Paul_KD7HB:
Your falcons are used to carrying little transmitters. Make a package of an IR lLED and a NE555 to flash the led at the normal IR remote frequency of 38 kHz. Make a sensor to detect the modulated LED that has a narrow vertical slit to minimize the side view.The sensor will detect the bird when it is in view of the sensor. You can take the project from there.
Paul
Is modulation alone going to be enough to make this setup work in direct sunlight reliably? Especially at range? Maybe so, but I think that's a long shot.