How did efforts to build up populations of cavity-nesting birds fare around British Columbia in 2020?
Thanks to SIBTS Nestbox Data Coordinator Kathy N., who compiled reports from monitors around the province. Here’s a summary, by geographical area.
Some areas normally have some of each bluebird species, Western (WEBL) and Mountain (MOBL). Other areas have only one species. Many areas also welcome Tree Swallows (TRES).
Sandy and Rita P. in Empire Valley had 103 MOBL nestings. There were 280 nestlings and 252 fledglings, a nice 90% success rate. TRES nested 33 times and had 113 nestlings with 90 fledging for a rate of 79.6%.
Sandy writes: “Wet, late spring resulted in a late start for season, but the Bluebirds had a pretty good year except not a lot of second broods because of the late spring. Tree Swallows did not fair very well, we had a lot of heavy prolonged rains. Not good conditions for Swallows. Bear problem was not as bad this year as last but did lose 8 Bluebird and 2 Swallow nests due to bear.”
Paula N. in Upper Ootishenia had 6 MOBL nestings that gave 27 nestlings, all of which fledged, i.e. 100%. She also had one nesting of TRES that was 100% successful with 5 fledging.
The Rocky Mountain Naturalists have many members monitoring trails throughout the area, with 344 boxes used. Collectively they had 145 WEBL nestings with 639 hatchings that produced 578 fledglings, a 90.5% success rate.
For MOBL, 89 nestings with 386 hatchlings and 345 fledglings, a 89.4% success rate.
TRES had 159 nestings, 757 hatchlings and 531 fledglings; 70.1%.
Ray and Judy F. found one MOBL nesting. It was 100% successful, producing 5 fledglings.
They also report that a House Wren built an entire nest late in the season but never laid any eggs.
“On another note, we had erected an outhouse near the garden last year but hadn't yet screened in the space under the back of the roof. A pair of Pacific-slope flycatchers decided that a short 2x4 shelf beside the door was a good place for a nest. They raised 5 young ones, and we opened the door enough when they were large enough so that the babies would not have to fly up to the roof opening when it came time to leave the nest. Now we can use the outhouse again, and it will get fully screened before next spring!”
At Black Mountain, Carol M. reported 4 WEBL nestings that had 20 nestlings, but only 10 fledglings, a 50% rate. One MOBL nesting was 100% successful with 6 fledged. Three TRES nestings produced only 5 fledglings from 11 hatchlings, a low 45.5% rate.
Carol writes: "With 15 boxes monitored, the results are disappointing. Especially, the number of bluebirds ready to fledge and then all be found dead in their nests. At least the cattle were out of the park so none of the boxes were knocked off their posts. At first we thought the unusual wet weather this year might have created a blowfly situation as one group of dead Western Bluebirds had maggots on them. However, after reading an article in the North American Bluebird Society summer 2020 journal, I wonder if the lack of insects was the cause of the deaths. Most of the deaths happened just before fledging, so perhaps the adults were unable to keep up with the hungry mouths. We saw adults around while the bluebirds were alive. It is possible that the adults died or abandoned the nests for lack of food.
The article I refer to is “Insect Populations Continue to Plummet – What Does This Mean for Bluebirds?” by Bernie Daniel, Ph.D. After sharing the recent drastic fall of populations of insects worldwide, a few possible causes are suspected:
--Intensification of agriculture (in our case the decimation of grassland just to the west of the bluebird trail).
--Development of newer generations of pesticides which are a little too effective on insects (phenylpyrazoles and neonicotinoids in particular).
--Biological factors such as pathogens introduced by species from other continents.
--Unfavourable conditions brought on by climate change.
“Next year we plan to remove boxes 7-12 which have not been productive for a few years, and put them and some extra boxes we have along the Gopher Creek fence line. We will do this and clean out the boxes in the fall. Maybe, we’ll have to start providing meal worms for the bluebirds!!! How will we do that?”
On the Gallagher’s Canyon and Mission Greenway trails, Rick G. had 4 WEBL nestings producing 16 nestlings and 13 fledglings for a rate of 81.3%. He also had 7 TRES nestings with 19 nestlings that gave 12 fledglings, a 63.2% rate.
At UBCO, Hamilton reported 13 nestings of WEBL with 62 hatchlings and 62 fledglings, a 100% success story.
Lake Country Area
On the Beaver Lake Trail, Stu W. and Ann G. had 1 WEBL nesting that had no fledglings. MOBL were a bit better with 4 nestings, 12 nestlings and 4 fledglings, a 33.3% success rate. TRES had 11 nestings, 20 nestlings, 8 fledglings and a 40% rate.
Stu adds: “Nest Boxes available – I have 31 boxes on my trail, however, an interloper has installed 11 + new boxes between mine, in no particular order. One of our club members, in early May, opened each of the 11 boxes and found evidence of occupation: MTBL, WEBL, HOWR, TRSW, including nests, eggs and sitting birds. These boxes were not monitored further.”
Lillooet Naturalists’ Club members look after trails Diamond S Ranch, OK Ranch and Kelly Lake. They enjoyed 58 MOBL nestings that gave 248 nestlings and 212 fledglings, a rate of 85.5%. There were also 52 TRES nestings, 162 nestlings, 118 fledglings, for a rate of 72.8%.
Logan Lake Area
Ray T. looks after many boxes. 114 nestings of MOBL resulted in 449 nestlings and 412 fledglings, a rate of 91.8%. From 200 TRES nestings there were 798 nestlings and 660 fledging; 82.7%.
At the Desert Centre, Leor O. reported 13 WEBL nestings, resulting in 59 hatchlings and 34 fledglings, for a disappointing 57.6% success rate. One TRES nesting produced a 100% success rate with 4 young fledging.
Bob S. writes: “This is a quick summary for 2020 of 8 bluebird boxes on the road up to Mount Kobau. I submitted a report form last year where the boxes did produce some successes. Not so for 2020, so no completed form.
“Out of a total of 4 boxes (2 with 6 chicks and 2 with 5), no young survived to fledge. By our best guesses, a bear destroyed one box, probably the mother was killed or abandoned another nest as the young were found dead and dessicated, and the two remaining nests were probably predated by snakes or weasels as evidenced by eggshell fragments (prior to hatching).
“With so much predator loss in a relatively wild area, the decision was made to retire the boxes from the Mount Kobau Road area and not attempt efforts there in the future.”
On the West Bench, above Sage Mesa, Myrna B. reported that there were 9 WEBL nestings, 46 hatchlings and 36 fledglings; 78.3%. MOBL had 2 nestings, 10 hatchlings and 10 fledging; 100%.
Myrna adds: “Some eggs and chicks lost to snakes, I’m assuming Gopher snakes. Nests clean and no other disturbance.”
The Quesnel Trail & Nature Club looks after trails at Dragon Lake and West Fraser. Combined, these locations produced 14 MOBL nestings with 43 nestlings and 38 fledglings, for a rate of 88.4%. TRES had 15 nestings producing 68 hatchlings and 57 fledglings; 83.8%.
The North Okanagan Naturalists’ Club had many active trails with a total of 302 nest boxes used.
There were 90 nesting of WEBL resulting in 377 hatchlings. 290 fledged, a 76.9% success rate. MOBL had 12 nestings with a 100% success rate for 54 hatchlings. Meanwhile TRES had 176 nestings, producing 678 nestlings and 406 fledging for a low rate of 60%.
White Lake/Willowbrook Area
Audrey M. had 5 nestings of WEBL, resulting in 20 hatchlings and 20 fledglings, 100% successful. MOBL had 3 nestings, 12 nestlings and 12 fledglings, 100%. Then there were 3 TRES nestings, 100% successful with 15 nestlings and fledglings.
Province-wide our reporters had a total of 1,884 nest boxes available, with 1,328 being used, a 70.5% occupancy which is lower than normal. The overall successful fledging rate was 84.2% for WEBL, 89.7% for MOBL and a low 72.2% for TRES.
Other cavity nesters that were reported in smaller numbers were House Wrens, Black-capped and Mountain Chickadees, European Starlings, Pygmy Nuthatches, White-breasted Nuthatches and House Sparrows. Monitors also found some mammals in boxes: Red Squirrel, Chipmunk and mice.
No reports were received for nest box trails in and around Kamloops, Trail, Kilpoola-Osoyoos, Summerland (Bald Range), other trails at White Lake, Williams Lake, or Bulkley Valley. If any monitors in these areas, or other non-reporting areas, have data or anecdotes to share, please send them in even now to Kathy.