1. Fresh: Immediately after death, the sparrow's body remains relatively unchanged. Some initial changes might include muscle relaxation and the beginning of rigor mortis, where the muscles stiffen.
2. Bloating: As bacteria and other microorganisms present in the environment begin to break down the soft tissues, gases are produced. This causes the body to bloat and swell.
3. Decomposition: The microorganisms continue to break down the body's tissues, including muscles, organs, and soft tissue. Fluids may leak from the body, attracting insects such as flies and beetles that further aid in decomposition.
4. Advanced Decomposition: As decomposition progresses, the body's organs liquify and eventually break down into a semi-fluid state. Bones and skin become exposed and may be damaged or scattered by scavengers or environmental conditions.
5. Skeletal Remains: Eventually, all the soft tissues are broken down, leaving only the skeletal remains of the sparrow. These bones might endure for a long time depending on the environment and whether they are buried or exposed.
6. Fossilisation: In some cases, the sparrow's bones might undergo fossilisation over a very long period of time, potentially millions of years, if they are buried in the right geological conditions and protected from further decay.
It is important to note that the exact rate and progression of decomposition can vary greatly depending on environmental factors such as temperature, humidity, and the presence of scavengers.