Searching a subset of content

A typical presentation for searching a subset of content on a site is to present a pull-down before the search field, as shown in these examples from the Amazon and Walmart web sites:

On Foodnetwork.com the selection control is contained within the search field:

I suspect the location in this position is more discoverable because it places the control between the typical starting point for a search task (the search field) and the end point (clicking the search field).