Many of our locally breeding migratory bird species were detected for the first time this past week. These species included blue-headed vireos, least flycatchers, rose-breasted grosbeak, western tanagers (our mascot), Swainson’s thrushes, magnolia warblers, Tennessee warblers, and ovenbirds. Lesser Slave Lake Bird Observatory (LSLBO) staff are excited to hear a diversity of warblers’ songs joining the local sparrows, but overall things have been unusually slow.
Most of these new arrivals are long-distance migrants. They travel from Central and South America to breed in the boreal forest. Their migrations seem to be triggered by changes in day length on their wintering grounds. Since day length changes predictably year to year, long-distance migrants’ departure dates and arrival dates tend to be roughly consistent.
Meanwhile short-distance breeders have arrived and are showing signs of active breeding efforts and early migrants have already left for their breeding grounds. These species come from the southern USA and northern Mexico and seem to depend on changes in the weather to trigger migrations. They migrate gradually, waiting for warmer weather at each stop before moving north. With exceptionally hot weather, their migrations have already completed. Unlike our more predictable long-distance migrants, short-distance migrants have a large range of dates that we see the last (or first) of them.
Since short-distance migrants can adapt their migration to weather conditions, they may be able to adapt to climate change. There is concern, however, for long-distance migrants – those pretty warblers and gifted singers that add diversity to our boreal forest in the summer.
Despite the lack of rain, our trees and shrubs are leafed out and the saskatoons are already in bloom. Comparing photos of the LSLBO station between years, shows that that this year’s green-up is three weeks earlier than last year’s. These plants are food for bugs and bugs are food for most songbirds. It is possible that the shift in leaf growth timing may lead to a shift in timing of peak insect abundances. This might not impact short-distance migrants much, but long-distance migrants may find themselves with little insect food for their young. Long-distance migrants do not know they are late to the game and cannot adjust their migrations much. To quantify trends in both leaf-out and insect abundances, LSLBO is continuing to contribute to Caterpillars Counts by doing standardized insect surveys roughly every 10 days.
By the time this is published, we will have finished our Great Canadian Birdathon run while Team Birds in the Park’s run may be underway. This big day is where we attempt to see as many species as possible within 24 hours to fundraise for the LSLBO and bird conservation efforts across Canada. If you like what we do, please consider visiting our website (www.LSLBO.org) to donate and stay tuned for our results next week.