Page 42 - Hand rearing birds second

24 Hand-Rearing Birds

Developmental Clues
If hatching is not witnessed, a chick’s age can be estimated without taking measurements other than
weight, via known developmental stages of the family group. Measurements of wing chord, tarsus,
gape, and culmen are reliable variables if there are standards available for the species for comparison.
Table 2.2 demonstrates age by feather development and typical behavior in most passerines. Eyes of
altricial young begin to open at a predictable age, thus helping to reinforce age estimates; however,
illness or injury may complicate evaluation. Eye color is helpful in aging species in which iris color
changes as the bird matures, such as Spotted Towhees, Brewer’s Blackbirds, and many hawks.

Putting It All Together

Consider a sample identification process. A baby bird arrives, found on the ground, no parents or nest
observed. Is the chick precocial or altricial? If fully covered in down, it’s precocial, so note the down
pattern on the dorsal view and check the type of foot (webbed, partially webbed, chicken‐like). If
naked or mostly naked with some down on the dorsal view, it’s altricial. Note the foot arrangement.
If zygodactyl, check for key features of woodpeckers; if they are not found locally, consider other
zygodactyl type birds. All passerine birds are altricial with an anisodactyl toe arrangement. Is it pas-
serine or nonpasserine? What is the weight and size? Then note the beak shape and length (relative
to head). What is the color of the mouth interior and gape flanges and are they thin or thick? If the
skin is pinkish, the baby could be one of several species. If its skin is yellowish‐orange, consider robin
or bluebird; if reddish, look at blackbird species. At this point, the identification should be narrowed
down to a family or two. Describe the natal color and abundance of the down or, if the bird has some
juvenile feathers, note the colors. Consult the tables on all clues found, and compare the chick’s
weight with that of the adult of the species being considered. Regardless of an early guess at an iden-
tification, go through all the steps for confirmation. Also, always consider geography and typical
species encountered in the area while remembering that nature can throw a curve ball.
The next tables present key nestling characteristics and developmental (age) markers for a selec-
tion of species from most taxonomic orders. Table 2.3 covers nonpasserine species organized by
type of development and foot topography. Tables 2.4 and 2.5, organized by interior mouth color,
cover a selection of passerine chicks of common or widely distributed North American breeding
species. Closely‐related species in other parts of the world with broad distribution may be present
as examples in the tables; close taxonomic relatives also often have similar captive requirements.
Data in the tables were extracted from the Birds of North America (BNA), an online reference of
the life histories of over 760 breeding birds in the U.S. and Canada (Rodewald 2015), numerous
scientific publications, data collected personally from bird carcasses (frozen and prepared), per-
sonal observations of wild and captive songbirds, and conversations with many songbird rehabili-
tators across the U.S. and Canada. Tables 2.4 and 2.5 are a sampling from a comprehensive
collection of key characters of 200+ passerine species, which will be included in a soon‐to‐be‐pub-
lished guide by the author on How to Identify Baby Birds.
Although learning to identify and age young birds takes practice, research, and patience, it can
be very rewarding. As the lives of birds become better understood, the standards of care for birds
in captivity improve. Caregivers – whether they specialize in a species, a family group, or birds
with similar lifestyles – are able to save time and costs and to provide housing enrichment and
social atmosphere that better simulates the birds’ natural lives. Early, definitive identification of
baby birds that must be hand‐raised by humans greatly enhances their ability to survive and thrive
in nature once released.