"Impact of invasive bird species monitored by Lab of Ornithology network"

According to this press release from May 2004, a citizen-science project called The Birdhouse Network (TBN) has initiated a Nest-Box Competitor Study for the purpose of "examining the effect of nest-box competition from invasive species on native cavity-nesting birds." Some excerpts:

According to 2003 data collected by TBN, house sparrows account for 43 percent of all competitor species (species that take over nest boxes intended for native birds). And although most nest-box (or bird-house) enthusiasts discourage nesting by house sparrows, the birds still comprise 10 percent of all reported nesting attempts when at least one egg is laid.

In head to head competition, house sparrows readily out-compete native species for nesting sites by evicting other nesting birds, destroying their eggs, killing nestlings and sometimes even killing the incubating female.

"India fines people for feeding pigeons"

"Civic officials [of Mumbai, the world’s most populous city] have begun imposing fines of 500 rupees ($11) on people caught feeding pigeons . . . in an attempt to keep their city clean and disease free . . . ."

"Introduced Birds of Kaua'i"

This site by Jim Denny lists 27 species that are introduced and established on the island of Kauai in the Hawaiian Islands.

"Introduced species"

A good introduction (no pun intended) to the subject from Wikipedia.