Answer:

There are several individual ducks in the image, the majority of which are either females or immatures. Since there are a plethora of duck species that occur in southern California, the first step to identification to species is to narrow down the possibilities.

The ducks with their heads up show bills that are all black and flattened, and rather wide in some of the birds. The females are all mostly brown and with intricate darker markings. These two features indicate that they are surface-feeding dabbling ducks. However, this still leaves us with quite a few possible species, so we still have some narrowing-down to do.

Genus mareca contains three local species: Gadwall, American Wigeon, and Eurasian Wigeon. The latter two have pale bluish bills, unlike the birds here. Male Gadwall have all-dark bills, but their bodies are almost entirely uniform slaty-gray in color. So, our birds do not appear to be any of these.

Genus anas contains the iconic Mallard, as well as Northern Pintail, Mexican Duck, and Green-winged Teal. Female Mallards share similar patterning to these birds, but have more orangey bills. Female Northern Pintails also have similar patterns, but are paler, usually being more tan than brown, and are longer and more slender structurally. Mexican Duck is very rare in LA County. Both sexes are similar to female Mallards, with either yellow or orangish bills, and have much darker plumage.

Now, Green-winged Teal seems to be a much closer match than the previous options. The third bird from left has a rusty-reddish head with a broad, iridescent green stripe — diagnostic of a male Green-winged Teal. The adjacent females appear to fit as well — they are about the same size and shape. The namesake “green wing”, a variably colored (usually green or blue) iridescent stripe in the secondaries, is visible in the leftmost bird. It also shows a fairly large patch of white beneath the tail; a good mark for female green wings. The other female is a little more obscured, but still shows us enough to identify it — a small, flat bill with a rounded tip, a brown face with darker stripes but no white markings, and a whitish belly.

The cluster of birds on the right are similarly sized, and the females similarly colored. We see one bird that is solidly reddish in color, which points to a male Cinnamon Teal. Then, there are two birds — one just behind, and one to the left of the Cinnamon Teal — that are differently patterned. They both show blue-gray heads, and a more uniform pattern with smaller black markings on the underside. One of them shows a prominent white patch behind the bill, confirming them both as male Blue-winged Teals.

The other females are somewhat similar to the Green-wings, but don’t look like a perfect match. We consider the females of Cinnamon and Blue-winged Teal. Female Cinnamon Teals are relatively plain-faced, showing few dark markings, small amounts (if any) white at the base of the bill, and no white eye-arcs. The two females with heads up and facing left fit this well. Northern Shoveler is another dabbling duck that shares a genus (spatula) with Blue-winged and Cinnamon teal. However, they are easily identified by their massive orange bills, which none of these birds show.

We’ve identified eight out of twelve birds now, so only the four females in the center-right remain. They’re all cool grayish in color, perhaps a tad colder than the Cinnamons. For the two females with their heads up, we note that they have bolder dark facial patterning, as well as prominent white eye arcs and a large patch of white behind the bill. These marks are all good for Blue-winged as opposed to Cinnamon Teal.

The final two birds are not so cooperative. Their heads are tucked in, so most of the field marks mentioned above are not easily visible. However, we can still note that they share the same color tone as the two females mentioned above, and the white eye-arcs and dark eyestripe can still be seen. These two are a much more tentative ID, but are likely also Blue-winged Teals (confirmed in-person). So, we end up with three Green-winged Teal (1 male, 2 females), three Cinnamon Teal (1 male, 2 females), and six Blue-winged Teal (2 males, 4 females).