ArticlePDF Available

Agricultural destruction of Northern Pintail nests on cropland in prairie Canada

Authors:

Abstract and Figures

It has been postulated that the decline of the Northern Pintail (Anas acuta) population is related to the propensity of female pintails to nest in cropland. Using spatial modeling at multiple scales, we estimated that the long-term average (1961-2009) breeding population of Northern Pintails in prairie Canada would have initiated a mean of 974,260 nests/year, of which 47% (457,900 +/- 43,270) would have been in cropland. Nest success rates are very low (5%) in spring-seeded cropland with predation and agricultural activity responsible for approximately 78% and 22% of the nest loss, respectively. We estimated that a long-term mean of 94,750 (+/- 19,680) nests representing 524,725 pintail eggs would have been destroyed by agricultural seeding and tillage operations on cropland annually. The number of nests/eggs lost in any given year would vary by an order of magnitude dependent primarily upon the size of the pintail population nesting on the prairies in that year. Our estimate of incidental take is quite robust because it is based on multiple, long-term studies using data from across the Canadian prairies. Our analysis provides additional support for the theory that the pintail's habit of nesting in cropland is the probable reason for the decline in the pintail population, irrespective of the cause of nest loss. Although predation is the primary cause of the loss of pintail nests in cropland, the proportion of nests lost to predation in cropland is similar to that in other upland habitats on the prairies. Thus the additional loss from agriculture could well be incremental and may be the proximate causative factor in the pintail population's decline and failure to recover in recent decades.
Content may be subject to copyright.
VOLUME 13, ISSUE 2, ARTICLE 6
Duncan, D. C., and J. H. Devries. 2018. Agricultural destruction of Northern Pintail nests on cropland in prairie Canada. Avian Conservation and
Ecology 13(2):6. https://doi.org/10.5751/ACE-01243-130206
Copyright © 2018 by the author(s). Published here under license by the Resilience Alliance.
Research Paper
Agricultural destruction of Northern Pintail nests on cropland in prairie
Canada
David C. Duncan and James H. Devries 1,2
1Ducks Unlimited Canada, 2Institute for Wetland and Waterfowl Research
ABSTRACT. It has been postulated that the decline of the Northern Pintail (Anas acuta) population is related to the propensity of
female pintails to nest in cropland. Using spatial modeling at multiple scales, we estimated that the long-term average (1961–2009)
breeding population of Northern Pintails in prairie Canada would have initiated a mean of 974,260 nests/year, of which 47% (457,900 +/-
43,270) would have been in cropland. Nest success rates are very low (5%) in spring-seeded cropland with predation and agricultural
activity responsible for approximately 78% and 22% of the nest loss, respectively. We estimated that a long-term mean of 94,750 (+/-
19,680) nests representing 524,725 pintail eggs would have been destroyed by agricultural seeding and tillage operations on cropland
annually. The number of nests/eggs lost in any given year would vary by an order of magnitude dependent primarily upon the size of
the pintail population nesting on the prairies in that year. Our estimate of incidental take is quite robust because it is based on multiple,
long-term studies using data from across the Canadian prairies. Our analysis provides additional support for the theory that the pintail’s
habit of nesting in cropland is the probable reason for the decline in the pintail population, irrespective of the cause of nest loss.
Although predation is the primary cause of the loss of pintail nests in cropland, the proportion of nests lost to predation in cropland
is similar to that in other upland habitats on the prairies. Thus the additional loss from agriculture could well be incremental and may
be the proximate causative factor in the pintail population’s decline and failure to recover in recent decades.
Destruction de nids de Canard pilet causée par l'agriculture sur les terres cultivées des Prairies
canadiennes
RÉSUMÉ. Une des raisons avancées pour expliquer la diminution de la population de Canard pilet (Anas acuta) est en lien avec la
propension des femelles à nicher sur les terres cultivées. Au moyen de modélisation spatiale à de multiples échelles, nous avons estimé
que la population nicheuse moyenne de longue date (1961-2009) de Canard pilet des Prairies canadiennes aurait initié une moyenne
de 974 260 nids/année, dont 47 % (457 900 +/- 43 270) se seraient trouvés sur les terres cultivées. Le taux de succès des nids est très
faible (5 %) sur les terres à culture de printemps, où la prédation et les activités agricoles sont responsables de 78 % et de 22 % des pertes
de nids, respectivement. Nous avons estimé qu'une moyenne de 94 750 (+/- 19 680) nids équivalant à 524 725 oeufs de pilets auraient
été détruits annuellement par les opérations de travail du sol et d'ensemencement sur les terres cultivées. Le nombre de nids/oeufs
détruits au cours d'une année donnée variait d'abord en fonction de la taille de la population de pilets nichant dans les Prairies cette
année-là. Notre estimation de la prise accessoire est assez fiable parce qu'elle est fondée sur de multiples recherches de longue date
utilisant des données provenant des Prairies canadiennes. Notre analyse corrobore la théorie selon laquelle la diminution de la population
de Canard pilet serait probablement attribuable à l'habitude de l'espèce de nicher sur les terres cultivées, peu importe la cause sous-
jacente à la perte de nids. Même si la prédation est la cause première de la perte des nids de pilets sur les terres cultivées, la proportion
de nids détruits par la prédation sur les terres cultivées est similaire à celle observée dans d'autres milieux secs des Prairies. Ainsi, la
perte additionnelle causée par les activités agricoles pourrait être incrémentielle et se révéler être le facteur causal direct de la diminution
de la population de pilets et de l'échec de son rétablissement dans les récentes décennies.
Key Words: agriculture; Anas acuta; bird mortality; egg loss; incidental take; nest success; Northern Pintail
INTRODUCTION
Human-related activities result in the direct inadvertent killing of
hundreds of millions of birds and eggs annually in Canada
(Calvert et al. 2013). Calvert et al. (2013) found that most
estimates of incidental take of birds in Canada were < 1% of the
population, well below the 10% that they considered might cause
a detectable population impact. There are very few instances
where the current impacts of direct incidental human-related
mortality are thought to result in population-level declines
(Arnold and Zink 2011, Calvert et al. 2013). Although Longcore
and Smith (2013) cautioned against focusing only on species
where such mortality might cause population declines, it is
reasonable to do so because priority-setting exercises based on
conservation concern are the norm in conservation biology
(Mehlman et al. 2004, Beston et al. 2016). In this paper, we
quantify the nonintentional anthropogenic mortality for one of
the few avian species in North America where it has been proposed
that direct human-caused mortality may be responsible for the
population decline.
Address of Correspondent: David C. Duncan, 30 - 22549 Township Road 510, Leduc County, AB , Canada, T0B 3M1, daveduncan000@gmail.com
Avian Conservation and Ecology 13(2): 6
http://www.ace-eco.org/vol13/iss2/art6/
Fig. 1. Estimated long-term average (1961–2009) breeding Northern Pintail (Anas acuta) pair
density (pairs/km²) as a function of wetland, upland, and geographic covariates in the Prairie
Pothole Region (PPR; outlined in red) of Canada (Devries 2014).
The North American population of the Northern Pintail (Anas
acuta; hereafter pintail) has declined from about 10 million in the
mid-1950s to approximately 3 million in recent years (USFWS
2016). Multiple lines of evidence indicate that the reason for this
decline is related to reduced productivity as opposed to changes
in survival rates (Hestbeck 1995, Miller and Duncan 1999,
Herbert and Wassenaar 2005, Rice et al. 2010). Miller and
Duncan (1999) postulated that the decline of the pintail
population was a result of its unusual readiness to nest in cropland
where very few nests survive (Goelitz 1918, Milonski 1958, Klett
et al. 1988, Greenwood et al. 1995, Devries et al. 2018). Pintails
in prairie Canada lay their largest clutches in April (Duncan 1987,
Guyn and Clark 2000, Richkus 2002), and these early nests are
vulnerable to subsequent spring seeding operations. With
approximately 70–75% of the Canadian prairies now cultivated
(Gauthier and Wiken 2003) and pintails nesting in cropland
roughly in proportion to its availability on the landscape (Richkus
2002, Devries 2014, Devries et al. 2018), cropland appears to be
sink habitat for pintails (Miller and Duncan 1999, Podruzny et
al. 2002, Devries et al. 2018). Early estimates of nest destruction
in cropland indicated that agricultural activity caused 34–56% of
the nest losses (Milonksi 1958, Higgins 1977). Although Miller
and Duncan (1999) considered loss to agricultural activities to be
an important source of pintail nest destruction in cropland, a
number of more recent studies have suggested that predation is
the predominant cause of duck nest loss in cropland (Richkus
2002, Devries et al. 2008a, Devries 2014, Skone et al. 2015, Devries
et al. 2018). Although a number of studies have documented the
habitat nesting preferences of pintails (Klett et al. 1988,
Greenwood et al. 1995, Devries et al. 2018), we are unaware of
any estimate of numbers of nests initiated in cropland and
impacted by incidental take from agriculture.
In this study, we quantify the exposure of pintail nests in cropland
to loss from accidental anthropogenic destruction (incidental
take) versus predation on their primary breeding grounds in
prairie Canada. We use field data, geospatial models of pintail
distribution, and nest habitat selection models to estimate the
proportion and number of pintails that nest on cultivated land in
prairie Canada, and then calculate the number and proportion of
pintail nests and eggs destroyed by cultivation versus predation.
Our multimodel approach represents a unique and powerful
method to estimate potential impacts of anthropogenic
disturbance on demographic processes while accounting for
geographic variation in population and habitat distribution across
large spatial scales, an approach at the nexus of conservation and
ecology (Beissinger et al. 2006).
METHODS
We took a four-part modeling approach to estimating exposure
of pintail nests to agricultural disturbance in prairie Canada.
First, we used a species distribution model (SDM) developed by
one of us (JHD) for pintails in the Prairie Pothole Region (PPR)
of Canada and the U.S. (Devries 2014; Fig. 1). The pintail SDM
was developed using pintail count data from 809 systematically
located permanent survey transect segments as part of the May
Breeding Waterfowl Population and Habitat Survey (MBWPHS)
conducted annually by the U.S. Fish and Wildlife Service and the
Avian Conservation and Ecology 13(2): 6
http://www.ace-eco.org/vol13/iss2/art6/
Fig. 2. Network of 41-km² grids (n = 13,285) used in ArcGIS to extract estimated Northern Pintail
(Anas acuta) breeding pairs, and habitat availability, for input into a productivity model that
estimated the number of pintail nests initiated in spring-seeded cropland.
Canadian Wildlife Service (Benning 1976). Long-term average
breeding pair estimates (1961–2009) were modeled as a function
of various GIS-based habitat covariates associated with each
survey segment using negative binomial regression. The SDM
pair density layer for the PPR was then created by applying the
best fitting model to continuous covariate values extracted in
ArcGIS. From this layer, we extracted the estimated breeding pairs
in each of 13,285 41-km² grid cells covering the Canadian portion
of the PPR (Fig. 2).
Second, for each grid cell, we determined contemporary habitat
composition for each of eight habitat classes (spring-seeded
cropland, fall-seeded cropland, idle grassland, grazed grassland,
hayland, wetland, trees/shrubs, and other) using Agriculture and
Agri-Food Canada’s (AAFC) 2014 annual crop mapping digital
layer (http://open.canada.ca/data/en/dataset/ba2645d5-4458-414d-
b196-6303ac06c1c9). Because wetlands are poorly captured in
AAFC’s crop mapping layer, we recalculated habitat composition
after including estimated wetland habitat area from Ducks
Unlimited Canada’s (DUC) adjusted CanVec hydrology layer
(Natural Resources Canada 2011). DUC CanVec adjustments are
based on a spatial model contrasting CanVec versus DUC wetland
inventory data (i.e., digitized wetlands at a scale of 1:5000 or
better; imagery resolution 0.5 m–2.5 m, DUC unpublished data).
The DUC adjusted wetland layer has previously been used to
estimate waterfowl distribution across the Canadian and U.S.
portion of the PPR (Doherty et al. 2015).
Third, we used a deterministic model of pintail productivity
(hereafter, productivity model), based on pintail nest habitat
selection and habitat-specific nest survival estimates, to calculate
potential exposure of pintail nests to incidental take in croplands.
These estimates were developed from multiple nesting studies
conducted across 62 study sites in prairie Canada (1997–2009)
and included nest attributes and fate of 1005 pintail nests found
with equal nest searching effort across habitats (Devries et al.
2018). Nest habitat selection was estimated using resource
selection functions comparing the distribution of used versus
random locations among habitats at the scale of the 41-km² study
areas (Devries et al. 2018). The productivity model generally
follows the structure of a similar model developed for the Mallard
(Anas platyrhynchos; Johnson et al. 1987). In each grid cell
(above), the productivity model was used to generate a population
of nests from the estimated breeding pairs based on duck nesting,
renesting propensity, and nesting effort estimates from the
published literature as follows. Because nesting propensity has
not been estimated for prairie-breeding pintails, we used the
average nesting propensity (0.90) for a large sample of radio-
marked female Mallards studied in the Canadian PPR (Devries
et al. 2008b). We set declining renest probabilities of 0.85, 0.5,
and 0.2 for early, mid, and late-season based on seasonally
declining renest probabilities observed for Mallards (Arnold et
al. 2010, Devries 2014). The model allowed a maximum of three
nest attempts per season based on pintail renesting behavior
reported by Grand and Flint (1996) and Guyn and Clark (2000).
Nests were distributed into available habitats based on temporally
(within season) and spatially varying (habitat availability) habitat
selection algorithms (Devries et al. 2018).
Avian Conservation and Ecology 13(2): 6
http://www.ace-eco.org/vol13/iss2/art6/
Table 1. Summary of statistics for habitat availability (productivity model input) and proportion of Northern Pintail (Anas acuta) nests
in each habitat (productivity model output) across 41-km² grid cells (n = 13,285) covering the Canadian portion of the Prairie Pothole
Region.
Nest Habitat
Model Input /
Output
Statistics Spring-seeded
Cropland
Fall-seeded
Cropland
Idle Grass Grass
Pasture
Hayland Wetland Trees/
shrubs
Other
Mean 0.499 0.007 0.027 0.215 0.082 0.049 0.103 0.017
Std.Dev. 0.297 0.011 0.084 0.190 0.078 0.093 0.172 0.048
Habitat Availability
Median 0.541 0.003 0.008 0.161 0.057 0.020 0.029 0.007
Min 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
Max 0.997 0.169 1.000 0.880 0.445 0.997 0.985 0.994
Mean 0.468 0.011 0.040 0.274 0.118 0.089 0.000 0.000
Std.Dev. 0.261 0.018 0.095 0.213 0.092 0.160 0.000 0.000
Median 0.494 0.004 0.022 0.223 0.100 0.034 0.000 0.000
Proportion of
Nests in Habitat
Min 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
Max 0.994 0.219 1.000 0.910 0.399 1.000 0.000 0.000
The pintail productivity model includes “Trees/shrubs” and “Other” as available habitat, however, no nests are distributed in these habitats because
nest site selection estimates are 0.
Finally, we reviewed information from the literature on nest
survival rates and causes of nest loss, and used best estimates
combined with the modeled estimates of the number of nests in
croplands and clutch size to estimate the mean number of nests/
eggs lost to agricultural activities and predation. We restricted
our analysis to pintails nesting on the Canadian prairies because
this is where a majority of pintails nest and much of our ancillary
data was derived from this region (e.g., Greenwood et al. 1995,
Miller and Duncan 1999, Devries et al. 2018). We estimated
variation in the annual number of nests destroyed by agricultural
machinery using the Delta method (Oehlert 1992) to combine
estimated variances in the following: (1) the number of nests
initiated in spring-seeded cropland; (2) the nest survival rate in
spring-seeded cropland; and (3) the proportion of nests lost to
agricultural machinery reported in the literature. Unless
otherwise indicated, we present estimates + 1 SE.
RESULTS
We estimated that an average of 731,160 pintail pairs settled to
breed in prairie Canada between 1961 and 2009, and that these
birds initiated a mean of 974,260 nests. Based on contemporary
habitat availability inputs for prairie Canada, and long-term
average pintail population distribution, the productivity model
estimated approximately 47% of pintail nests would be initiated
in spring-seeded cropland, 27% in grassland pasture, 12% in
haylands, and 9% in wetlands (Table 1). Thus our model-based
estimate of the number of pintail nests initiated in spring-seeded
cropland is 457,900 nests/year. We assumed nest numbers vary
directly with the pintail population size in prairie Canada and
therefore used the coefficient of variation in the annual breeding
population estimates from prairie Canada (Waterfowl Breeding
and Habitat Survey, Benning 1976) and applied it to our estimate
of nests in spring-seeded cropland to develop the standard error
(SE = + 43,270; Table 2).
To determine the number of nests and eggs destroyed in cropland,
we first reviewed waterfowl nest survival estimates in cropland.
Nest survival of ducks in spring-seeded cropland is low compared
to most other habitat types (Klett et al. 1988, Greenwood et al.
1995), ranging from < 1–4% (Richkus 2002), 2% (Greenwood et
al. 1995), and 7% (Klett et al. 1988). Devries et al. (2008a) reported
a relatively high nest success rate of 12% in spring-seeded cropland
and opined that this may have been a result of their inclusion of
late-season nests because success rates in spring-seeded cropland
can increase substantially throughout the growing season (Emery
et al. 2005). Recently, one of us (JHD) modeled mean pintail nest
success in spring-seeded cropland to be 5.1% (i.e., daily survival
rate = 0.9111 + 0.0146; Table 2) based on the fate of 153 nests in
cropland (Devries et al. 2018). Thus for estimates herein, we used
a nest loss rate of 95% in spring-seeded cropland, which produced
an estimate of 435,000 pintail nests destroyed annually in
cropland.
To estimate the loss caused by the incidental take from agricultural
operations, we reviewed causes of duck nest loss in cropland.
Early studies (Milonksi 1958, Higgins 1977) reported that
agricultural activities such as seeding and tillage were responsible
for the loss of 34–56% of duck nests on cultivated land. However,
these studies had small sample sizes, were localized in geographic
coverage, were not conducted in prairie Canada, and occurred at
a time when farming practices would have differed from those of
today. More contemporary studies from prairie Canada have
found that predation is the predominant cause of duck nest loss
in cropland rather than farming operations. Greenwood et al.
(1995) and Devries et al. (2008a) reported that 17% and 22%,
respectively, of nests of various duck species in cropland
(primarily spring-seeded) in prairie Canada were lost to
agricultural activity. Pintail nest loss from agricultural practices
in spring-seeded cropland estimated from various sources
averages 21.8% (+ 1.3%; Table 2). In all studies reviewed,
predation caused the loss of the remainder of the nests that were
not abandoned. These more contemporary studies consistently
demonstrate that agricultural activities are not the primary cause
of pintail nest loss in cropland. Given the above mean and
variance estimates for the number of pintails nesting in cropland,
cropland nest survival and proportion of nests destroyed by farm
machinery, we estimate 94,750 (+ 19,680; based on Delta method)
pintail nests were destroyed annually by agricultural operations
=
~
Avian Conservation and Ecology 13(2): 6
http://www.ace-eco.org/vol13/iss2/art6/
Table 2. Parameter estimates and standard errors used in the calculation of Northern Pintail (Anas acuta) eggs lost to destruction by
agricultural machinery annually in spring-seeded cropland in prairie Canada.
Parameter Source Estimate (SE) Details
Pintail nests initiated in
spring-seeded cropland
Model-based 457,900 (43,270) SE based on coefficient of variation in prairie
Canada pintail population estimates, 1961–2015
Pintail daily nest survival
rate (DSR) in spring-seeded
cropland
Devries et al. 2018 0.911 (0.01465) n = 153 pintail nests in cropland; nest survival rate =
5.1% (i.e., DSR32)
Greenwood et al. 1995 0.1830 17 of 97 pintail nest losses (Table 11)
Devries et al. 2008a0.2140 6 of 28 pintail nest losses
Devries 2014 0.2360 26 of 110 pintail nest losses
Klett et al. 1988 0.2390 22 of 92 pintail nest losses (Table 5)
Proportion of pintail nests
in spring-seeded cropland
lost to machinery
0.2180 (0.0129)§
Clutch size Ducks Unlimited Canada,
unpublished data
7.8 (0.122) n = 145 pintail nests in cropland with full clutch
known
Benning (1976)
Table reference in cited publication
§ Mean (SE) of listed estimates
in prairie Canada, with the remainder lost to predation. We
extended this estimate to the number of eggs lost given
approximately 42% of nests are lost with a full clutch of 7.8 eggs
(Table 2; DUC, unpublished data) and we assumed the remainder
were lost with half that number during laying, yielding
approximately 524,725 eggs destroyed annually.
DISCUSSION
Many estimates of anthropogenic-related bird mortality use
extrapolations from small-scale studies, which were not designed
to be scaled up and often are based on limited data (Calvert et al.
2013, Machtans and Thogmartin 2014). Calvert et al. (2013)
considered most recent Canadian estimates of incidental take to
be accurate only within an order of magnitude. Our estimates of
the proportion and number of pintail nests destroyed in cropland
overcome these shortcomings because they are derived from large
datasets from multiple, geographically broad, long-term studies
in prairie Canada. Furthermore, our modeling approach allowed
us to not only account for the average distribution of the pintail
population within prairie Canada (and hence its exposure to
available cropland/grassland at the prairie-wide scale) but also for
nest-site selection from among the available habitats at a local
scale. These advantages, combined with the similarity of our
overall proportion of pintails nesting in cropland to that of other
studies (see below), lead us to a high degree of confidence in the
robustness of our estimates, unlike many other estimates of
incidental take. In addition, we have incorporated well
documented sources of variance in our estimates that wholly or
partially account for the following: (1) total continental pintail
population size, which has been declining over time (USFWS
2016); (2) number of pintails settling on the prairies, which is
partly related to annual wetland conditions (Hestbeck 1995,
Miller and Duncan 1999); (3) settling distribution of pintails
within the prairies relative to variances in land use and habitat
availability (Devries et al. 2018); (4) annual variation in nest
success (Greenwood et al. 1995, Guyn and Clark 2000); and (5)
renesting persistence (Duncan 1987, Guyn and Clark 2000).
Although the absolute number of pintail nests in cropland can
fluctuate greatly among years, the 47% proportion of pintail nests
estimated in cropland is considerably less variable because of the
relative stability in the regional amount of cropland over time
(Devries et al. 2018) and the minimal influence of varying
population size on habitat selection. Greenwood et al. (1995)
estimated that 45% and 34% of pintail nests were in cropland on
the Canadian prairies and parklands, respectively, using less
sophisticated methodology. Because many more pintails nest in
the prairies as compared to the parkland (Miller and Duncan
1999), Greenwood et al.’s (1995) 45% figure would be more
representative of the pintail population. Richkus (2002) estimated
that 51% of pintails in southern Saskatchewan nested in cropland,
although his study was conducted in a much more localized area.
Thus our overall estimate of 47% of the pintail nests in the
Canadian prairies being initiated in spring-seeded cropland is
consistent with other sources, despite differences in years and
methodologies.
From a conservation perspective, the large proportion of pintails
nesting in cropland is more important than a given number of
nests destroyed in cropland in any particular year. Low duck nest
success in cropland compared to native grassland is well
established (Klett et al. 1988, Greenwood et al. 1995, Devries et
al. 2018) and the negative impact of conversion of native
grassland to cropland on duck populations over time has been
demonstrated at various scales (Bethke and Nudds 1995,
Podruzny et al. 2002, Drever et al. 2007). Pintails have been
particularly impacted by cultivation and their decline has been
attributed to the conversion of grassland to cropland (Miller and
Duncan 1999, Podruzny et al. 2002). Our findings herein that
almost half of the pintail nests in prairie Canada occur in
cropland where they suffer a very low nest success rate provides
additional support for the hypothesis that the pintail’s proclivity
to nest in cropland is the cause of its decline.
We cannot definitively say that the additional pintail nests lost to
incidental take by agriculture is the cause of the decline in the
Avian Conservation and Ecology 13(2): 6
http://www.ace-eco.org/vol13/iss2/art6/
pintail population, however the evidence is suggestive and our
estimates are near the 10% range suggested by Calvert et al. (2013)
as potential for population level impact (after fledging rates are
considered). Although predation rather than agriculture causes
the bulk of pintail nest loss on cropland, predation generally
causes 70–80% loss of duck nests on the prairies in virtually all
upland habitat types (Klett et al. 1988, Greenwood et al. 1995).
Pintails are unique in that (i) they are the only prairie duck species
that has exhibited a long-term decline and failed to respond
positively to high pond numbers over the past decade, and (ii)
they have a large proportion of their population nesting in
cropland where nest success is lower than most other habitat types.
The fact that duck nest success is relatively high, e.g., > 20%, in
fall-seeded crops (Cowan 1982, Duebbert and Kantrud 1987,
Devries et al. 2008a, Skone et al. 2015) and higher than in most
other habitat types (Klett et al. 1988, Greenwood et al. 1995),
suggests that in the absence of spring tillage, nest success on seeded
cropland can be quite high. Although the high nest success in fall-
seeded cropland is confounded by its taller vegetative cover earlier
in the summer compared to spring-seeded crops, the evidence is
suggestive that the loss from agricultural activities may indeed be
additive and responsible for the decline in the pintail population.
It should also be recognized that the general habitat category of
cropland includes land that is fallowed, a practice that has greatly
decreased over time. This change in agricultural practice on
cropland may have significantly influenced pintail nesting and
success (Podruzny et al. 2002), although that study did not include
the very high pintail populations of the mid-late 1950s in its
analysis.
There have been very few studies of birds nesting in cropland in
prairie Canada, most likely because there are few bird species that
nest in cropland in relatively high densities (e.g., Owens and Myres
1973, DeJong et al. 2004), and there are many logistical challenges
to conducting nest searches on actively farmed lands (Devries et
al. 2008a). A few other prairie-nesting bird species that readily
nest in cropland are Horned Larks (Eremophila alpestris),
longspurs (Owens and Myre 1973, McMaster and Davis 2001,
Martin and Forsyth 2003,), Killdeers (Charadrius vociferus;
Higgins 1975), Long-billed Curlew (Numenius americanus;
Devries et al. 2010), and Marbled Godwit (Limosa fedoa; Garvey
et al. 2013). Because of the prevalence of cropland on the prairies,
a substantial proportion of the population of these species could
nest in cropland. Tews et al. (2013) modeled the potential effect
of agriculture on Horned Larks and estimated that the loss of
Horned Larks from farming operations was low, however their
estimates were coarse and subject to high uncertainty, e.g., their
two estimates of the size of the prairie-breeding Horned Lark
population varied by an order of magnitude. We encourage others
to pursue studies of bird species that are prone to nest in cropland
to more accurately determine the potential impact of tillage and
cultivation on those species.
CONCLUSION
Almost half of the pintail nests on the Canadian prairies are
initiated in cropland, a habitat in which nest loss is extremely high
and greater than in most other habitat types. Predators are
responsible for three-quarters of the nest loss on cropland with
agricultural activities being responsible for the remainder. A
number of those nests that are destroyed by agricultural activities
would undoubtedly be lost to predation even in the absence of
human-caused destruction. Although it remains to be determined
whether the additive effect of agricultural activity causes sufficient
incremental loss as to be the cause of the persistently low pintail
population size, the high nest success observed in fall-seeded crops
(Cowan 1982, Duebbert and Kantrud 1987, Devries et al. 2008a,
Skone et al. 2015) suggests that nest success in annual crops can
be quite high in the absence of spring seeding and tillage. Our
finding of a high proportion of pintail nests in cropland,
combined with the relatively low nest success rate, provide
additional support for the hypothesis that cropland nesting is the
causative factor behind the pintail population’s decline,
irrespective of the cause of nest loss. We encourage further
investigation of this question using tools like integrated
population models (Arnold et al. 2018). In the absence of any
readily acceptable method of reducing mechanical destruction of
duck nests during spring seeding or tillage operations, fall-seeded
crops like winter wheat or fall rye and/or conversion of annual
cropland to perennial crops appear to offer the best solutions to
improve pintail nest success rates on the prairies.
Responses to this article can be read online at:
http://www.ace-eco.org/issues/responses.php/1243
Acknowledgments:
We are grateful to Environment and Climate Change Canada for
funding of the analyses and manuscript preparation, and to Ducks
Unlimited Canada for use of their modeling systems. We thank L.
Armstrong for her assistance with the statistical analyses, and J.
Ingram, B. Bartzen, and two anonymous reviewers for their helpful
comments on the manuscript.
LITERATURE CITED
Arnold, T. W., R. G. Clark, D. N. Koons, and M. Schaub. 2018.
Integrated population models facilitate ecological understanding
and improved management decisions. Journal of Wildlife
Management 82:266-274. http://dx.doi.org/10.1002/jwmg.21404
Arnold, T. W., J. H. Devries, and D. W. Howerter. 2010. Factors
that affect renesting in Mallards (Anas platyrhynchos). Auk
127:212-221. http://dx.doi.org/10.1525/auk.2009.09028
Arnold, T. W., and R. M. Zink. 2011. Collision mortality has no
discernible effect on population trends of North American birds.
PLoS ONE 6(9):e24708. http://dx.doi.org/10.1371/journal.
pone.0024708
Beissinger, S. R., J. R. Walters, D. G. Catanzaro, K. G. Smith, J.
B. Dunning, Jr., S. M. Haig, B. R. Noon, and B. M. Smith. 2006.
Modeling approaches in avian conservation and the role of field
biologists. Ornithological Monographs 59:1-56. http://dx.doi.
org/10.2307/40166820 http://dx.doi.org/10.2307/40166820
Benning, D. S. 1976. Standard procedures for waterfowl population
and habitat surveys: operating manual. U.S. Fish and Wildlife
Service, Office of Migratory Bird Management, Laurel,
Maryland, USA.
Avian Conservation and Ecology 13(2): 6
http://www.ace-eco.org/vol13/iss2/art6/
Beston, J. A., J. E. Diffendorfer, S. R. Loss, and D. H. Johnson.
2016. Prioritizing avian species for their risk of population-level
consequences from wind energy development. PLoS ONE 11(3):
e0150813. http://dx.doi.org/10.1371/journal.pone.0150813
Bethke, R. W., and T. D. Nudds. 1995. Effects of climate change
and land use on duck abundance in Canadian prairie-parklands.
Ecological Applications 5:588-600. http://dx.doi.org/10.2307/1941969
Calvert, A. M., C. A. Bishop, R. D. Elliot, E. A. Krebs, T. M.
Kydd, C. S. Machtans, and G. J. Robertson. 2013. A synthesis of
human-related avian mortality in Canada. Avian Conservation and
Ecology 8(2):11. http://dx.doi.org/10.5751/ACE-00581-080211
Cowan, W. F. 1982. Waterfowl production on zero tillage farms.
Wildlife Society Bulletin 10(4):305-308.
DeJong, J. R., D. E. Naugle, K. K. Bakker, F. R. Quamen, and
K. F. Higgins. 2004. Impacts of agricultural tillage on grassland
birds in western South Dakota. Pages 76-80 in D. Egan and J. A.
Harrington, editors. Proceedings of the 19th North American
Prairie Conference: the Conservation Legacy Lives On. University
of Wisconsin-Madison, Madison, Wisconsin, USA.
Devries, J. H. 2014. Fitness consequences of avian habitat selection
in dynamic landscapes: multi-scale evaluations in northern pintails.
Dissertation, University of Saskatchewan, Saskatoon, Saskatchewan,
Canada.
Devries, J. H., L. M. Armstrong, R. J. MacFarlane, L. Moats, and
P. T. Thoroughgood. 2008a. Waterfowl nesting in fall-seeded and
spring-seeded cropland in Saskatchewan. Journal of Wildlife
Management 72:1790-1797. http://dx.doi.org/10.2193/2007-513
Devries, J. H., R. W. Brook, D. W. Howerter, and M. G. Anderson.
2008b. Effects of spring body condition and age on reproduction
in Mallards (Anas platyrhynchos). Auk 125:618-628. http://dx.doi.
org/10.1525/auk.2008.07055
Devries, J. H., R. G. Clark, and L. M. Armstrong. 2018. Dynamics
of habitat selection in birds: adaptive response to nest predation
depends on multiple factors. Oecologia 187(1):305-318. http://dx.
doi.org/10.1007/s00442-018-4134-2
Devries, J. H., S. O. Rimer, and E. M. Walsh. 2010. Cropland
nesting by Long-billed Curlews in southern Alberta. Prairie
Naturalist 42:123-129.
Doherty, K. E., J. S. Evans, J. Walker, J. H. Devries, and D. W.
Howerter. 2015. Building the foundation for international
conservation planning for breeding ducks across the U.S. and
Canadian border. PLoS ONE 10(2):e0116735. http://dx.doi.
org/10.1371/journal.pone.0116735
Drever, M. C., T. D. Nudds, and R. G. Clark. 2007. Agricultural
policy and nest success of prairie ducks in Canada and the United
States. Avian Conservation and Ecology 2(2):5. http://dx.doi.
org/10.5751/ACE-00175-020205
Duebbert, H. F., and H. A. Kantrud. 1987. Use of no-till winter
wheat by nesting ducks in North Dakota. Journal of Soil and
Water Conservation 42:50-53.
Duncan, D. C. 1987. Nesting of Northern Pintails in Alberta:
laying date, clutch size, and renesting. Canadian Journal of
Zoology 65:234-246. http://dx.doi.org/10.1139/z87-038
Emery, R. B., D. W. Howerter, L. M. Armstrong, M. G. Anderson,
J. H. Devries, and B. L. Joynt. 2005. Seasonal variation in
waterfowl nesting success and its relation to cover management
in the Canadian prairies. Journal of Wildlife Management 69
(3):1181-1193. http://dx.doi.org/10.2193/0022-541X(2005)069[1181:
SVIWNS]2.0.CO;2
Garvey, M. E., E. Nol, D. W. Howerter, and L. M. Armstrong.
2013. A spatial analysis of factors affecting nest success of
shorebirds in the Canadian prairies. Condor 115(1):58-66. http://
dx.doi.org/10.1525/cond.2012.110146
Gauthier, D. A., and E. B. Wiken. 2003. Monitoring the
conservation of grassland habitats, prairie ecotone, Canada.
Environmental Monitoring and Assessment 88(1-3):343-364.
http://dx.doi.org/10.1023/A:1025585527169
Goelitz, W. A. 1918. The destruction of nests by farming
operations in Saskatchewan. Auk 35:238-240. http://dx.doi.
org/10.2307/4072879
Grand, J. B., and P. L. Flint. 1996. Renesting ecology of Northern
Pintails on the Yukon-Kuskokwim Delta, Alaska. Condor
98:820-824. http://dx.doi.org/10.2307/1369862
Greenwood, R. J., A. B. Sargeant, D. H. Johnson, L. M.
Cowardin, and T. L. Shaffer. 1995. Factors associated with duck
nest success in the prairie pothole region of Canada. Wildlife
Monographs 128:3-57.
Guyn, K. L., and R. G. Clark. 2000. Nesting effort of Northern
Pintails in Alberta. Condor 102:619-628. http://dx.doi.
org/10.2307/1369793
Hebert, C. E., and L. I. Wassenaar. 2005. Stable isotopes provide
evidence for poor Northern Pintail production on the Canadian
prairies. Journal of Wildlife Management 69(1):101-109. http://dx.
doi.org/10.2193/0022-541X(2005)069<0101:SIPEFP>2.0.CO;2
Hestbeck, J. B. 1995. Response of Northern Pintail breeding
populations to drought, 1961-92. Journal of Wildlife Management
59(1):9-15. http://dx.doi.org/10.2307/3809109
Higgins, K. F. 1975. Shorebird and game bird nests in North
Dakota croplands. Wildlife Society Bulletin 3(4):176-179.
Higgins, K. F. 1977. Duck nesting in intensively farmed areas of
North Dakota. Journal of Wildlife Management 41(2):232-242.
http://dx.doi.org/10.2307/3800600
Johnson, D. H., D. W. Sparling, and L. M. Cowardin. 1987. A
model of the productivity of the Mallard duck. Ecological
Modelling 38(3-4):257-275. http://dx.doi.org/10.1016/0304-3800
(87)90100-1
Klett, A. T., T. L. Shaffer, and D. H. Johnson. 1988. Duck nest
success in the prairie pothole region. Journal of Wildlife
Management 52:431-440. http://dx.doi.org/10.2307/3801586
Longcore, T., and P. A. Smith. 2013. On avian mortality associated
with human activities. Avian Conservation and Ecology 8(2):1.
http://dx.doi.org/10.5751/ACE-00606-080201
Machtans, C. S., and W. E. Thogmartin. 2014. Understanding the
value of imperfect science from national estimates of bird
mortality from window collisions. Condor 116(1):3-7. http://dx.
doi.org/10.1650/CONDOR-13-134.1
Avian Conservation and Ecology 13(2): 6
http://www.ace-eco.org/vol13/iss2/art6/
Martin, P. A., and D. J. Forsyth. 2003. Occurrence and
productivity of songbirds in prairie farmland under conventional
versus minimum tillage regimes. Agriculture, Ecosystems, and
Environment 96:107-117. http://dx.doi.org/10.1016/S0167-8809
(02)00234-7
McMaster, D. G., and S. K. Davis. 2001. An evaluation of
Canada’s permanent cover program: habitat for grassland birds?
Journal of Field Ornithology 72(2):195-210. http://dx.doi.
org/10.1648/0273-8570-72.2.195
Mehlman, D. W., K. V. Rosenberg, J. V. Wells, and B. Robertson.
2004. A comparison of North American avian conservation
priority ranking systems. Biological Conservation 120:383-390.
http://dx.doi.org/10.1016/j.biocon.2004.03.013
Miller, M. H., and D. C. Duncan. 1999. The Northern Pintail in
North America: status and conservation needs of a struggling
population. Wildlife Society Bulletin 27(3):788-800.
Milonski, M. 1958. The significance of farmland for waterfowl
nesting and techniques for reducing losses due to agricultural
practices. Transactions of the North American Wildlife and Natural
Resource Conference 23:215-227. Wildlife Management Institute,
Washington, D.C., USA.
Natural Resources Canada. 2011. CanVec feature catalogue.
Natural Resources Canada, Centre for Topographic Information,
Sherbrooke, Québec, Canada.
Oehlert, G. W. 1992. A note on the delta method. American
Statistician 46:27-29. http://dx.doi.org/10.1080/00031305.1992.10475842
Owens, R. A., and M. T. Myres. 1973. Effects of agriculture upon
populations of native passerine birds of an Alberta fescue
grassland. Canadian Journal of Zoology 51(7):697-713. http://dx.
doi.org/10.1139/z73-104
Podruzny, K. M., J. H. Devries, L. M. Armstrong, and J. J. Rotella.
2002. Long-term response of Northern Pintails to changes in
wetlands and agriculture in the Canadian Prairie Pothole Region.
Journal of Wildlife Management 66:993-1010. http://dx.doi.
org/10.2307/3802932
Rice, M. B., D. A. Haukos, J. A. Dubovsky, and M. C. Runge.
2010. Continental survival and recovery rates of Northern
Pintails using band-recovery data. Journal of Wildlife
Management 74(4):778-787. http://dx.doi.org/10.2193/2008-598
Richkus K. D. 2002. Northern Pintail nest site selection, nest
success, resending ecology, and survival in the intensively farmed
prairies of southern Saskatchewan: an evaluation of the ecological
trap hypothesis. Dissertation. Louisiana State University. Baton
Rouge, Louisiana, USA.
Skone, B. R., J. J. Rotella, and J. Walker. 2015. Waterfowl
production from winter wheat fields in North and South Dakota.
Journal of Wildlife Management 80(1):127-137. http://dx.doi.
org/10.1002/jwmg.993
Tews, J., D. G. Bert, and P. Mineau. 2013. Estimated mortality of
selected migratory bird species from mowing and other technical
operations in Canadian agriculture. Avian Conservation and
Ecology 8(2):8. http://dx.doi.org/10.5751/ACE-00559-080208
U.S. Fish and Wildlife Service. 2016. Waterfowl population status,
2016. U.S. Department of the Interior, Washington, D.C., USA.
Editor-in-Chief: Ryan Norris
... Increased agricultural intensification, driven by the conversion of ca. 9 M hectares of idled cropland (summer fallow) to continuous spring-seeded cropland under minimum tillage, has occurred over the past three decades 47,48 . The resultant increase in availability and use of spring-seeded versus idle cropland for nesting is the likely driver of declining reproduction levels 49,50 . At the observed level of annual funding for waterfowl habitat conservation ($31.3 ...
... This study also found that productivity was negatively correlated with agricultural intensification at the subregional scale. Indeed a growing body of evidence from North America suggests that the decline in abundance of the pintail, a species that readily nests in residual crop stubble prior to seeding, may be linked to the increase in conservation tillage practices that reduce the availability of undisturbed stubble provided by fallowed cropland 49,50,108 . The economic value of birding and hunting associated with pintails in North America is estimated at >$100 M (2014 USD) annually 10 . ...
... Canada's (AAFC) 2016 annual, 30-m crop raster (http://open.canada.ca/data/en/dataset/ba2645d5-4458-414d-b196-6303ac06c1c9) to estimate landscape composition in 2016 for eight habitat classes (spring-seeded cropland, fall-seeded cropland, idle grassland, grazed grassland, hayland, wetland, trees/shrubs, and other). Because wetlands are poorly captured in AAFC's crop mapping layer, we recalculated base habitat composition after including estimated wetland habitat area from the CanVec hydrology layer 116 after adding small wetlands missed by the AAFC and CanVec layers 49 . This approach yielded the 2016 land-cover map for modeling pintail distribution and reproduction throughout the PPR. ...
Article
Full-text available
Land-use intensification on arable land is expanding and posing a threat to biodiversity and ecosystem services worldwide. We develop methods to link funding for avian breeding habitat conservation and management at landscape scales to equilibrium abundance of a migratory species at the continental scale. We apply this novel approach to a harvested bird valued by birders and hunters in North America, the northern pintail duck (Anas acuta), a species well below its population goal. Based on empirical observations from 2007–2016, habitat conservation investments for waterfowl cost $313 M and affected <2% of the pintail’s primary breeding area in the Prairie Pothole Region of Canada. Realistic scenarios for harvest and habitat conservation costing an estimated $588 M (2016 USD) led to predicted pintail population sizes <3 M when assuming average parameter values. Accounting for parameter uncertainty, converting 70–100% of these croplands to idle grassland (cost: $35.7B–50B) is required to achieve the continental population goal of 4 M individuals under the current harvest policy. Using our work as a starting point, we propose continued development of modeling approaches that link conservation funding, habitat delivery, and population response to better integrate conservation efforts and harvest management of economically important migratory species.
... The Prairie Pothole Region (PPR) is the most important breeding region for many North American waterfowl species (Batt, Anderson, Anderson, & Caswell, 1989;Doherty, Howerter, Devries, & Walker, 2018;Johnson & Grier, 1988). Among waterfowl species that breed primarily in the PPR, northern pintails (Anas acuta; hereafter pintails) are especially vulnerable to agricultural practices given their propensity for nesting in croplands (Devries, Armstrong, MacFarlane, Moats, & Thoroughgood, 2008;Devries, Clark, & Armstrong, 2018;Duncan & Devries, 2018;Klett, Shaffer, & Johnson, 1988;Richkus, 2002). ...
... Hierarchical partitioning revealed that on average, productivity had a 57.2% (95% CI: 30.9%, 85.7%) independent contribution to pintail population growth, which was greater than contributions of female survival (mean: 17.8%, 95% CI: 1.2%, 42.9%) and male survival (mean: 24.9%, 95% CI: 7.1%, 46.7%; Figure 6). Given the propensity of pintails to nest in cropland stubble (Duncan & Devries, 2018), and the vast shift in crop management to current continuous cropping practices, we believe this specific land-use change is a plausible explanation for pintail population declines that began in the 1970s. Under summer fallow practices that were common through the 1970s, farmers retained previous crop residues on approximately half their acreage and delayed tillage until mid-summer after most pintails had completed nesting (Carlyle, 1997 (Devries et al., 2008;Duncan & Devries, 2018;Richkus, 2002). ...
... Given the propensity of pintails to nest in cropland stubble (Duncan & Devries, 2018), and the vast shift in crop management to current continuous cropping practices, we believe this specific land-use change is a plausible explanation for pintail population declines that began in the 1970s. Under summer fallow practices that were common through the 1970s, farmers retained previous crop residues on approximately half their acreage and delayed tillage until mid-summer after most pintails had completed nesting (Carlyle, 1997 (Devries et al., 2008;Duncan & Devries, 2018;Richkus, 2002). ...
Article
Full-text available
1.Knowledge of land use patterns that could affect animal population resiliency or vulnerability to environmental threats such as climate change is essential, yet the interactive effects of land use and climate on demography across space and time can be difficult to study. This is particularly true for migratory species, which rely on different landscapes throughout the year. 2.Unlike most North American migratory waterfowl, populations of northern pintails (Anas acuta; hereafter pintails) have not recovered since the 1980s despite extended periods of abundant flooded wetlands (i.e. ponds). The mechanisms and drivers involved in this discrepancy remain poorly understood. While pintails are similar to other ducks in their dependence on ponds throughout their annual cycle, their extensive use of croplands for nesting differentiates them and makes them particularly vulnerable to changes in agricultural land use on prairie breeding grounds. 3.Our intent was to quantify how changes in land use and ponds on breeding grounds have influenced pintail population dynamics by developing an integrated population model to analyse over five decades (1961–2014) of band‐recovery, breeding population survey, land use and pond count data. We focused especially on the interactive effects of pond counts and land use on pintail productivity, while accounting for density dependent processes. 4.Pintail populations responded more strongly to annual variation in productivity than survival. Productivity was positively correlated with pond count and negatively correlated with agricultural intensification. Further, a positive interaction between pond count and agricultural intensification was insufficient to overcome the strong negative effect of agricultural intensification on pintail productivity across nearly all pond counts. The interaction also indicated that pintail populations were more negatively impacted by the decrease in ponds associated with climate change under higher agricultural intensification. 5.Our results indicate that pintail populations have become more vulnerable to climate change under intensified land use, which suggests that future conservation strategies must adapt to these altered relationships. The interactive effects of land use and climate on demography should be considered more frequently in animal ecology, and integrated population models provide an adaptable framework to understand vital rates and their drivers simultaneously. This article is protected by copyright. All rights reserved.
... In this study, we developed an IPM with region-specific population processes and used this model to prioritize region-specific conservation strategies for a model species, northern pintail (Anas acuta; hereafter pintail). In North America, pintails have shown a declining population trajectory (U.S. Fish and Wildlife Service, 2018) that is similar to many other farmland birds (Rosenberg et al., 2019;Stanton et al., 2018), which may be due to their strong reliance on cropland habitats for nesting Devries et al., 2008;Duncan and Devries, 2018). Meanwhile, climate change has driven, and is likely to continue driving the distribution and population dynamics of wetland-dependent species (Lehikoinen et al., 2013;Van de Pol et al., 2010) including waterfowl (Zhao et al., 2019b). ...
... Over the last half century, the largest changes in prairie cropland management have been the intensification of agriculture including vast reductions in the practice of leaving cropland unplanted in alternate years (i.e., summer fallow) and increased adoption of continuous cropping with at least 30% crop stubble/residue left on the soil surface between harvest and planting the following year (i.e., minimum or zero tillage; hereafter conservation tillage; Awada et al., 2014;Carlyle, 1997;Statistics Canada, 2012). Conservation tillage is expected to increase pintail nest destruction and thus negatively impact pintail productivity (Best, 1986;Duncan and Devries, 2018). We calculated the proportion of each ecostratum in conservation tillage, and used this proportion as an index of agricultural intensification (see Zhao et al., 2019a). ...
Article
Accounting for the spatial variation of environmental drivers and demographic mechanisms in population predictions is essential for conservation prioritization under climate and land use changes but is often ignored. We developed an integrated population model (IPM) with region-specific population processes and used the model to prioritize region-specific conservation strategies for northern pintail ( Anas acuta ; hereafter pintail). Pintail are of high conservation concern in North America due to low productivity related to extensive use of cropland for nesting and wetland (pond) loss related to anthropogenic disturbance and climatic variability. We analyzed 25 years (1990–2014) of pintail breeding population survey, band-recovery, pond count, climate and land use data to estimate regional demography- environment relationships. We then predicted regional population responses under potential future changes in climate, wetland drainage, and agricultural intensification. Our IPM predicted that pintail populations will be sensitive to climate changes throughout the entire study area. Drainage was predicted to have more deleterious impacts in Parkland regions due to more extensive wetland drainage in these regions. Agricultural intensification was predicted to have more deleterious impacts in Saskatchewan-Prairie due to a stronger response of pintail productivity to agricultural intensification in this region. Our study highlights the importance of considering region-specific conservation strategies to accommodate regional variation in future global changes and demographic response to such changes. Our IPM that accommodates spatial variation in environmental changes and demographic responses is flexible for other systems, and thus is highly relevant to diverse studies in conservation prioritization given global change.
... Waterfowl in North America, for example, have benefited from proactive wetland conservation across their northern prairie breeding grounds in Canada and the United States. Although population trends of many species have increased, northern pintails (Anas acuta) have declined due to unforeseen impacts of shifting agricultural practices misaligned with behavioral traits of nesting hens (Podruzny et al., 2002;Duncan and Devries, 2018). Understanding the complexity of similar tradeoffs will become crucial as escalating water scarcity restructures the timing and availability of wetland habitats throughout wetland habitat networks (Kirby et al., 2008). ...
Article
Full-text available
Migratory waterbirds (i.e., shorebirds, wading birds, and waterfowl) rely on a diffuse continental network of wetland habitats to support annual life cycle needs. Emerging threats of climate and land-use change raise new concerns over the sustainability of these habitat networks as water scarcity triggers cascading ecological effects impacting wetland habitat availability. Here we use important waterbird regions in Oregon and California, United States, as a model system to examine patterns of landscape change impacting wetland habitat networks in western North America. Wetland hydrology and flooded agricultural habitats were monitored monthly from 1988 to 2020 using satellite imagery to quantify the timing and duration of inundation—a key delimiter of habitat niche values associated with waterbird use. Trends were binned by management practice and wetland hydroperiods (semi-permanent, seasonal, and temporary) to identify differences in their climate and land-use change sensitivity. Wetland results were assessed using 33 waterbird species to detect non-linear effects of network change across a diversity of life cycle and habitat needs. Pervasive loss of semi-permanent wetlands was an indicator of systemic functional decline. Shortened hydroperiods caused by excessive drying transitioned semi-permanent wetlands to seasonal and temporary hydrologies—a process that in part counterbalanced concurrent seasonal and temporary wetland losses. Expansion of seasonal and temporary wetlands associated with closed-basin lakes offset wetland declines on other public and private lands, including wildlife refuges. Diving ducks, black terns, and grebes exhibited the most significant risk of habitat decline due to semi-permanent wetland loss that overlapped important migration, breeding, molting, and wintering periods. Shorebirds and dabbling ducks were beneficiaries of stable agricultural practices and top-down processes of functional wetland declines that operated collectively to maintain habitat needs. Outcomes from this work provide a novel perspective of wetland ecosystem change affecting waterbirds and their migration networks. Understanding the complexity of these relationships will become increasingly important as water scarcity continues to restructure the timing and availability of wetland resources.
... for using the habitat selection model (see below for more detail). The estimated 238 strata-level abundance is then scaled down (by dividing by the number of segments within 239 a strata) to represent an expected number of pintail per segment given no habitat selection. 240 The segment-level model (see Habitat Selection and Observation Process section to the expected number of pintail on a segment (given the strata-level process) as a result 246 of habitat selection. ...
Article
1. Anthropogenic landscape alteration and climate change can have multi-scale and inter-related effects on ecological systems. Such changes to the environment can disrupt the connection between habitat quality and the cues that species use to identify quality habitat, which can result in an ecological trap. Ecological traps are typically difficult to identify without fine-scale information on individual survival and fitness, but this information is rarely available over large temporal and spatial scales. 2. The Prairie Pothole Region (PPR) of the United States and Canada has undergone extensive changes in the latter half of the 20th century due to advancements in agricultural technologies, water management practices, and climate change. Historically, the PPR has been a highly productive area for breeding waterfowl. While the overall trends for dabbling ducks in the PPR have exhibited increasing abundances since the late 1980s, some species, such as the northern pintail, have been declining in abundance. 3. We used a long-term data set of pintail counts across the PPR to separate count data into a demographic process and a habitat selection process using a hierarchical model. The hierarchical model provided an alternative way of identifying ecological traps in the absence of individual survival and fitness. Our model also allowed us to account for the indirect pathways by which climate and agriculture impact pintail through their additional contribution to wetland availability, which is a primary driver of pintail demography and habitat selection. 4. Decoupling these processes allowed us to identify an ecological trap related to increasing cropland land cover, in which pintail selected for cropland over alternative nesting habitat, likely due to the similarities with productive native mixed-grass prairie. However, large proportions of cropland within a region resulted in fewer pintail the following year, likely due to nest failures from predation and agricultural practices. In addition, we identified several regions in Canada where this ecological trap is contributing significantly to mismatches between habitat selection and demographic processes.
Article
Full-text available
As many as 500,000 waterfowl reside in California, USA, during summer, but little is known about the availability or quality of their habitats. Wetland size and distribution serve as proximate cues for habitat selection by breeding waterfowl in other parts of North America such as the Prairie Pothole Region. In heavily modified landscapes such as California's Central Valley, disturbance from factors like crop cultivation and urban development may limit access , affect survival, and decrease reproductive success. Water limitations due to recurring seasonal droughts pose another potential threat to breeding waterfowl. Spatial and temporal disparities in environmental resources may provide clearer indications of ultimate habitat selection. We addressed waterfowl habitat selection in 9 regions surveyed annually by California's Department of Fish and Wildlife to determine relative importance of drought severity, wetland area, and habitat quality on mallard (Anas pla-tyrhynchos) and other waterfowl population dynamics from 2007-2019. High-quality habitat supports long-term population persistence of waterfowl. This study period included an extended drought (2012-2015) and flooding (2016-2017). Statewide, habitat quality was the best predictor of mallard and other waterfowl population fluctuations. The model that included intermediate habitat quality, which accounted for influence of adjacent land-use, outperformed models that included wetland area alone. At the regional level, drought severity out‐ranked other variables inmost regions, suggesting management at regional scales must ac-count for climate. Drought accounted for bird declines in some regions and possible increases in others. This information could be used to identify areas for conservation priority based on projected drought frequency and severity.
Article
Full-text available
According to theory, habitat selection by organisms should reflect underlying habitat-specific fitness consequences and, in birds, reproductive success has a strong impact on population growth in many species. Understanding processes affecting habitat selection also is critically important for guiding conservation initiatives. Northern pintails (Anas acuta) are migratory, temperate-nesting birds that breed in greatest concentrations in the prairies of North America and their population remains below conservation goals. Habitat loss and changing land use practices may have decoupled formerly reliable fitness cues with respect to nest habitat choices. We used data from 62 waterfowl nesting study sites across prairie Canada (1997–2009) to examine nest survival, a primary fitness metric, at multiple scales, in combination with estimates of habitat selection (i.e., nests versus random points), to test for evidence of adaptive habitat choices. We used the same habitat covariates in both analyses. Pintail nest survival varied with nest initiation date, nest habitat, pintail breeding pair density, landscape composition and annual moisture. Selection of nesting habitat reflected patterns in nest survival in some cases, indicating adaptive selection, but strength of habitat selection varied seasonally and depended on population density and landscape composition. Adaptive selection was most evident late in the breeding season, at low breeding densities and in cropland-dominated landscapes. Strikingly, at high breeding density, habitat choice appears to become maladaptive relative to nest predation. At larger spatial scales, the relative availability of habitats with low versus high nest survival, and changing land use practices, may limit the reproductive potential of pintails.
Article
Full-text available
Recent growth in the wind energy industry has increased concerns about its impacts on wildlife populations. Direct impacts of wind energy include bird and bat collisions with turbines whereas indirect impacts include changes in wildlife habitat and behavior. Although many species may withstand these effects, species that are long-lived with low rates of reproduction, have specialized habitat preferences, or are attracted to turbines may be more prone to declines in population abundance. We developed a prioritization system to identify the avian species most likely to experience population declines from wind facilities based on their current conservation status and their expected risk from turbines. We developed 3 metrics of turbine risk that incorporate data on collision fatalities at wind facilities, population size, life history, species' distributions relative to turbine locations, number of suitable habitat types, and species' conservation status. We calculated at least 1 measure of turbine risk for 428 avian species that breed in the United States. We then simulated 100,000 random sets of cutoff criteria (i.e., the metric values used to assign species to different priority categories) for each turbine risk metric and for conservation status. For each set of criteria, we assigned each species a priority score and calculated the average priority score across all sets of criteria. Our prioritization system highlights both species that could potentially experience population decline caused by wind energy and species at low risk of population decline. For instance, several birds of prey, such as the long-eared owl, ferruginous hawk, Swainson's hawk, and golden eagle, were at relatively high risk of population decline across a wide variety of cutoff values, whereas many passerines were at relatively low risk of decline. This prioritization system is a first step that will help researchers, conservationists, managers, and industry target future study and management activity.
Article
Full-text available
This review grew out of our realization that models play an increasingly important role in conservation but are rarely used in the research of most avian biologists. Modelers are creating models that are more complex and mechanistic and that can incorporate more of the knowledge acquired by field biologists. Such models require field biologists to provide more specific information, larger sample sizes, and sometimes new kinds of data, such as habitat-specific demography and dispersal information. Field biologists need to support model development by testing key model assumptions and validating models. The best conservation decisions will occur where cooperative interaction enables field biologists, modelers, statisticians, and managers to contribute effectively. We begin by discussing the general form of ecological models- heuristic or mechanistic, "scientific" or statistical- and then highlight the structure, strengths, weaknesses, and applications of six types of models commonly used in avian conservation: (1) deterministic single population matrix models, (2) stochastic population viability analysis (PVA) models for single populations, (3) metapopulation models, (4) spatially explicit models, (5) genetic models, and (6) species distribution models. We end by considering the intelligent use of models in decision- making, which requires understanding their unique attributes, determining whether the assumptions that underlie the structure are valid, and testing the ability of the model to predict the future correctly.
Thesis
According to theory, habitat selection by organisms should reflect the associated probability of survival or reproductive success. Understanding habitat selection, at multiple scales, is of interest not only from a theoretical perspective, but from an applied perspective for species conservation. Northern pintails (Anas acuta) are migratory, temperate-nesting birds that breed in greatest concentrations in the prairies of North America. Declining populations suggest that habitat loss and changing land use may have decoupled formerly reliable fitness cues from selection of suitable nest habitat. I used data from 62 waterfowl nesting study sites in prairie Canada (1997–2009), to examine whether nest survival, a primary fitness metric, at nest and habitat patch scales, was predictive of habitat selection at corresponding scales. In addition, I used systematic long-term annual pintail population monitoring data (1961–2009), and recruitment indices (juvenile:adult female ratio) from hunter harvest, to examine adaptive habitat selection among landscapes within the Prairie Pothole Region (PPR). The influences of breeding population density and landscape composition were examined at all scales. At nest and patch scales, pintail nest survival varied with nest initiation date, nest habitat, pair density, and landscape composition. Nest habitat preference reflected patterns in nest survival suggesting nest habitat preference is adaptive. Preference was generally low for habitats with low nest survival (e.g., spring-seeded cropland) and high for habitats with high nest survival (e.g., idle grassland). Differences in preference among habitats weakened at high breeding density and in landscapes with more grassland. Population-level recruitment tended to be greater when pintails settled in landscapes that were wetter than normal, contained more grassland, and were moderately variable in local elevation. Pintails were strongly associated with wetter than normal landscapes but shifted into cropland-dominated landscapes and flatter landscapes when populations were high. My results indicated that pintails express adaptive habitat associations with density-dependence acting through buffer mechanisms. Finally, I use the results of the above analyses to, 1) model and map the estimated long-term average spatial abundance of pintail pairs across the PPR as a function of landscape-level covariates, and 2) construct a deterministic model predicting pintail productivity given habitat and landscape attributes. These models allow conservation efforts to be targeted to affect the most birds, and they allow estimation of the demographic response to conservation actions.
Article
The Prairie Pothole Region of North America has been modified by agriculture during the past 100 yr, resulting in habitat loss, fragmentation, and degradation that have reduced the abundance and productivity of many wildlife species. The 1985 U. S. Farm Bill provided economic incentives to agriculture that are considered by many to be beneficial to nesting waterfowl and other wildlife. Canada has not experienced an equally comprehensive legislative initiative, which would seem to indicate that benefits to waterfowl in Canada should lag behind those in the United States. However, with the removal of some agricultural subsidies in Canada during the 1990s, the amount of perennial cover in the Canadian prairies increased to levels similar to those of the 1970s. Therefore, it is unclear whether and how the U. S. and Canadian prairies might differ with regard to habitat quality for nesting waterfowl. We used historical and contemporary data to compare temporal trends in duck nest success between the United States and Canada and to assess how mean nest success varied with proportion of cropland and wetland density. The data best supported models with nonlinear temporal trends that varied between the two countries and suggested that mean nest success in Canada declined from its high point in 1930s and remained below the long-term value of 0.16 until the end of the time series in 2005. Mean nest success in the United States also declined from its high point in the 1930s, but increased to above the long-term value of 0.25 during the early 2000s. Mean nest success varied negatively with proportion of cropland in both the United States and Canada. Mean nest success was positively correlated with pond density at Canadian sites, but showed only a weak association with pond density at U. S. sites. All models explained the low proportions of the variation in nest success, suggesting that unmeasured factors such as the abundance and identity of nest predators may have strong effects on nest success. Nonetheless, these results support earlier suggestions that agricultural policy that encourages permanent cover positively influences duck reproductive success. We also found that, for reasons that are not entirely clear, nest success for the same intensity of row cropping was generally higher in the United States than in Canada. Further research is required to elucidate the exact nature of the composition, size, and distribution of permanent cover that coincides with greater average nest success by dabbling ducks in the United States. In addition, the data suggest that the benefits that might accrue from increases in the amount of perennial cover in Canada would be better realized if these efforts are accompanied by strong measures to conserve wetlands.
Article
Nests of 5 duck species were found: blue-winged teal Anas discors, northern pintail A. acuta, mallard A. platyrhynchos, gadwall A. strepera, and northern shoveler A. clypeata. Average number of nest found was 8/100 ha in 1984 and 6/100 ha in 1985. Nest success for all species averaged 26% in 1984 and 29% in 1985. Predation by mammals was the principal cause of nest destruction. No egg or hen mortality could be attributed to pesticide use. Only 6 of 151 nests (4%) were abandoned during the 2 years. Nests of 7 other ground-nesting bird species were also found. The trend toward increased planting of no-till winter wheat in the prairie pothole region should benefit production of ducks and other ground-nesting birds. -from Authors
Article
We studied nesting effort and success of Northern Pintails (Anas acuta) in southern Alberta. Annual nesting success estimates ranged from 6-18%. Clutch size averaged 7.2, and declined in a simple curvilinear fashion with nest initiation date. We found no relationship between egg size and clutch size or evidence from one year to the next of a trade-off between current and future investment in eggs. Within-year renesting rate ranged from 55%, based on a sample of 20 decoy-trapped females that lost their first nests to predators, to 85% based on a sample of 13 nest-trapped females forced to renest when we removed their clutches. Greater investment in initial clutches led to longer delays in laying replacement clutches. Because delays in renesting are costly (late-nesting females produce fewer offspring), females must contend with a trade-off between maximizing reproductive output in initial clutches versus the risk of delayed renesting if the first clutch should fail. We suggest that pintail reproductive traits have evolved primarily in response to short nesting seasons and variable environments.
Article
The Prairie Pothole Region (PPR) of North America produces more than 50% of North America's upland-nesting ducks. With the recent increase in economic value of some cash-crops and the potential to lose productive nesting habitat enrolled in the Conservation Reserve Program (CRP), there has been interest in evaluating the efficacy of alternative farming practices to provide additional breeding habitat for waterfowl. We evaluated and compared daily survival rates (DSR) of duck nests (Anas spp.) in winter wheat with those in perennial cover. We also examined the number of hatched nests/ha in each habitat and compared them to estimates in spring wheat to put habitat-specific estimates of nest survival in perspective. We monitored 1,195 nests in winter wheat and 3,147 in perennial cover in North and South Dakota on 13–19, 10.36-km2 sites each year from 2010 to 2012. In 2010, we also monitored 75 nests in spring wheat. We used an information-theoretic approach to develop and evaluate a set of competing models based on plausible and previously established covariates affecting nest survival. Across all species, nest survival was at least as high in winter wheat as in perennial cover, and for northern pintails and mallards, estimated nest survival rates were greater in winter wheat. Nest survival also varied by year and study area, was positively related to nest age, and was negatively related to the number of wetland basins, the proportion of cropland in the landscape, and vegetation density. Density of hatched nests in perennial cover (0.14/ha) was on average twice as high as nests in winter wheat fields (0.07/ha), which was in turn 4 times higher than estimates for spring wheat fields (0.02/ha). Our results provide evidence that winter wheat could be a useful tool for wildlife managers seeking to add productive nesting habitat in landscapes under intensive crop production. © 2015 The Wildlife Society.