Differentiating juvenile light harlani and juvenile kriderii

Distinguishing between juvenile light morph harlani and kriderii can be difficult. The two are extremely similar, being overall quite pale with high contrast markings. They also interbreed, causing individuals that are intermediate in plumage.

As with any bird identification, it is best not to not focus on one trait alone. Instead, it is better to make a holistic assessment of plumage characters and come to a well-reasoned and conservative assessment. Below is an outline of plumage features to aid in distinguishing the two that together with the plate above should provide a helpful guide.

Tail pattern

The upperside of the tail is very helpful trait for differentiating the two juvenal plumages. Although both tend to be lighter in their base color and quite high contrast, kriderii generally average much thinner in their tail bands and many decrease in markings towards the base of the tail. This contrasts with the often irregular and thicker bands on harlani tails that are on average against a darker base color.

Uppertail coverts

Much like adult kriderii, juveniles can have limited to no markings in their upper tail coverts, enhancing the pale tail base appearance. In contrast, harlani tend to have white uppertail coverts with relative thick bands that contrast with the somewhat darker tail coloration. In general, this creates prominent uppertail coverts instead of the seemingly hidden or blended uppertail coverts in kriderii.

Wings

Like tail markings, kriderii have secondary and primary banding that is relatively thin and less distinct. The primary panels on kriderii are also quite pale, and the banding in the inner primaries is a unique thin web-like pattern. Unlike most harlani that have noticeable banding to the tip of the outer primaries, most kriderii have darker outer primaries where the banding to the tip is not as distinct. Together with a very limited and sparse patagium, largely unmarked underwing and unmarked greater underwing coverts, the entire underwing of kriderii averages much paler than harlani.

Head pattern

The main difference in head pattern between these taxa is the organization of markings. On average, harlani is much more heavily marked in the head but more importantly the markings are spread throughout the head and nape causing a messier appearance. Contrastingly, kriderii generally have more organized markings restricted to particular patches on the head including a prominent dark posterior eyeline, limited crown markings, variable amounts of markings on the nape, and variable amounts of markings on the malar.

Bellyband

While the bellyband averages sparse and less marked on kriderii, there is considerable variation in this trait. Because of overlap between the two taxa, reliance on this trait alone can be misleading.

Below are examples of these features in a selection of photos from the Macaulay Library. Each photo is numbered corresponding to the links listed below, from which the eBird checklist housing other photos of each link can be accessed.

harlani

Underside

1. https://macaulaylibrary.org/asset/520147291

2. https://macaulaylibrary.org/asset/24203713

3. https://macaulaylibrary.org/asset/109270341

4. https://macaulaylibrary.org/asset/386042981

5. https://macaulaylibrary.org/asset/616692248

Topside

1. https://macaulaylibrary.org/asset/408065021

2. https://macaulaylibrary.org/asset/194793571

3. https://macaulaylibrary.org/asset/613774344

4. https://macaulaylibrary.org/asset/536978231