Nature Notes from Big Creek, 1991

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April 1991 May 1991 July 1991 September 1991 October 1991 November 1991 December 1991

April 1991. Until the rains in March, Big Creek was as low as anyone had ever seen it (it was running 3-4 cubic feet per second instead of 6-10 which is a "normal" base flow in the fall). On the slopes and ridges the soil was dry, and the annual plant cover on the hillsides was sparse and about one inch high. Even in the canyon bottom the banana slugs were inactive. I have noticed that some weeds seem to be hard-hit by the drought, including Milk Thistle (Silybum sp.). We are trying to control this species and are hoping to really knock back the thistle on our grassy ridges between 500 and 1500 feet elevation and give the bunch grass and native flowers some good soil!

The Harbor Seals are back in full numbers after their annual disappearance in August and September (does anyone know where they go?). Several Mountain Lions returned to the lowland areas of the reserve, after an absence of about 6 months. A group of three lions have been active near Boronda Camp (probably a mother and two young). They were sighted on February 23, and that evening one or more lions made screaming and growling noises around a UCSC environmental writing class. On March 4 a young lion walked through our yard and sat under a cypress tree for an hour while it rained. It was thin and lanky, even for a mountain lion, and had a pretty face with huge tawny eyes and a cream colored chin. Rosie was fascinated! Lions rarely bother people, but children are vulnerable, especially to young animals. We have no dogs and are always careful with our two little ones. We didn't see our little black cats for two days.

The Black Oystercatchers are beginning to hang around their nest rock in Big Creek cove. Last year they raised two chicks in the nest (one survived). These birds are very sensitive to disturbance because they must guard their nest from gulls 24 hours a day. Gulls seem to "hang around" the nest, and, if the parents are scared off the gulls eat the eggs and chicks immediately.

The bay trees are in full flower now, as are pink flowering currants and manzanitas. The redwood sorrel has sprung up after the rain, and a few milkmaids are blooming. Up on the ridges there are a few buttercups, lilies and yellow violets, but really very few flowers are in bloom. Maybe the rain will make a difference and we'll get some spring flowers soon.
A reminder: We are planning our annual open house for Saturday May 11 this year, between 9 and 4. We will have displays about the reserve, including our facilities planning efforts, and I invite you to come and see what we are up to. Like last year, we will lead hikes on the trails, so bring your lunch and plan to spend all day if you can. Unlike last year, I don't expect to discover a dead mountain lion in the trail, but who knows? (3/5/91)


May 1991. I received a report that Monarch Butterflies marked here at Big Creek in December have been sighted at Esalen (4mi north) and at Plaskett Creek (15mi south). These sightings suggest that central California Monarchs move up and down the coast in the winter, much like their southern California cousins.

The spring bloom (what there is of it) is very late this year, probably because of the drought and the cold winter weather. In early April the most common flower on the Gamboa ridge was the shooting star, normally a February/March bloomer. It will be very interesting to see how the spring progresses. The perennial bunchgrasses seem to be doing very well on the ridges. The drought and the elimination of cattle grazing (in early 1980's) may be favoring their spread.

A second reminder: We are planning our annual open house for Saturday May 11, between 9 and 4. We will have displays about the reserve, including our facilities planning efforts, and I invite you to come and see what we are up to. Like last year, we will lead hikes on the trails, so bring your lunch and plan to spend all day if you can. Unlike last year, we don't expect to discover a dead mountain lion in the trail, but who knows? (4/x/91)


July 1991. The Harbor Seals whelped their pups on the beaches in late April, including several on the Big Creek cove beach. On May 15 I counted 152 seals between Dolan Rock and the seal beach. The Black Oystercatchers have apparently settled down to brood their eggs this spring. One adult has been settled on the nest for the last three weeks. The bird biologists at UCSC are very interested, since nests of these birds are normally very hard to observe.

Several deer fawns have been sighted this May, all very young. It will be interesting to see if the trend away from twinning continues. In the fall of 1988 nearly all does were observed with twins, with the frequency declining each year. So far I have sighted three does with young this year, none of which included twins.

Last fall Jeff Norman alerted me to some caterpillars he saw feeding on French Broom (also called Genista or Cytissus monspessulanus), one of the most invasive weeds in our area. I visited Gail and David at Morning Glory Ranch near Lucia, and collected several caterpillars. After raising them for about 6 weeks in plastic bags containing French Broom leaves, they pupated in little woven cocoons. The moths emerged last month. They had brown forewings, orange hindwings, and had brush-like palps extending on the front of the head. I called Professor Jerry Powell at UC Berkeley and described them. He informed me that they are called Uresiphita reversalis, and that in California they feed primarily on French Broom, although in some areas they attack garden ornamental brooms. He was excited to learn that they are in Big Sur since this was the first record in our area. Apparently the moths invaded the San Francisco Bay area in the last 10 years from Southern California.

Jerry sent me some literature on this moth. Apparently the caterpillars are "aposematic," that is brightly colored and highly visible to birds, and they store "quinolizidine" alkaloids in their gut and cuticle tissues. The toxic alkaloids probably protect the larger larvae from most predators. Jerry thinks the caterpillars are not capable of killing most broom plants. However, it is an encouraging sign that effective herbivores are beginning to attack this non-native plant, and it is possible that the combination of several species might actually control it. In most cases the success of non-native plants derives from the fact that they leave most of their herbivorous "enemies" behind when they immigrate to a new area. If anyone would like copies of the literature on this moth please call me at 667-2543 and I will mail you a copy.

The open house was not well attended this year, perhaps because of the lateness of the date and the competition with the Captain Cooper carnival. Next year we'll schedule earlier in the spring. (5/29/91)


September 1991. The young Red-tail Hawk that left its nest at Whale Point last month has been a noisy neighbor this month (July). It spent most of the month heavily flapping up and down the canyon, crying "keeyer, keeyer," while the mother soared nearby. I felt sorry for the harried mother! Sometimes the mother fed it snakes. This has happened in previous years, but never has the young hawk been so demanding (or, at least, so loud about it). Perhaps this one was extra hungry or maybe it was just the bird's "personality." On July 29 or so the activity tapered off, and it has been quiet in the canyon the last two days. I suspect the family left the nest area.

The last week of July has seen the arrival of migrants from the south, including flocks of Heerman's Gulls. These beautiful gray birds breed on islands off the coast of Mexico, including Ildefonso Island in the Sea of Cortez, and spend the late summer, fall, and winter along the Pacific coast. The Brown Pelicans appeared as well after their breeding season on the Channel Islands off southern California, and now are diving for fish in the kelp beds along the coast.

The three Pelagic Cormorant chicks I saw last month were still in the nest on July 13, very large but flightless. About seven adult birds were in the nest area but flew off at my approach. Since many safer and more convenient rocks are available for roosting, I wonder if the adults I saw were relatives (which may help feed the chicks). I assume at least two were the chicks' mothers. The Pelagic Cormorant has a white side patch, a long slender bill, and glossy blue-green feathers.

Up at Cone Peak I noticed that the Santa Lucia Fir trees lack cones this year for the fourth or fifth year in a row. This large, shapely tree is one of California's most spectacular endemic species, living only in the Santa Lucia Mountains. I wonder if the drought has affected them, or if their reproduction naturally goes in cycles. Many trees have what is known as "mast" fruiting in which they produce masses of seed an infrequent intervals. One theory to explain this is that it prevents seedeaters from building up their numbers to the point at which they eat all the seed.

Paddling a borrowed ocean kayak off Big Creek, I found that the Harbor Seals need a clear zone of about 400' feet from their haul out points. Approaching closer than about 200' drives them into the water. If you are out in the water and see the seals, be a good neighbor and give them room so they don't have to interrupt their "warm" time on the rocks. (7/31/91)


October 1991. Last June 15 we held the third annual "Fourth of July" butterfly count at Big Creek. I assisted four butterfly experts around the reserve, nets in hand, from about 9 AM to 5 PM. We counted all the butterflies seen, and identified them to species if possible. One type of butterfly, the Painted Lady, was so abundant that we could not effectively count them all, but nearly all the others seen were counted. Our counters (three from UC Berkeley and one from the Santa Cruz city museum) were so expert that, of 872 butterflies seen only 14 could not be identified. 36 species were seen, including 2 species of swallowtail, the California Orangetip, two sulfurs, a marble, a cabbage white, two hairstreaks, six blues, a copper, the California Sister, the Buckeye, an admiral, the Tortoiseshell, three checkerspots, two crescents, an anglewing, the Painted Lady, two fritillaries, the Monarch, the Ringlet, and five skippers! That's a lot of species, but only a small fraction (only 5%) of the total diversity of moths and butterflies found on the reserve.

Last year, with five counters, we saw roughly the same number and diversity of butterflies, but with seven different species! In general, there seemed to be fewer butterflies than last year, which the counters "made up for" by working harder and covering more miles. Julia Smith, a "birdologist" working at Big Creek, agrees. The Song Sparrows she is studying are laying fewer eggs, later in the season, than in previous years. Since they generally lay eggs in proportion to the amount of food they can gather, she concludes that there is a shortage of insect food this spring (including butterflies). Perhaps the cool weather in April and May is the cause. Insects generally thrive more and develop faster in warmer weather.

We have really "hit" the Milk Thistles hard this year, and relatively few of these spiny weeds can be found on the reserve. Five years ago these plants formed dense thickets on ridge tops and benches. Thanks to the cessation of cattle grazing (which creates bare ground favorable to thistle germination), improved road maintenance techniques, the drought, and the great efforts of our machete-wielding steward Feynner Arias, we still hope to reduce this weed to an "interesting exotic." (9/9/91)


November 1991. This fall we have a big crop of tan oak acorns, the most I have seen in the five years I have lived here. These trees have large leaves with noticeable "ribs" (veins). The acorns are very big and are a favorite food for wildlife. I also noticed that our acorn woodpeckers are busily stuffing acorns in holes and cracks all over the reserve. These amazing creatures are highly dependent for survival on acorns, which they store in large "granaries" or storage trees. During the fall and winter months they eat the intact acorns for food (they do not store acorns in order to eat the insects inside, as is commonly supposed). Their complex social life centers on ownership and defense of these granaries, which must be protected against other colonies of woodpeckers, jays, squirrels, and other animals. Researchers at Hastings Natural History Reservation in Carmel Valley have devoted many years to detailed study of these animals.

This month I also noticed that the acorn woodpeckers seem to have (temporarily?) abandoned their usual "granary" trees. Feynner (our reserve steward/naturalist) and I speculate that perhaps they have abandoned the central granaries in favor of gathering the tan oak acorns as rapidly as possible. Getting them up off the ground and jamming them in cracks (as we have observed) would save them from many would-be acorn eaters such as deer, wild pigs, quail, and band-tail pigeons. We will be watching to see if the acorns are subsequently moved to centralized granaries where they can be defended.
This year's tan oak acorn crop is another example of mast fruiting, (like the Santa Lucia Fir). Oaks are well-known "practitioners" of mast fruiting. In this case, the activities of the woodpeckers illustrate how mast fruiting may benefit the oak trees. If our speculations are correct then the woodpeckers are responding to the large "mast" crop by spreading acorns away from the parent trees and protecting them from immediate consumption on the ground. During the process of transport and storage many acorns probably get lost and fall to the ground, and thus have the opportunity to germinate and survive.

Last October 11 swarms of flying ants and termites made their appearance. These winged "reproductives" leave the home colonies and usually do not return. Once airborne, their goal is to mate successfully and found a new colony. Derek Sikes, a researcher working at Big Creek, reported swarms the same evening in the Santa Cruz mountains. The swarming was almost certainly triggered by the thunderstorms during the day. These insects frequently synchronize their mating flights by responding to thunderstorms and other dramatic weather events. In this way they increase the probability of encountering potential mates. (10/15/91)


December 1991. Cheryl Briggs, a doctoral student at UC Santa Barbara, has been spending quite a bit of time at Big Creek. She is setting up an experiment to study how tiny parasitic wasps control equally tiny flies. The flies she is studying are a species of gall midge (about 1/25" long). They lay their eggs in growing shoots of Coyote Brush. Upon hatching, the tiny fly maggots cause the plant to grow round galls about 3/4" across, within which the maggots grow into adult flies. If midge reproduction goes unchecked, galls will cover the plant within a year. In nature this usually does not happen. Tiny parasitic wasps (also 1/25" long) usually come along and lay their eggs in the galls. The wasp eggs hatch and kill the maggots, preventing the midges from reproducing while making new wasps. The wasps are called "parasitoids" because they begin life as a parasite of the host midge but, unlike a true parasite, they eventually kill their host.

This intricate relationship is an example of a field of study known as "parasitoid-host interactions." Understanding these interactions is crucial if we are to control insect pests without excessive use of pesticides. What Cheryl has done at Big Creek is to discover a natural example of this type of system, and to study the interaction under natural conditions. For example, Cheryl has found two species of parasitoid wasps attacking the Coyote Brush midges. After studying the details of the life cycles she developed mathematical equations, which describe how effectively the wasps should control the midges. The equations predict that the two species of wasp will be a less effective control than one species alone. The caging experiments are designed to see if this is actually true by putting one species of wasp in some cages and two species in others, and then counting the rate of gall formation. Using the data she gets, Cheryl will be able to modify the equations so as to give more accurate predictions. The equations can then be used in developing a general theory of how multiple parasitoids affect their hosts.

Cheryl's research demonstrates the use of nature reserves as places to test theories about the natural world. In her case the knowledge gained will be useful for deciding how many species of parasitoid wasps to release (when trying to control a pest), as well as improving our understanding of natural creatures. Big Creek Reserve is ideal for such work because (1) all the natural predators and competitors are present in a complex "balance," (2) Cheryl can set up her cages in the field without danger of their being vandalized, and (3) we can help support her work by providing grant funds.
Other notes: After five years of drought the flow in Big Creek is low. The March rains made a difference, though. For example, this September the creek is about 2/3 of an inch deeper than last September, which means 1-2 gallons per second more water. During the recent rains the creek rose about 8" for a short time and fell back quickly to base flow.

During October, deer moved into the reserve in large numbers. Many are feeding on tanoak acorns. We have not yet seen numerous mountain lion tracks but I expect the lions will move down from the high country soon. The other day I saw a doe and fawn run up a slope and almost collide with a bobcat hiding in the brush. They jumped sideways and ran down slope, the bobcat watching their progress. The bobcat then ran off the opposite direction. In Florida bobcats frequently eat deer, but the cats there are big and the deer very small. Here, I suspect only a very large bobcat would attack anything larger than a small fawn, but we have no data. One student (Tye DePena) is collecting cat scats on the reserve. He may shed some light on this question when he analyzes the dietary remains.
This fall the monarch butterflies seem very abundant, or perhaps they are just more active because of the warm weather. We have marked over 300 individuals this year (writing a small "BC" on the wings with a soft black "sharpie" pen). Please tell me if you spot these or any marked butterflies. Last season two of our marked monarchs were found, one at Esalen (4 miles north) and one at Plaskett Creek (15 miles south). This data is useful in understanding how much the butterflies move along the coast during the winter, one objective of a study undertaken by Walt Sakai of Santa Monica College. (11/7/91)

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