North American Raptor Monitoring
Strategy
NOTE TO CONTRIBUTORS: PLEASE FOLLOW THIS
OUTLINE GENERALLY. IF THERE ARE ADDITIONAL TOPICS RELATIVE TO YOUR
SPECIES, EXPAND THE OUTLINE TO ACCOMMODATE THEM.
Loren W. Ayers, Philip F. Schempf,
and Stanley H. Anderson
Introduction
Merlins (Falco columbarius) are
widely distributed throughout North America during the breeding
season. Their range includes portions of the intermountain West,
the northern Great Plains, and the entire boreal forest region of
the United States and Canada. Merlin populations are difficult to
monitor due to a variety of problems including; species (and subspecies)
identification, low density of breeding pairs, low detection rates,
improper timing of current survey efforts relative to merlin breeding
phenology, and the wide variety of habitats they utilize. In the
past, population monitoring has relied almost solely on the Breeding
Bird Survey and migration counts; however, trend estimation and
interpretation of these data can be problematic, especially if subspecific
analyses are desired. Numerous localized field studies have addressed
population issues, especially in Saskatchewan (Sodhi et al. 1993),
Alaska (Laing 1985, USFWS unpubl. data), and to a lesser extent,
the Great Lakes region (Solinski 1996) and Wyoming (Ayers and Anderson
1998). In this account we evaluate existing datasets and methodologies
and identify a standardized, population monitoring approach specifically
tailored for Merlin populations throughout North America.
Species Characteristics
Subspecies and Subpopulations. Three distinct
subspecies of the merlin occur in North America. This includes the
taiga merlin (F. c. columbarius), which inhabits the boreal
and northern forest regions of North America, the black merlin (F.
c. suckleyi), which inhabits coastal coniferous forest in Canada
and Alaska, and the prairie merlin (F. c. richardsonii),
which is found in the northern prairies and aspen parklands of north
central United States and Canada (Fig. 1). F. c. columbarius is
the most broadly distributed of the subspecies, inhabiting the entire
longitudinal breadth of North America (Fig. 2).
Figure 1. Breeding distributions of the three North
American subspecies of merlin (F. c. columbarius, richardsonii,
and suckleyi).
Figure 2. Suspected wintering distributions of the
three North American subspecies of merlin (F. c. columbarius, richardsonii,
and suckleyi).
Annual Activity Budget
NOTE TO CONTRIBUTORS: In the following sections, up to Population
Monitoring, do NOT "rehash" general species’ life
histories; rather, cite comprehensive material such as Palmer’s
Handbook (1988) and The Birds of North America Series (e.g., Sodhi
et al. 1993 for the merlin). Biology, behavior, ecology, etc., used
under the topics below must be DIRECTLY relevant to monitoring!
Breeding Season Distribution, Timing, and
Habitat
Breeding season distribution
by subspecies
a. State/provincial Atlases
b. Literature – text accounts and/or additional
maps
Specific,
breeding season schedule
a. Starting & ending dates
– isocline map, and or tables, but convey differences in
timing associated with latitude, elevation, etc.
b. Daily activity budget - Incubation,
hunting, nest defense, intra-pair interaction, etc.
FOCUS ON: what time(s)
are birds most readily detected?
Habitat associations
Breeding Season Survey –relative probabilities
of detectability, and other factors affecting surveys, based on
habitats and behaviors throughout breeding season.
SUMMARIZE HOW TOPICS
ABOVE AFFECT ABILITY TO SURVEY AND THUS, MONITOR THE SUBSPECIES,
THROUGH THEIR GEOGRAPHIC RANGES, DURING THE BREEDING SEASON.
Migration Season Distribution, Timing, and
Habitat
Migration routes and timing
a. Literature – text accounts
and/or additional maps
b. Observations
c. Band recoveries
d. Telemetry
Habitat associations
Migration Season Surveys –relative probabilities
of detectability, and other factors affecting surveys, based on
habitats and behaviors throughout migration.
SUMMARY OF HOW EACH TOPIC
ABOVE AFFECTS ABILITY TO SURVEY AND THUS, MONITOR THE SUBSPECIES,
THROUGH THEIR GEOGRAPHIC RANGES DURING MIGRATION SEASONS.
Winter Season Distribution, Timing, and Habitat
Winter season distribution
a. Literature – text accounts
and/or additional maps
b. Observations
c. Band recoveries
d. Telemetry
Habitat associations
Winter Season Surveys –relative probabilities
of detectability, and other factors affecting surveys, based on
habitats and behaviors throughout winter.
SUMMARY OF HOW EACH TOPIC ABOVE AFFECTS ABILITY
TO SURVEY AND THUS, MONITOR THE SUBSPECIES, THROUGH THEIR GEOGRAPHIC
RANGES, DURING THE WINTER SEASON.
If a species has substantial range outside
the North America continent, note this. If it is known that important
issues relevant to a species status occur outside the North America
continent, note these and relevant monitoring considerations for
that area (e.g., the contaminants threat to the majority of adult
Swainson’s hawk, which spend the austral summer in central
Argentina).
Evaluate usefulness of various survey methodologies
to adequately monitor status and trend(s) of Merlin populations
in North America. This includes effectiveness of conventional means,
(e.g., Breeding Bird Survey, Christmas Bird Counts) as well as species-specific
studies conducted to date.
EVALUATE APPROPRIATE EXAMPLE
(S) OF SPECIES SPECIFIC SURVEY(S) AND RESULTS IN THE SECTIONS
BELOW. THE EVALUTIONS SHOULD BE BASED ON THE FOLLOWING GENERAL
CRITERIA:
GEOGRAPHIC (SPECIES’
RANGE IN NORTH AMERICA) COVERAGE AT TWO BASIC SPATIAL SCALES:
1) THE NORTH AMERICAN CONTINENT AS FAR SOUTH AS THE SUBTROPICAL
FORESTS OF MEXICO, AND 2) THE NORTH AMERICAN
BIRD CONSERVATION REGIONS. IF THERE ARE SURVEYS DONE AT
A MORE LOCAL (i.e., SMALLER SPATIAL SCALE) SCALE THAT LIKELY
COULD BE APPLIED AT THE BROADER SCALES, EVALUATE THEM AND PRESENT
YOUR RECOMMENDATIONS.
COVERAGE BY SEASON;
ADEQUATE DATA TO TEST FOR A
TREND AND ACHIEVE THE POWER CRITERIA SPECIFIED.
IDENTIFY SHORTCOMINGS, THEN THE
SURVEY METHODS, SAMPLING ALLOCATION NEEDED TO PROVIDE A REPRESENTATIVE
SAMPLE FOR GEOGRAPHIC AND SEASONAL SURVEYS THAT MEET THE STATISTICAL
CRITERIA TO BE APPLIED:
Ensure the ability to detect
a 50% reduction in the count or index over a 25-year period
with alpha = 0.10 and beta = 0.20. Gould and Lewis (1997) provide
discussion material about the use of such criteria as applied
to the counts of migrant raptors, and that material is a useful
focus for further consideration
Sampling Adequacy
1. Definition of trend
a. Unit of measure / response
variable
A SIGNIFICANT CHANGE
IN THE COUNT PER YEAR; ULTIMATELY COMPARED TO A SIGNIFICANT
CHANGE IN THE COUNT BASED ON ABOVE STATISTICAL CONSIDERATION.
b. Time frame
STATE TIME FRAMES OF
EXISTING DATA BASES
c. Extent of change
STATE AMOUNT OF CHANGE,
THE TREND, REVEALED BY THE EXISTING DATA AND ANALYSES
2. Power analyses
DETERMINE POWER OF EXISTING DATA AND TESTS
AND COMPARE TO OUR STATISTICAL CRITERIA
3. Sample size considerations
BREEDING SEASON SURVEYS
Breeding Bird Survey
1. National trends
a. Data from BBS homepage
b. Maps
2. Regional trends
a. Bird Conservation Areas (for
most species, even subspecies, you might need to pool surveys
from more than one region to meet statistical criteria)
b. Political boundaries
c. Subspecies
3. Statistical Adequacy
a. Sample sizes
b. Beta level (% change detectable)
c. Power
4. Overall effectiveness
a. Literature comments
b. Sources of error / problems
1. BBS timing, merlin breeding
phenology
2. Species identification error
3. Lacking coverage –
by subspecies
c. Statistical summary
d. Final recommendation
Nest Surveys
1. Breeding population size
a. Counts vs. estimates
b. Statistical adequacy
1. Sample sizes
2. Beta level (% change detectable)
3. Power
2. Reoccupancy and reproductive success
a. Data needed for baseline
b. Resurvey methodology - feasibility
of repeated studies
c. Results -
3. Demographic modelling
a. Productivity data
b. Mortality data
c. Examples if available
4. Conclusions, all breeding season surveys
a. Population trend with available
data
b. Statistical Adequacy
1. Area of inference
2. Sample sizes
3. Beta level
4. Power
5. Overall effectiveness
a. Literature comments
b. Sources of error / problems
c. Statistical summary
d. Final recommendation
MIGRATION SEASON SURVEYS
Migration Counts
1. Distribution
a. Observations & counts
b. Band recoveries
2. National population trends
a. Plot stations relative to
species distribution
b. Present data from select stations
3. Regional population trends
a. Bird Conservation Regions
b. Political boundaries
c. Subspecies
4. Statistical Adequacy
a. Area of inference
b. Sample size
c. Beta level (% change detectable)
d. Power
5. Overall effectiveness
a. Literature comments
b. Sources of error / problems
1. Unknown source population
and/or destination
2. Subspecies identification
3. Visibility bias
4. Low sample size
c. Statistical summary
d. Final recommendation
WINTER SEASON SURVEYS
Christmas Bird Count
1. National trends
a. Data sources
b. Maps
2. Regional trends
a. Bird Conservation Regions
b. Political boundaries
c. Subspecies
3. Statistical Adequacy
a. Sample sizes
b. Beta level (% change detectable)
c. Power
4. Overall effectiveness
a. Literature comments
b. Sources of error / problems
1. Low detection rates
2. No coverage Central &
South America
c. Statistical summary
d. Final recommendation
Other Surveys
1. Roadside counts
2. Feeder Watch
3. Roost Counts
4. Etc.
SUMMARY
1. Overview
a. Existing methods
b. Existing databases
2. Final survey recommendation
a. Monitoring method(s) chosen
b. Justification
c. Feasibility
d. New data and methodologies
needed
e. Action plan & General recommendations
Does recommended method(s)
work for other species in the range of the species addressed in
this account?
Literature Cited
Appendices
Tables
Figures
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