Questions Flashcards
What do you mean by rich and eclectic avifaunal assemblages?
- Borneo has more frogmouths, trogons, hornbills, barbets, broadbills, pittas, flowerpeckers, and spiderhunters than of any place in the world.
- More endemic species than any other Sundaic landmass (Java, Sulawesi, Sumatra)
Why did you choose species richness as your diversity metric?
- broad preliminary exploratory investigation
- comparative element
- simple
- limited time, funding and expertise: need efficiency
- ignores evenness, dominance and functionality
Why did you choose to add directionality to your third hypothesis?
Beginning to narrow the preliminary investigation.
What are the advantages of a point count methodology?
- good for a closed sites
- not restricted to breeding season
- easy to randomly allocate
- efficient
- non-intrusive
What are the disadvantages of a point count methodology?
- need more investigators for 20; camera-trapping equipment
- not good for skulking or highly mobile birbs
- rain
- time spent travelling between point count stations
- detectability
- assumes sampling of constant proportion across time and space
Why does a change in abundance or diversity imply flight behaviours?
Change in abundance means birds have flown away. Change in diversity means that there a fewer species present in the assemblage. This would imply that a select set of species may have flown, which led to my third hypothesis.
What is a bias?
systematic error that distorts your estimate, resulting in skew
What is a limitation?
restricts the scope of the study, resulting in less data
When you say “blinding” your experiment, what do you mean?
In our experiment, the identity of the treatment, and the hypotheses for which this treatment was being applied, was known to those conducting the sample. Hence, there could have been subconscious effects on sampling effort. Blinding this sample would either mean having the investigators wear headphones during the call, though this would tradeoff with auditory identification capacity, or by having different investigators generate the hypotheses and conduct the samples.
What is a logistic regression and how did you implement it?
A logistic regression is used to assess the probability of a binary event occuring – in this case; response. I partioned the responses within our dataset as flying, or remaining, based on the independent variable of distance away from stimulus. This adds a complicating factor, covariate.
How would you run that suggested experiment at the end?
To test for whether opening up landscapes would result in predation of closed-habitat birds, you could do the following:
Question: are birds adapted to closed-habitat more at risk of predation when habitats are opened at logging
Conservative null hypothesis: no
Alternative hypothesis: yes
Methodology: assign a list of “closed-habitat adapted” birds. Measure the abundance of these species’ using species-specific distance model point count surveys. Compare the abundance is closed and recently opened environments – are they different? Maybe compare the abundance of predators too? You would expect no change.
How do you think detectability may have played a role in your experiment?
Detectability is a key component of distance modelling. Different birds exhibit different detectabilities with regards to their colouration, vocalisation, time of point count, time within season and habitat type. Moreover, this is not constant across time. Using distance functions can allow calculations of the decay of identification with distance. However, distance functions require a high degree of distance estimation accuracy by the observers. For example, our open and closed sides would have showed different detect abilities. For this, we introduced preliminary distance modelling by introducing boundaries at 50m; Q3 of our open sites.
What are the key assumptions of distance methods?
- all birds actually at the counting station are recorded (for cryptic and shy species this might not be true)
- point count stations are systematically located
- birds do not move in response to the observer prior to detection
- distances are measured without error
- detection curve has a shoulder: detection rates are higher closer to the observer but fall away with distance (this was true in our case)
Further improvements?
- go back and repeat in a different season (early and late breeders, seasonal variation of detectability and migration behaviours)
- use an open habitat predator to recapitulate [look for one]
Explain the importance of distance sampling:
Distance sampling models the ‘distance function’ and estimates density taking into account both the birds that were observed and those that were present but were not detected. The distance function differs among species, observers and habitats.
