SPECIES OF SPECIAL INTEREST

Birds

Birds are widespread, readily observed, feed at many levels of the food web, and are responsive to environmental change, making them good indicators of ecosystem health. Birds play an important ecological role, providing food for other species, dispersing seeds, controlling insects, pollinating plants, and modifying habitat. Many also have economic and cultural significance – providing humans with food, recreation, enjoyment, and study and playing an important role in many cultures.

Over the past 20 years, the status of the world’s birds has deteriorated, with more species moving closer to extinction.¹ Of particular concern are declines in formerly common species.¹ In the last 40 years, 20 common North American bird species lost over 50% of their populations.^{1, 2} Birds are also shifting their ranges northward in response to climate change – nearly 60% of the 305 species found in North America in winter moved northward by an average of 1.4 km per year (56 km over the last 40 years)³ and breeding ranges of southern North American species have shifted north by an average of 2.4 km per year.⁴

Canada provides crucial breeding, migrating, and wintering habitat for a significant percentage of the world populations of many species. Nevertheless, the status and trends of birds in Canada are only partially understood. Good data exist for many species, particularly in southern Canada; however, only localized data exist for many others, particularly in the North.

This section is further divided into the following four topics:

• Shorebirds
• Seabirds
• Waterfowl
• Landbirds

Global Trends

Globally, over 150 species of birds have been lost since the 16th century and one in eight is currently threatened with extinction. The last 20 years have witnessed a steady decline of bird species in terrestrial, freshwater, and marine ecosystems. Between 1988 and 2008, the status of 225 bird species was elevated to a higher level of risk.¹

Shorebirds

Sixty percent of North American shorebirds breed in the Arctic, with the Canadian Arctic providing 75% of the breeding range for 15 of 49 common species.⁵ Canada has migration sites of great importance as well, including at least three of hemispheric significance – the Bay of Fundy, the Fraser River estuary, and Chaplin/Old Wives/Reed Lakes in Saskatchewan.⁶ Some southern breeding areas, for example the Prairies, are of global importance to some species.⁷

Data on shorebird populations are patchy in Canada, but most information indicates declining trends.^7-9 Of the 35 species examined in 2000, 49% showed significant declines somewhere in their range.⁵ The most complete datasets in Canada include the Breeding Bird Survey and the Atlantic Canada Shorebird Survey. Results from these surveys indicate:

• Between 1976 and 2007, 4 of 12 species (33%) of shorebirds breeding in southern Canada declined significantly. There were no significant increases.¹⁰
• Between 1974 and 2006, 5 of 15 migrating shorebird species (33%) on the Atlantic coast showed significant declines.^{11, 12}

Potential causes of declines of shorebirds include loss and degradation of habitat, climate change, changes in predator regimes (for example, increasing numbers of peregrine falcons may cause shorebirds to move through an area more quickly, leading to an apparent decline¹³), human disturbance, contaminants, and disease.⁵ Changes are expected to accelerate due to anticipated changes in Arctic breeding habitat,¹⁴ as well as flooding and droughts elsewhere in shorebird ranges⁷ as a result of climate change.

Populations of northern gannets like this one on Bonaventure Island, Quebec, have increased in North America since the 1950s

Trends in status of breeding seabird populations in Canada

Number of populations in each category, 1980s to 2000s

Note: only populations with significant breeding populations, long-term datasets, and those unaffected by terrestrial human activities are included.

Source: adapted from Gaston et al., 2009¹⁵

Worldwide, the status of seabirds is deteriorating faster than any other bird group.¹ In Canada, trends are regional in nature and result from a variety of factors, including climate change, fishing by-catch, resource extraction, transportation, and pollution.^15-20 A trend to an earlier breeding date has been found in several populations,^21-23 as have changes in diet and condition.²⁴

• Pacific – southern populations, influenced by the changes in sea surface temperature related to the upwellings of the California Current, have been declining since the 1970s.¹⁵ Declines may also be due in part to a mismatch in timing between breeding and peak of food availability.²⁵ Populations north of the influence of the current, however, have generally increased since the 1980s.¹⁵
• Atlantic – prior to 1990, populations generally showed positive trends. A major cold-water event in 1990, however, coinciding with overfishing, disrupted food webs,^26-29 resulting in immediate change in diet, condition, and population, particularly for gulls.²⁴ Populations of most diving seabirds increased over this period, in part due to closure of the gillnet fishery that had been drowning many birds.³⁰
• Arctic – with the exception of ivory gulls, which are declining rapidly, change in Arctic seabird populations is slow and possibly the result of events on wintering grounds in the Northwest Atlantic.^{31, 32} Changes in seabird diet and growth have been found to be related to reduction of Hudson Bay sea ice. This may have negative consequences for populations in the long term.³² Conversely, in the High Arctic, less sea ice may benefit the birds.^{33, 34}

Waterfowl

Waterfowl have been monitored cooperatively by Canada and the U.S. since 1948. Concern over declines in populations in the 1980s led to the development of a large international cooperative initiative, the North American Waterfowl Management Plan, to address the declines. Although many duck populations fluctuate widely among years and regions, overall trends for most inland breeding ducks show increases or no significant change between 1961 and 2009.^{43, 44} Nevertheless, the populations of some species remain low; for example, northern pintail, American wigeon, and greater and lesser scaup have declined significantly in the prairie and western boreal regions.^{43, 44}

Population trends for ring-necked ducks and scaup, western boreal region

Millions, 1961 to 2009

Source: Canadian Wildlife Service Waterfowl Committee, 2009⁴³

 

 

 

 

 

 

 

 

Approximately 70% of scaup and ringnecked ducks breed in the western boreal forest and the two species share many life history traits.⁴⁵ Nevertheless, scaup declined at an average of 1.7% per year between 1961 and 2009 while ring-necked ducks increased by 2.5% per year.⁴³ Reasons for the decline in scaup remain unclear but hypotheses include: contamination or change in food resources; and reduced female survival or reproductive success due to changes in the boreal forest.^{46, 47} Another possible cause is a mismatch between timing of nesting and food availability due to temperature change for late- nesting species such as scaup.⁴⁵ Population declines have also been found in other late-nesting species such as scoters.^{43, 45} Ring-necked ducks breed earlier.

Landbird populations in Canada

Percent change by habitat type, 1970s to 2000s

Note: data for the 2000s decade includes only 2000 to 2006.

Source: Downes et al., 2010,³⁵ adapted from Breeding Bird Survey data, 2007³⁶

Populations of landbirds in all habitat types except forest declined significantly from 1968 to 2006.³⁵ No significant positive trends in any landbird groupings (by habitat, by foraging, or by migration strategy) were evident between 1968 and 2006, although significant positive trends were found for some individual species.³⁵

• Grassland birds, with more than 40% loss of total population since the 1970s, show significant steep declines in all regions of the country and for most species. This is consistent with declines throughout North America^{10, 37} and is thought to be due to a combination of habitat loss and the intensification of agriculture.³⁵
• Birds of other open habitats have been declining since the late 1980s. The assemblage contains several species of aerial-foraging insectivores, many of which are showing declines.³⁵
• The urban group is heavily influenced by two introduced species, European starling and house sparrow, which, although still abundant, are showing declines in Canada and Europe.³⁵
• The decline in shrub/early succession birds is strongly influenced by declines in relatively abundant sparrows.³⁵ Significant declines were found in the Atlantic Maritime, Boreal Plains, and Boreal Shield ecozones⁺.
• Similar to the U.S.,³⁷ forest birds show little change overall, although data indicate a decline since the 1990s.³⁵ Trends for individual species vary, with some showing declines while others are stable or increasing. There have been varying degrees of decline in the Pacific Maritime, Montane Cordillera, and Western Interior Basin ecozones⁺, and increases in the Prairie and Mixedwood Plains where birds have responded to increased forest cover. About 60% of Canada’s landbirds breed in the boreal forest.³⁸
• Aerial and ground-foraging birds show significant declines of 35 and 27% respectively since the 1970s.³⁵ Aerial-foraging insectivores, such as swallows and flycatchers, stand out as a group showing large declines.^{39, 40} Causes remain unknown but likely include changes in food, climate, and habitat.
• Long-distance and short-distance migrants showed significant declines of 21 and 24% respectively, while resident birds were unchanged.³⁵ Short-distance migrants include many grassland species. Long-distance migrants include many aerial-foraging insectivores. Loss and fragmentation of habitat on the wintering grounds is one possible cause for decline.^{41, 42}