Kleptoparasitism

A long time ago, well 30 years ago does seem like a long time,
when I was a small mammal ecologist studying cryptic, nocturnal
rodents I built four 1/2 acre enclosures with dug-in flashing and
fences to study the interactions and breeding ecology in
Microtus californicus, Reithrodontomys megalotis, and 
Peromyscus maniculatus. After a month of long, cold nights
trapping and marking and mapping the animals I was ready for
breeding season in early spring. A pair of Great-blue Herons
discovered my enclosures and within a couple of days it was
their favorite hang out. Then a pair of Red-tailed Hawks arrived
to nest in some eucalyptus trees bordering "my" field and
complete carnage ensued. When the Red-tails weren't stealing
mice from the Great-blues they were using my fence to perch
on and just knocking the furry little guys off themselves. A pair
of Loggerhead Shrikes arrived at the same time and found
that Reithrodontomys were a perfect sized meal. Within two
weeks, trap success had dropped 90%. With the abundance
of food the Herons barely noticed the Hawks, they just
jumped and dropped what they had and caught another one. 
Fairly soon thereafter I dropped my interest in small mammals
and changed my dissertation to population and evolutionary
ecology of Central African birds - they are diurnal and colorful
and it was a warm place to work. And save the occasional
owl or falcon in my nets, there was little carnage to behold.   

Mike Gellerman