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Although
the Bonelli´s Eagles can capture a wide range of preys, in practice
they feed on a restricted group of vertebrates, such as mammals, birds
and some reptiles.
Their
basic preys are rabbits, squirrels, rats, partridges, pigeons, doves,
lizards, although their diet changes according to the geographical
areas, the habitats and the presence of certain preys. Their diet
includes also small mice and birds, and even small raptors such as
goshawks, buzzards, eagle owls and young foxes.
Rabbits,
and to a lesser extent partridges, are considered their optimal preys,
for they mean a greater quantity of food with a lesser effort.
When these optimal preys are not plentiful, the eagles
usually capture doves, pigeons, or smaller preys such as crows,
squirrels or lizards. That means a lesser energy profit, for the eagles
have to go hunting more often to capture more preys and get the same
quantity of food they could obtain with only an optimal prey.
The diet of the Catalan
population
In
Catalonia, as in the rest of Europe where the Bonelli´s Eagle lives,
the rabbit is generally the most captured prey, since it fulfils all
the requirements to be an optimal prey: it lives in open areas where it
can be easily captured, is very nourishing and may be plentiful in
suitable habitats.
In a study on Catalonian pairs done in the early 90s,
rabbits represented just a 25% of the eagles diet, since their
populations have declined in the last few years. Other important preys
were doves (20%), squirrels (12%), red-legged partridges (11%), pigeons
(9%) and lizards (9%).
The kind of captured preys varies according to the seasons
and the kind of habitat present in the different areas of Catalonia.
For example, the pairs near to rubbish dumps, where yellow-legged gulls
usually gather, may capture a great quantity of these birds.
The diet as a indicator parameter of the
ecosystem condition
In the same way as the environment conditions determine the
abundance of preys available to the eagle, the eagles diet is a good
indicator of the condition of this environment.
In
the last few years the decrease of rabbits and red-legged partridges
populations led to a change of the eagles diet, adding less
profitable preys, such as doves, squirrels and crows.
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