Blackbirds are a common sight across much of North America, with several species native to the continent. While blackbird populations tend to fluctuate naturally throughout the year, many people have noticed a dramatic surge in the number of blackbirds in their neighborhoods and communities recently.
What types of blackbirds are increasing?
There are several species of blackbirds that are becoming more abundant across North America:
- Red-winged Blackbirds
- Common Grackles
- Brown-headed Cowbirds
- Brewer’s Blackbirds
Of these, Red-winged Blackbirds and Common Grackles are most responsible for the influx of blackbirds many are noticing. Both species have adaptable diets and can thrive in both rural and urban environments.
Why blackbird populations are surging
There are several factors that could explain the recent surge in blackbird populations across North America:
Climate change
Warmer temperatures allow blackbirds to expand their ranges northward. Milder winters also increase overwinter survival. The changing climate likely supports larger blackbird populations.
Urbanization
As cities grow, blackbirds have more manmade structures to nest on and access to lawns and gardens for foraging. Urban areas can support larger densities of blackbirds.
Agricultural changes
In rural areas, changes in farming practices may benefit blackbirds. Greater crop diversity and conservation lands offer more food resources. Milder winters also allow more blackbirds to overwinter in agricultural areas.
Decreased competition
Populations of predators and competitors of blackbirds, like hawks and blue jays, may be declining in some areas. With less competition, blackbird populations can increase.
Fewer insecticides
The use of broadcast insecticides has declined since the 1960s. With fewer insecticides suppressing insect populations, blackbirds have an abundant food source.
Adaptive behavior
Blackbirds have proven able to adapt well to manmade environments. Their ability to nest on structures and scavenge urban and suburban areas enables their populations to grow.
When did blackbird populations begin increasing?
Red-winged blackbird and Common Grackle populations have been increasing steadily since the 1960s, according to long-term monitoring surveys like the North American Breeding Bird Survey. The trends show blackbird numbers rising gradually over decades across North America:
Decade | Average % change per year |
---|---|
1960s | +2.5% |
1970s | +2.1% |
1980s | +1.8% |
1990s | +1.4% |
2000s | +0.9% |
2010s | +1.2% |
These long-term trends indicate blackbird populations have been increasing steadily for 60 years across North America.
What regions are seeing the biggest increases?
According to breeding bird survey data, some of the regions seeing the largest increases in blackbirds include:
- Midwestern states like Nebraska, Kansas, Iowa
- Northeastern states like Maryland, New York, Maine
- Pacific Coast states like Oregon and Washington
- Provinces in central Canada like Manitoba, Saskatchewan
In these regions, both rural and urban habitats appear to support growing blackbird populations. Milder winters and expanding urban areas likely enable the increases.
When do blackbird numbers peak annually?
Blackbird populations fluctuate throughout the year as a result of seasonal patterns in breeding, migration, and dispersal. The peak times when blackbird numbers are highest include:
Late summer
In late summer just after the breeding season, blackbird populations are at an annual high. Young birds have fledged and are traveling with adults in large mixed flocks.
Fall migration
During fall migration from September-November, large flocks of blackbirds congregate and feed together as they stopover at migration hotspots before moving south.
Early spring
As blackbirds return north in February-March, flocks congregate at warm roosting sites and feed in agricultural fields and wetlands.
Will blackbird populations continue increasing?
Blackbird populations may continue to increase but could stabilize in the future. Here are two scenarios:
Populations stabilize
As blackbird numbers reach carrying capacity limits, their populations could stabilize. Lack of additional nesting habitat in urban areas and increased disease transmission may limit further growth.
Populations crash
If future conditions change, such as through extreme weather events or reduced food supplies, blackbird populations could crash from a peak high. Cyclical crashing has occurred before during the 1970s and 1990s.
How can blackbird numbers be reduced?
If desired, some options to potentially reduce local blackbird numbers include:
- Removing artificial food and water sources
- Limiting access to nesting sites
- Using noise deterrents and reflections to disperse roosts
- Increasing predator habitats like perches to encourage hawks
- Applying repellents to discourage feeding
- Population control measures like egg-oiling or euthanasia
However, lethal control is controversial and non-lethal methods require diligent application. Blackbird populations may rebound quickly after control efforts.
Conclusion
In summary, Red-winged Blackbird and Common Grackle populations have been gradually increasing across North America since the 1960s due to factors like climate change, urbanization, agricultural changes, and adaptive behaviors. Their numbers tend to peak in late summer, fall, and early spring when flocks congregate. While populations may stabilize naturally, control measures can also potentially limit local surges where blackbirds cause damage or nuisance problems.