Most waterfowl can be quickly put into groups. Most of us in the Master Birder program can place birds like cormorants and grebes into identifiable groups in the field without much trouble. But within the group of ducks in general, it’s more problematic. Let’s consider several groupings.
Dabblers and Divers: These groups are perhaps overly generic, but they work in the big sense. That is, most of us can see quickly whether a duck is dabbling for food in shallow water, only immersing his\her neck into the water to feed, or the bird is diving in deep water fully submersing the entire body under water to feed.
There are ducks that are intermediate in this regard. But at the far end of the spectrum, dabbling ducks would include all mallards, teal, gadwall, wigeon, and shoveler. The Wood Duck is more of a dabbler in the sense that it rarely strays outside shallow water marsh habitats. Diving ducks, on the other hand, are generally birds like scoters, goldeneye, bufflehead, mergansers, and stiff-tailed ducks like Ruddy Duck and Masked Duck. Many of the dabblers and divers can be seen infrequently outside their normal habitat preferences, but as a very general rule the diving ducks like deeper water and the dabblers like shallow water.
The “tweeners” – birds that infrequently dive – are the scaup (including Ring-necked Duck) Redhead and Canvasback. For the record, most birds can dive to escape predators and occasionally feed. It’s just that for most dabblers and tweeners it’s not a common practice.
There are other behavioral clues related to local status and distribution. For example, I never see even small groups of Canvasback any more in North-central Texas, yet I have seen hundreds on lakes in Connecticut during certain months of the year. Canvasback is becoming a very uncommon bird in this area. Scaup, on the other hand, can sometimes be seen rafting by the dozen on any North-central Texas lake. Occasionally, small groups of other ducks will join scaup on the perimeter of their raft, but almost never in large numbers.
Another species capable of large rafts are Ruddy Ducks. I have seen rafts of hundreds on White Rock Lake in years past, but there are fewer Ruddy Ducks wintering on Texas lakes now than there were 20 years ago – not because of population decline but because there is frequently open water north of Texas now. In decades past, those northern lakes would be frozen over and those ducks would be forced to over-winter here.
Mergansers are generally seen in pairs or very small groups in this area of the state. Hooded Mergansers are uncommon for the area but can be seen on a few lakes or quiet streams with wooded banks. I mostly see 2-8 birds in winter, but occasionally I have seen as many as 25 on White Rock Lake Creek below the dam. The other two mergansers are much harder to see in North-central Texas. Red-breasted Mergansers prefer salt water habitats, and Common Mergansers generally don’t find Texas lakes to their liking much. Historically, very few Common Mergansers are seen in North-central Texas. Still, there are always one or two sightings of both species around metroplex lakes each winter.
In Texas, the three scoter species and the Long-tailed Duck are usually a very uncommon inland bird and rarely seen in pairs or groups, only as individuals. On the Atlantic and Pacific oceans, however, scoters can be rafting in the hundreds.
Bufflehead in our neck of the woods can be common on some ponds and lakes and entirely absent from others. However, they usually return to the same lakes every year. Most of the times, they are seen in pairs or very small groups. Common Goldeneye, on the other hand, is very uncommon in North-central Texas anywhere. There are odd years where we have no sightings of this species at all. Barrow’s Goldeneye is a boa-fide state rarity and review species. There are only three documented records for North-central Texas. The females can be very hard to identify from American Goldeneye, so extreme caution is needed when looking at any female goldeneye species.
For North Central Texas, there are several identification issues, but three species stand out: Mottled Duck\Mallard identification, scaup identification, and teal separation. I’m going to lay out the identification issues related to these three problem ducks.
Mottled Duck\Mallard – In general, most published work simply points you to the obvious fact that MODU are slightly darker than female MALL. But this can be a very hard characteristic to bank on unless both birds are seen close together. The other common diagnostic feature is the bill color. On MODU the bill color is significantly brighter yellow or yellowish green than MALL. Once again, however, this can be misleading when looking at only one individual.
Here is a picture I took of two Mottled Ducks next to a Mallard (MALL on the left side of the image). You can see the MODUs are darker when seated next to the MALL, but in this image you can also see the bill color might be difficult to separate.
However, let me show you a very good distinguishing characteristic that can help you separate these two species.
Here is a picture I shot a few seconds later of the same Mottled Ducks. Look carefully at the bird on the right. You will notice a small black spot on the gape of the bill. It’s almost square looking. This small feature is diagnostic for MODU. Many field guides do not discuss it, although most new field guides actually show it in the paintings. Sibley actually mentions it as a diagnostic feature and has an arrow pointing to it (even the Sibley iPhone app has it), but in other guides you rarely find any discussion of it in the text. The Peterson guides I have don’t show it at all, but other photographic bird guides almost always show this mark even if they don’t discuss it. Strangely, it can be fairly conspicuous if you’re close enough.
In flight, the MALL will have the wing speculum (a patch of color on the secondaries) outlined in bold white lines. It’s usually a blue-green color. On MODU, that same speculum is not outlined in white and always appears to me to be a deeper purple color than the MALL speculum.
Greater\Lesser Scaup – In the case of separating Greater and Lesser Scaup, we should probably just cut to the chase. Yes, Lesser Scaup have generally flatter heads, particularly from the nape to the top of the crown. Yes, Greater Scaup can more often show a greenish glossy head. However, if it’s at all possible, you should try to find another field mark. The flat head is fairly reliable on LESC, but perception can be deceiving and you would hope for a long look. The greenish head of a Greater Scaup should not be used at all independently of other field marks. Light can make blue-green colors change hue, and from the wrong angle you could misinterpret the color.
Greater Scaup on a pond. Notice the roundish head.
Lesser Scaup with a nice flat head silhouette.
It is a little better if you can catch scaup pulling their wings out or beginning their take off from water. The field mark here is the white feathering along the secondaries in the trailing edge of the wing. On Greater Scaup, this field mark of white color goes from one end of the wing all the way to the tip (although the white begins to turn a light gray as it nears the wingtip). This occurs on both male and female.
Here is a Greater Scaup holding its wings out (hat tip to Ken Nanney again).
On Lesser Scaup, the whitish feathering almost ends completely at mid-wing. It doesn’t just become a slightly lighter gray towards the tip. The light color fades and becomes a much darker gray, sometimes to the point where on some LESC it very abruptly ends and, from a distance at least, turns dark.
Here is a female LESC in flight.
Here is a male LESC in flight.
Kaufman says in his Advanced Birding book, that there is a tiny fraction of birds that overlap in the wing coloration, but, in total, when taken with other field marks, this wing pattern is a good identification characteristic.
One other noteworthy characteristic of GRSC is that they always appear to me thicker necked birds. This can be helpful when you have a few LESC to look at for comparison. In fact GRSC are actually slightly larger in size, but unlike the Blue-winged and Green-winged teal separation below, size is harder to differentiate between the two scaup.
The problem with Greater Scaup in general is that many of us in North-central Texas don’t get prolonged looks. Our basis for comparison is limited unless we've traveled extensively in some northern states or visited Alaska during the summer months. If you travel and have the opportunity to watch Greater Scaup, consider that a golden opportunity. Fortunately for us in Texas, there are usually some GRSC sightings every winter somewhere around North-central Texas. Since scaup are usually found in small groups, you’re like to see more than one when you finally do catch up to them.
Teal – Cinnamon and Blue-winged Teal are closely related and have most of the same field marks with the lone exception of the dark cinnamon color of the CITE. Since this coloration is fairly conspicuous in the field, I’ll discuss mostly the female Blue-winged Teal and Green-winged Teal characteristics (the male BWTE has such a significant mark around the face that it should be obvious in most situations).
While sitting on water, both female BWTE and female GWTE are largely plain brown ducks. If you are close enough to separate them from larger female Mallards, then you are probably close enough to separate female BWTE from GWTE. In general appearance, BWTE is a lighter brown with a lighter face than GWTE. The dark line through the eye appears on both birds, but because the BWTE is lighter in general, the line through the eye is more conspicuous.
The colored speculum on the wing is not particularly a good field mark while the birds are sitting. The BWTE may appear more slender and longer in general, but it helps to have other ducks to compare it to. When the BWTE raises its neck, it’s clearly a longer neck. The GWTE simply appears smaller and more squarely built in general.
When the birds are in flight, it may be less of challenge… but then again, the viewing is usually brief.
On BWTE, both male and female have a bluish-green speculum, but the color is more drab and muted in the female BWTE. However, please remember that the speculum is only a small block of color on the trailing edge of the secondaries (see Mottled Duck picture above). The conspicuous pastel bluish-white coloration above the speculum on all BWTE is actually part of the covert feathers and covers a big, square playing-card section of the entire wing, not just a small rectangular block on the trailing edge like Mallards and Mottled Ducks. This is what stands out on a BWTE. Concentrate on this large pastel blue wing patch in flight.
Ken Nanney took a wonderful photograph of BWTE in flight.
Contrast flying Green-winged Teal here. Although this is a male, the same speculum pattern holds true for females but perhaps not as bright.
The GWTE in flight does look smaller and browner, but again viewing can be very brief. The speculum on GWTE is more dark green with no really strong white outline bordering the speculum that you might get in, say, a Mallard. There’s also no other color on the coverts so the speculum in general can sometimes be almost an unnoticeable part of the brown bird. You might just get a hint of dark green.
In BWTE, you’ll likely see something lighter blue around the mid-length area of the wing even on females. However, in very poor light, size may be a more reliable characteristic. And from a distance, it may be better just to call it a “teal sp.”
If you are fairly close to a female GWTE, you may also note a browner smudge just below the ear on the face of GWTE… as the image above shows.
Personally, I can think of several other ducks that force me to pause, especially in flight. For the moment, however, I think these three species are the most problematic for our area.