1. One cannot make something Hekdesh if he does not own it.
2. If a person acquires the eggs or chicks when the mother is not around, he is exempt from the Mitzvah.
3. If a person slaughters an undomesticated Hekdesh animal, he is not obligated to cover its blood.
4. One is not obligated to look for a nest in order to perform Shiluach ha’Ken.
5. Shiluach ha’Ken only applies to kosher birds.
A BIT MORE
1. Even if one sees an ownerless object, he cannot dedicate it to Hekdesh without first performing an act of acquisition and acquiring it.
2. Since he acquired them, they are no longer considered ownerless.
3. However, if he slaughters it and then immediately proclaims it to be Hekdesh he is obligated to cover its blood, as the obligation set in before the Hekdesh status.
4. This is also derived from the verse, "if you chance upon etc.," implying that one is not obligated to search for the opportunity to perform this Mitzvah.
5. This is derived from the word, "Tzipor," which always refers to a kosher bird.