Another example of fixed action patterns is the red-bellied stickleback (fish). The male turns a bright red/blue colour during the breeding season. During this time they are also naturally aggressive towards other red-bellied sticklebacks, another FAP. However anything that is red, or has the appearance of being red, will bring about this FAP. The proximate response to this is that due to the stimuli, a nerve sends a signal to attack that red item. The ultimate cause of this behavior stems from the fact that the stickleback needs the area in which it is living for either habitat, food, mating with other sticklebacks, or other purposes. This is an inherited behavior, but it is has been found that this behavior may be more flexible than scientists thought at first. This interaction was studied by Niko Tinbergen. The threat display of male stickleback (fish) is also a fixed action pattern triggered by a stimulus.
Now, FAPs, to my mind, raise a couple of interesting questions vis a vis EP. Here's one.
Maybe FAPs are both rote and smart, i.e. "specialized". Does the red-bellied stickleback have a mechanism just for detecting males? Although the wikipedia doesn't mention a dedicated neural circuit, other accounts of other FAPs do:
Fig. 2. Female goose behavior of picking eggs up. When it sees an egg outside the nest (key stimulus), it begins a repeated movement of dragging the egg with its beak and neck. However, if the eggs slides off or if it is removed by the researcher, the goose continues to repeat the stereotypic movements even if the egg is absent, until it reaches the nest, when then it does it all over again. FAP seems to correspond to a fixed neural circuitry elicited by the overall trigger stimuli. (italics added)So, FAPs could be examples of mechanisms that are both rote and smart.