Community-level density estimate

[Stefanny Sirleg Villagomez Palma]

Hi, 

I have been working on calculating the density of a terrestrail bird community and want to see how it changes during different times of the year (spring and fall). First, I separated the birds into groups and assessed whether detection probabilities were similar across the groups I assigned (e.g., sparrows, warblers), and then I used those groups as covariates. However, for some species, detections were very few, so I decided to keep only those species with a sufficient number of detections that together represented more than 50% of the total detections. The models improve significantly when species are included as covariates, since detection probabilities vary among species, but I would like to know whether there is a better way to estimate community-level densities.

Another question is that within my study area, there are points with zero detections. I think it's important to consider these points when estimating true density. I created the sample table, including all points, even those with no detections, and an observation table with only the detected individuals and their distances. Is there a different way to account for this?

Thank you very much in advance for your help. 

Best