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Research
 Interim
Report
Feb 1998
(752k)
Interim
Report
(232k)
More
info about
Marbled Murrelets
PNW
Funded Projects
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PNW
Project Overview 1997
Evaluation
of the Marbled Murrelet Inland Forest Survey Protocol (IFSP) with Radar
Principal
Investigator:
Brian Cooper, ABR,
Inc.
Awarded: $42,947
Project
Description:
This
study uses radar techniques to evaluate Inland Forest Survey Protocol
(Ralph et al. 1994) for marbled murrelets. The null hypothesis for this
project is: There is no difference in number of radar targets observed
using a stand and a number of audiovisual detections of murrelets in that
stand. The project is a continuation of a study funded by ONRC in 1996,
and builds upon data collected in 1997. In addition to increasing sample
sizes, multiple years of data are necessary to determine if the wide
annual variation in terrestrial survey counts of murrelets is related to
actual changes in number of murrelets at inland stands, or if variation
reflects other changes (e.g., changes in flight behavior or calling
rates). Establishing the
cause of these variations affects the proportion of audiovisual detections
to actual number of murrelets. Results from the study will be used to
continue to analyze the problems and effectiveness of the survey protocol
so that managers and biologists have a better understanding of what the
numbers derived from the standard survey protocol actually mean in terms
of numbers of murrelets using a particular timber stand.
Objectives:
The goal of this research is to evaluate the terrestrial survey protocol
by comparing the results of concurrent radar surveys. The specific
objectives of the study are to:
-
Evaluate the relationship between detection rates and numbers
of murrelets and develop an error rate or correction factor for the
terrestrial survey counts;
-
Measure the proportion
of murrelets that fly into a stand before audiovisual detections begin
to occur (these may be the breeding birds of primary interest);
-
Assess the proportion
of murrelets that are double-counted as they circle or fly over the
stand;
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Measure the proportion
of murrelets that are detected by the audiovisual observers that fly
over a survey stand and then continue on to another stand;
-
Begin
to determine the effects that weather, time of year and time of day
have on the aforementioned proportions and relationships.
Project
Status:
ABR,
Inc. submitted a final report for this project in December 1998.
Final
report abstract:
There
was substantial among site and among day variation in the proportion of
Marbled Murrelets that audio-visual observers detected during IFSP
surveys. Further, the
relationship between radar counts and numbers of audio-visual detections
at a site was weak but significant (r2 = 0.39).
Establishing a correction factor for audio-visual counts is not
recommended because of the large variation among sites and days in the
detection of murrelets. Results of this project suggest that the
current IFSP calling for 4 surveys in 2 years to determine
presence accurately is inadequate in stands with low densities of
murrelets. Further, because only approximately 15% of all audio-visual
observations are visual and because it may take several visual
observations before an “occupied” sub-canopy behavior is observed, the
current IFSP of 5 surveys/year for 2 years is also inadequate for
accurately determining occupancy in stands with low breeding densities of
Marbled Murrelets.
This
study has provided some of the first quantitative evidence of the
limitations of the Inland Forest Survey Protocol for Marbled Murrelets.
These limitations notwithstanding, however, the IFSP still may be
the most practical technique for determining whether or not a stand is
occupied by Marbled Murrelets. The
data suggest that, although it is possible for the audio-visual observers
to record birds at a stand incorrectly, it is far more likely that
audio-visual observers will miss birds at a stand.
One obvious way to improve the probability of detecting birds is to
increase the number of survey visits to a stand.
Efforts to determine the appropriate number of surveys to detect
stand occupancy with high accuracy are ongoing.
ONRC has funded this research in 1998 and
1999.
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