Aural detections and conventional distance sampling

[Eleonora Milea]

Hi,

Does anyone know if aural detections of birds can be considered when using conventional point transect sampling?? Or is it not possible because assumptions would not hold?

Thanks

Eleonora

[Tiago Marques]

Hi Eleonora,

No problem at all in using those, provided you can get distances to the place where the animal was singing from. Arguably that is harder to do than with visual detections, so measurement error might be an issue. There is literature on that. And if the animals often move without you noticing and then relocate to some different place and you record it as a different bird you will naturally end up with positive bias in density. The duration of your point count should be a balance between detecting all animals at the point (to ensure the g(0)=1 assumption) and short enough that undetected movement is not an issue. Many potential problems arise, but there are dozens of papers out there just based on aural detections, namely on dense forest birds.

Cheers,

Tiago

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[Eleonora Milea]

Hi Tiago, 

Thank you for your reply. 

So this would mean that I do not necessarily need to consider cue rate when using aural detections?

You mentioned there is literature that covers the issue of accurate distance measurements when using aural detections. Would you be able to provide with a link for this?

Thanks again,

Eleonora

[Eric Rexstad]

Eleonora

Stepping in to relieve Tiago, here is the measurement error reference by the man himself

Marques, T. A. (2004). Predicting and correcting bias caused by measurement error in line transect sampling using multiplicative error models. Biometrics, 60(3), 757–763. https://doi.org/10.1111/j.0006-341X.2004.00226.x

and another

Camp, R. (2007). Measurement errors in Hawaiian forest bird surveys and their effect on density estimation (Technical Report HCSU-005). Hawai’i Cooperative Studies Unit. University of Hawai’i at Hilo.

Regarding cue rate, you have two options:  if you believe the animal movement issue Tiago described is trivial, then you do not need to perform a cue counting survey where you measure density of cues then convert to density of animals via the cue rate that needs to be estimated.  Alternatively, if you believe animal movement to be problematic, then take the cue rate survey approach.  The cue rate survey and analysis is more complex because it is trying to overcome the problem induced by animal movement.

To view this discussion on the web visit https://groups.google.com/d/msgid/distance-sampling/1e2aeb19-ab89-4f3e-88ff-af7b2624468bn%40googlegroups.com.

-- 
Eric Rexstad
Centre for Ecological and Environmental Modelling
University of St Andrews
St Andrews is a charity registered in Scotland SC013532

[Eleonora Milea]

Great, all clear now! Thank you both for your help. 

Eleonora