Species at Risk Update: Olive-sided Flycatcher and Common Nighthawk

September 04, 2014

At its recent Board meeting in July, the WRRB agreed to support listing draft Recovery Strategies for two bird species at risk --the Olive-sided Flycatcher and the Common Nighthawk.  Both are migratory insect-eating birds, traveling as far as South America in winter, and both are experiencing significant declines in many areas outside of the Northwest Territories.  They were listed as Threatened under the federal Species at Risk Act (SARA) in 2010. 

From 1996-2006, the Canadian population of the Olive-sided Flycatcher declined by 79%, and survey numbers tell a similar story for the Common Nighthawk.  Its Canadian population decreased by almost half between 1995 and 2005. 

The short-term objective of both Recovery Strategies is to slow the natural decline of the species within 10 years of listing, while ensuring that the population does not decrease more than 10% over this time.  The long term goal is to ensure a positive 10-year population trend—in which each species’ population continues to grow each year for a sustained period of 10 years.   The draft Strategy documents describe broad research and management approaches to address the threats to the survival and recovery of these birds.

Fact Box
  • A Threatened Species is a wildlife species that is likely to become endangered if nothing is done to change the factors leading to its decline or disappearance.
  • Once a species is listed as Threatened under SARA, recovery planning begins.  Wildlife management boards and affected Aboriginal organizations are involved in developing a Recovery Strategy.
  • A Recovery Strategy includes measures to deal with known threats to a species and its habitat, and sets goals for recovering the species. 
What may be causing these population declines?

While the causes for these declines are not completely understood or known, a number of likely factors have been suggested.   

Olive-sided Flycatcher

The causes of the Olive-sided Flycatcher’s decline are uncertain, but are thought to be related to changes in habitat or in the abundance of its insect prey.  The Olive-sided flycatcher is a songbird of the boreal forest, often found along natural forest edges and openings near water or wetlands. There may be fewer of these birds in part due to loss of or changes to this important habitat, particularly in their southern breeding and wintering ranges.  Practices such as widespread clearing of forests and forested wetlands, for example, contribute to loss of habitat.  Climate change may also play a role in the Olive-side Flycatcher’s declining population.  For example, extreme weather on its breeding grounds that decreases the availability of insects could delay nesting or reduce nestling survival.  Pesticide use may also contribute to declining numbers of insects that these birds rely on as their main food source. 

Common Nighthawk

Common Nighthawks have likely been affected by a decrease in the abundance of insects –their main food sources-- and an increase in habitat loss and alteration.  The use of pesticides in some parts of its range may be partly responsible for this species’ decline.   The impacts of climate change may be another factor driving the Common Nighthawk’s decline. Tropical storms, climate fluctuations in spring at breeding sites and during migration, and cold wet weather during breeding can all cause mortality.  Tropical storms can kill these birds migrating in the autumn in large numbers. As well, changes in average temperatures, precipitation and the frequency of forest fires may affect the timing, diversity and abundance of the insect food supply –and restrict the amount of insect prey at the time when the birds need to feed their young at the nest. 

Increased predation of the Common Nighthawk’s nests may be another factor, as a result of increasing numbers of predators around urban areas.  Accidental deaths through collisions with vehicles and planes is another potential threat. 

 

Interesting Facts
 
The Olive-sided Flycatcher
  • The Olive-sided Flycatcher has a broad breeding range across Canada and the western and northeastern U.S.  Just over half the range is found in Canada where it breeds in every province and territory except Nunavut.  Its NWT breeding range includes the south-west portion of Wek’èezhìı.
  • It arrives in the NWT late May –early June and leaves again in late July – early August to winter primarily in South America. 
  • The Olive-sided Flycatcher is frequently associated with burned forests. The opened area and the abundant snags –standing dead or dying trees-- may help it to catch flying insects.
  • The Olive-sided Flycatcher perches on a tall tree or snag, and waits for an insect to fly by.   It then makes a dashing flight from its high perch, captures its prey in the air, and often returns to the same perch. 
  • Olive-sided Flycatchers often forage for insects near or above the forest canopy where the light is brightest. 
The Common Nighthawk
  • The Nighthawk breeds across much of North America and Central America; its NWT breeding range includes the south west part of Wek’èezhìı.  It arrives in the NWT to breed in mid-May to early June and begins its fall migration in late August-early September, leaving the NWT to winter in Central and South America.
  • It lays its eggs directly on the ground in open land and forest clearings where it can catch insects.
  • The Common Nighthawk is not a hawk but similar to a hawk, it can detect its prey in flight.  It chases flying insects at dusk and dawn, catching them in mid-air.   A single bird can catch up to 500 mosquitoes in a day. 
  • A specialized reflective structure in its eyes improves its vision in low light conditions. 
  • Common Nighthawks may forage near the ground or water, or more than 500 feet into the sky.