|
|||||||||||
   |
 |
|
 |
 |
 |
 |
 |
  |
 |
||
 |
 |
||||||||||
 |
 |
 |
|||||||||
|
|
 |
|
|
Eastern Loggerhead Shrikes haven’t bred in the Maritimes since 1972, while the last recorded nest in Quebec dates back to 1995. In Ontario and Manitoba, there are currently only a few dozen breeding pairs left in the wild, with the majority of confirmed pairs in the Carden Plain and Napanee Plain areas of Ontario. In 1991, the
Eastern Loggerhead Shrike was declared endangered under the federal
Committee on the Status of Wildlife in Canada. It is also protected
under the federal Migratory Birds Convention Act, 1994, the Federal
Species at Risk Act, 2003 and by various provincial endangered
species legislation.
The exact reasons for the decline of shrikes across North America remain unclear. However, ongoing research by shrike biologists and wildlife groups suggests that there are several possible causes: Loss of habitat and Fragmentation Due to changing land use patterns, new farming methods, increasing urbanization and other factors, shrike habitat is disappearing. The amount of unimproved pasture in the Prairie provinces shrunk 39 per cent between 1946 and 1986. In southern Ontario, 65 per cent of prime Eastern Loggerhead Shrike habitat has vanished over the past 50 years.
Chemicals Pesticides,
herbicides and other chemicals have contributed to the decline
of many bird species in Canada and elsewhere. Scientists are
now working to find out whether chemicals are affecting the health
of shrikes, and if so, to what extent. Accidents Many of the trees and shrubs that shrikes use for nesting and perching are located close to roads. Unfortunately, that means that shrikes are sometimes killed by passing vehicles. One way to reduce collisions is to encourage drivers to slow down by posting "Endangered Species Ahead" road signs in appropriate areas.
West Nile Virus Eastern Loggerhead Shrikes are extremely susceptible to West Nile Virus, which is carried by infected mosquitoes. However, we have not seen a marked decline in the number of wild shrikes since WNV hit Ontario in 2002. Climate Change Climate change is a potential threat. Although warmer global temperatures are encouraging insects to hatch out earlier, shrikes are still arriving at their breeding grounds at their usual time. This may mean their nesting period no longer matches the spike in insect numbers, so there’s less food available to sustain them. Migration and Over-wintering We’re still not sure where Canadian shrikes spend the winter or what routes they take when they fly south. However, more and more evidence suggests that factors during migration or over-wintering are contributing to the drop in shrike numbers.
Hundreds of species are considered "at risk" in Canada. Why focus on the Eastern Loggerhead Shrike? One compelling reason is that grassland birds, and the loggerhead shrike in particular, have shown a more persistent and drastic decline than any other group of birds. In fact, the Eastern Loggerhead Shrike has shown the greatest rate of population decline of any perching bird in Canada between 1970 and 1991. Shrike numbers have been in decline throughout North America since the International Breeding Bird Survey began in 1966. This is significant because wildlife scientists consider shrikes an "indicator" species among grassland birds. What affects the shrike also affects the boblink, eastern meadowlark, the short-eared owl, the upland sandpiper and other grassland birds that are becoming increasingly rare. But the decline is also important on a broader scale because healthy shrikes mean a healthy environment. As predators, shrikes are near the top of the food chain. Their bodies accumulate insecticides and other chemicals that their prey have already absorbed. Thus, like
the proverbial canary in the coal mine, the shrike's declining
numbers suggest an environment out of balance. |
|
