Distance sampling using point transects in half a circle

[agoro...@gmail.com]

Dear all,

My name is Antonella from Argentina. I am working with a set of data of bird species using point transects. I have experience in working with Density Surface Models and line transects, but not with point transects.

In this case, I want to apply a Hierarchical Distance Model in R for each surveyed species to estimate the abundance of each one considering the effect of different habitats and seasons in a semi-urban area. Points were randomly distributed in each habitat and each season. However, the observations were done only in half a circle of each point, because in most cases there were buildings.

I was wondering if there is a way to analyze this data using Distance, considering only a half-circle to model the detection probability. For the abundance estimation, I was thinking of including the surveyed area of each point as half the circle area. Also, it would be very helpful if you could recommend me some papers or examples for me to follow.

Thank you in advance for your help

Best regards,

Antonella

Dra. Antonella Gorosábel

Becaria doctoral CONICET

Grupo de Recursos Naturales y Gestión Ambiental, IPADS INTA-CONICET, Balcarce, Argentina

gorosabel...@inta.gob.ar

agoro...@gmail.com

[Eric Rexstad]

Antonella

The Distance R package does not perform hierarchial distance sampling to model point-specific estimates of abundance.  However it can accommodate point transect sampling in which only a portion of the disks surrounding the stations are able to be sampled.  That is accomplished by specifying the Effort field associated with each point transect the proportion of the disk that is sampled.

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[Len Thomas]

Antonella,

Further to Eric's message, there is a point transect density surface
modelling example (using the dsm package in R) at

https://examples.distancesampling.org/

(direct link to this particular example is

https://examples.distancesampling.org/dsm-point/hare_point_transect_dsm-distill.html

). That example uses only spatial coordinates (x, y) as spatial density
covariates, while it sounds like you have additional/alternative
potential covariates such as habitat and season - but this works just
the same was as for line transect analyses so hopefully your experience
there will be helpful.

With best wishes, Len

On 21/04/2021 20:02, 'Eric Rexstad' via distance-sampling wrote:
> Antonella
>
> The Distance R package does not perform hierarchial distance sampling to
> model point-specific estimates of abundance.  However it can accommodate
> point transect sampling in which only a portion of the disks surrounding
> the stations are able to be sampled. That is accomplished by specifying
> the Effort field associated with each point transect the proportion of
> the disk that is sampled.
>

> Get Outlook for Android <https://aka.ms/AAb9ysg>
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> <distance...@googlegroups.com> on behalf of agoro...@gmail.com
> <agoro...@gmail.com>

> *Sent:* Wednesday, April 21, 2021 5:03:32 PM
> *To:* distance-sampling <distance...@googlegroups.com>
> *Subject:* {Suspected Spam} [distance-sampling] Distance sampling using

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[Antonella Gorosabel]

Dear Eric and Len, 

Thank you very much for your answers. 

Indeed, I will run the hierarchial distance sampling with the unmarked package, not the distance one. 

I will specify the effort associated with each point transect and check the DSM examples!

Thank you again

Best wishes

Antonella

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