Locusts are a type of grasshopper that can undergo a remarkable transformation, changing their behavior, appearance, and physiology under crowded conditions. These insects, typically solitary, become gregarious and form vast, highly mobile swarms that can devastate agricultural crops and vegetation. Birds are natural predators of these insects and play a role in managing their populations.
Birds That Prey on Locusts
A diverse array of bird species preys on locusts. Many common birds, including wrens, crows, jays, and sparrows, consume locusts, along with domestic birds like chickens, ducks, and turkeys. Specialized species, sometimes called “locust birds,” include the African black-winged pratincole and the rose-colored starling in India, known for consuming many locusts.
Raptors such as Swainson’s hawks voraciously eat these insects. Kestrels, lanner falcons, black kites, and Montagu’s harriers also prey on locusts, often catching them in flight. Other predators include storks, golden orioles, drongos, and roller jays. These birds typically employ direct attacks, swooping down to capture locusts from the ground or in mid-air.
The Role of Birds in Locust Control
Birds serve a significant ecological function in regulating locust populations, particularly during outbreaks. Their predatory activities can help mitigate damage caused by locust swarms to crops and natural vegetation. Birds can reduce locust populations by as much as 50% within a 17-day period. For instance, a single drongo can consume up to 150 insects per hour, demonstrating the substantial impact individual birds can have.
Historical accounts and modern studies indicate that birds have long been recognized for their role in locust control. While they may not halt a massive invasion entirely, birds contribute to managing populations at lower densities and can reduce the severity of outbreaks. This natural predation can support more sustainable pest management practices by reducing reliance on chemical interventions.
Factors Influencing Bird Predation
The effectiveness of birds in preying on locusts is influenced by several environmental and biological factors. The density and size of locust swarms play a role, as birds are generally more effective at controlling low to medium density populations, while extremely large swarms can overwhelm their predatory capacity. Habitat conditions, including the availability of nesting sites and water sources, can also affect bird populations and their ability to contribute to locust control.
Pesticide use significantly impacts bird predation on locusts. Broad-spectrum chemical insecticides can directly harm bird populations and reduce prey availability, causing population declines. In contrast, biopesticides, such as the fungus Metarhizium acridum, do not harm birds and can even enhance predation by making infected locusts more sluggish and visible, increasing their vulnerability to avian predators. Birds often exhibit a preference for larger locusts, particularly females, which aids population control by limiting reproduction.