Nest encounter histories; found during laying & other Q's

questions concerning analysis/theory using program MARK

Nest encounter histories; found during laying & other Q's

Postby alae_ula » Sat Mar 05, 2022 5:48 pm

Hello,

I have read through Chapter 17 in the Gentle Introduction book and have run a few nest survival analyses in MARK recent months but now that I'm about to run my full nest survival analysis I'm combing back through my dataset and have a couple of specific questions about the encounter history dates specifically. I keep coming back to the idea that the DSR is calculated based on the typical incubation period for your species (i.e. when you raise your DSR to the power of the # of incubation days), and so I'm worried that if my encounter histories span too long of a period, the calculations will be incorrect or less accurate?

1) "Day of the nesting season on which the nest was found"

In the species I'm studying, the bird lays one egg per day and then begins incubating full time after the last egg was laid, but I commonly found nests that were still being laid, i.e first I saw one egg, then two, etc. I am only interested in that period of incubation after the last egg has been laid, so do I need to adjust my "find" dates for the nests that I found during laying, to the day that the last egg was laid?

2) "The last day the nest was checked when alive"
3) "The last day the nest was checked"

This seems straightforward enough, but I have some nests that were eventually abandoned by adults after the eggs failed to hatched (i.e. main incubation period is 19-24 days) where the adult was actively incubating the eggs for 26-42 total days, or 2-18 extra days past when the nest should have hatched. For these nests, should I adjust the encounter histories 2&3 so that they do not extend past the 24 maximum days of incubation, under the assumption that the eggs themselves were likely no longer "active or alive" past 24 days, even though the adult was actively incubating.?

Thank you so much for your help!
alae_ula
 
Posts: 2
Joined: Sat Mar 05, 2022 5:13 pm

Rotella

Postby Rotella » Wed Mar 09, 2022 5:41 pm

Based on your note, it seems that you are focused on incubation only. If so, then it seems reasonable to (1) only include data for the incubation stage, (2) trim your observations to begin when incubation has begun or is underway, (3) trim off observations that occur for nests with non-viable eggs after the end of a typical incubation stage, and (4) use the daily survival rate (DSR) that you estimate for the incubation stage to estimate the probability that a nest will survive the entire incubation stage, e.g., DSR raised to the number of days in the incubation stage.

I would also note that if you also have data for the laying stage or nestling stages (may or may not be relevant for your species of interest), you can also include those and estimate the probability of surviving from nest initiation to nest completion, e.g., if DSR is estimated as constant across stages, you can raise DSR to the
appropriate power (number of days it takes to go from nest initiation to nest completion).
Rotella
 
Posts: 72
Joined: Mon Jun 09, 2003 11:32 am

Re: Nest encounter histories; found during laying & other Q'

Postby alae_ula » Tue Apr 05, 2022 5:52 pm

Excellent, thank you so much. I cleared up my confusion with my advisor on Q1, and trimmed off observations that occurred in nests with non-viable eggs.

Appreciate it!
alae_ula
 
Posts: 2
Joined: Sat Mar 05, 2022 5:13 pm


Return to analysis help

Who is online

Users browsing this forum: Google [Bot] and 9 guests