Red-winged Blackbirds have been visiting the northwest corner of the park since January, but they were all males, and there was nothing to detain them. Now females have arrived, and it’s serious business. The first bird in the video above — the plain brown one — is a female. I first saw her in the low vegetation on the ground upslope from the fennel, possibly building a nest. Later, when the new fennel grows thick and provides visual privacy, females will build nests off the ground in the fennel stalks; see this example. The males are the ones with the red epaulets, and they work hard to display them. Apparently the females are keenly tuned in to the qualities of these shoulder patches and pick their mates accordingly. The blackbirds will do their mating and nesting in and around the fennel forests on the northwest side of the park until around the Summer Solstice, when parents and new fledglings will take wing and depart.