Zevachim 66 - Invalidations of Bird Offerings
The proper place for the service of the bird sin-offering is the lower part of the wall of the Altar, below the red line, and that of the bird burnt-offering - above the red line. If one changed the procedure and performed the bird offering on the wrong part of the Altar, the offering became invalid. The same is true if he exchanged the other aspects of the bird service.
Nevertheless, disqualified offerings do not convey ritual impurity. As a rule, an animal or a bird that was not properly slaughtered conveys ritual impurity - the animal by being carried, and the bird by being eaten, at the moment it enters the throat. The offerings above are purified from it.
In addition, one who uses a disqualified bird offering for his purposes, commits misappropriation of Temple property. Normally, the bird sin-offering, after being killed properly by the method of melikah, is eaten by the kohanim and thus does not have the prohibition of misappropriation. These offerings, however, never became allowed for consumption and remained the property of the Temple, subject to misappropriation.
Art: Momo Chidori Kyoka Awase - Cockerel And Hen On The Right With A Bunting On The Left, From An Album Birds Compared In Humorous Songs, 1791