If someone is looking for:yourdomain.com: Building a chicken coop: metal, wood, chicken wire, simple to do, easy instructions, how to, red, green, make in a day,
Building a red chicken coop
Building a green chicken coop
Building a chicken coop in day
Easy instructions to build a chicken coop in day
your site may appear in SERPs and you may also get #1, but the keywords like red/green/in a day/easy instructions etc will truncated.
They will only see 'Building a Chicken Coop' and people want the keywords they are looking for in the title..if they don't see red/green/in a day/easy instructions etc in title they wont click through to your site..
However, if the site below you has the exact words in the title then he will get whatever traffic you lose.
On the other hand, your page may get traffic for metal/wire/wood KWs... If you want, create another page for red/green/in a day/easy instructions...
As for me, I always go with 'One Page, One Keyword'