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Management Implications of Molt Migration by the Atlantic Flyway Resident Population of Canada Geese, Branta canadensis

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Abstract

We used satellite-tracked transmitters in 2001 and 2003 to document the timing, location, and extent of molt migrations by female Canada Geese (Branta canadensis) affiliated with the Atlantic Flyway Resident Population (AFRP) of Canada Geese that breed in the temperate region of eastern North America. Twenty-seven adult females were captured during the nesting period in late May and fitted with a satellite transmitter mounted either on a plastic neck collar or backpack harness. Nests of 24 birds were destroyed late in incubation to prevent renesting and ensure nest failure; three females did not have nests. Twelve of the 27 birds (44%) made a northward migration to molt in northern Quebec, Canada: seven to the eastern coast of Hudson Bay (58°12'N, 76°60'W), three to lowland areas east of James Bay (53°30'N, 79°02'W), and two to interior locations south of Ungava Bay (55°54'N, 68°24'W). Molt migrants were present in northern Quebec from June to September, a period that coincides with breeding ground aerial surveys and banding operations conducted for Atlantic Population (AP) Canada Geese that breed in this same region of northern Quebec. With >1 million AFRP geese estimated in the Atlantic Flyway, the potential exists for substantial numbers of yearling, sub-adult, and nest-failed or non-breeding adults to molt migrate to northern breeding areas and bias efforts to survey and mark AP geese. Within AFRP breeding areas, many local flocks have reached nuisance levels. We hypothesized that by inducing molt migration in breeding adults, through destruction of nests late in incubation, we would lessen recruitment, reduce numbers of summer resident adults with young, and increase adult mortality from hunting. However, molt migration behavior was not uniform throughout our study area. Molt migrants were from rural areas in New York, Pennsylvania, and Vermont, whereas marked birds that did not make molt migrations were from more coastal regions of the flyway. The 14 birds that did not make a molt migration remained within 60 km of their banding site. A genetic comparison of these two groups revealed no detectable differences. We conclude that failure to undergo a molt migration is likely attributed to the historical origin of captive-reared birds of mixed subspecies that comprise AFRP flocks in the eastern regions of the flyway and the availability of quality local habitat, distinct from brood-rearing areas, for molting.
313
Canada Geese (Branta canadensis) often undergo a
late spring migration, flying long distances from their
breeding locations to more northerly areas, where they
undergo an annual molt. A form of molt migration,
these movements have been documented for Canada
Geese from both subarctic-nesting populations, which
typically breed in remote areas of northern Canada
(Sterling and Dzubin 1967; Abraham et al. 1999), and
temperate-nesting populations, that breed in southern
Canada and the United States (Zicus 1981; Davis et al.
1985; Lawrence et al. 1998). Birds that undergo a molt
migration are primarily nonbreeding subadults and un -
successful breeding adults (Salomonsen 1968; Law -
rence et al. 1998).
There are two subarctic-nesting populations (Atlantic
Population [AP] and North Atlantic Population [NAP])
associated with the states of the Atlantic Flyway, where-
as temperate-nesting geese are collectively recognized
as the Atlantic Flyway Resident Population (AFRP;
Atlantic Flyway Waterfowl Council 1999*). Because
these populations are mostly indistinguishable when
they mix in the field on migration routes and wintering
locations, their population and harvest management
depends on monitoring efforts directed at their popu-
lation-specific breeding areas. For example, annual
assessments of population size are dependent on spring
aerial surveys of breeding areas. However, movement
of molting groups of temperate-nesting geese from
Michigan to subarctic breeding areas in northern
Canada has been confirmed through monitoring with
satellite-tracked transmitters (Mykut et al. 2004). If
molt migrations by temperate-nesting geese occur while
spring surveys are being conducted on northern breed-
ing grounds, then population estimates for subarctic-
nesting populations can be positively biased by the
inclusion of molt migrants (Abraham et al. 1999).
Management Implications of Molt Migration by the Atlantic Flyway
Resident Population of Canada Geese, Branta canadensis
SUSAN E. SHEAFFER1,6, RICHARD A. MALECKI2,6, BRYAN L. SWIFT3, JOHN DUNN4, and KIM SCRIBNER5
1Department of Natural Resources, Cornell University, Ithaca, New York 14853 USA
2U.S. Geological Survey, New York Cooperative Fish and Wildlife Research Unit, Department of Natural Resources, Cornell
University, Ithaca, New York 14853 USA
3New York State Department of Environmental Conservation, Bureau of Wildlife, Game Bird Unit, 625 Broadway, Albany,
New York 12233 USA
4Pennsylvania Game Commission, 911 Big Spring Road, Shippensburg, Pennsylvania 17257 USA
5Department of Fisheries and Wildlife, Michigan State University, East Lansing, Michigan 48824 USA
6Present address: Livingston Ripley Waterfowl Conservancy, P.O. Box 210, Litchfield, Connecticut 06759 USA
Sheaffer, Susan E., Richard A. Malecki, Bryan L. Swift, John Dunn, and Kim Scribner. 2007. Management implications of molt
migration by the Atlantic Flyway resident population of Canada Geese, Branta canadensis. Canadian Field-Naturalist
121(3): 313-320.
We used satellite-tracked transmitters in 2001 and 2003 to document the timing, location, and extent of molt migrations by
female Canada Geese (Branta canadensis) affiliated with the Atlantic Flyway Resident Population (AFRP) of Canada Geese
that breed in the temperate region of eastern North America. Twenty-seven adult females were captured during the nesting
period in late May and fitted with a satellite transmitter mounted either on a plastic neck collar or backpack harness. Nests of
24 birds were destroyed late in incubation to prevent renesting and ensure nest failure; three females did not have nests.
Twelve of the 27 birds (44%) made a northward migration to molt in northern Quebec, Canada: seven to the eastern coast of
Hudson Bay (58o12'N, 76o60'W), three to lowland areas east of James Bay (53o30'N, 79o02'W), and two to interior locations
south of Ungava Bay (55o54'N, 68o24'W). Molt migrants were present in northern Quebec from June to September, a period
that coincides with breeding ground aerial surveys and banding operations conducted for Atlantic Population (AP) Canada
Geese that breed in this same region of northern Quebec. With >1 million AFRP geese estimated in the Atlantic Flyway, the
potential exists for substantial numbers of yearling, sub-adult, and nest-failed or non-breeding adults to molt migrate to
northern breeding areas and bias efforts to survey and mark AP geese. Within AFRP breeding areas, many local flocks have
reached nuisance levels. We hypothesized that by inducing molt migration in breeding adults, through destruction of nests
late in incubation, we would lessen recruitment, reduce numbers of summer resident adults with young, and increase adult
mortality from hunting. However, molt migration behavior was not uniform throughout our study area. Molt migrants were
from rural areas in New York, Pennsylvania, and Vermont, whereas marked birds that did not make molt migrations were
from more coastal regions of the flyway. The 14 birds that did not make a molt migration remained within 60 km of their
banding site. A genetic comparison of these two groups revealed no detectable differences. We conclude that failure to
undergo a molt migration is likely attributed to the historical origin of captive-reared birds of mixed subspecies that comprise
AFRP flocks in the eastern regions of the flyway and the availability of quality local habitat, distinct from brood-rearing
areas, for molting.
Key Words: Branta canadensis, Canada Geese, molt migration, temperate-nesting, Resident Population, Atlantic Flyway.
11_07034_geese.qxd:CFN 120(2) 11/27/08 6:01 PM Page 313
Similarly, population-specific assessments of harvest
rely on band recoveries obtained from birds marked on
their breeding grounds as flightless adults and young.
In recent years, recaptures on subarctic breeding
grounds of previously banded adults and young from
temperate-nesting areas (Abraham et al. 1999; Nichols
et al. 2004) have raised concern over the potential bias
in the banded samples of subarctic-nesting geese.
Molt migrations of temperate-nesting geese to north-
ern breeding areas can also increase competition for
resources and potentially degrade brood-rearing habi-
tat for subarctic-nesting geese. Previous studies have
demonstrated that a large proportion (50% – 60%) of
temperate-nesting flocks potentially undergo a molt
migration (Zicus 1981; Lawrence et al. 1998). Given
that estimated numbers of temperate-nesting geese cur-
rently exceed 1 million birds in each of the Mississippi
and Atlantic flyways (United States [U. S.] Fish and
Wildlife Service 2007*), the potential problems with
survey efforts and impacts to habitat could be substan-
tial.
Temperate-nesting Canada Geese also are of con-
cern within their breeding range, where they often
occur in areas with few natural predators. Because of
their relatively high survival and stable reproductive
rates, local flocks can rapidly reach nuisance levels in
urban areas and rural areas with low harvest pressure.
Given that some unsuccessful breeders undergo a molt
migration, we reasoned that deliberate nest destruction
late in the incubation period, to ensure nest failure,
would induce these birds to molt migrate. This proce-
dure has the potential to reduce annual recruitment of
young into the population, lessen the number of adults
and young residing in local areas during the summer,
and expose this component of the population to hunt-
ing pressure in other regions when they return in the
fall. Our objective was to assess both the efficacy of
this technique and to monitor the resultant timing, loca-
tions, and extent of molt-migration movements as they
relate to management of AFRP Canada Geese in the
Atlantic Flyway.
Methods
In 2001, eight female Canada Geese were captured
at four locations in New York during late May (Table
1). Nests of five birds were destroyed during the last
7-10 days of incubation; no nests were detected for
three of the eight (Table 1). Each goose was fitted with
a 30 g satellite-tracked transmitter (PTT Model 100,
Microwave Telemetry, Inc., Columbia, Maryland; men-
tion of trade names or commercial products does not
constitute endorsement or recommendation for use by
the U.S. Government) attached dorsally with a harness
constructed of Teflon ribbon. Transmitters had speci-
fications for ~480 hours of battery life and were pro-
grammed to transmit for an eight-hour period every four
days. Expected battery life was about eight months.
We expanded the study in 2002 to include 19 nesting
females captured under similar nesting conditions in
New York (n= 4), Pennsylvania (n = 6), New Jersey
(n = 4), Massachusetts (n = 2), Connecticut (n= 1),
Vermont (n= 1), and Maine (n= 1). To simplify attach-
ment procedures and reduce costs, we switched to trans-
mitters mounted on plastic neck collars produced by
Telonics, Inc. of Mesa, Arizona. Program features were
similar to those used in 2001. Unfortunately, most of
the transmitters deployed in 2002 did not provide
sufficient signals to the satellites to produce usable
locations. The 2002 transmitters were replaced by the
manufacturer and 19 nesting females were marked in
2003: New York (n= 4), Pennsylvania (n= 4), New
Jersey (n = 4), Massachusetts (n= 2), Connecticut
(n= 2), Vermont (n= 1), Maine (n = 1), and Maryland
(n= 1) (Table 1).
Data from the radio transmitters were obtained from
the Argos satellite system of the French Space Agency
via a preferential tariff agreement with the U. S. Depart-
ment of Commerce’s National Oceanic and Atmos-
pheric Administration. Location estimates were classi-
fied by Argos based on their estimated accuracy and
the number of transmissions received from a transmit-
ter during a satellite overpass. Location classes 3, 2, and
1 had accuracy ratings within 1000 m. Accuracy for
location class 0 was >1000 m, and location classes A
and B did not receive enough transmissions during an
overpass for accuracy to be estimated (Service Argos
1996*). However, Britton et al. (1999) demonstrated
that poor locations (classes 0, A, and B) received from
satellite transmitters (30 g) averaged 35 km from the
true location of the transmitter. We therefore included
all locations with a classification of 3, 2, 1, 0, A, or B,
because the accuracy of these classes was sufficient to
describe large-scale movements.
Argos estimated locations by measuring the Doppler
shift of the received signals, which produces two pairs
of latitude and longitude coordinates from an individ-
ual satellite overpass. Argos designates the location
with the better frequency continuity as the most prob-
able location (location 1), and the alternate location is
designated as the image (location 2). Examination of
our data occasionally indicated that sometimes loca-
tion 2 was a more probable fix than location 1 based on
the flight dynamics of Canada Geese. We developed a
sorting routine similar to that of Britton et al. (1999)
that sequentially examined the location pairs to iden-
tify locations that appeared most probable. The initial
location for each bird was the site of banding. For each
subsequent pair of locations, flight speed (distance/hr)
was calculated from location 1 in the previous location
pair to location 1 of the next location pair. If the bird
had flown <65 km/hr to reach both locations 1 and 2,
we selected location 1. If the bird had flown >65 km/hr
to reach location 1, but <65 km/hr to reach location 2,
we selected location 2. If both locations violated our
65 km/hr rule, we deleted both. We retained all loca-
tions with an accuracy classification of 3, 2, and 1.
When an 8-hour transmission period contained only
locations with a classification of 0, A, and B, we esti-
314 THE CANADIAN FIELD-NATURALIST Vol. 121
11_07034_geese.qxd:CFN 120(2) 11/27/08 6:01 PM Page 314
mated one location for that period as the centroid of
the most probable latitude and longitude coordinates.
During the course of our study, we hypothesized that
the differential propensity to undergo a molt migration
could be related to genetic differences among geese
from interior and coastal areas comprising our sample.
In 2004, we attempted to test this by collecting blood
samples from molting adult geese with young in rural
areas of central New York (n= 15) and Pennsylvania
(n= 15) and compared these with similarly collected
samples from more coastal and urban/suburban areas
of Long Island, New York (n= 5), New Jersey (n = 15),
Massachusetts (n= 5), and Connecticut (n= 5). Genet-
ic testing of microsatellite markers and mitochondrial
DNA was done using methods described by Scribner
et al. (2003a).
We used seven microsatellite loci that have previous-
ly been described for Canada Geese for other popula-
tions across North America (Scribner et al. 2003a,
2003b). Loci included TTU-CG-1, TTU-CG-5 (Cathey
et al. 1998) and Bcaµ7, Bcaµ9, Bcaµ11, and Hhi1,
(Buch hollz et al. 1998), and CRG (Baker, unpublished
data). After electrophoresis on denaturing 6% acry-
lamide gels, PCR products were visualized using an
FMBIO II laser scanner (Hitachi Software Engineering
Co., Alameda, California). Genotypes were scored
based on 20 base-pair standards and reference samples
of known allelic size.
We obtained sequence information from a 385 base-
pair (bp) fragment of the 5' end of the Canada Goose
mitochondrial DNA control region using primers and
conditions described in Pearce et al. (2000). Sequenc -
ing was performed using a SequiTherm Excel DNA
sequencing kit (Epicentre, Inc.), following product
protocols for use of fluorescently labeled primers.
Sequences were aligned manually.
We estimated degree of differentiation in allele and
haplotype frequency between Canada Geese sampled
from coastal and interior regions using a Fisher’s exact
test in program GENEPOP and using F-statistics (Weir
1996) using the program F-STAT (Goudet 1995). Mea -
sures of inter-population variance in allele frequency
were summarized as pair-wise estimates of population
Fst. Significance of mean Fst values (across the seven
loci) were determined by jack-knifing procedures (Weir
1996). Analyses of population differences in mtDNA
haplotype frequency were conducted using an analy-
sis of molecular variance (Excoffier et al. 1992).
Results
Of the eight birds marked in New York in 2001,
seven made molt migrations to areas in Quebec, Cana-
da: four traveled to the eastern coast of Hudson Bay
(58o12'N, 76o60'W), two went to lowland areas east of
James Bay (53o30'N, 79o02'W), and one moved to an
interior location ~350 km southwest of Ungava Bay
(56o06'N, 70o04'W) (Figure 1). Locations from four
transmitters deployed in 2002 (two from Pennsylvania,
one from New York, and one from Vermont) suggested
that these birds also made a molt migration to northern
Quebec; however, the data were not sufficient to iden-
tify migration timing or provide reliable locations.
Only five of the 19 birds marked in 2003 made molt
migrations to northern Quebec (three from Pennsylva-
nia, one from New York, and one from Vermont). Three
traveled to the eastern coast of Hudson Bay (58o12'N,
76o60'W), one went to eastern James Bay (53o54'N,
79o00'W), and one moved to an interior location south
of Ungava Bay (57o00'N, 74o36'W) (Figure 1). The
14 females that did not make a molt migration exhibit-
ed little movement during June through early Novem-
ber; movement of these geese was limited to within
60 km of the banding site. All of the birds that did not
make a molt migration were from more coastal regions
of the flyway (Figure 2).
Molt migrations in both 2001 and 2003 occurred in
June. Marked geese that molt migrated (n= 12) were
located in the U.S. as late as 30 May – 20 June. They
arrived at terminal locations in northern Quebec (Fig-
2007 SHEAFFER, MALECKI, SWIFT, DUNN, and SCRIBNER: CANADA GEESE 315
TABLE 1. Bird identification numbers, state and year of band-
ing (cohort), latitude and longitude of banding location, and
approximate distance between banding and molting location
(km). Females with no nest are identified with an (*).
Banding location
ID Cohort latitude longitude km
33115 NY-2001 43o06'N 78o30'W 1122
33116* NY-2001 43o06'N 78o24'W 897
33117 NY-2001 42o12'N 78o54'W 1830
33118 NY-2001 42o06'N 78o36'W 1295
33119* NY-2001 41o36'N 74o06'W 1641
33120 NY-2001 41o36'N 74o06'W 60
33121* NY-2001 42o42'N 75o30'W 1941
33122 NY-2001 42o42'N 75o30'W 1725
19873 CT-2003 41o20'N 71o32'W 60
19874 PA-2003 40o39'N 77o45'W 1830
19875 MD-2003 38o35'N 76o07'W 60
19876 CT-2003 41o32'N 73o04'W 60
19909 ME-2003 44o43'N 68o54'W 60
19911 MA-2003 41o37'N 71o06'W 60
19916 MA-2003 41o17'N 71o27'W 60
19922 NJ-2003 40o42'N 74o30'W 60
19923 NJ-2003 40o25'N 74o29'W 60
19930 NJ-2003 39o35'N 75o29'W 60
19932 NJ-2003 41o00'N 74o09'W 60
19934 NY-2003 41o05'N 73o51'W 60
19940 NY-2003 42o50'N 73o50'W 1573
19955 NY-2003 40o45'N 73o07'W 60
19957 NY-2003 40o37'N 73o15'W 60
19962 PA-2003 39o48'N 80o03'W 1396
19973 PA-2003 40o07'N 72o24'W 564
19978 PA-2003 40o32'N 75o95'W 60
20024 PA-2003 40o36'N 80o00'W 60
20036 PA-2003 42o09'N 80o02'W 60
20043 PA-2003 41o15'N 75o18'W 60
20059 VT-2003 44o05'N 73o20'W 1521
NY = New York, CT = Connecticut, PA = Pennsylvania,
MD = Maryland, ME = Maine, MA = Massachusetts,
NJ = New Jersey, VT = Vermont
11_07034_geese.qxd:CFN 120(2) 11/27/08 6:01 PM Page 315
ure 1) between 9 and 26 June. Fall migration of these
molt migrants occurred primarily in September. Birds
were located in northern Quebec as late as 28 August
– 29 September. They arrived in southern Canada or
the U.S. between 6 September and 3 October (Figure
3). There was no distinguishable difference in timing
of molt and fall migrations between marked geese in
2001 and 2003. Molt migrations ranged in distance
from 564 – 1941 km (Table 1).
Genetic analysis of the two groups of geese showed
no evidence across loci of significant differences in
microsatellite allele frequency (F= 0.005, P> 0.05).
Likewise, analysis of variance results for mtDNA hap-
lotype frequencies also revealed no evidence of sig-
nificant differences between the two groups (Φ= 0.00,
P > 0.40). When analyses were extended to include
reference samples from the two subarctic-nesting Cana-
da Goose populations (AP and NAP), we observed dif-
ferences in allele frequencies among all three popula-
tions for both microsatellite loci and mtDNA haplotype
(P< 0.05 for both markers).
Discussion
Our results provide convincing evidence of the
move ment of some molting AFRP geese to the north-
ern breeding ground of AP geese at a critical time dur-
ing the spring population monitoring and summer pre-
hunting season banding periods. Zicus (1981) and
Law rence et al. (1998), working with temperate-breed-
ing Canada Geese in Wisconsin and Illinois, each re -
ported 50-60% of their spring population departing on
molt migrations. Mykut (2002) satellite-tracked female
Canada Geese in Michigan, whose nests were des -
troyed, as in this study, late in incubation. He found
62% (n= 37) in 2000 and 73% (n= 52) in 2001 of
these birds molt-migrating to James and Hudson Bays
in northern Canada. The literature is replete with other
reports of long distance molt migrations in temperate-
nesting geese.
The propensity to molt migrate, observed in nest-
failed females from rural New York and Pennsylvania,
but not for birds nesting in more coastal areas of the
flyway, prompted us to suspect a possible genetic dif-
ference resulting from regional differences in the ori-
gin of these birds. Blandin and Heusmann (1974) re -
ported that geese breeding in eastern Massachusetts
were of mixed racial stock, nonmigratory in nature, and
the progeny of decoy birds released in the late 1930s.
Morphometric measurements of these birds (Pottie and
Heusmann 1979) indicated a probable mixing of sev-
eral sub-species, in which B. c. maxima (Giant Canada
Goose) predominated. In contrast, geese in rural New
York and Pennsylvania are primarily large Canada
Geese of the B. c. maxima and B. c. moffitti (Great
Basin Canada Goose) stock introduced after the 1950s
to areas previously devoid of breeding geese. These
birds may be more similar to mid-continent temperate-
nesting populations of restored or reintroduced giant
Canada Geese. Molt migration in giant Canada Geese
is considered a common behavior (Abraham et al. 1999).
We were able to detect genetic differences of sufficient
magnitude to discern the AFRP geese we sampled from
subarctic-nesting populations of geese occurring in the
flyway (AP and NAP), but we did not detect genetic
differences between the two regional cohorts sampled
within the AFRP.
Two factors favoring movement of waterfowl to re -
mote regions to molt are the reduced risk to survival
and greater food availability (Hohman et al. 1992;
Baldassarre and Bolen 2006). In Canada Geese, suc-
cessful breeders also are often behaviorally dominant
over nonbreeders (Raveling 1970), which may influ-
ence movement of the nonbreeding segment away
from nesting areas. However, in New Jersey, Nichols
et al. (2004) estimated that only 22-31% of resident
Canada Geese migrated out of the state to molt. They
suggested that birds in and near urban-suburban dom-
inated landscapes may have many suitable molting sites
consisting of large expanses of lush, fertilized lawns
interspersed with water bodies and few predators. The
gathering of nonbreeders into larger flocks to molt on
or near breeding areas may also lessen stress associat-
ed with behavioral interactions of adults with young.
Lawrence et al. (1998) also noted that in more recent
times, with greater emphasis on hunting of temperate-
nesting geese to manage their numbers, birds leaving
the sanctuary of local breeding areas are more likely
to be harvested.
The coastal region of our study, from which molt
migration did not occur (Connecticut, Massachusetts,
Maryland, and New Jersey), contains ~21% (N=
245351) of the AFRP spring population estimate (Unit-
ed States Fish and Wildlife Service 2007*) in the U.S.
Geese in New York, Pennsylvania, and Vermont make
up ~45% (N= 514181) and the coastal states of Dela -
ware and Virginia, where geese were not sampled as
part of this study, comprise ~14% (N= 163655). If we
assume that 50% of the geese in New York and Penn-
sylvania are molt migrant non-breeders or unsuccess-
ful breeders (Zicus 1981; Lawrence et al. 1998), then
the potential exists for a substantial movement of geese
(250 000) to subarctic breeding areas in northern
Canada. This number is further increased by temper-
ate-nesting birds moving into subarctic regions from
the Mississippi Flyway.
The population estimate for AP geese in northern
Quebec, where we suspect most AFRP birds molt mi -
grate to, is ~1.2 million (Harvey and Rodrique 2007*).
However, the authors caution that differences in survey
timing and the abundance of molt migrants can clearly
introduce substantial variability in the total population
estimate. Similar conflicts are reported by Abraham et
al. (1999) for Southern James Bay Population Canada
Geese in northern Ontario. Spring surveys of AP geese
are timed to cover the mid to late incubation period;
generally the last two weeks in June. Arrival of AFRP
316 THE CANADIAN FIELD-NATURALIST Vol. 121
11_07034_geese.qxd:CFN 120(2) 11/27/08 6:01 PM Page 316
2007 SHEAFFER, MALECKI, SWIFT, DUNN, and SCRIBNER: CANADA GEESE 317
molt-migrants coincides very closely with the begin-
ning of these surveys. Similarly,summer banding of
AP geese, which usually takes place in late July –
early August, also occurs when molt migrants are
still on the AP breeding grounds. Given that molting
large Canada Geese can require up to 40 days to
obtain the 85% of primary feather development
required to regain flight (Hanson 1965), geese arriving
in mid-June have the potential still to be flightless
when subarctic-breeding adults with young are being
banded. This mixing of populations re-enforces the
need to (1) monitor the status of subarctic-breeding
populations using numbers of breeding pairs surveyed,
rather than total counts in volving groups of geese of
unknown origin, and (2) band only flightless adults
with young during the summer pre-season banding
period to ensure a representative sample of subarctic-
nesting populations of Canada Geese.
In the late 1980s, as an aid in the control of increas-
ing numbers of temperate-nesting geese, the U.S. Fish
and Wildlife Service endorsed the implementation of
special hunting seasons in September and late-winter,
when subarctic-nesting goose populations would be
less likely affected (Heusmann et al. 1998). While
effective in many rural areas, geese in urban and sub-
urban environments often receive little exposure to
hunter harvest (Smith et al. 1999). Efforts to control
nuisance geese generally rely on non-lethal methods
involving addling and oiling of eggs in nests (Chris-
tens et al. 1995) and harassment techniques to move
birds from heavily used residential and industrial areas
(Holevinski et al. 2007). Both methods provide only
a moderate degree of relief, at best.
FIGURE 1. Locations of Atlantic Flyway Resident Population Canada Geese during spring molt migration in 2001 and 2003.
Locations were identified using birds marked with satellite-tracked transmitters. Birds arrived at terminal molting
areas in northern Quebec between 9 June and 16 June.
11_07034_geese.qxd:CFN 120(2) 11/27/08 6:01 PM Page 317
Many studies have demonstrated that altering sur-
vival of adult geese is much more effective in changing
population size than altering recruitment rates (Trost
et al. 1986; Schmutz et al. 1997). However, direct
culling of molting birds continues to remain a socially
unacceptable option for population control in many
areas. One alternative, transplanting flightless adults
with young from nuisance areas to rural areas prior to
the fall hunting season, successfully reduced survival
of adults in comparison to non-transported birds, but
was both time consuming and costly (Holevinski et al.
2006). Inducing molt migration of adult breeding geese
by destroying nests late in incubation, as demonstrated
in this study, showed potential for both removal of birds
from their breeding area during the spring and sum-
mer period and exposing them to hunting outside the
region. However, our failure to demonstrate this in
coastal areas, which have more prominent nuisance
Canada goose issues, was problematic. We can only
assume that the reason for this was attributed to the
historical origin of captive-reared birds of mixed sub-
species making up AFRP flocks in this part of the fly-
way and the availability of quality local molting
habitat distinct from brood-rearing areas.
Acknowledgments
We acknowledge the valuable assistance and fund-
ing received from the following individuals and their
respective agencies: P. Castelli and T. Nichols, New
Jersey Division of Fish and Wildlife; H. W. Heusmann,
Massachusetts Division of Fisheries and Wildlife; M.
Huang, Connecticut Department of Environmental
Protection; W. Crenshaw, Vermont Fish and Wildlife
Department; B. Allen, Maine Department of Inland
Fisheries and Wildlife; L. Hindman, Maryland Wildlife
and Heritage Service; and the agencies and university
affiliates of the authors. Valuable editorial comments
were provided by G. Baldassarre, College of Environ-
mental Science and Forestry at Syracuse University, L.
Hindman, and the anonymous referees for this journal.
Documents Cited (marked * in text)
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318 THE CANADIAN FIELD-NATURALIST Vol. 121
FIGURE 2. Banding locations of Atlantic Flyway Resident Population Canada Geese marked with satellite-
tracked transmitters during May 2001 and 2003.
11_07034_geese.qxd:CFN 120(2) 11/27/08 6:01 PM Page 318
2007 SHEAFFER, MALECKI, SWIFT, DUNN, and SCRIBNER: CANADA GEESE 319
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Received 8 August 2006
Accepted 7 May 2008
320 THE CANADIAN FIELD-NATURALIST Vol. 121
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... During the early 2010s, New Jersey had the densest populations in the Atlantic Flyway at 4.5 birds/km 2 (Atlantic Flyway Council 2011). Survival, movements, and nest survival of Canada geese in the AFRP are well studied (Conover 1998, Jacobs and Dunn 2004, Nichols et al. 2004, Sheaffer et al. 2007, Guerena et al 2016; however, gosling mortality is not well documented. Our objectives were to document post-hatch survival by estimating 1) gosling survival from hatch until near-fledge, 2) total brood loss, 3) partial brood loss 4) brood survival, combining total and partial brood loss estimates, and 5) daily gosling mortality during the first 2 weeks following hatch. ...
... We captured 2 marked adults >2 km away from the nesting site without broods. Additionally, 1 observation was reported to the BBL of 1 marked female parent with no goslings near Varennes, Quebec, Canada on 15 June 2010, a straight-line distance of 710 km from the nest site, apparently undergoing a molt migration (Sheaffer et al. 2007), after hatching 3 goslings on 30 April 2010. We did not recapture any of the goslings from her nest. ...
... Many studies attempt to measure total brood loss through marked adults (Lawrence 1986, Bruggink et al. 1994, Peters et al. 2004) usually by examining the number of marked adults that are recaptured without broods. However, because molt migration can be common in failed breeders (Nichols et al. 2004, Sheaffer et al. 2007), a failed breeder is less likely to be recaptured in the same brood rearing area 2 months after peak hatch (Eberhardt et al. 1989b). In observing adults with neck collar-mounted radio-transmitters, we were able to identify adults that experienced total brood loss prior to leaving the nesting area. ...
... Juveniles stay with their adult parents to a large extent throughout the first year (Mowbray et al. 2002, Beaumont et al. 2013. A portion of subadults (primarily 2-and 3-yrold geese) and nonbreeding adults migrate north from breeding areas to molt (Sheaffer et al. 2007, Luukkonen et al. 2008, Dieter et al. 2010, Conover 2011. Once geese become breeding adults, they typically show site fidelity to the areas from which they hatched (Hestbeck et al. 1991, Mowbray et al. 2002, Baldassarre 2014, Pilotte et al. 2014. ...
... Most recoveries occurred near banding areas, and, as predicted, subadults had broader recovery distributions than juveniles and adults ( Fig. 1; Table 2). This was consistent with other studies of temperate-nesting Canada geese (Sheaffer et al. 2007, Luukkonen et al. 2008, Sanders and Dooley 2014, Beston et al. 2015 and consistent with the notion that most harvest of local temperate-nesting Canada goose populations can be affected by state-or Flyway-specific hunting regulations. As predicted, there was some decrease in adult and subadult survival estimates with liberalized harvest regulations, and decreases were greatest in North Dakota and South Dakota, which implemented the most intensive management actions among states. ...
... For instance, egg-oiling might delay nuisance problems locally prompting adults to stay longer on their nesting territories located far from human development. Given that breeding failure may prompt molt migration (Sheaffer et al. 2007), nest removal in urban areas might induce northward migration, reducing local flock size during summer, and exposing molt migrants to a greater hunting pressure in fall (Luukkonen et al. 2008). Alternatively, egg-oiling may preclude molt migration if the extended incubation period reduces time devoted to feeding and energy intake. ...
... Such movements may reduce survival through natural or hunting mortality, which could contribute to population control (Luukkonen et al. 2008). On the other hand, the arrival of temperate-nesting geese on the breeding grounds of subarctic-nesting geese may induce competition for foraging sites (Sheaffer et al. 2007). Anecdotal observations along the eastern Hudson Bay coasts indicate that both groups of geese do not mix together, but it is still unknown whether they share the same foraging sites (S. S. Orichefsky, Canadian Wildlife Service, personal communication). ...
Article
Full-text available
Controlling overabundant goose populations remains a wildlife management challenge. Although reducing adult survival is considered more effective than reducing fecundity, egg‐oiling, and egg removal are often preferential techniques for controlling temperate nesting Canada geese (Branta canadensis) in urban and peri‐urban settings. Little is known about the effect of these methods on the subsequent behavior of geese and their potential effects on population dynamics. We aimed to determine how long Canada geese nesting in southern Quebec, Canada remain at the nest site following egg‐oiling, whether birds submitted to egg‐oiling or nest removal persist in the area to molt and whether they return to breed in the study area the following year, and if so, how far do they nest from their previous nest location. We studied 996 nests initiated by 442 neck‐collared females between 2006 and 2012 including 76 that were oiled, 91 that were removed, 143 that suffered complete loss of the clutch by predators, were flooded, or abandoned, and 686 that were successful. We found that egg‐oiling delayed nest abandonment past the expected hatching date and that the delay increased when applying the treatment later in incubation. We observed only 10 cases of renesting and most occurred after nest flooding. Females that had their nests removed or whose nest failed had a greater probability of leaving the study area to molt elsewhere than females that were successful or those that had their eggs treated with oil. The probability that a female survived and returned to nest in the area was not related to the fate of its nest in the previous year and was estimated at 0.71 (95% CI = 0.67–0.74). The mean distance between successive nesting attempts was not related to the previous year nest fate and averaged 78 ± 8 m. Nest success and thus recruitment was reduced during years with the experimental treatments, but strong philopatry indicates that treatments must be repeated every year to have an effect on the local population growth. If the goal is to keep the geese longer at their nest site, then coating eggs with oil as late as possible in incubation will result in geese remaining at the nest site well past the expected hatch date. If the goal is to cause the geese to leave the nest site, then nest removal should be favored. © 2018 The Wildlife Society.
... These individuals may bias our ability to determine location-based differences between urban versus rural resident geese. Researchers studying the Atlantic Flyway Resident Population of Canada geese reported that movement associated with molt migration (which we did not explicitly account for), was more prevalent in rural-banded geese compared with geese banded closer to the coast in more urbanized landscapes (Sheaffer et al. 2007). Despite these potential biases, when testing for general differences among hunt zones, there was support for the urban refugia hypothesis where resident geese from the more urbanized Atlantic and Southern James Bay hunt zones had higher survival rates than resident geese within the more rural Western hunt zone. ...
Article
Full-text available
Resident populations of Canada geese (Branta canadensis) are of particular management interest throughout the eastern United States given increased human‐wildlife conflicts due to regional increases in the Atlantic Flyway Resident Population. Within Virginia, USA, growth rates of resident goose populations have been reduced through extended harvest seasons and increased bag limits. Our objective was to investigate spatiotemporal patterns in survival rates and harvest rates of resident geese in Virginia over the past 25 years. We estimated annual survival, recovery, and harvest rates using mark‐recapture data from 1990–2015 for individuals that were banded as resident birds during summer throughout the state. We tested for differences in annual survival probability and harvest rates of resident geese banded and recovered in 3 distinct goose hunt zones: the Atlantic, Southern James Bay, and Western hunt zones, each of which had different hunting regulations. We also tested for differences in survival and harvest rates between individuals banded in rural or urban sampling locations, and between age classes (i.e., after hatch‐year or hatch‐year). In general, survival rates of resident geese over the past 25 years in Virginia are declining. Differences in survival among the 3 goose hunt zones also suggests that current harvest management strategies have reduced survival rates of resident geese. Upon closer examination, we found differences in survival among zones, with resident geese in the Atlantic and Southern James Bay hunt zones showing more negative declines compared to resident geese in the Western zone. Resident geese banded in rural areas had higher survival than urban‐banded geese. We also investigated the effects of sampling effort on survival estimates and found no difference in survival estimates among groups when using 75%, 50%, 25%, or 5% of the data randomly sampled from the full data set, suggesting that banding efforts of resident geese could be reduced and continue to inform adaptive management strategies for these populations throughout Virginia. © 2020 The Wildlife Society. Using 25 years of mark‐recapture data from resident Canada geese in Virginia, on average, survival rates are declining and harvest rates are increasing. These trends indicate that hunting regulations across the state are effective and are aiding in the achievement of established management goals for resident geese in Virginia. We were able to detect observed trends in survival and harvest rates despite using much‐reduced data sets, suggesting the potential to reallocate resources for banding of resident geese to other population reduction methods.
... As adults, resident Canada geese within the Atlantic Flyway have few natural predators; therefore, annual mortality is generally low after recruitment of goslings into the population (Sheaffer et al. 2007). Regulated hunting offers a means to harvest resident geese and to reduce their breeding populations. ...
... Similarly, the identification of discrete migratory flyways allows for more effective designation of management regions that may warrant varied harvest regulations (Krapu et al. 2011). A classic example of the importance of population delineation in waterfowl is "migratory" and "resident" populations of Canada Geese (Branta canadensis (Linnaeus, 1758)) in the Atlantic Flyway of the United States (Heusmann 1999;Sheaffer et al. 2007). Differential survival and harvest pressure led to steep declines in some migratory populations, while sedentary residents exploded to nuisance levels (Heusmann 1999), leading biologists and managers to develop targeted hunting seasons to reduce harvest of the migratory population. ...
Article
Full-text available
Understanding full annual cycle movements of long-distance migrants is essential for delineating populations, assessing connectivity, evaluating crossover effects between life stages, and informing management strategies for vulnerable or declining species. We used implanted satellite transmitters to track up to 2 years of annual cycle movements of 52 adult female White-winged Scoters (Melanitta fusca (Linnaeus, 1758)) captured in the eastern United States and Canada. We used these data to document annual cycle phenology; delineate migration routes; identify primary areas used during winter, stopover, breeding, and molt; and assess the strength of migratory connectivity and spatial population structure. Most White-winged Scoters wintered along the Atlantic coast from Nova Scotia to southern New England, with some on Lake Ontario. White-winged Scoters followed four migration routes to breeding areas from Quebec to the Northwest Territories. Principal postbreeding molting areas were in James Bay and the St. Lawrence River estuary. Migration phenology was synchronous regardless of winter or breeding origin. Cluster analyses delineated two primary breeding areas: one molting area and one wintering area. White-winged Scoters demonstrated overall weak to moderate connectivity among life stages, with molting to wintering connectivity the strongest. Thus, White-winged Scoters that winter in eastern North America appear to constitute a single continuous population. Résumé : La compréhension des déplacements sur un cycle annuel complet d'espèces qui migrent sur de longues distances est fondamentale pour délimiter les populations, évaluer la connectivité et les effets de chevauchement de différentes étapes du cycle biologique et élaborer de stratégies de gestion pour les espèces vulnérables ou en déclin. Nous avons utilisé des émetteurs satellitaires implantés pour suivre le cycle de déplacement annuel pendant jusqu'à deux ans de 52 macreuses à ailes blanches (Melanitta fusca (Linnaeus, 1758)) femelles adultes capturées dans l'est des États-Unis et du Canada. Nous avons utilisé ces données pour documenter la phénologie du cycle annuel, délimiter les routes de migration, cerner les principales aires d'hivernage, de séjour, de reproduction et de mue et évaluer la force de la connectivité migratoire et la structure spatiale de la population. La plupart des macreuses à ailes blanches hivernaient le long de la côte atlantique, de la Nouvelle-Écosse au sud de la Nouvelle-Angleterre, certaines passant plutôt l'hiver sur le lac Ontario. Les macreuses à ailes blanches suivaient quatre routes de migration vers des aires de reproduction allant du Québec aux Territoires-du-Nord-Ouest. Les principales aires de mue après la reproduction étaient dans la baie James et l'estuaire du fleuve Saint-Laurent. La phénologie de la migration était synchrone, quelles que soient les aires d'hivernage ou de reproduction d'origine. Des analyses typologiques ont délimité deux principales aires de reproduction, une aire de mue et une aire d'hivernage. Les macreuses à ailes blanches présentaient globalement une connectivité faible à modérée entre les étapes du cycle biologique, la connectivité entre la mue et l'hivernage étant la plus forte. Ainsi, les macreuses à ailes blanches qui hivernent dans l'est de l'Amérique du Nord semblent constituer une seule population continue. [Traduit par la Rédaction] Mots-clés : macreuse à ailes blanches, Melanitta fusca, délimitation des populations, connectivité migratoire, cycle annuel, télémétrie satellitaire, phénologie.
... Understanding migratory connectivity is especially vital for species of conservation concern, as environmental events and stressors during the non-breeding season are well documented to affect population dynamics and productivity during the breeding season (Oosterhuis and van classic example of the importance of population delineation in waterfowl is "migratory" and "resident" populations of Canada Geese (Branta canadensis (L., 1758)) in the Atlantic Flyway of the United States (Heusmann 1999;Sheaffer et al. 2007). Differential survival and harvest pressure led to steep declines in some migratory populations, while sedentary residents exploded to nuisance levels (Heusmann 1999), leading biologists and managers to develop targeted hunting seasons to reduce harvest of the migratory population. ...
Article
Full-text available
Understanding full annual cycle movements of long-distance migrants is essential for delineating populations, assessing connectivity, evaluating crossover effects between life stages, and informing management strategies for vulnerable or declining species. We used implanted satellite transmitters to track up to 2 years of annual cycle movements of 52 adult female White-winged Scoters (Melanitta fusca (Linnaeus, 1758)) captured in the eastern United States and Canada. We used these data to document annual cycle phenology; delineate migration routes; identify primary areas used during winter, stopover, breeding, and molt; and assess the strength of migratory connectivity and spatial population structure. Most White-winged Scoters wintered along the Atlantic coast from Nova Scotia to southern New England, with some on Lake Ontario. White-winged Scoters followed four migration routes to breeding areas from Quebec to the Northwest Territories. Principal postbreeding molting areas were in James Bay and the St. Lawrence River estuary. Migration phenology was synchronous regardless of winter or breeding origin. Cluster analyses delineated two primary breeding areas: one molting area and one wintering area. White-winged Scoters demonstrated overall weak to moderate connectivity among life stages, with molting to wintering connectivity the strongest. Thus, White-winged Scoters that winter in eastern North America appear to constitute a single continuous population.
... Although several studies combined the use of neck collars and backpack attachments [6,63,78], a proper comparison of effects is lacking. Blouin et al. [6] report that none of the Greater Snow Geese equipped with backpack transmitters reached the breeding grounds in 1993 and 1994 (due to signal loss, natural mortality or being shot), while four out of 11 birds equipped with neck collar transmitters did reach the breeding grounds in 1995. ...
Article
Full-text available
Since the first studies in the mid-twentieth century, lightweight electronic tracking devices have been increasingly used to study waterfowl movements. With half a century of experience and growing sample sizes, it has become clear that the attachment of a tracking device can affect a bird's behaviour and fitness. This becomes problematic when it introduces uncertainty about whether the recorded data represent natural behaviour. Waterfowl may be particularly prone to tag effects, since many species are migratory and tracking devices can disrupt their waterproof plumage. The primary aim of this paper is to identify how tracking devices may affect waterfowl survival, migration and reproduction, and how better measuring and reporting of such effects can improve our understanding of the risks, providing a first step towards reducing their impact in future studies. We reviewed literature on electronic tracking of waterfowl to create an overview of currently recognized effects of harness-attached backpacks, implants, subcutaneous attachments and neck collars. Additionally, we analysed developments in the use of attachment methods, the weight of tracking devices relative to bird body mass, and the reporting rate of effects of tracking devices in 202 original tracking studies. We found that although the number of waterfowl tracking studies described in peer-reviewed literature has steeply increased over the past decades, reporting rates of potential effects have decreased from 65.0 to 26.5%. Meanwhile, the mean weight of the tracking devices relative to the bird's body mass remained stable around 2.0%. Major negative effects were reported in 17% of all studies and were found for all attachment methods. Overall, large differences exist in the occurrence and type of negative effects between species and studies, even if the same tracking methods were used. Inconsistent reporting of effects, lack of control groups to measure effects and incomplete descriptions of the methodology hamper the identification of factors contributing to these effects. To accomplish a reduction in adverse effects of tracking, it is necessary to improve the measuring and reporting of effects. We propose a framework for standardized reporting of methods in primary tracking studies and standardized protocols to measure effects of tracking devices on waterfowl.
Article
Molt migration is an annual movement from the breeding grounds to a different, distant molting area often north of the breeding grounds. Such movements are only completed by a segment of a population, typically nonbreeding individuals or failed breeders. Although molt migration is common among waterfowl, especially large-bodied species such as geese, it remains unknown whether the Trumpeter Swan (Cygnus buccinator), a species whose population is rapidly growing and expanding throughout the mid-continental United States, engages in molt migration. Here, we provide the first empirical description of an apparent molt migration of a nonbreeding male Trumpeter Swan using location data collected by a GPS-GSM collar. The swan departed its natal wetland in north-central Iowa, USA, on 1 June 2019 and arrived at a complex of small wetlands near Great Slave Lake in the Northwest Territories, Canada, on 4 July 2019, a straight-line distance of 2,420 km. For the next 43 d, the swan restricted its movements to a small wetland with a mean distance between sequential points of 126.15 m (range = 0.332,910.72 m), suggesting it was flightless during this time period. Both the timing and duration of this presumed flightless period coincide with the second prebasic molt in swans. La muda durante la migracin es un movimiento anual del rea de reproduccin a una diferente rea para la muda, frecuentemente al norte de sus reas reproductivas. Dichos movimientos solamente son completados por un segmento de la poblacin, tpicamente individuos no-reproductivos o anidantes fallidos. Aunque la muda durante la migracin es comn entre aves acuticas, especialmente especies de tamao grande como los gansos, an desconocemos si el cisne Cygnus buccinator, una especie cuya poblacin est creciendo rpidamente y expandindose a lo largo de la regin continental media de los Estados Unidos, tiene muda de migracin. Aqu damos la primera descripcin emprica de una aparente muda de migracin en un macho no-reproductivo de este cisne, usando datos de localidades colectadas por medio de un collar GPS-GSM. El cisne parti de su humedal natal en Iowa norcentral, EUA, el 1 de junio de 2019 y lleg a un complejo de pequeos humedales cerca del lago Great Slave en Northwest Territories, Canad, el 4 de julio de 2019, una distancia lineal de 2,420 km. Por los prximos 43 d, el cisne limit sus movimientos a un pequeo humedal con una distancia lineal entre puntos secuenciales de 126.15 m (rango = 0.332,910.72 m), lo que sugiere que no poda volar durante este periodo. Ambos, la temporalidad y duracin de este periodo presumiblemente sin volar coinciden con la segunda muda prebsica en cisnes. Palabras clave: aves acuticas, Iowa, movimiento, reintroduccin, transmisor GPS-GSM.
Thesis
Full-text available
The Atlantic Flyway Resident Population segment of Canada geese (Branta canadensis) is above population objectives set by the Atlantic Flyway Council. We know little about the movement dynamics in the population, which is information needed in order to effectively manage it. Besides establishing an annual banding program, there has been little research conducted on birds breeding in the state of Maine. My objectives are to identify the fall migratory pathway and the extent of the wintering range of Maine-banded Canada geese, explore whether Maine individuals conduct a molt migration, and calculate harvest rate for the years 2016, 2017, and 2018. I found that Canada geese banded in Maine stay close to their banding areas during the months of September and October, and a proportion of the population migrates south to Massachusetts, Rhode Island and Long Island, New York to spend the winter. I found no difference in migratory propensity between males and females and between adults and juvenile individuals. An unknown proportion of Canada geese spend the winter on the coast of Maine, although the proportion is small in comparison to the migratory portion. I collected feather samples in order to differentiate between migrants and residents based on the latitude of summer molt. I was able to separate residents and migrants, and by introducing temporal factors, molt migrants were discerned from migrants. Detection of migrant and molt migrant Canada geese is possible using δ2H to discern molting latitude. Stable isotopes can differentiate between populations with little morphometric difference and also identify the proportion of molt migrants within a sample of the population. Harvest rate has averaged 22% over the past 16 years, with a slight trend upwards, which is comparable to other states in New England.
Article
We used microsatellite markers, mitochondrial DNA (mtDNA), and satellite telemetry to infer the North American geographic origin and racial composition of Canada Geese (Branta canadensis) from newly colonized habitats in Greenland. Using likelihood-based assignment tests we determined that multilocus genotypes of Greenland Canada Geese were consistent with the hypothesis of origin from birds of the Atlantic Population breeding around southern Ungava Bay, Quebec, Canada. The Atlantic Population, based on previous studies of seasonal movements and demography, appeared to be reproductively isolated from the North Atlantic Population. We found that these two populations were genetically differentiated based on microsatellite allele and mtDNA haplotype frequencies. Findings of high levels of genetic discordance among North American breeding populations are consistent with migratory movements, despite high levels of distributional overlap of birds from the North Atlantic and Atlantic Populations during migration and on wintering areas. Findings based on genetic markers were concordant with satellite telemetry conducted during spring migration, which showed that birds destined for Greenland migrate through the southern Ungava Bay breeding colony. Genetic differences among these populations are useful for addressing other issues of ecological or management concern. Identificación de la Población Fuente de los Gansos Branta canadensis de Groenlandia: Evaluación Genética de una Colonización Reciente Resumen. Utilizamos marcadores microsatélites, ADN mitocondrial (ADNmt), y telemetría de satélite para inferir el origen geográfico en Norte América y la composición racial de los gansos Branta canadensis en hábitats recientemente colonizados en Groenlandia. Mediante pruebas de asignación basadas en verosimilitud, determinamos que los genotipos multilocus de los gansos de Groenlandia eran consistentes con la hipótesis de origen de aves de la población del Atlántico que se reproduce alrededor del sur de Ungava Bay, Quebec, Canadá. Con base en estudios previos de movimientos estacionales y demografía, la población del Atlántico pareció estar aislada reproductivamente de la población del Atlántico Norte. Encontramos que estas dos poblaciones son genéticamente diferentes en términos de frecuencias alélicas de microsatélites y haplotipos de ADNmt. El hallazgo de altos niveles de discordancia genética entre poblaciones reproductivas norteamericanas es consistente con los movimientos migratorios, a pesar de los altos niveles de superposición de las distribuciones de aves de las poblaciones del Atlántico y el Atlántico Norte durante la migración y en las áreas de invernada. Los resultados basados en los marcadores genéticos concordaron con la telemetría satelital llevada a cabo durante la migración de primavera, la cual mostró que las aves con destino a Groenlandia migran a través del sur de la colonia reproductiva de Ungava Bay. Las diferencias genéticas entre estas poblaciones son útiles para abordar otros asuntos de interés ecológico o de manejo.
Article
Using molecular genetic markers that differ in mode of inheritance and rate of evolution, we examined levels and partitioning of genetic variation for seven nominal subspecies (11 breeding populations) of Canada Geese (Branta canadensis) in western North America. Gene trees constructed from mtDNA control region sequence data show that subspecies of Canada Geese do not have distinct mtDNA. Large and small-bodied forms of Canada Geese were highly diverged (0.077 average sequence divergence) and represent monophyletic groups. A majority (65%) of 20 haplotypes resolved were observed in single breeding locales. However, within both large and small-bodied forms certain haplotypes occurred across multiple subspecies. Population trees for both nuclear (microsatellites) and mitochondrial markers were generally concordant and provide resolution of population and subspecific relationships indicating incomplete lineage sorting. All populations and subspecies were genetically diverged, but to varying degrees. Analyses of molecular variance, nested-clade and coalescencebased analyses of mtDNA suggest that both historical (past fragmentation) and contemporary forces have been important in shaping current spatial genetic distributions. Gene flow appears to be ongoing though at different rates, even among currently recognized subspecies. The efficacy of current subspecific taxonomy is discussed in light of hypothesized historical vicariance and current demographic trends of management and conservation concern.
Article
A Canada goose (Branta canadensis) genomic library was created and screened for clones containing various microsatellite motifs. Fourteen positive clones were identified and sequenced; five primer pairs were developed and utilized to screen approximately 460 Canada geese for genetic variation. Each of these primer pairs were consistently scorable and polymorphic (average heterozygosity of 55%). DNA was isolated and successfully amplified from 2-year-old goose tail fans which received no special care other than storage at 4°C. Two of the five goose primers also amplified DNA from a partial family of wood ducks (Aix sponsa; n =5), but no variation was detected at either locus. In geese, the number of alleles per locus ranged from 7 to 24. PIC values ranged from 0.41 to 0.91, while average levels of observed heterozygosity varied between 0.34 and 0.78. The high levels of polymorphism exhibited by these markers should be useful in addressing population genetic issues in Canada geese.
Article
Recent technological advances have resulted in small (30 g) satellite platform transmitter terminals (PTTs) that can be used to track animals with masses as little as 900-1,000 g. While larger PTTs (>80 g) often yield locations accurate to within hundreds of meters, the location accuracy of smaller PTTs has not been tested. We did these tests while using the PTTs to document migration routes and nonbreeding areas of American peregrine falcons (Falco peregrinus anatum). We PTT-tagged 42 female peregrines from 2 breeding areas (upper Yukon River in eastcentral Alaska and Lake Powell on the Colorado Plateau in southern Utah and northern Arizona) late in the breeding seasons of 1993-95. Only 2 of the PTTs failed prematurely (4.7% failure rate). Active PTTs (i.e., PTTs on live birds that eventually stopped transmitting due to battery exhaustion) averaged 280 transmission hours for 1993-94 (n = 3), 380 transmission hours for 1994-95 (n = 7), and 430 transmission hours for 1995-96 (n = 15). Using an estimate of maximum ground speed of peregrines (104 km/hr) based on empirical observations and aerodynamic calculations, we determined that 4.48% of all locations provided to us by Argos (n = 2,323) were biologically implausible. We also received many poor-quality locations (68% of records were in Argos location classes 0, A, and B) typical of small, relatively underpowered PTTs. To estimate location accuracy of these poor-quality locations, we compared Argos-estimated locations with known locations of 11 rock doves (Columba livia) tagged with PTTs. The location types with the highest precision averaged 4 km from the true location, while the location types with the lowest precision averaged 35 km from the true location. These results indicate the PTT locations were sufficient to document animal movements over broad spatial scales such as identifying migration routes and nonbreeding areas of birds. This technology is more efficient and less biased than the current approaches used to obtain this information (mark-resighting of banded animals or standard radiotelemetry techniques). However, the PTTs currently available are not suitable when position accuracy <35 km is needed.
Article
Molt migrations of Canada geese (Branta canadensis) from Crex Meadows, Wisconsin were examined in 1972-74. Yearling siblings and non-nesting pairs formed flocks in early May and remained together until departure in late May or early June. Flock sizes increased as pairs unsuccessful in raising young left breeding marshes. Ninety-seven percent of the non-nesters and 90% of the unsuccessful nesting pairs migrated by mid-June. Although nesting was 2 weeks earlier in 1973 than in 1972 or 1974, departure dates were the same each year. In 1973 and 1974 nearly 58 and 64% of the local spring population left for molting areas. Observations and recoveries of marked birds indicated that some geese molted in northern Manitoba. Molters started returning in late August, a return migration that continued until nearly November. Return of yearlings (48-85%) differed (P < 0.01) between years, whereas older non-nesters and unsuccessful pairs returned in similar proportions (75-100%) each year. By the next spring, homing was similar (88-96%) in all 3 age-classes of molters.