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Shorebird declines and climate change in Hudson Bay

Authors:
  • Environment and Climate Change Canada
  • National Wildlife Research Centre, Environment and Climate Change Canada, Ottawa

Abstract

Shorebirds are declining in Hudson Bay and throughout the arctic, but the cause is unknown. We present current information on the status of the shorebird populations of Hudson Bay, and the research being conducted to understand the declines. We discuss the environmental changes predicted to occur in the region, and their potential impacts on shorebirds. Finally, we identify the preliminary steps we have taken to engage northern communities in the monitoring of these important and declining populations.
Shorebird Declines and Climate
Change in Hudson Bay
Paul Smith, Grant Gilchrist and Victoria
Johnston1
Abstract
Shorebirds are declining in Hudson Bay and throughout the
arctic, but the cause is unknown. We present current
information on the status of the shorebird populations of
Hudson Bay, and the research being conducted to understand
the declines. We discuss the environmental changes predicted
to occur in the region, and their potential impacts on
shorebirds. Finally, we identify the preliminary steps we have
taken to engage northern communities in the monitoring of
these important and declining populations.
Introduction
Only a small percentage of Canadians would recognise a Red-
necked Phalarope (Phalaropus lobatus). Fewer still are aware
that these boldly coloured birds have largely disappeared from
the Bay of Fundy, where they once congregated by the
millions en route to the low-arctic habitats, such as the tundra
wetlands of northern Hudson Bay, where they will breed.
Where the birds have gone, and why, remains largely a
mystery. Survey data from the breeding grounds are too scant
to determine the extent to which Red-necked Phalarope
populations have truly declined, but these birds have become
scarce in the area around Churchill, Manitoba, where they
were once abundant (Figure 1, Jehl & Lin 2001). Sadly,
stories such as these are common for shorebirds; many
populations appear to be in a state of decline yet the cause and
even the true extent of the decline are poorly understood.
Perhaps more alarming is the lack of public awareness about
these widespread declines.
With 47 species breeding or occurring regularly in
Canada, shorebirds are a vital component of our avian
biodiversity. While some species breed in Canada’s temperate
habitats, at least 20 species are regular arctic breeders, and 9
additional species breed in the taiga shield and Hudson plains.
Shorebirds are long distance migrants as a rule, with
spectacular migrations carrying them from wintering grounds
throughout Central and South America to breeding grounds as
far north as northernmost Ellesmere Island. These globe-
spanning migrations make it difficult to identify the causes of
declines, and harder still to manage populations. What’s
more, shorebirds are atypically sensitive to environmental
change because of a number of specialised biological “life-
history” traits.
Most shorebird species lay a maximum of four eggs
per year. This comparatively low rate of reproduction is offset
by a long adult lifespan. Because of this, shorebird
populations are highly susceptible to changes in adult
survival, and have a limited ability to recover quickly from
population declines. Shorebirds make among the longest
migrations of any animals, and congregate in large numbers at
a limited number of migratory stopover sites. Rich food
resources are required to fuel these energetically challenging
migrations, and small-scale changes at important staging areas
could have dramatic implications for a species at the
population level (Alexander and Gratto-Trevor 1997).
Because of their migratory lifestyle, shorebirds are reliant on
a network of habitats that can span the hemisphere. As they
make their annual voyages, they are exposed to a wide variety
of anthropogenic stressors, from coastal development and
pesticide exposure in the South to potentially negative effects
of climate change and development of resource-based
economies in the North. Given their high exposure to
environmental change and their limited ability to cope with it,
shorebirds are arguably at a high risk of decline.
Residents of northern Hudson Bay have expressed
concern about perceived shorebird declines, but species-
specific information about population trends for this region is
scarce. To date, local knowledge of shorebirds has not been
collected in a systematic way. The limited research and
monitoring conducted in the area suggests declines, but there
is no question that more work is needed to establish a baseline
of data, monitor changes in shorebird abundance, and
understand the threats faced by shorebirds in the changing
environments of Hudson Bay.
Below, we summarise the ecological importance of
shorebirds in the Hudson Bay region, present current
information on population status and trends, and discuss the
environmental changes and challenges faced by shorebirds
across their range, and in Hudson Bay specifically. We
describe briefly the research that the Canadian Wildlife
Service and others have undertaken to improve our
understanding of the ecology of the shorebirds of Hudson
Bay. Finally, we identify the steps needed to engage northern
communities in the monitoring of these important and
declining populations.
Shorebirds and Tundra Ecosystems
Shorebirds prefer open habitats throughout the year. In winter,
they congregate in large numbers on tidal mudflats, in coastal
wetlands, or in rocky intertidal areas. During the summer,
arctic breeders are generally most numerous in tundra
wetlands near the coast. In sub-arctic Hudson Bay, some
birds, such as the Semipalmated Plover (Charadrius
semipalmatus) nest on gravel river beds or raised beaches
(Nol & Blanken 1999), while others, such as the Lesser
Yellowlegs (Tringa flavipes) nest in wet bogs or open
muskegs (Tibbitts & Moskoff 1999).
Shorebirds migrate north to capitalize on the immense
burst of insect productivity characteristic of high-latitude
ecosystems. They are voracious insectivores, and can alter the
composition of the insect community on which they feed
(Dodson & Egger 1980). Their breeding is timed to ensure
that their chicks have easy access to an abundant supply of
food; by the end of the short summer, chicks must be
developed enough to make the challenging journey south. In
addition, they and their eggs are an important source of food
for predatory birds such as jaegers, ravens and gulls, as well
as mammals such as arctic and red fox (Alopex lagopus,
Vulpes fulva).
While shorebirds play a critical role in the functioning
of northern ecosystems, the reverse is also true; the North is
of critical importance to shorebirds as a whole. Over 60% of
Canada’s breeding shorebird species nest regularly in the
arctic or subarctic. At least 23 species of shorebirds are
regular breeders in the Hudson Bay region, making shorebirds
the most diverse and abundant group of birds in many
locations.
Traditional Use and Cultural Importance
Many species of shorebirds are small, non-descript and of
little cultural significance to indigenous peoples, however, the
larger species were an important source of food historically.
The Eskimo Curlew (Numenius borealis), once among the
most abundant tundra birds, was snared at the nest for food by
the Inuit and Cree of the Hudson Bay area. Known by
European epicures as the dough-bird, its immense populations
were brought to the brink of extinction by market hunting at
migration stop-over sites in the end of the 19th century. The
hunting of most shorebirds was made illegal with the signing
of the Migratory Birds Treaty Act in 1918, but the 1995
Parksville Protocol amended the act to legalize the
subsistence harvest of migratory birds, including shorebirds,
for Canadian aboriginals. However, the Nunavut Wildlife
Harvest Study (Priest & Usher 2004) found that neither
shorebirds nor their eggs are intentionally harvested by
Nunavummiut. A small subsistence harvest of shorebirds still
occurs in arctic Alaska.
Status of Shorebirds in Hudson Bay
Across North America, shorebirds appear to be in a state of
widespread decline. Of the 35 shorebird species for which we
have reasonable survey data, 28 species (80%) show negative
trends, and 19 species show statistically significant declines
from 1970’s population levels (Morrison et al. 2001a). A
disproportionate number of declines have been noted for
arctic breeding species that migrate along the eastern coast of
North America, including many of the species breeding in the
Hudson Bay area. Of the 23 species that regularly breed in the
Hudson Bay region, 16 species showed significant population
declines between 1974 and 1998, and an additional 2 species
show persistent, but not statistically significant declines
(Morrison et al. 2001a).
While we have some limited information about the
range-wide status of shorebird populations, little is known
about the numbers breeding in the Hudson Bay area
specifically. Through regular community consultation, we’ve
become aware that some communities in the region have
concerns about general declines in shorebird numbers. For
example, the Aiviit Hunters and Trappers Organization of
Coral Harbour, NU, has noted that shorebirds have become
less numerous at traditional summer camping areas, but no
specific species of concern were identified (Willie Nakoolak,
pers. comm.).
Two common shorebirds that are declining
significantly across their range, and are likely to be declining
in the Hudson Bay region are the Semipalmated Sandpiper
(Calidris pusilla) and the Dunlin (Calidris alpina hudsonia).
The Hudsonian Godwit (Limosa haemastica), while not
known to be declining significantly, is an example of a
species of conservation concern because of its heavy reliance
on restricted regions of Hudson Bay.
The Semipalmated Sandpiper is a small bird, locally
abundant across the Canadian sub- and low-arctic tundra. It
nests among grass and sedge tussocks, or heath hummocks,
and is estimated to have a Canadian breeding population of
roughly 3.5 million individuals (Morrison et al. 2001b).
Populations of this species have shown declines from 1970’s
levels in nearly all analyses conducted (Donaldson et al.
2000). Particular concern exists for the “long-billed”
population which migrates along the Atlantic coast, and
breeds in the Eastern Arctic, including parts of Hudson Bay.
This bird was once abundant at Churchill, but has now
become rare (Jehl & Lin 2001). The cause of these declines is
entirely unknown.
The Dunlin breeds across the circumpolar North, in
the coastal tundra of the Arctic and Subarctic. The eastern, or
hudsonia, race of Dunlin breeds from Victoria Island to the
west coasts of Hudson and James Bay. This population has an
estimated size of roughly 150,000 300,000 individuals
(Morrison et al. 2001b). Although the estimates are crude,
counts of migrating birds passing through the Maritime
Provinces suggest a significant population decline of
approximately 7% per year between 1974 and 1998 (Morrison
et al. 2001a). The Dunlin is one of three shorebird species
listed by the Conservation of Arctic Flora and Fauna (CAFF)
as an “indicator species” for assessing the health of holarctic
ecosystems (CAFF 1996).
The Hudsonian Godwit is a mysterious bird,
congregating in only a few remote sites throughout the year.
This large shorebird was historically trapped and hunted for
food on the breeding grounds, and was market hunted heavily
throughout the late 19th and early 20th century. Though our
knowledge of its distribution is far from complete, it appears
that the entire eastern North American breeding population
nests along the western coast of Hudson Bay, in the area of
Churchill, Manitoba, and Cape Henrietta Maria, Ontario. The
world population of this bird is roughly 50,000 individuals,
and a significant number of these, possibly tens of thousands,
are of the eastern race, nesting along the Hudson Bay coast
(Elphick & Klima 2002). The numbers of birds staging in this
region during fall migration appears to have decreased
between the late 1970’s and early 1990’s (Morrison et al.
2001b), but no current program monitors this species
adequately, despite its restricted breeding range.
These three species highlight the nature of shorebird
declines, but sadly, stories such as these are common. Most
shorebird species (80%) appear to be declining across their
range, but we have insufficient survey data to draw firm
conclusions about the extent of the declines, and our limited
understanding of the factors which regulate populations
means that we are unable to identify the cause of the declines.
The Shorebird Research Group of the Americas has
collected information from shorebird biologists across Canada
and the United States and generated hypotheses to explain the
widespread declines of shorebirds. While it is thought that the
majority of disturbance and habitat degradation is occurring at
stop-over and wintering sites in the south, the shorebird
research community at large recognises the possibility that
climate change on the breeding grounds could be playing a
role in the declines, and will almost certainly have a profound
influence on the future of shorebird populations.
Changes Predicted to Occur in Hudson Bay
As for many arctic regions, climate change is predicted to
have dramatic effects on the habitats and wildlife of the
Hudson Bay area. Though eastern Hudson Bay has
experienced a recent cooling trend, with delayed spring snow
melt (McDonald et al. 1997), the area as a whole is predicted
to warm (ACIA 2005). The tundra ecozone of northern
Hudson Bay will retreat northward, taking with it the
shorebird species nesting in coastal tundra. Some scenarios
predict that essentially all of Hudson Bay’s coastal tundra
could be replaced by evergreen forest by 2100 (Kaplan et al.
2003). Intertidal mudflats, which are important staging
grounds, may be degraded or lost as sea levels rise (Galbraith
et al. 2002). The shallow water wetlands that are the preferred
nesting and feeding habitats of many species are sensitive to
changes in permafrost depth and precipitation regime.
Warmer summer weather and a deepening active layer could
lead to the drying of wetland habitats, with potentially
negative effects on the abundance of the invertebrate prey on
which shorebirds depend. Though long-term predictions about
habitat change are tenuous, it’s clear that large-scale
alterations to habitats in a warming arctic could have dramatic
implications.
While the predicted changes in habitat are based on
long-term climate projections, a changing climate could affect
shorebirds directly in the short term. To maximise the chance
of chick survival in the harsh arctic climate, shorebird eggs
should hatch when the weather is most favourable for the
small chicks to maintain their body temperature, and when
insect prey is most available. As summer weather becomes
more variable, chicks may hatch before or after peak
emergence of insects and reproductive success may suffer.
However, the predicted increases in summer air temperatures
could also have positive effects on shorebird breeding success
in the short term. In the Siberian arctic, breeding seasons with
warmer June and July temperatures have been linked to
increased chick survival (H. Boyd, unpublished).
Our understanding of the effects of future
environmental change on shorebirds is far from complete, but
it is clear that the dramatic changes predicted will not be
without consequence. As shorebird populations are already
showing signs of widespread decline, there is an urgent need
for a baseline of data with which to gauge future impacts.
Understanding and Monitoring Shorebirds
These alarming declines have prompted action. In recent
years, the Canadian Wildlife Service has undertaken an
initiative to dramatically increase our ability to detect changes
in shorebird populations. We have also established research
camps in northern Hudson Bay to study the factors that
influence reproductive success in shorebirds (Figure. 1).
However, we have made only minor progress towards two
important steps: increasing public awareness about shorebird
declines, and enlisting the help of Northerners to monitor and
manage these declining populations.
Because of their migratory nature, shorebirds require
an internationally coordinated approach to conservation
(CHASM 2004). To facilitate this coordination, biologists
from Canada and the United States have developed the
Program for Regional and International Shorebird Monitoring
(PRISM, Skagen et al. 2004). By setting accuracy targets for
range-wide monitoring, and coordinating regional monitoring
programs to achieve these targets, PRISM allows shorebird
biologists to work towards a fixed and measurable goal.
Because arctic work is expensive and logistically difficult, the
majority of shorebird monitoring takes place at migration
stop-over sites and wintering areas. However, some level of
monitoring on the arctic breeding grounds is crucial if we are
to understand and manage shorebird declines.
Basic information about shorebirds, such as breeding
distributions, densities and habitat relationships are lacking
for most of the Arctic. The PRISM program will generate
these data, along with population estimates and trend
information, across the entire Canadian Arctic. An effort of
this scale takes a great deal of time to design and implement;
the PRISM program has been taking shape since 1997, and is
still gaining momentum. In the Hudson Bay Region, we have
completed surveys of Southampton Island, Coats Island and
the north-eastern coast of Hudson Bay near Puvirnituq.
Though our ability to monitor shorebirds on the
breeding grounds is improving, we lack a complete
understanding of the factors that regulate populations. Basic
ecological parameters such as preferred nest habitat and
annual breeding success are unknown for most species. If we
are to halt, reverse or prevent declines, it is clear that we need
not only this basic information, but also more detailed
information on the factors that influence reproductive success,
and in turn population size.
To study these issues, the authors have established two
shorebird research camps at the northern end of Hudson Bay.
Shorebird research has taken place at the camp at East Bay,
Southampton Island, Nunavut, since 1999, making it among
the longest running shorebird projects in the Canadian Arctic.
A second camp, on Coats Island, Nunavut, at the mouth of
Hudson Bay, was established in 2004. Research at these
camps has identified unique nest habitat preferences for a
number of shorebird species (Smith 2003), and has shown that
nest success can vary with subtle factors such as proximity to
the nests of other species (Smith et al. in press). An important
factor influencing birds’ reproductive success throughout the
North is the cycle of rodent abundance (e.g. Summers et al.
1998). Predators such as arctic foxes prey heavily on rodents
in times of abundance, but turn to the eggs of birds at times
when rodents are scarce. Our research will help us to better
understand the impact of these natural cycles on shorebird
populations, and allow us to understand why some species of
shorebirds are more influenced by this cycle than others.
Because cycles of predation on the breeding grounds can have
profound effects on the numbers of birds seen on migration
(e.g. Blomqvist et al. 2002), our research will allow us to
better interpret migration survey data, and help us to
distinguish natural fluctuations from unnatural declines.
An improved scientific understanding of arctic
shorebirds is an important step towards their conservation,
and the PRISM monitoring program promises enhanced
monitoring of arctic species across their range. However, the
arctic breeding grounds are so vast that it is impractical to
monitor local populations, or even monitor shorebirds
regionally on an annual basis. Consequently, we see a
potentially strong role for local ecological knowledge (LEK)
or “citizen science” to contribute to the monitoring of arctic
shorebirds.
Several northern communities, including Coral
Harbour at the north end of Hudson Bay, are concerned about
general declines in shorebird numbers, but no LEK studies
have been conducted to identify specific species or areas of
concern. Under scenarios of climate change, we predict
extensive shifts in the range of some shorebirds. Studies of
local knowledge now and in the future may prove useful to
document changes in species’ distributions and relative
abundance. For those individuals with a particular interest in
birds, the Canadian Wildlife Service has developed the
Northwest Territories and Nunavut Bird Checklist Survey
(www.mb.ec.gc.ca/nature/migratorybirds/nwtbcs), which
allows citizens to contribute directly to a nationwide program
monitoring the abundance and distribution of birds.
To derive the maximum benefit from LEK, we must
understand the quality of the information for different species.
While some species are conspicuous and well known by many
northern residents, others are difficult to distinguish and in
some cases appear to share a common Inuktitut name
(Sijjariaq). To increase awareness about shorebirds, the
Canadian Wildlife Service has created a poster with English
and Inuktitut names for several of Nunavut’s common
species. Space was provided for individuals to record local
names, as names vary regionally for some species. These
posters were mailed to schools and HTA’s across the North,
and if they prove to be effective, should help us to identify the
species with which northerners from different communities
are most familiar. We expect the value of the LEK available
to be related to familiarity with particular species (Gilchrist et
al. 2005), and we regard this awareness campaign as an
important first step in understanding the species for which
Northern residents have concerns.
While we recognise the potential benefits of public
involvement in the monitoring of arctic shorebirds, only the
preliminary steps have been taken. Through LEK surveys and
citizen-based science, we could document the current
distribution and relative abundance of shorebird species
across a wide area more quickly than would otherwise be
possible. As we take on the enormous challenge of monitoring
arctic shorebird populations, we must make better use of the
baseline of information already available from northern
residents, because they are among the few Canadians who
miss the Red-necked Phalarope.
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Figure 1: The Hudson Bay area, with the locations of our
research camps and selected communities highlighted.
1 Paul Smith is a PhD candidate studying the breeding ecology of
eastern arctic shorebirds at the National Wildlife Research Centre,
Carleton University. Grant Gilchrist is a research scientist with the
Canadian Wildlife Service. Victoria Johnston is the Canadian Wildlife
Service shorebird biologist for the Northwest Territories and Nunavut, and
leads Canada’s arctic shorebird monitoring program.
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Global warming is expected to result in an acceleration in current rates of sea level rise, inundating many low-lying coastal and intertidal areas. This could have important implications for organisms that depend on these sites, including shorebirds that rely on them for feeding habitat during their migrations and in winter. We modeled the potential changes in the extent of intertidal foraging habitat for shorebirds at five sites in the United States that currently support internationally important numbers of migrating and wintering birds. Even assuming a conservative global warming scenario of 2°C within the next century (the most recent projections range between 1.4°C and 5.8°C), we project major intertidal habitat loss at four of the sites (Willapa Bay, Humboldt Bay, San Francisco Bay, and Delaware Bay). Projected losses range between 20% and 70% of current intertidal habitat. Such losses might jeopardize the ability of these sites to continue to support their current shorebird numbers. The most severe losses are likely to occur at sites where the coastline is unable to move inland because of steep topography or seawalls. The effects of sea level rise may be exacerbated by additional anthropogenic factors. In southern San Francisco Bay, for example, sea level rise may interact with land subsidence due to aquifer depletion, and the constraints imposed by existing seawalls on the landward migration of habitat, resulting in the greatest habitat loss. At the fifth site (Bolivar Flats) we project smaller losses as the intertidal habitats are unconstrained by sea walls and will be able to migrate inland in response to rising sea level. Installation of additional coastal protection barriers at this site and others is likely to exacerbate the rate and extent of intertidal habitat loss.
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