Most people who live in the Columbia Valley are familiar with the large unmistakable, white and black raptors that nest along Highway 95.
The mighty osprey… many of them build nests on pole platforms and as such are quite conspicuous making them easy to observe. But how many people know much about them? This summer, a biologist working on the Columbia Wetlands Waterbird Survey inventoried them and determined the population and breeding success of ospreys nesting in the Columbia Valley.
“In order to determine the number of ospreys actively nesting in the Valley we first worked to locate all of the nests that we could, enlisting the help of volunteers,” states conservation biologist Rachel Darvill. “We then visited each of the known nest sites two to three times during July and August in order to determine the breeding success of those nests.”
Darvill and her small team were able to locate 59 nests adjacent to the wetlands, but there were likely more nests that were not located.
“Of the 59 nests we were able to locate, 42 were active this year and 32 produced chicks or fledglings as of August 19. That gives a breeding success rate of about 76 per cent,” Darvill said.
Darvill also observed that some nests appeared as though they had never been used, or they had not been used in several years.
“Three of the nests ended up with known chick fatalities,” reports Darvill.
Two chicks were reportedly killed by passing cars and another pair of chicks was found dead in their nest located within the Town of Golden. Of the nests, 50 were located on poles (most put up through a BC Hydro program), whereas eight were tree nests, and one nest was located on the top of a communication tower. Osprey nests are reused each year, and are usually located in relatively close proximity to open (often shallow) water that supports a plentiful supply of fish.
Ospreys are superb fishers and eat little else – fish make up some 99 per cent of their diet. Nest sites are normally within four kilometres of water, but they can be found as far as 10 to 20 kilometres from water where it is energetically feasible. All ospreys and their nests are protected under the Migratory Birds Convention Act.
“We are hoping that bird data such as this, along with other data collected through the Columbia Wetlands Waterbird Survey, will enable the wetlands to become part of the Important Bird and Biodiversity Area (IBA) program,” states Darvill.
During the 1990s it was reported that the Columbia River (along with other B.C. southern interior rivers) was considered to be one of the highest breeding densities of osprey in the world, but there had been no known systematic osprey inventories completed in the Columbia Valley.
“By getting an accurate count of ospreys in the Columbia Valley, I think it will help increase the opportunity of having the Columbia Wetlands designated as an IBA,” Darvill said.
The osprey is a very adaptable bird, it has variable migration strategies, and unlike many raptors, it is very tolerant of human activity near its nests. However, North American osprey populations became endangered in the 1950s due to chemical pollutants such as DDT, which thinned their eggshells and ham≠pered reproduction. Ospreys have rebounded significantly in recent decades, though they remain scarce in some locales. Monitoring osprey populations is a useful indicator of the persistence of toxic contaminants and the relative health of aquatic ecosystems throughout the species range.
For anyone interested in learning more about ospreys or other waterbirds, volunteer opportunities to get involved in the Columbia Wetlands Waterbird Surveys are coming up. Survey dates are Sunday, September 29, Saturday, October 5, and Tuesday, October 15, from 10 a.m. to 1 p.m. on each date. There will be free bird identification training sessions available for volunteers, participants can be paired up, and high quality optical gear can be lent to those in need. Those who are interested, can contact Darvill at 250-344-5530 or firstname.lastname@example.org. The Columbia Wetlands Waterbird Survey is funded by the Columbia Basin Trust, Columbia Shuswap Regional District, Regional District of East Kootenay’s Local Conservation Fund, Province of B.C., The McLean Foundation, Wings Over the Rockies, Columbia Wetlands Stewardship Partners and the Vancouver Foundation’s Stewart Fund.