The combined mark-recapture and line transect sampling methodology proposed by Alpizar-
Jara and Pollock [Journal of Environmental and Ecological Statistics, 3(4), 311–327, 1996; In
Marine Mammal Survey and Assessment Methods Symposium. G.W. Garner, S.C. Amstrup,
J.L. Laake, B.F.J. Manly, L.L. McDonald, and D.C. Robertson (Eds.), A.A. Balkema,
Rotterdam, Netherlands, pp. 99–114, 1999] is used to illustrate the estimation of population size
for populations with prominent nesting structures (i.e., bald eagle nests). In the context of a bald
eagle population, the number of nests in a list frame corresponds to a ‘‘pre-marked’’ sample of
nests, and an area frame corresponds to a set of transect strips that could be regularly monitored.
Unlike previous methods based on dual frame methodology using the screening estimator
[Haines and Pollock (Journal of Environmental and Ecological Statistics, 5, 245–256, 1998a;
Survey Methodology, 24(1), 79–88, 1998b)], we no longer need to assume that the area frame is
complete (i.e., all the nests in the sampled sites do not need to be seen). One may use line transect
sampling to estimate the probability of detection in a sampled area. Combining information
from list and area frames provides more efficient estimators than those obtained by using data
from only one frame. We derive an estimator for detection probability and generalize the
screening estimator. A simulation study is carried out to compare the performance of the
Chapman modification of the Lincoln–Petersen estimator to the screening estimator. Simulation
results show that although the Chapman estimator is generally less precise than the screening
estimator, the latter can be severely biased in presence of uncertain detection. The screening
estimator outperforms the Chapman estimator in terms of mean squared error when detection
probability is near 1 wheareas the Chapman estimator outperforms the screening estimator when
detection probability is lower than a certain threshold value depending on particular scenarios
