When this woman came upon a dead pigeon, her heart must have been feeling pretty big. Rather than just reflect sadly on the transience of life, she decided that she was going to perform CPR on the little guy - including the mouth-to-mouth rescue breathing.
Unfortunately, it didn't work. The pigeon was already dead.
If you've ever been trained to administer CPR, you're probably aware that this was never going to work. Despite what Hollywood would have you believe, CPR is just a way to keep someone's blood circulating while their heart isn't working right. It pumps blood through the victim's body, helping to prevent brain damage and other consequences from lack of oxygen circulation.
CPR does not bring the dead back to life. CPR does not restart a heart which has stopped. CPR does not fix cardiac arrest or atrial fibrilation (an irregular heartbeat). People who need CPR generally don't suddenly wake up and say "Thanks, you saved me!" without the use of a defibrillation device (that thing where doctors shout "CLEAR!" and then shock the patient).
That's something worth keeping in mind before you put your mouth on a dead pigeon.