Aristotle’s biological works are quite fascinating and lively. They contain abundant experiential reports, including some hearsay, intermixed with thoughtful reflection. Ultimately it is the reflective aspect that gives them their enduring value.
Sometimes, the content is surprising. For instance, book 1 of Parts of Animals is the place where he thoroughly criticizes the notion of classification by dichotomy. With concrete illustrations from the animal kingdom, he shows that commonly recognized kinds cannot be arrived at by successive dichotomous distinctions. Aristotelian distinction is n-ary rather than binary, pluralist rather than dualist.
Elsewhere (Metaphysics 982b) he famously said that philosophy begins in wonder. At Parts of Animals 645a, he added, “We therefore must not recoil with childish aversion from the examination of the humbler animals. Every realm of nature is marvelous: and as Heraclitus, when strangers who came to visit him found him warming himself at the furnace in the kitchen and hesitated to go in, is reported to have bidden them not to be afraid to enter, as even in that kitchen divinities were present, so we should venture on the study of every kind of animal without distaste; for each and all will reveal to us something natural and something beautiful. Absence of haphazard and conduciveness of everything to an end are to be found in natures’s works in the highest degree, and the end for which those works are put together and produced is a form of the beautiful” (Complete Works, revised Oxford edition vol. 1, p. 1004; see also Natural Ends; Sentience).