foraging and breeding success and this protection could be crucial for more vulnerable species (e.g. endangered).
I will keep this page updated with significant results (if there is any!) and some interesting articles on this subject. I hope you all find it interesting!
Results
Body mass
One of the most statistically significant result is that larger birds have higher FIDs (i.e. they fly away at a larger distance).
Why?
- They may detect predators earlier due to larger eye and brains sizes that correlate with body mass
- It may take them more time to take flight so therefore start earlier
- Larger birds expend less energy in flight than smaller birds so it doesn't cost them as much to take flight
- They are more vulnerable to predators as they are detected easier
Habitat
Those birds in open, wetland habitats had higher FID's than those in closed habitats such as woodland.
Why?
- Increased visibility in open areas means that predators are detected quicker
- Those birds in wetland habitats may decide to enter the water as an escape to ground predators instead of flying away
Diet
Carnivorous species had the highest FID, followed by omnivores then herbivores.
Why?
- Carnivores are likely to be more attentive to movement as they prey on mobile species so therefore may detect predator movement quicker.
Sociability
This produced more of a variable response so I consulted the literature to examine what possible outcomes that sociability could produce on FID
Large groups
- Higher FID: due to the fact that there are more birds to detect predators.
- Lower FID: there is a dilution of predation risk as there is more prey available to predators. Also, birds may also be less likely to flee as they are likely to be aggregated at an area with good resources (e.g. food) so it may benefit them more to stay.
These are the conclusions I have drawn but there could be many possible reasons to explain these results, animals are unpredictable after all! I hope that these general trends are investigated further to produce more conclusive results that can contribute to the protection and conservation of a variety of bird species.
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