After seeing a posting about an oddly-plumaged American Kestrel in Lancaster County by Kris Miller, I decided to run down today and try to find the bird myself for some photos. Although I figured it would be a long shot, I was happy to find her and her (normal looking) male hunting grasshoppers together along PA272, just south of Buck.
This female is unusual in that her cap and front mustachial stripe are a burnt orange color; just slightly richer in color than the dark-orange of the bird’s mantle. A typical ‘Northern’ female would have a blueish cap with dark orange on the very top of the head, and a black front mustachial stripe. The underside streaking of this kestrel is more finely patterned with darker, pointed markings that almost form loose barring across the front of the kestrel compared to the longer, and more blob-shaped streaks on a typical female. Tail patterns are highly variable among female kestrels, and this one has a fairly normal type with a thick subterminal bar and 6 thin inner tail bands. At first glance these unusual markings give the impression of a small female Eurasian Kestrel.
Concerning what sort of genetic mutation may have caused this plumage anomaly, Jane Marlow (from National Aquarium) had this to say: “As far as a color mutation, a fully ) bird would lack all black/gray pigment, leaving only red/red-brown pigment, while this bird retains black pigment (eumelanin) on its wings. While generally uncommon for birds to be erythristic only on an isolated part of the body, it’s certainly not unheard of. A well-known example is the “opaline” mutation in budgerigars – these birds have reduced eumelanin on the head, while retaining its production on the rest of its body, albeit in a somewhat distorted pattern – very similar to a description of this bird’s aberrant coloration! Falcons and parrots make up sister taxons, so it definitely makes you wonder if these mutations could be related.”
Please, if you go to see this bird – be mindful that it is hunting along a busy road and it could potentially be put in to a dangerous situation if flushed towards traffic. Scoping the bird from the nearby gas station parking lot (or other nearby pull-off) would be best. eBird checklist: http://ebird.org/ebird/view/checklist?subID=S26889803