some of the postings have suggested that the various feral
parrot/parakeet species might be negatively affecting other, indigenous
species. this raises two questions in ecological theory:

1. in a mature, undisturbed ecosystem, are all "niches" filled so
that the introduction of a new species is necessarily at the expense of
an established species?

2. in a disturbed ecosystem -- such as seattle -- is this the case?

i recognize that there are questions of whether there is any significant
actual difference between 1 and 2, i.e., mature, undisturbed ecosystems
are themselves dynamic and nonequlibrium things -- though they probably
change more slowly than seattle.

it does not seem improbable that there are empty "niches" in seattle
because some species have been eliminated.

dale -- curious in moscow -- goble