The Recovery of California Brown Pelicans in the Southern California Bight

The California Brown Pelican (Pelecanus occidentalis californicus) is the western North American subspecies of a wider-ranging species. Large groups of pelicans roost at Año Nuevo Island, Elkhorn Slough, and Point Lobos, although they don’t breed in the Monterey Bay National Marine Sanctuary. So population studies focused on other areas within the species’ range can provide important information about the health and status of the pelicans seen in the sanctuary.

An adult California Brown Pelican in full breeding plumage, photographed at Isla Pelícano, Puerto Refugio, Gulf of California. Two other subspecies in North America and three more in South America do not have the bright red pouch seen in this individual, which we consider to be one of several distinguishing morphological features of the “California subspecies.” photo 1973 Daniel W. Anderson

Because of reproductive failure discovered in the late 1960s, this subspecies was declared endangered in 1970. The 1983 Brown Pelican Recovery Plan (U.S. Fish and Wildlife Service, Portland, OR) delineated four breeding populations: the Southern California Bight (SCB), the lower west coast of Baja California, the Gulf of California, and the coastal estuaries along the western Mexican mainland coast south to Colima. There is much mixing among the populations, especially during the non-breeding season.

Much has happened since 1983. California Brown Pelicans have benefited from the conservation measures of the recovery plan. From the 1960s through the early 1980s, SCB population declines were caused by the effects of DDE (dichlorodiphenyldichloroethylene), the environmentally-persistent metabolite of DDT (dichloro-diphenyltrichloroethane). When industrial inputs of DDT were reduced by the mid-1970s, eggshell condition, DDE levels, and population performance of SCB birds improved. Yet the recovery for SCB birds has taken at least two decades.

We began studies of SCB populations in 1970, concentrating major efforts in California at West Anacapa Island (off Ventura), a part of the Channel Islands National Park and Channel Islands National Marine Sanctuary. SCB populations there have steadily improved from near extinction, so that by the early 2000s, breeding populations were back to, or even higher than, historical numbers. Our goals for the average size of stabilized breeding efforts in the U.S. and northwest Mexico breeding colonies have been (approximate numbers):

• Anacapa Island: 4,000 to 5,000 breeding pairs
• Santa Barbara Island: 500 to 800 breeding pairs
• Islas Los Coronados: 500 to 750 breeding pairs
• Isla San Martín: 100 to 300 breeding pairs
• Reproductive rates: 0.6 to 0.9 young fledged per nest attempt

During the 1960s and 1970s, numbers at both Anacapa Island and Islas Los Coronados went as low as 200 to 300 pairs, with no breeding at Santa Barbara or San Martín Islands; reproduction was almost zero for several years in the late 1960s. In contrast, today – in a good year – SCB populations approach or exceed our target numbers (above).

We have studied California Brown Pelicans in Mexico since 1971, where larger populations have continuously remained stationary. In colonies of the Midriff Region of the Gulf of California in a good year, there are 35,000 to 40,000 nesting pairs producing an average of 0.8-1.2 young per nesting attempt. The Gulf is so important to pelicans that we have come to term the species, “the King of the Cortéz.” South in the mangroves of western Mexico and on some offshore islands, 8,000 to 10,000 additional nesting pairs occur.

Breeding populations and productivity fluctuate around environmental conditions. This is related to the abundance and availability of food over periods long enough to raise viable young. For a California Brown Pelican raising young is a major investment, as it takes almost five months to establish nests and then raise young to independence. Varying food conditions naturally involve cyclical oceanographic phenomena, such as El Niño/Southern Oscillation (ENSO). When strong ENSOs occur, these birds stop or reduce their breeding efforts. ENSO events rarely cause extensive pelican mortality like that reported in Peru in many El Niño years, but pelican mortality in Baja California was noted in the record event (1997-1998). ENSO warming events have a reducing effect on the species’ breeding effort and productivity; reproduction varies with the strength of each event. In some years, ENSO effects reach into the northern Gulf of California and north to the SCB. In others, the effect may only extend to the colonies of the Midriff area of the central Gulf.

These birds are affected by many other environmental factors, in addition to natural variations, that need to be considered in their conservation:

• Interactions with commercial fishing activities produce mostly negative effects but also the potential for short-term positive effects, through provision of “offal” and unwanted fish in some commercial catches (mostly in the Gulf of California).
  
  
• Nesting and roosting pelicans frequently abandon their nests and suffer other disturbances through various kinds of human-related disruptions. (Nesting pelicans need undisturbed places to nest and roost throughout the year.) • Contaminants such as oceanic debris and spilled or discarded chemicals (e.g., oil products, persistent contaminants), as seen, can have devastating effects.

Protection of off-colony roosts might be the most immediate need off California because the major nesting colonies are secure (other than the SCB colonies to the south in Mexico), protected by the U.S. National Park Service, U. S. Fish and Wildlife Service, and California Department of Fish and Game. In the Gulf of California, the Mexican federal government also conducts a large program of seabird colony-site and island protection and management. But still, the major challenge throughout the range of California Brown Pelicans will be to develop management plans and marine sanctuaries for commercially and otherwise valuable species that will take into consideration the needs of seabirds and other marine wildlife as well as long-term ecosystem health. We currently recommend down-listing the species from “endangered” to “threatened” – to reflect the amazing recovery of pollution-reduced populations in the SCB – yet continuing to address the many other threats throughout their range.

Daniel W. Anderson and Franklin Gress
Department of Wildlife, Fish, and Conservation Biology
University of California Davis

The Rise and Fall of Humpback Whale Numbers

Since the mid-1980s, biologists with Cascadia Research have been monitoring humpback and blue whales along the West Coast using photographic identifications of individual animals. For humpback whales especially we have been able to use these data to determine the species abundance and the population trends along that coast. We have documented not only the steady increase in humpback whale numbers but also apparent evidence of a recent sharp drop in the number of humpback whales.

Humpback whale breaching. photo 2003 John Calambokidis

Cascadia began its research in 1986, initially funded by the Gulf of the Farallones National Marine Sanctuary (GFNMS). The goals were to document the return of humpback whales to this newly formed sanctuary as well as to determine how many animals were using the sanctuary and to what areas they migrated. Humpback whales had been commercially hunted from whaling stations along the California coast up to 1966, and some of the last whaling occurred in the Gulf of the Farallones area. Commercial whaling had dramatically reduced humpback whales along California, and from the mid-1960s through the early 1980s they were seen in numbers only fairly rarely.

Early work was able to document information not only on humpback whales but also on the blue whales encountered frequently in our research. We determined that humpback whales use a much broader area than just the waters of the GFNMS. In fact, from southern California north to Washington was a discrete feeding area for humpback whales. Within this region there was quite a bit of movement and interchange, but there was little to no inter-change with the humpback whales that fed further north off British Columbia and Alaska. We were also able to identify that humpback whales along the California coast migrate mostly to the waters off Mexico and Central America (south to Panama) to breed and give birth.

Our catalog of humpback whales, identified by natural markings on the underside of their flukes, has grown steadily and now numbers more than 1,400. This is actually higher than the abundance we estimate, because the catalog spans more than fifteen years and not all these individuals were alive at the same time. We now have the vast majority of humpback whales that use west coast waters identified and have long sightings histories on many of these animals.

Figure 1. Humpback whale abundance off the U.S. West Coast using capture-recapture estimates with annual samples.

To estimate the true abundance of whales, we need to employ mathematical procedures called capture/recapture statistics. These involve models developed for use on a wide variety of species, including small mammals and fish, that try to estimate total abundance from repeated resightings of individuals known from tags (or in our case natural marks). In essence, these procedures allow us to estimate the abundance of all animals, those we have identified and those we have not. These procedures can be fairly simple to use but have a number of requirements in order to work properly, so they require careful consideration in sampling and how they are employed.

One problem with the initial humpback whale studies was the limited study area. The whales clearly ranged much more broadly than just the GFNMS, even during the summer months. By 1991, with support from Southwest Fisheries Science Center, a federal agency interested in estimates of humpback whale abundance, we had expanded our identification research of humpback whales (and blue whales) to the entire U.S. West Coast. We were attempting to get fairly broad and even coverage so that our new capture/recapture estimates would accurately estimate the entire population that feeds along the West Coast.

From 1991 through 1998 humpback whale abundance estimates increased steadily – from 569 to 1,016 (Figure 1). This represented an increase of 9 percent per year. The data looked very solid, showing a very consistent pattern. This was exciting news since this was not only a larger population of humpback whales than had previously been thought to be using California waters, but the increase was up near the maximum of what was possible for humpback whales.

Then came a big surprise: after 1998 the estimate dropped almost 30 percent, down to 709 whales. The following year, estimates increased only slightly, to 774 animals. The estimates from 1999 to 2001 represented the first substantial decline in numbers we had seen. Looking at the data in more detail revealed that this drop was caused by a dramatic mortality (or departure from the region) of animals occurring sometime between late 1998 and early 1999.

The two possible short-term phenomena suspected to be responsible for a decreased survival in humpback whales were the 1997-98 El Niño and the domoic acid outbreak in 1998. That particular El Niño was considered severe and resulted in lower upwelling and productivity off California from the spring of 1997 through the fall of 1998. Zooplankton declines appeared to be more severe in many areas in 1998. Lower prey availability for humpback whales during the 1998 feeding seasons could produce a lower survival of animals over the following winter fasting period. Domoic acid consumed in fish prey was determined to be the cause of a dramatic increase in California sea lion mortality in central California in 1998.

Our most recent estimates on humpback whales show that since the drop in 1998-1999, humpback whale numbers have been recovering and are now returning close to the levels they were before the recent decline. In fact, the most recent estimate took one of the largest recorded upward jumps.

While the impression has been that blue whales have undergone a similar increase along this coast, the data do not support this. It is clear that blue whales are more abundant now than they were in the 1960s or 1970s, but our data from the 1990s have not shown much of a change in the past ten years.

Despite the larger than expected numbers of both humpback and blue whales that feed along the West Coast, there is reason for vigilance. Blue whales, hunted widely in the twentieth century, remain at very low abundances in most of the other areas of the world where they were formerly abundant. The world-wide populations of both these species remain well below pre-whaling levels. There are also concerns about declines in plankton that have been noted in areas of southern California. California is fortunate to have some of the highest densities of humpback and blue whales in the world; this should be viewed not as something we take for granted but as a reason to protect these valuable waters.

John Calambokidis
Cascadia Research