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| Photo : Goshawk Ecotours |
Birds of prey, or raptors, include many species of birds that primarily hunt and feed on
vertebrates that are large relative to the hunter. Additionally, they have keen
eyesight for detecting food at a distance or during flight, strong feet
equipped with talons for grasping and killing prey, and powerful, hooked beaks
for tearing flesh. The term raptor is
derived from the Latin word rapere,
meaning to seize or take by force. In
addition to hunting live prey, many may also eat carrion, at least occasionally.
Fourteen
raptor species have already been documented at Camp Baker, and 17 species are
likely to occur here. These include the
following raptor groups: vultures, ospreys, eagles, harriers, accipiters,
buteos and falcons.
Why counting raptors is important
Birds are
excellent indicators of environmental health.
Since raptors are apex predators, they are susceptible to a variety of
threats including; pesticides, habitat loss, climate change, poisoning,
collisions, electrocution, persecution and disease. Since these threats often have the most
impact on apex predators, we refer to raptors as an indicator species.
Additionally, since many raptors are migratory, migration counts may
also provide insights regarding the health of the habitats along their
migratory pathways and within their wintering grounds.
Threats to Raptors
Habitat Loss, degradation and fragmentation
Loss and
degradation of their native habitat has the largest impact on raptor
populations. Habitat degradation is
occurring throughout the western U.S. from conversion to intensive agriculture,
urban sprawl, and the introduction of non-native species. When habitat is fragmented or destroyed in a
piecemeal fashion, the remaining fragments of habitat occur in smaller patches.
Hence, survival of native wildlife and plant communities becomes increasingly
difficult.
Climate
Disruption
Over time,
climate disruption is likely the most significant factor that will adversely
impact future bird populations on a global scale.
Poisoning
Lead poisoning is one of the most common types of poisoning raptors suffer. Agricultural pesticides may also adversely
impact raptors, although more studies are needed to quantify this probable
threat. Additionally, some land owners intentionally put out poisons with the
intent of killing prairie dogs, ground squirrels, and other raptor prey
considered to be a nuisance. Occasionally raptors themselves (or corvids) are
targeted. This latter practice, however,
is illegal, but often difficult to enforce.
Collisions
Raptors
are susceptible to collisions including: vehicles, wind turbines, powerlines,
windows, trains, airplanes and barbed wire fences.
Electrocution
Raptors perching on utility poles are susceptible to electrocution when the bird completes a circuit by spanning two energized parts of equipment. Unfortunately, raptors use utility poles to perch, both for resting and especially as a vantage point to hunt from.
Raptors perching on utility poles are susceptible to electrocution when the bird completes a circuit by spanning two energized parts of equipment. Unfortunately, raptors use utility poles to perch, both for resting and especially as a vantage point to hunt from.
Persecution
The
trapping and shooting of raptors are still prevalent in the U.S. For example, in March of 2018 one resident of Susanville, CA killed 126 raptors. Most
were Red-tailed Hawks, but at least one dead owl and one Ferruginous Hawk were
found.
Disease
Several
diseases are known to threaten raptors, including West Nile Virus and Avian Flu.
