In response to When to Use Subdomains vs. Subfolders, reader Elena asked:
Would ducks.birdies.com compete with swans.birdies.com?What about birdies.com/ducks and birdies.com/swans?
To answer her in part I’m going to dig a bit into keyword cannibalization and then invite others to comment as I’m a bit stronger on the creative content and community interaction side of SEM than the technical 
What Keyword Cannibalization is:
When your site competes with itself for the same keyword.
My Answer to Elena’s question:
Ultimately Elena, neither would compete with the other so long as the ducks pages of birdies.com don’t contain title tags, content and have links - on and off the site - pointing to them that emphasize swans.
They would certainly compete with themselves differently within the subdomains vs. subfolders context, but that’s way over my head so I’ll stick to avoiding cannibalization 
Title tags for birdies.com/ducks should go something like this:
Ducks and Duckies - Your Ultimate Guide to Ducks from Birdies.com
The text should include:
the terms duck, ducks and duckies
Link building for your ducks page:
The text you create internally or request externally that links to this page of your site should ideally include the word ducks, and/or come from sites or pages that also specialize in ducks.
And the term swan should appear as little as possible in the ducks section. Only in rare cases, such as the ugly ducking who became a swan, would you want to discuss both words on the same page for optimal rankings.
No birds were harmed in the writing of this post, but I did draw heavily for insight from Rand Fishkin’s recent How to Solve Keyword Cannibalization.
Fishkin describes succinctly the dangers it sounded like you were asking about here, Elena:
“It typically starts when a website’s information architecture calls for the targeting of a single term or phrase on multiple pages of the site. Many times this is done unintentionally, but results in several or even dozens of pages that have the same keyword target in the title and header tags.”
Avoiding Cannibalization on Your Site:
It comes down to keyword research at the outset of site design and a well built architecture that keeps the “ducks” away from the “swans” and still makes sense to ALL your site visitors.
(note: Luckily I’ve never been personally responsible for this kind of work - I’m usually the one making sure the ducks content really sings and that it’s getting links
Checking your site’s LINKS for Keyword Cannibalization:
It would be a bit of a pain to use if you have a large site, but this site link analyzer will show you page by page what you’re linking to and the anchor text you’re using:
Site Link Analyzer
Does anyone know of more robust tools out there? What other tools would you recommend for analyzing a site for other aspects that create keyword cannibalization?
Oh - and Elena - did this answer your question?
Posted on March 16, 2007
