Bird Ecology and Conservation A Handbook of Techniques

periods, but movement studies with shorter time intervals are also possible. Data
from such a study can again be summarized as capture histories, with one history
for each bird in the study. If A and B are two study locations, then we can denote
capture in each location by the location letter and noncapture by 0. Thus, we can
write an example capture history as 0 A 0 A B, denoting a bird that was caught
and released in location A at period 2, not captured at period 3, caught again in
location A at period 4 and caught in location B at period 5 of a 5-period study.
We define the following parameters to model multistate capture–recapture
data:

SiR
probability that a bird alive in location R at sample period iis still

alive and in the study system (consisting of the set of sampled

locations) in period i+1 (note that this survival is again an apparent

or local survival in the sense that its complement includes both

death and permanent emigration from the study system);

ψiRS
probability that a bird alive in location R at sample period ithat

survives in the study system until period i1 is located in

locationSati 1

piR
probability that a bird in location R at period iis recaptured or

resighted during sample period i.

Using these parameters, we can write the probability associated with the example
capture history as:

The bird is initially caught in location A and released at period 2. The bird
is known to survive until period 3 (because it was seen after that period), and the
probability associated with this event is. The bird is not caught in period 3,
hence its location in period 3 is unknown. The probability model for events
occurring between periods 2 and 4 is thus written as a sum of two probabilities
(in brackets) corresponding to the two alternative locations where the bird
could have been in period 3. The bird could have remained in location A the
entire time, , or it could have moved to location B
at period 3 and then back to location A at period 4,.
Regardless of which of the two paths was taken, the bird was caught in location A at
period 4 (associated probability ), survived until period 5 (probability ),
moved from A to B (probability ), and was caught in location B at period 5
(probability ).p 5 B

 4 AB

p 4 A S 4 A

 2 AB(1p 3 B)S 3 B 3 BA

(1 2 AB)(1p 3 A)S 3 A(1 3 AB)

S 2 A

S 2 A[(1 2 AB)(1p 3 A)S 3 A(1 3 AB) 2 AB(1p 3 B)SB 3  3 BA]pA 4 S 4 A 4 ABpB 5

P(0 A 0 A B
release in location A, period 2)

132 |Estimating survival and movement