When the Sexes Look Different
Sexual dimorphism (Whoa!! Don't leave yet) is a term to refer to species in which the sexes look different. It means the sexes (sexual) appear in two forms (dimorphic). In most cases the male is the brighter and
more patterned bird. Females, in general, are more inclined to be burdened with the nest sitting duties. This
requires days of sitting, hopefully out of sight. A more subdued coloration and pattern is a great benefit for this
Beginners sometimes have a difficult time identifying females where the males are easy to identify. I
suppose that one way out is to just wait around to see what kind of male they are hanging around with. Seriously though, take a moment to open your field guide to examine some females. Note the female Rose-
breasted and Black-headed Grosbeaks, check out the orioles, and how about the female buntings. Field marks
are the answer. We read about using field marks a few months ago and here are some cases where learning
them is essential to success.
We mentioned Rose-breasted and Black-headed Grosbeak. A study of the field marks for these two
females would reveal that the Black-headed female has less streaking in the breast In fact, the center of the
breast is nearly devoid of it. And the streaking has an orangish or buffy background. The streaks on a Rose-
breasted female, while fine, are more dense all across the breast and are on a white background. Rose-breasted
usually has a pretty light mandible, while Black-headed is darker and usually the upper mandible is even darker
than the lower.
Now that you can see how easy that was, take a look at female Purple and House Finches. Not only
do folks have difficulty separating them from each other but they even look a little like the grosbeaks. Examine
the bill, see that the bills of the finches are much smaller than the bills of the grosbeaks. The female House
Finch has a pretty plain face while the female Purple Finch has a fairly strong face pattern. It has a light area
above a dark whisker mark. That and a whitish eyebrow frame a brownish gray ear patch making a distinctive
pattern on the face. Now look at the Siskin, both male and female. We have yet another look alike that looks
amazingly like a female House Finch. Look first for any yellow at all on the wing feathers. This is particularly
visible in flight. Also check the bill, the Siskin's bill is quite sharp and pointed.
Buntings, like grosbeaks and finches, are seed eaters. They have the same conical bill the finches
have. Also, like the others, the females can be confusing The Painted Bunting male is unmistakable with his
spectrum of color, he resembles Joseph's coat. Females, however, might resemble the female Indigo Bunting.
The female Painted Bunting has a bill just like the finches, but is greenish in color and has no hint of a wingbar. Female Indigo Buntings have a warm tan color overall, and a faint hint of darker streaking on the breast.
A female Indigo Bunting might also resemble a female Blue Grosbeak. They are also a warm brown but have
obvious wing-bars and lack any streaking on the breast. They also have that very large grosbeak bill.
How about a plan?
First, try starting with the bill. Be sure that your bird is indeed a finch, bunting, or grosbeak. Many
new birders try to make something like a female Red-winged Blackbird into all sorts of things. If the bill is
very large you probably have a grosbeak. A smaller conical bill probably means a finch or bunting. Finally the
Pine Siskin is the one with the sharply pointed bill.
Second, look for streaking on the breast. If present is it on the whole breast or just on the sides? Is it
faint or bold? Are the streaks heavy or thin?
Third, look for wing-bars. Are they present? Are they white or another color? Are the faint or bold?
Armed with this information, you'll be able to make the ID.
Another sexually dimorphic group of birds includes the tanagers and the orioles. Male orioles seen
regularly on the Upper Texas coast (UTC) tend toward orange and golden while the tanagers have red (Western
Tanagers have a red face, throat and crown). Females of these species are yellow and, as mentioned before,
careful attention to learning and using field marks will enable you to identify them. We'll take a look at the
Summer, Scarlet, and Western Tanagers, and Orchard. Baltimore, and Bullock's Orioles.
Start with the bill (by now you may have noticed that this is often a good place to start). The orioles
tend to have a slimmer sharper bill while tanagers have bills that are heavier and more blunt. Summer Tanager