Broad-winged hawks (Buteo platypterus) are medium-sized raptors found throughout eastern North America. These secretive forest-dwelling hawks have experienced significant population declines in recent decades, leading to their current classification as a species of conservation concern. There are several key factors contributing to the endangerment of broad-winged hawks.
Habitat Loss
The primary threat facing broad-winged hawks is loss of habitat. As their name suggests, broad-winged hawks require extensive forests to meet their ecological needs. They build nests high up in mature trees and hunt small mammals, birds, reptiles, and amphibians among the forest understory.
Unfortunately, forests have been heavily logged and developed over the past century. It is estimated that over 80% of old growth forest habitat in the eastern United States has been destroyed. This has severely impacted broad-winged hawks by removing critical nesting sites and decreasing prey availability.
Studies have shown broad-winged hawk numbers are lowest in small, fragmented woodlots. The reduction of contiguous forest has been directly correlated with declining broad-winged hawk populations in many areas. Without adequate habitat, this species struggles to establish breeding territories and successfully raise young.
Migratory Difficulties
Broad-winged hawks are unique among North American raptors for their long distance seasonal migrations. Each fall, virtually the entire population will migrate from the United States and Canada to wintering grounds in Central and South America.
This journey across thousands of miles is perilous, requiring broad-winged hawks to navigate diverse geography and weather conditions. Exhaustion, starvation, and collisions with manmade structures take a toll on migrating hawks each year.
Habitat loss has further exacerbated migratory difficulties. Deforestation in Central and South America has reduced the amount of wintering grounds available. Competition for fewer suitable forests results in higher mortality rates among wintering broad-winged hawk populations. Surviving the migration south is only half the battle if insufficient habitat is available at their destination.
Climate Change
A warming climate has altered weather patterns and environmental conditions in ways that negatively impact broad-winged hawks. Rising temperatures are linked to heat stress, changes in precipitation, increased frequency of severe storms, and reduced availability of prey species.
Hotter summers may make it difficult for broad-winged hawks to thermoregulate, leading to heat exhaustion. Altered rainfall could flood nests or make it harder for hawks to locate food. More intense and frequent severe weather like hurricanes can destroy nesting sites and directly kill chicks and adults.
Climate change is also shifting geographic ranges of species broad-winged hawks rely on for food. Prey may become less abundant in areas long used as hawk breeding grounds. This can force broad-winged hawks to hunt less suitable prey or expend more energy locating food, impacting health and reproductive success.
Pollution
Various types of pollution pose threats to broad-winged hawk survival. Pesticides applied to agricultural areas can accumulate in prey species and cause secondary poisoning of broad-winged hawks through bioaccumulation. Heavy metal contamination has similar risks.
Oil pits and waste ponds at drilling sites are particularly deadly to broad-winged hawks, which can become coated in oil as they attempt to drink water in these locations. Birds that contact oil suffocate and die. Acid rain also impacts broad-winged hawk reproductive rates by leaching essential nutrients from soils and reducing calcium availability.
Shootings
Though currently protected under the Migratory Bird Treaty Act, broad-winged hawks were historically shot in large numbers. Some illegal shooting persists today, primarily on wintering grounds where enforcement is lax.
Adult hawks may be targeted by poachers eager for raptor specimens, while farmers may shoot broad-winged hawks perceived as a threat to livestock like chickens. Power lines modified to electrocute perching raptors also pose a danger. Each unnecessary shooting chips away at an already diminished broad-winged hawk population.
Competition and Disease
Broad-winged hawks face heightened competition for nesting sites and prey from other bird species. Great horned owls often commandeer old broad-wing hawk nests early in the breeding season, leaving the rightful owners displaced. Expanding populations of blue jays and American crows outcompete broad-winged hawks for food sources.
West Nile Virus emerged as a significant threat to broad-winged hawk health in the 1990s. Mosquitoes transmit the disease which impairs respiratory and neurological function in raptors. Though a mortality rate is hard to establish, research indicates susceptibility to West Nile Virus incubation decreases breeding success.
Small Population Size
Due to declining numbers, broad-winged hawks are now considered rare throughout much of their range. It is estimated only 1 million individuals remain in the global population. Small populations face greater risks of inbreeding depression and localized extinction events.
Random factors like severe weather, disease outbreaks, or food shortages can wipe out a significant percentage of an endangered species low in overall numbers. The smaller the total population, the less likely it is able to absorb and rebound from these stochastic elements. A species in decline becomes increasingly vulnerable each year.
Year | Estimated Global Population |
---|---|
1980 | 3 million |
2000 | 2 million |
2020 | 1 million |
Slow Reproductive Rate
Broad-winged hawks are slow to sexually mature and have small average clutch sizes. Females don’t start breeding until 2-3 years of age and lay just 1-3 eggs per season. Compared to other raptors that frequently lay 4-5 eggs, broad-winged hawks have lower reproductive output.
This makes population recovery challenging despite broad-winged hawks potentially living up to 16 years in the wild. The number of surviving chicks must exceed adult mortality rates for the population to stabilize, let alone increase. Unfortunately, fledgling success is also limited by habitat loss, pollution, climate change, and other factors.
Average Clutch Size Comparison Among Raptors
Species | Average Clutch Size |
---|---|
Broad-winged Hawk | 2 eggs |
Red-tailed Hawk | 3 eggs |
Great Horned Owl | 4 eggs |
Conservation Actions Needed
To stabilize declining broad-winged hawk populations, conservation efforts must focus on protecting and restoring critical habitat, enforcing legal protections, mitigating climate change impacts, reducing pollution, and increasing environmental education.
Forest preservation and sustainable land management are top priorities. Broad-winged hawks would benefit greatly from habitat corridors that connect fragmented forest sections and more designated wilderness areas kept roadless and pristine. Agencies should work with private landowners to restrict deforestation and reward conservation easements.
Overseas partnerships focused on reducing habitat loss on tropical wintering grounds could significantly improve broad-winged hawk survival rates. Continued multinational cooperation is vital to enforce protections for broad-winged hawks and other migratory birds that cross international borders.
Climate change poses a complex threat requiring diverse policy changes to address emissions, support scientific research, and respond to alterations already underway. Broad-winged hawks would benefit from rapid global action to limit climate impacts.
Reducing widespread use of pesticides and better containment of industrial pollutants are also important steps. Transitioning to sustainable green energy like wind and solar power lessens emissions related to acid rain and oil contamination.
Finally, community outreach and education can make the general public invested in protecting rare species like the broad-winged hawk. Engagement campaigns centered on ecotourism could even make broad-winged hawks a source of pride and revenue for local economies.
Conclusion
Broad-winged hawks are classified as Near Threatened globally and endangered at the state level across much of their range. A variety of synergistic anthropogenic factors have reduced the population to just 1 million individuals, with numbers continuing to decline each year.
Habitat loss, climate change, pollution, shootings, competition, disease, small population size, and slow reproductive rates all contribute to the endangerment of broad-winged hawks. Concerted conservation action on many fronts is needed to preserve this important raptor species and the forests they call home. With prudent management of remaining habitats and mitigation of human impacts, it is possible to take the broad-winged hawk off the endangered list.