Bluebird Numbers Plummet in 2008

Sept. 26, 2008 - PRLog -- The soft, plaintive cries of the bluebird were eerily silent this past summer. Mountain bluebirds seem to have taken a population nose-dive all across Alberta. People monitoring bluebird nest boxes reported a marked reduction in nesting pairs. This is significant for a species that was once declared ‘at risk’ and has since made a great recovery. At this point in time, there are no definitive answers or explanations from the scientific community and no one can estimate how long it will take them to rebound.
   Many wild species fluctuate from time to time, either in yearly or multi-year cycles. So the question remains, is this year’s decline in mountain bluebirds a natural occurrence? If so, how serious is it and will they soon recover? Other cavity nesters such as tree swallows and chickadees seemed unaffected which is why some biologists are speculating the abnormally harsh spring may be the dominating factor.
    Songbirds are susceptible to pesticide use, outdoor cats, window strikes, and a myriad of other human factors that scientists say claim the lives of millions upon millions of wild birds each year. Birds are also threatened by natural causes such as weather anomalies and disease, though it should be noted the latter can also be exacerbated by human activities. For example, some studies link toxoplasmosis in songbirds to feral cats.
   What makes the summer ‘08 picture so alarming is the historical demise of North American bluebirds witnessed in the last two centuries. Tree management across much of their range resulted in the loss of critical nesting sites and pesticides have taken a huge toll as well, but the biggest threat came from the invasion of two non-native songbirds: the house sparrow and the starling.  Brought to North America from England in the late 1800’s, both species are cavity nesters that compete aggressively for appropriate cavities. Starlings are very early migrants and take advantage of the best nest spots early in the breeding season. House sparrows, also known as English sparrows and English weaver finches, don’t migrate at all so they also dominate nesting locations early.
   By the 1960’s and 70’s, bluebirds had reached all-time low numbers. Youth groups, birding societies, and naturalists, were among those who built huge numbers of nest boxes and placed them in rural locations to assist the bluebird’s return. This program was hugely successful.  Decades later, people are still buying and building bluebird houses in great quantities and several species are making great use of them. Other species, such as the tree swallow also benefit from bird houses as well. Though there is some competition between bluebirds and tree swallows, the two species have co-existed successfully for millennia.
   One particular biologist in Alberta has been working hard for two decades, educating people about hazards for wildlife that are created by human activity.  Long time director of the Alberta Institute for Wildlife Conservation, Dianne Wittner noticed an apparent shortage of bluebirds as early as March, the month they return from the south. As summer progressed, the nest boxes normally occupied by bluebirds remained vacant.
Wittner suspected the cold, snowy spring may have impacted bluebirds though she also noted that unfavourable spring weather is the norm in Alberta. “Year after year, we see bluebirds forced to abandon nests when sudden cold weather affects food supply (insects). Inspection of bluebird houses during these events often reveals frozen eggs and starving adults.”  Furthermore, bluebirds are able to produce two clutches per season if conditions are right, which has not been the case in recent years. Wittner speculates several bad springs in a row may have caused gradual population reductions. However, she is quick to add no one really knows for sure what is going on. “It could be several factors working together. A combination is often the case.”
   It will be interesting to see if other species of bluebirds show a significant decline across the continent. All three species have suffered setbacks since the introduction of the house sparrow and the starling and all three have been assisted with the advent of artificial nest boxes. The true test will come next March when bluebirds return.
   In the meantime, when Wittner is not saving wild lives, she is busy encouraging people to erect bird houses for a variety of species. Through her website, www.northernbirdhouses.com  she offers information on proper placement of species-specific nest boxes and ledges to help offset habitat loss. “There is no substitute for habitat conservation,” she says, “But everyone can help wildlife in their own yards with a few simple steps. One of those is the addition and maintenance of a good bird house. You will be rewarded year after year by this very simple act and who knows how many wild birds will benefit?”

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