Descriptions of embryonic development exist for a handful of bird species.
Such standard information is essential for the evaluation of species-specif
ic features and detecting abnormal morphology. The American Kestrel (Falco
sparverius) is a common North American raptor that is frequently used in ex
perimental Studies as a model raptor species. We described the normal progr
ession of embryonic development in the American Kestrel. This provides a st
andard for assessing American Kestrel embryos. and potentially those of oth
er raptors. During the first half of incubation. the developmental progress
ion of American Kestrel embryos corresponded closely to developmental stage
s established in the chicken (Gallus domesticus). Morphological parameters
that we measured were correlated significantly with incubation day. These q
ualitative and quantitative descriptions provide useful benchmarks For dete
rmining age and identifying abnormalities of experimentally-treated embryos
or embryos of unknown history.