It is in beginning of the annual cycle of birth and renewal for the remaining water birds at the lake. The five small islands adjacent to the Rotary Nature Center at Perkins and Bellevue streets on the north side of the lake become a breeding site, a great rookery. From March to May, Snowy and Great Egrets are joined by Double-crested Cormorants and Great Blue and Black-crowned Night Herons (and to a lesser extend Canada Geese) as they count, preen and mate in the trees of the islands.

During this time, large groups of birds, resplendent in their breeding plumes, can be seen standing sentinel or incubating eggs at their nests. Snowy and Great Egrets, immaculate in their pure white plumage, stab their long slender bills into the lake's shallow waters to pluck small fish such as gobies or smelt to feed their voracious young. Below the haze of herons and egrets flying among the islands, nestled among the bushes and shrubs, Canada Geese also breed. (According to Rotary Nature Center naturalist Stephanie Benavidez, although the geese have a bad reputation because of their droppings on the lawn adjacent to the rookery, only a small number of the geese actually breed at the lake.)

Because the islands are relatively close to shore (all less than 100 yards from the water's edge), the birds can be seen with the naked eye, but a pair of binoculars or spotting scope with allow viewing of their nests and young in detail. For the most part, the cormorants, herons, and egrets nest separately. The Double-crested Cormorants, the large black water birds who "hang their wings out to dry," occupy trees of their own, as do the Great Egrets and Great Blue Herons. The Black0crowned Night Herons and Snowy Egrets nest on shore. During this time the birds can also be observed in their courtship rituals prior to mating -- flapping their wings, bowing and curtsying to one another, fanning their beautiful breeding plumes, and occasionally exchanging nuptial offerings of small sticks (that is, nesting material.)

In fact, the long feathery breeding plumes that the herons and egrets grow in the spring have been both their boon and bane in the last 125 years. The plumes give them much of their charisma and beauty, but also led to their near extinction at the end of the 19th century. Plume hunters, moving from one rookery to another, killed the egrets in the tens of thousands throughout the southern United States, merely to decorate women's hats. The millinery plume trade was a huge business, as pictures of women in their feather-draped hats from the period testify. Plumes went for $ 32 an ounce, about twice their weight in gold.

The wildlife conservation movement grew in response to this slaughter. In the last decades of the century Audubon chapters rallied thousands to protest and limit this destruction, influencing President Teddy Roosevelt's decision to establish the National Wildlife Refuge system in 1903. The breeding plumes have even given birds their name: "egret" is from the French aigrette, or plume.

The birds are, of course, only the most visible part of the lake's ecosystem. Originally a large tidal marsh with some open water that stretched as far as Telegraph Avenue to the west, the "lake" was formed in 1869 by damming and controlling its outlet to the bay at 12th Street. It is stil essentially a tidal estuary, so its levels change with the tides. Fed by several creeks, mostly culverted, such as the Pleasant Valley, Indian Gulch, and Woodside creeks, and flushed twice a day by the tidal action of the bay, the brackish waters of the lake have a rich marine life that includes polychaete worms, mussels, and fish such as gobies, topsmelt, sculpin, and stickleback. Occasionally striped bass, halibut, salmon, or even sharks swim in from the bay.

Preceding Roosevelt's establishment of the national wildlife refuge system, Lake Merritt was declared a refuge in 1870 - the first in the nation - to protect the migrating waterfowl that sheltered in its waters. The islands of the lake and the site of the rookery are man-made. The first island was created in 1930 from dredge spoils. Protected by the lake waters, the rookery has grown to host its present population of several hundred breeding birds, reputed to be the largest urban water bird rookery in the country.

As idyllic as the rookery and nearby Lakeside Park appear in April, washed by sunshine and clothed in the spring finery of endless flowers and ornamental fruit trees, the annual breeding ritual is a life-and-death drama for the birds. Hundreds of herons, egrets and cormorants are born each year, but like all wild animals, relatively few- typically two-thirds or less - survive the dangers of infancy. The Black-crowned Night Herons, dark and sinister, fly among the nests of the egrets at night and pick off the nestlings from under the eyes of inexperienced parent birds, others fall from their perches, some starve. But even the predatory night herons are not without their own birdly beauty: long white breeding plumes cascade down their backs, and they fly with the usual grace of their tribe.

However improbably and miraculously set in the heart of Oakland, Lake Merritt's rookery remains one of the great wildlife spectacles of the East Bay. Each spring, a stone's throw away from shore, hundreds of birds, renowned for their beauty, add their elegance to the lake and the skies above it. It is so close by and familiar that continuous parades of strolling lovers, parents and toddlers, joggers, and bikers pass by it on a daily basis, often taking no notice.

Oblivious to the passing traffic and intent on their roles in the great drama of rebirth, the birds congregate in immense numbers to perform their nuptial duties, moving with the fluidity of ballet dancers with feathers.