How to create a Wireless RF circuit activated by an ultrasonic sensor for interesting project?

[bluejets]

@crazydiamond101

Basically I have a bird that visits my garden everyday and likes me to feed him, he arrives on a perch in my garden at various points throughout the day and if I'm not looking out the window i wont know he is there. I want to make a project where I can have an ultrasonic sensor (or any other better detection sensor detect the bird when it is on it's perch

It may be that the sensor will detect any movement say from surrounding plant or animal life.
I'd be sorting that out first up.