Altricial vs. Precocial?? Some rehabbin language

In my previous post I mentioned that our September e-newsletter will have information about the licensing requirements for becoming a rehabber in Arizona. What I did not mention, is that wildlife rehabilitators learn what amounts to a new “language” of terms, used when talking about their profession. Two terms that are fairly common for bird (avian) rehabbers…altricial and precocial. These are two frequent terms in an avian rehabilitators vocabulary. The word altricial comes from the Latin word altrix: “nurse”. It describes birds that hatch in a helpless condition and that must be ‘nursed’ until they are able to leave the nest. The word precocial – like the more familiar word precocious – refers to birds that hatch fully developed and are able to leave the nest soon after hatching. In this case, size does matter when it comes to eggs. Some birds that have precocial young have eggs relatively larger in size than the eggs of similar sized birds that have altricial young. Precocial eggs (the larger eggs) contain more nutritive material and require longer to hatch, the young emerge more developed. For an example, the adult killdeer is about the size of a robin. Killdeer chicks are precocial and the killdeer eggs are larger than those of the altricial robin. Killdeer eggs require about 26 days to hatch, while robin eggs require about 13 days. The killdeer young emerge from the egg and are able to run, while the robin’s babies are helpless. The young robins stay in the nest another 10 to 14 days until they are able to leave the nest, then they still flutter around and are under the care of the parents until they learn to fly. There are also semi-altricial and semi-precocial birds, but more about those later!

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