When Hollister writes a carrier pigeon note following the police visit, in the long shot he is writing in a landscape orientation but in the closeup showing the message the notepad is in letter orientation.
The handwritten note Hollister is shown sending by carrier pigeon is not the same one seen as read on the receiving end.
The date on the newspaper with the headline about Dr. Spires is 8 days later than the date on the telegram about the pigeon that was received the same day the newspaper was printed.
The wire attached to the carrier pigeon's leg to prevent it from flying off is visible a number of times.
The boom mic is visible reflected in the paint on the upper left side of the rumble seat when the guard goes to open it up at the gate as the car is leaving the Hennessey Estate on Larkspur Lane.