Bubo virginianus


         Used with permission
         Bubo virginanus,
 also known as great horned owls, have interactions with a variety of species. Most interaction are a part of a predator prey relationship. Great horned owls are the top of their food chain, making them the greatest predator (Vuilleumier 2009). In fact, to a crow, the great horned owl is the most feared predator. Because of this, it is found often that masses of crows vocally harass the owls as a defense mechanism (Elphick et al. 2001). Other birds such as red-tailed hawks, ravens, or northern harriers will physically harass great horned owls (Rohner 2000). Bubo virginianus are carnivorous birds that eat a variety of other animals. Mammals that they eat can range from as small as a rat to as large as other owls or skunks(Elphick et al. 2001). One mammal they particularly like are snowshoe hares. The owls will typically go for the young because adult snowshoe hares have learned to avoid predation while the young are vulnerable (Rohner and Krebs 1996). They will also eat larvae, insects, and even frogs (Elphick et al. 2001, Vuilleumier 2009). Since the females are typically larger than the males, the females tend to eat larger species or larger individuals within a species (Longland 1989).
         Bubo virginianus have many adaptions for obtaining food for their young and themselves. These owls are nocturnal, meaning they hunt at night (Alderfer 2005). This hunting tactic eliminates competition for obtaining food and keeps the food from getting stolen by other competitors (Elphick et al. 2000). Another tactic includes hunting in open areas; this eliminates obstacles when hunting (Rohner and Krebs 1996). Great horned owls are also aerial hunters that swoop in to capture their prey (Elphick et al. 2001, Vuilleumier 2009). Since the males are smaller, it is easier for them to maneuver and capture their prey (Longland 1989). They have specialized toes that rotate inward; this allows the owls to easily grab their prey with their claw-like feet (Elphick et al. 2000). Their young call out with a begging call; this squawk or sometimes hiss helps the mother owls locate her fledglings so she can feed them (Kinstler 2009). If an owl is not hunting for their young, it is common for the owl to eat its prey right away whole; this is another technique to eliminate the possibility of food getting stolen. Like other owls, the indigestible materials, including feathers, bones, and exoskeletons, are compacted into a pellet; this pellet is later ejected out of their mouths (Elphick et al. 2001). To learn more adaptaions of great horned owls, go to our adaptations page.
         Another interaction Bubo virginianus has with another species negatively affects their health; this species are black flies. Black flies carry and distribute avian malaria. If a great horned owl, the host, were to be infected by flies, the fitness of the owl would be reduced.Used with permission The hosts' blood cells and hemoglobin levels would decrease. A more obvious effect is decreased clutch size. Luckily great horned owls have learned to avoid black flies by specifically selecting their roosting sites. In the summer, Bubo virginianus tend to roost lower on stumps and the ground where black fly populations are lower than the mid canopy. In the winter, they move to the more hidden perches a couple meters off the ground when black fly populations overall decrease. Even though black flies do not live at the top of the canopy, great horned owls tend to avoid the top canopy year round due to harassment from other birds (Rohner 2000).
         Bubo virginianus
also have interactions that they cannot avoid. Parasitic organisms great horned owls interact with are mites, which include a variety of tick species such as deer ticks. Mites are found in the owls' nests and feed off the blood of the owl. This can cause the hosts' health to decline and reduce reproductive success; sometimes mites even feed on the fledglings and affect their development (Ritchison).




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