Outdoors_lol_09-05

Jeff Green | Feb 05, 2009

One of the more colourful winter visitors to area bird feeders is the Evening Grosbeak. Many people enjoy seeing this stocky yellow, black and white finch at their feeders, although the amount of seed these birds can consume can be quite daunting when they descend on a feeder in good numbers. I have heard stories of people going through several pounds of sunflower seeds per day in the middle of an invasion of these gregarious birds!

In the last few years, however, sightings of Evening Grosbeaks seem to have been fewer and further between. Anecdotal evidence from long-term residents and rural property owners in Eastern Ontario and Western Quebec suggests that these birds are much less common that they used to be. In some areas, recent winters have passed without a single sighting. So what’s going on?

Before we look at this question, let’s review the recent history of Evening Grosbeaks in Ontario. They formerly nested only in the west before spreading eastward in more modern times. For example, the first breeding record in Ontario is from 1920 at the Lake of the Woods, and records show that it reached Algonquin Park in 1932. In Quebec, Evening Grosbeaks were unknown, even as winter visitors, until the 1890s, and the first evidence of Evening Grosbeaks nesting in that province wasn't discovered until the 1940s. Populations in Ontario continued to grow until they reached a peak, probably in the mid-1980s.

Three reasons have been suggested to explain why Evening Grosbeaks expanded eastwards, all related to food supply. First, the planting of Manitoba Maples on farms and in towns in the east enticed the birds eastward – some people refer to this as a “baited highway” to the east. Second, spruce budworm outbreaks in the spruce and fir forests of eastern North America provided them with an excellent food supply for the breeding season. Finally, extensive logging of eastern boreal forests led to an explosion of berry producing trees and shrubs like wild cherries.

Evening Grosbeaks nest in mature or second growth coniferous or mixed forests, generally north of our area. Often the highest numbers of breeding birds are found in areas experiencing outbreaks of spruce budworm. These birds are known as “irruptive migrants” – meaning that their migration is irregular and often in response to food availability. Normally they move south in good numbers only in winter, sometimes travelling as far as the southern US in search of reliable food supplies. As a result, they may be locally common in any given area one year, and virtually absent the next year. I recently read a report from a bird fan in New Mexico who noted she had some at her feeder in 1996 and again in 2001, but not in between.

Project Feederwatch is annual survey of North American birds that visit backyard feeders in winter. In Canada, it is run by Bird Studies Canada. According to their data, in most geographical regions across North America the probability of seeing grosbeaks during winter has declined. While the pattern is clear, they have not been able to determine the cause. Because Evening Grosbeaks are irruptive migrants, declining observations could mean that the birds are changing their wintering locations or that there are real declines in abundance.

According to the second Ontario Atlas of Breeding Birds (2007), populations of Evening Grosbeaks showed an annual decline of 8.2% in Canada and an even higher 11.9% annual decline in Ontario since 1981. In addition, the atlas project revealed that the likelihood of observing an Evening Grosbeak declined by 30% in the 20 year period between the first and second atlases. The atlas also noted that the decline in Ontario began at roughly the same time as when outbreaks of spruce budworm began to decline in the province, and – happily – that populations of this likeable bird have probably stabilized.

Let’s hope that Evening Grosbeaks will be back at our feeders soon – despite how much they eat, a visit by these beautiful birds can really brighten up a winter day.