What lives in our creeks?

We have a lot to learn about what lives in our creeks, and we welcome help in finding out. Please contact us if you're interested, or have useful information!


Friends of Five Creeks' area includes two year-round creeks - Codornices and Cerrito. Before European settlement, these creeks probably were home to more than dozen kinds of fish. Best known are salmon and rainbow trout and their seagoing equivalent, steelhead (Onchorhynchus mykiss). Our creeks also may have had runs of longfin smelt (Spirinchus thaleichthys), small seagoing fish that spawn in fresh water.

Other fishes included small minnow-like speckled dace (Rhinichthys osculus) and California roach (Hesperoleucus symmetricus), and probably some larger minnow-like fishes such as Sacramento squawfish (Ptychocheilus randis), Sacramento blackfish (Orthodon microlepidotus), hitch (Lavinia exilicauda), and hardhead (Mylopharodon conocephalus).There were bottom-dwelling sculpins (Cottus gulosus and asper); bottom-feeding, schooling Sacramento suckers (Catostomus occidentalis); probably Sacramento perch (Archoplites interruptus) and the unrelated tule perch (Hysterocarpus traski, a member of the surfperch family); and the small three-spined stickleback (Gasterosteus aculeatus), whose pugnacious males build nests and guard eggs and young.

Today, the most common fish in our creeks is probably the introduced mosquito fish (Gambusia affinis), widely planted in an attempt to control mosquitos. Unfortunately, these little fish also prey on frog eggs and tadpoles. Our creeks have one and probably two other kinds of small fish, probably sticklebacks and dace or roach. We would like help identifying them. Restoring some of the smaller native fish also is a realistic goal - such re-introductions appear to be succeeding in nearby Strawberry Creek.

Our measurements indicate that Cerrito Creek is too warm for salmon or trout, but Codornices Creek has trout of varying sizes in a number of pools from approximately Monterey Avenue downstream. These fish have been definitely identified as belonging to the species Onchorhynchus mykiss but it is hard to be certain whether they are rainbow trout or steelhead (even from the same group of eggs, some may remain in fresh water, while others go to sea and become the much larger steelhead). It seems likely that these fish are steelhead, as large steelhead have been seen swimming upstream in lower Codornices Creek, and there are no barriers that would stop their upstream migration. Protecting and restoring habitat for these fish is one of our goals.


Our common native frog is the Pacific chorus frog, Pseudacris regilla (also known as Pacific tree frog, Hyla regilla). This small frog, less than 2" long, spends most of its life on land, in shrubs and high grass though it can climb trees well. The frogs are well camouflaged, changing from green through tan, gray, and brown. If you do see one, you can identify it by the black stripe through its eye.

In late winter and early spring, these frogs lay eggs in seasonal ponds, puddles, or slow-moving water. Our larger creeks generally are too fast for their purposes - eggs would be swept away. During this annual breeding season, males inflate throat sacs and "sing." Individuals sound like the familiar "ribbit," but a chorus is loud, high-pitched, and continuous. Protecting and restoring the remaining habitat for these frogs is one of our goals.

Our creeks probably once harbored the larger red-legged frog (Rana aurora), a larger frog that requires fairly deep pools. Red-legged frogs are now an endangered species, and it is doubtful that any remain in our urbanized area. Our area may still have some Western toads (Bufo boreas) and possibly has introduced bullfrogs (Rana catesbeiana). Since bullfrogs are fierce predators on other frogs, we are happy that our annual survey has not yet found any.

Our creeks once were home to many newts and salamanders - children enjoyed hunting these moist-skinned "mud puppies," that spend most of their lives on land but generally return to water to breed. As with frogs, their numbers have been greatly reduced by urbanization, in particular the elimination of ponds and slow-moving small creeks, and the flash-flood-like flows of the remaining larger creeks, which receive the rapid runoff from paved and built-on surfaces.

It still is possible to find the California slender salamander (Batrachoseps attenuatus), with such short legs that it looks at first like a tiny snake or worm, and Ensatina (Ensatina eschscholtzi), both able to breed without ponds. We would like information on where these, or possibly other newts and salamanders survive.


Undeveloped areas along our creeks harbor harmless snakes such as the rubber boa (Charina bottae), gopher snake (Pituophis melanoleucus), and common and Western aquatic garter snakes (Thamnophis sirtalis and couchi). As the name implies, the Western aquatic garter snake is often seen swimming. Western pond turtles (Clemmys marmorata), a species of concern, have been seen in lower Codornices Creek. But the fast flows and loss of pools resulting from urbanization make it unlikely that the creek now has good habitat for this increasingly rare species. Restoring such slow-flow areas is a worthy restoration goal.


Codornices Creek has crawfish (or crayfish), but these are not our small native members of this lobster-like family. Rather, they are survivors of a failed attempt to raise larger commercial crawfish. These dark red relatives of lobsters eat almost anything -- plants, decaying matter, worms, insects, and snails. They also eat smaller crawfish and frog and salamander eggs and larvae, making them a possible detriment to native species.

Benthic Macroinvertebrates

Fish and other water-dwelling animals depend for food on insect larvae, worms, snails, and other small invertebrates found on the bottom, sheltering in plants, burrowing, or clinging to rocks. The number and type of these organisms are a useful gauge of health of a creek. Some of the characteristics to note are the variety of types (usually indicates a healthy, balanced community), whether one type of organism is dominant (may indicate an unbalanced community), the types of food consumed (e.g. upper headwaters should have types that shred organic matter, while slower streams may have algae-feeding grazers), and the presence or absence of species that require very pure, cold, well-oxygenated water, e.g. many members of the orders Ephemeroptera (mayflies), Plecoptera (stoneflies) and Trichoptera (caddisflies). Their absence may indicate that the creek is degraded by too-warm temperatures, lack of oxygen, or pollutants.

Here is the summary of macroinvertebrates collected in Codornices Creek in 1999, at the Ohlone Greenway crossing on March 21, and from below and above 8th St. on June 19. All numbers are approximate. While these findings are fairly typical of urban creeks, they indicate that there is plenty of room for improvement. Friends of Five Creeks could use volunteer help in continuing and extending these kinds of surveys.


Common name or description (tolerance of pollution) Ohlone Greenway 3/21 Above 8th Below 8th
mayfly larvae, family Baetidae (moderate) 130 45 43
aquatic earthworms, class Oligochaeta (moderate) 12 20 13
mites, order Acari (moderate) 11 - 23
damselflies (tolerant) 3 5 27
red midges, family Chironomidae (tolerant) 4 4 56
black fly larvae, family Simuliidae (tolerant) 2 17 43
snails (tolerant) - 1 5
green/yellow midge (moderate) - 1 -
crayfish (tolerant) - 1 -
crane fly (moderate) - 1 -
polychaete (moderate) - - 1


The grizzly bears that once hunted our area are gone, along with elk, but coyotes are still seen near upper tributaries of Cerrito Creek, and our wooded creek canyons still shelter deer, skunks, raccoons, and the introduced opossum. Urban garbage and pet food commonly support larger populations of raccoons and skunks than would have been found originally; these large populations in turn may make difficulties for their prey species, such as frogs. Fox squirrels, the big rusty-bellied squirrels common in our urban creekside parks and yards, are an introduced species. Eating bird eggs and baby birds as well as acorns, they may make it more difficult for songbirds to breed successfully. (Our mostly grassy area probably never supported significant numbers of native Western gray squirrels, Sciurus griseus, or Douglas squirrels, Tamiasciurus douglasii).

Native burrowers -- pocket gophers (Thomomys), California ground squirrels (Spermophilus beecheyi); and the coast mole (Scapanus orarius) survive nearby, but not as far as we know along the creeks. These are meadow creatures, as are Western harvest mice (Reithrodontomys megalotis), deer mice (Peromyscus maniculatus), and the California vole (Microtus californicus). When our area was mostly grasslands, these creatures flourished, probably especially in the moist meadows along our creeks. Creation of the Eastshore State Park provides them with a chance at a small refuge; some can be found there, along with black-tailed jackrabbits. The Albany salt marsh is potential habitat for the endangered salt marsh harvest mouse, Reithrodontomys raviventris, but none has been seen there.

Fog and damp west of the Berkeley Hills makes our area less desirable for bats than the dryer east side. Bat numbers may never have been large. But as bats need water and loose tree bark (or the equivalent) with a sunny exposure, trees near our creeks probably were homes to common bats such as the little and brown Myotis. Placing bat houses in appropriate trees may be a worthwhile project.


Before European settlement, the Friends of Five Creeks area was mostly grasslands. Moist meadows and salt marshes provided homes for such birds as goldfinches, meadowlarks, sparrows, and yellowthroats, including the Alameda song sparrow and salt marsh common yellowthroat, both now rare due to loss of their habitat. The salt marshes at creek mouths were vital for the now-endangered California clapper rail, herons and bitterns hunting frogs and small fish, and a variety of mud-probing shorebirds including avocets, stilts, yellowlegs, snipe, and dowitchers.

Along the creeks were thickets of willow and elderberry and strips of woodland dominated by oak and bay trees. These creekside (riparian) thickets and woods were important nesting places for quail (Codornices means "quail" in Spanish) and migrant songbirds including a variety of flycatchers, wrens, thrushes, and warblers. Quail still sometimes venture into headwaters of Cerrito Creek, but domestic dogs and cats make it almost impossible for them to raise young successfully. The depredations of these pets; large populations of jays and squirrels that flourish on garbage but also eat eggs and baby birds; and loss of thickets, are important reasons why we no longer see the variety of songbirds that once flourished along our creeks. Creekside property owners and parks can help birds by planting, or retaining, some dense thickets where they can nest in relative safety, by controlling dog and cat populations, and by not leaving garbage available to other animals.

Woodpeckers depend on dead and dying snags. Our most common species probably were the small downy and hairy woodpeckers, with black-and-white markings and red caps, that still can be seen tapping near our creeks. Holes they excavated were and are used in turn by smaller birds such as chickadees. Zealous removal of dead and dying trees for safety and fire protection makes urban life difficult for such birds. Bird houses can help some species, but holes must be small enough to keep out starlings and house sparrows, aggressive non-native competitors that flourish in cities.

Native hunting birds still migrate through our area and sometimes nest in parks along our creeks. It is not difficult to spot the gaily decorated little Kestrel, the marsh-loving Northern Harrier, the woodland-hunting Coopers Hawk, and the large Red-Tailed Hawk that seeks out the tallest trees. Kingfishers hunt along the Bay and lower creeks, plummeting from telephone poles or branches to catch small fish. Burrowing owls have been reported in the Eastshore State Park (where surviving burrowing mammals, discussed above, dig the homes they later use).