A New Visitor to Our Watershed
Article by CVC’s Sarah Labrie.
The Dickcissel is said to be one of the most abundant breeding birds found in North American prairie grasslands. Its sparrow-like appearance and tendency to reside in similar habitats often leads people to think it’s a member of the Sparrow family, Emberizidae. Adding to the confusion is the Latin scientific name of this species, Spiza americana, translates into American finch. The Dickcissel is neither finch nor sparrow.
The Dickcissel actually belongs to the Cardinalidae family, which includes familiar species such as Northern cardinal, Rose-breasted grosbeak and Indigo bunting, who all share a similarly large conical bill. Most of us living in Ontario have probably never heard of this supposedly “abundant” grassland bird, and it would be for good reason. It’s the same reason we were extremely excited to find one while conducting breeding bird surveys this past summer – this species isn’t really supposed to be in Ontario.
A New Record
As sightings of Dickcissel spread across southern Ontario in summer it was hard for us not to get excited over the possibility of seeing one in the Credit River Watershed, even though we’ve never recorded them on the watershed species list. Adding to our doubt was the fact that we had only one breeding bird survey site this year that even remotely resembled the grassland habitat this species would normally be found in. One morning in June while we sat at that particular site, waiting for the fog to clear, we were greeted with an unfamiliar vocalization that stopped us dead in our tracks. We scanned the area in front of us and located a peculiar looking bird a few meters to our left. We almost couldn’t believe our eyes as we confirmed the identification. It was a beautiful adult male Dickcissel, signing his heart out. We ended that day spotting a total of three male Dickcissel, and I was thrilled to confirm the presence of a probable breeding pair on a subsequent visit in late July. We were excited to see this species for the first time and add a new species of bird to the Credit River Watershed species list. It will be interesting to see if they ever return.
Breeding Range and Irruptions
The core breeding range of the Dickcissel includes the US Midwest; specifically the prairie grassland regions of South Dakota, Nebraska, Iowa, Kansas, Missouri, Illinois, and central Oklahoma, down to parts of Texas and Arkansas. Despite its affinity for this geographic area it is notorious for irregular movements far outside of this core breeding range. As a result, this semi-nomadic species sees dramatic annual changes in distribution and abundance, especially in areas just outside of their core breeding range. Years in which these dramatic irregular movement events occur are known as irruption (or invasion) years.
This is the same type of movement event that periodically brings large numbers of northern species such as Snowy owls, Pine siskins and White-winged Crossbills, to name a few, down into southern Ontario. Although these species may occur in small numbers in southern Ontario in any year, an irruption year is characterized by significantly large numbers of unexpected birds. Ornithologists generally agree that irruption events in some species are triggered by food availability. For example, changes in prey populations may trigger large numbers of Snowy owls to move south.
Dickcissel may irrupt into Ontario during their breeding season, but they still spend their winters in South America, particularly Venezuela. Research into the cause of irruptions has found a link between irruption events and climate conditions. Irruptions in 1964, 1973 and 1988 were linked to drought conditions in their core breeding range.
Dickcissel are omnivorous during breeding season but rely mostly on grains during migration and on wintering grounds. Dickcissel have had to adjust to major habitat changes on both their breeding and non-breeding ranges. Changing land-use practises and destruction of grassland habitat have resulted in severe population declines of more than 30 per cent between 1966 and 1978. Populations have since stabilized but haven’t recovered to pre-1966 levels. As a result of habitat loss, they have to adapted to alternate habitats and can now be found in weedy fields, pastures and restored grasslands.