| Crucial nesting habitat for gunnison sage-grouse: A spatially explicit hierarchical approach | Aldridge, Cameron L. | 2012 |
KeywordsCentrocercus minimus; Colorado; extrapolation; Gunnison sage-grouse; habitat; hierarchical model; nesting; resource selection; sagebrush AbstractGunnison sage-grouse (Centrocercus minimus) is a species of special concern and is currently considered a candidate species under Endangered Species Act. Careful management is therefore required to ensure that suitable habitat is maintained, particularly because much of the species' current distribution is faced with exurban development pressures. We assessed hierarchical nest site selection patterns of Gunnison sage-grouse inhabiting the western portion of the Gunnison Basin, Colorado, USA, at multiple spatial scales, using logistic regression-based resource selection functions. Models were selected using Akaike Information Criterion corrected for small sample sizes (AICc) and predictive surfaces were generated using model averaged relative probabilities. Landscape-scale factors that had the most influence on nest site selection included the proportion of sagebrush cover >5%, mean productivity, and density of 2 wheel-drive roads. The landscape-scale predictive surface captured 97% of known Gunnison sage-grouse nests within the top 5 of 10 prediction bins, implicating 57% of the basin as crucial nesting habitat. Crucial habitat identified by the landscape model was used to define the extent for patch-scale modeling efforts. Patch-scale variables that had the greatest influence on nest site selection were the proportion of big sagebrush cover >10%, distance to residential development, distance to high volume paved roads, and mean productivity. This model accurately predicted independent nest locations. The unique hierarchical structure of our models more accurately captures the nested nature of habitat selection, and allowed for increased discrimination within larger landscapes of suitable habitat. We extrapolated the landscape-scale model to the entire Gunnison Basin because of conservation concerns for this species. We believe this predictive surface is a valuable tool which can be incorporated into land use and conservation planning as well the assessment of future land-use scenarios. (C) 2011 The Wildlife Society. AuthorsAldridge, Cameron L.; Saher, D. Joanne; Childers, Theresa M.; Stahlnecker, Kenneth E.; Bowen, Zachary H. Year Published2012 PublicationJournal of Wildlife Management LocationsDOI10.1002/jwmg.268 |
| Linking occurrence and fitness to persistence: Habitat-based approach for endangered Greater Sage-Grouse | Aldridge, Cameron L. | 2007 |
KeywordsAlberta, Canada; Centrocercus urophasianus; Cox proportional hazard; fitness; GreaterSage-Grouse; habitat; logistic regression; occurrence; persistence; population viability; sagebrush AbstractDetailed empirical models predicting both species occurrence and fitness across a landscape are necessary to understand processes related to population persistence. Failure to consider both occurrence and fitness may result in incorrect assessments of habitat importance leading to inappropriate management strategies. We took a two-stage approach to identifying critical nesting and brood-rearing habitat for the endangered Greater Sage-Grouse ( Centrocercus urophasianus) in Alberta at a landscape scale. First, we used logistic regression to develop spatial models predicting the relative probability of use ( occurrence) for Sage-Grouse nests and broods. Secondly, we used Cox proportional hazards survival models to identify the most risky habitats across the landscape. We combined these two approaches to identify Sage- Grouse habitats that pose minimal risk of failure ( source habitats) and attractive sink habitats that pose increased risk ( ecological traps). Our models showed that Sage- Grouse select for heterogeneous patches of moderate sagebrush cover ( quadratic relationship) and avoid anthropogenic edge habitat for nesting. Nests were more successful in heterogeneous habitats, but nest success was independent of anthropogenic features. Similarly, broods selected heterogeneous high- productivity habitats with sagebrush while avoiding human developments, cultivated cropland, and high densities of oil wells. Chick mortalities tended to occur in proximity to oil and gas developments and along riparian habitats. For nests and broods, respectively, approximately 10% and 5% of the study area was considered source habitat, whereas 19% and 15% of habitat was attractive sink habitat. Limited source habitats appear to be the main reason for poor nest success ( 39%) and low chick survival ( 12%). Our habitat models identify areas of protection priority and areas that require immediate management attention to enhance recruitment to secure the viability of this population. This novel approach to habitat- based population viability modeling has merit for many species of concern. AuthorsAldridge, Cameron L.; Boyce, Mark S. Year Published2007 PublicationEcological Applications LocationsDOI10.1890/05-1871 This article contributed by:Ecological Society of America |
| ACCOUNTING FOR FITNESS: COMBINING SURVIVAL AND SELECTION WHEN ASSESSING WILDLIFE-HABITAT RELATIONSHIPS | Aldridge, Cameron L. | 2008 |
Keywordsfitness, greater sage-grouse, habitat, occurrence, persistence, sagebrush,selection, survival AbstractAssessing the viability of a Population requires understanding of the resources used by animals to determine how those resources affect long-term population persistence. To understand the true importance of resources, one must consider both selection (where a Species Occurs) and fitness (reproduction and survival) associated with the use of those resources. Failure to do so may result in incorrect assessments of habitat quality and inappropriate management activities. We illustrate the importance of considering both Occurrence and fitness metrics when assessing habitat requirements for the endangered greater sage-rouse in Alberta, Canada. This population is experiencing low recruitment, so we assess resource use during the brood-rearing period to identify management priorities. First, we develop logistic regression occurrence models fitted with habitat covariates. Second, we use proportional hazard survival analysis to assess chick survival (fitness component) associated with habitat and climatic covariates. Sage-grouse show strong selection for sagebrush cover at both patch (smaller) and area (larger) spatial scales, and weak selection for forbs at the patch scale only. Drought conditions based on an index combining growing degree days and spring precipitation strongly reduced chick survival. While hens selected for taller grass and more sagebrush cover, only taller grass cover also enhanced chick Survival. We show that sage-grouse may not recognize all ecological cues that enhance chick survival. Management activities targeted at providing habitats that sage-grouse are likely to use in addition to those that enhance survival are most likely to ensure the long-term viability of this population. Our techniques account for both occurrence and fitness in habitat quality assessments and, in general, the approach should be applicable to other species or ecosystems. AuthorsAldridge, Cameron L.; Boyce, Mark S. Year Published2008 PublicationIsrael Journal of Ecology & Evolution LocationsDOI10.1560/IJEE.54.3-4.389 |
| Assessing chick survival of sage-grouse in Canada. Final project report for 2000. | Aldridge, Cameron L. | 2000 |
Assessing chick survival of sage-grouse in Canada. Final project report for 2000.KeywordsNo keywords available AbstractThe Alberta greater sage-grouse population has declined by 66-92% over the last thirty years. Previous research in Alberta suggested that the population has declined as a result of poor recruitment. Low levels of recruitment appear to be linked to poor chick survival as a result of limited mesic sites important for brood rearing habitat. Due to the inaccuracies of brood flushing counts, and the limits of technology to produce transmitters small enough for chicks, it has been difficult to accurately assess and understand chick survival. A population model developed from data gathered in 1998 and 1999 suggested that the population would decrease in 2000, resulting in a decrease in the number of males observed on leks from 140 to 132. I counted 140 males at leks in 2000, suggesting that the population remained relatively stable, at between 420 and 622 individuals. While sample sizes were small, measures of productivity in 2000 were quite low compared to previous years, suggesting a better understanding of the variability in the parameters in the model is needed. I also performed a 2-stage pilot experiment, focusing on attaching transmitters to sage-grouse chicks. I first practiced the technique by suturing transmitters to 10 chicken chicks, and then tested the technique on 4 sage-grouse chicks in the field. The transmitters did not appear to harm the chicks at all, and none of them showed signs of infection, bleeding, or scaring from the transmitter attachment. This technique appears to be a viable method for assessing chick survival. AuthorsAldridge, Cameron L. Year Published2000 PublicationAlberta Species At Risk Report Locations |
| Nesting and reproductive activities of Greater Sage-Grouse in a declining northern fringe population | Aldridge, CL | 2001 |
KeywordsCanada, Centrocercus urophasianus, Greater Sage-Grouse, nesting, reproductive effort, reproductive success AbstractIn Canada, Greater Sage-Grouse (Centrocercus urophasianus) are at the northern edge of their range, occurring only in southeastern Alberta and southwestern Saskatchewan. The population in Canada has declined by 66% to 92% over the last 30 years. We used radio-telemetry to follow 20 female Greater Sage-Grouse and monitor productivity in southeastern Alberta, and to assess habitat use at nesting and brood-rearing locations, All females attempted to nest. Mean clutch size (7.8 eggs per nest) was at the high end of the normal range for sage-grouse (typically 6.6-8.2). Nest success (46%) and breeding success (55%) were within the range found for more southerly populations (15% to 86% and 15% to 70%, respectively). Thirty-six percent of unsuccessful females attempted to renest. Fledging success was slightly lower than reported in other studies. Thus, reproductive effort does not appear to be related to the population decline. However, chick survival to greater than or equal to 50 days of age (mean = 18%) was only about half of that estimated (35%) for a stable or slightly declining population, suggesting that chick survival may be the most important factor reducing overall reproductive success and contributing to the decline of Greater Sa.-e-Grouse in Canada. AuthorsAldridge, CL; Brigham, RM Year Published2001 PublicationThe Condor: Ornithological Applications LocationsDOI10.1650/0010-5422(2001)103[0537:NARAOG]2.0.CO;2 |
| Occurrence of Greater Sage-Grouse x Sharp-tailed Grouse hybrids in Alberta | Aldridge, CL | 2001 |
KeywordsAlberta, DNA, Greater Sage-Grouse, hybrid, Sharp-tailed Grouse AbstractTwo distinct grouse were regularly observed at two Greater Sage-Grouse (Centrocercus urophasianus) 1eks in both 1999 and 2000 in southeastern Alberta. Physically and behaviorally, the birds exhibited characteristics of both Greater Sage-Grouse and Sharp-tailed Grouse (Tympanuchas phasianellus), suggesting they were hybrids. DNA analyses of blood and feather samples indicated that both birds were males with Greater Sage-Grouse mothers and thus, fathers that were likely Sharp-tailed Grouse. AuthorsAldridge, CL; Oyler-McCance, SJ; Brigham, RM Year Published2001 PublicationThe Condor: Ornithological Applications LocationsDOI10.1650/0010-5422(2001)103[0657:OOGSGS]2.0.CO;2 |
| Adaptive management of prairie grouse: how do we get there? | Aldridge, CL | 2004 |
Keywordsadaptive management, Alberta, Centrocercus urophasianus, conservation plans, grazing, greater sage-grouse, habitat, Manitoba, policy planning, prairie sharp-tailed grouse, Tympanuchus phasianellus AbstractManaging prairie grouse has been largely a reactive process without any "true" management experiments being implemented, thereby limiting our ability to learn from management and enhance conservation efforts for declining prairie grouse populations. In a few cases where the potential existed for a passive or active adaptive approach, monitoring was insufficient to detect effects of changes in management practices. Similar problems appear to occur at planning stages in attempts to implement adaptive management for prairie grouse populations, preventing proper consideration of sound adaptive experiments that advance learning. Successful adaptive management begins with stakeholder gatherings following a policy planning process, which includes many steps, beginning with goal identification and understanding of uncertainties and culminating in model simulations to understand potential management policies. By following this process, the opportunity to implement successful management experiments can be enhanced. We discuss the successes and failures of prairie grouse management using 2 case studies, 1 for prairie sharp-tailcd grouse (Tympanuchus phasianellus) in Manitoba and 1 for greater sage-grouse (Centrocercus urophasianus) in southern Alberta. We describe ways in which active adaptive management could improve our understanding of prairie grouse population declines and outline a policy planning process that, if followed, will allow adaptive management to be successfully implemented, enhancing prairie grouse management and conservation. AuthorsAldridge, CL; Boyce, MS; Baydack, RK Year Published2004 PublicationWildlife Society Bulletin LocationsDOI10.2193/0091-7648(2004)32[92:AMOPGH]2.0.CO;2 |
| Sage-Grouse Nesting and Brood Habitat Use in Southern Canada | Aldridge, CL | 2002 |
KeywordsNo keywords available AbstractGreater sage-grouse (Centrocercus urophasianus) populations have declined from 66 to 92% during the last 30 years in Canada, where they are listed as endangered. We used radiotelemetry to examine greater sage-grouse nest and brood habitat use in Alberta and assess the relationship between habitat and the population decline. We also identified the patch size at which sage-grouse were selecting nest and brood-rearing sites. Nest areas were in silver sagebrush (Artemisia cana) stands that had greater amounts of tall cover (P less than or equal to 0.001) at a patch size of 7.5 to 15 m in radius. Within those sagebrush stands, nests were located beneath the densest sagebrush present. Areas used for brood rearing had greater amounts of taller sagebrush cover in an area : 15 m in radius than at random locations. Brood locations were not selected based on forb content; mesic areas containing forbs (20-40% cover) as a food resource for chicks were limiting (only 12% cover available). Overall cover of sagebrush is considerably lower in Canada (5-11%) compared with sagebrush (Artemisia spp.) cover in other areas throughout the range of greater sage-grouse (15-25%). If management goals are to provide suitable nesting and brood-rearing habitat, efforts should be directed toward protecting and enhancing sagebrush stands greater than or equal to30 m(2) and increasing overall sagebrush cover. Management strategies also should focus on increasing the availability of mesic sites and increasing the abundance of sites with >10% forb cover, to enhance brood rearing habitat. AuthorsAldridge, CL; Brigham, RM Year Published2002 PublicationThe Journal of Wildlife Management LocationsDOI10.2307/3803176 |
| Distribution, abundance, and status of the Greater Sage-Grouse, Centrocercus urophasianus, in Canada | Aldridge, CL | 2003 |
Distribution, abundance, and status of the Greater Sage-Grouse, Centrocercus urophasianus, in CanadaKeywordsgreater sage-grouse, Centrocercus urophasianus, distribution, endangered status, Saskatchewan, Alberta, Canada AbstractWe reviewed the historic and present distribution of Greater Sage-Grouse (Centrocercus urophasianus) in Canada and found that the species has been eliminated from approximately 90% of its estimated historic distribution. Sage-grouse have been extirpated from British Columbia and reduced to remnant populations in Alberta and Saskatchewan. Estimates of the size of the population decline in Canada range from 66 to 92% over the last 30 years based on currently occupied habitat. As a result. sage grouse have been listed as Endangered in both Alberta and Saskatchewan by provincial governments an federally in Canada by COSEWIC. Intensive surveys from 1994 to 1999 in both provinces suggest that the 1999 spring breeding population had declined to between 813 and 1204 individuals. The number of active lek sites has continued to decline. suggesting that some habitats have become unsuitable to support viable sage-grouse populations. Number of yearling males recruiting to leks each spring has been low, suggesting that production and overwinter survival of young are the major problems related to the decline. Low chick survival rate, with only 18% surviving to 50 days of age, is the most likely parameter contributing to the population decline. These declines could be related to one or any combination of habitat changes. livestock grazing pressure, oil and gas developments, or climate change, all of which could lead to increased predation rates and decreased survival. It is questionable if the present population of sage-grouse in Canada is large enough to remain viable. AuthorsAldridge, CL; Brigham, RM Year Published2003 PublicationCanadian Field-Naturalist Locations |
| Sage-grouse nesting and brood habitat use in southern Canada. (vol 66, pg 433, 2002) | Aldrige, CL | 2003 |
Sage-grouse nesting and brood habitat use in southern Canada. (vol 66, pg 433, 2002)KeywordsAlberta, Artemisia, broods, Centrocercus urophasianus, greater sage-grouse, nesting, sagebrush AbstractGreater
sage-grouse
(Centrocercus
urophasianus)
populations
have
declined
from
66
to
92%
during
the
last
30
years
in
Canada,
where
they
are
listed
as
endangered.
We
used
radiotelemetry
to
examine
greater
sage-grouse
nest
and
brood
habitat
use
in
Alberta
and
assess
the
relationship
between
habitat
and
the
population
decline.
We
also
identified
the
patch
size
at
which
sage-grouse
were
selecting
nest
and
brood-rearing
sites.
Nest
areas
were
in
silver
sagebrush
(Artemisia
cana)
stands
that
had
greater
amounts
of
tall
cover
(P
<
0.001)
at
a
patch
size
of
7.5
to
15
m
in
radius.
Within
those
sagebrush
stands,
nests
were
located
beneath
the
densest
sagebrush
present.
Areas
used
for
brood
rearing
had
greater
amounts
of
taller
sagebrush
cover
in
an
area
215
m
in
radius
than
at
random
locations.
Brood
locations
were
not
selected
based
on
forb
content;
mesic
areas
containing
forbs
(20-40%
cover)
as
a
food
resource
for
chicks
were
limiting
(only
12%
cover
available).
Overall
cover
of
sagebrush
is
considerably
lower
in
Canada
(5-11%)
compared
with
sagebrush
(Artemisia
spp.)
cover
in
other
areas
throughout
the
range
of
greater
sage-grouse
(15-25%).
If
management
goals
are
to
provide
suitable
nesting
and
brood-rearing
habitat,
efforts
should
be
directed
toward
protecting
and
enhancing
sagebrush
stands
230
m2
and
increasing
overall
sage-
brush
cover.
Management
strategies
also
should
focus
on
increasing
the
availability
of
mesic
sites
and
increasing
the
abundance
of
sites
with
>10%
forb
cover,
to
enhance
brood
rearing
habita AuthorsAldrige, CL; Brigham, RM Year Published2003 PublicationJournal of Wildlife Management Locations |
