"Hypothesis" (interim explanation until proof is secured) isn't the correct term, because what I think was the status of California condors in the Pacific Northwest is unlikely ever to be proven. Nevertheless, everything we've learned about condors supports my premise that condors were permanent residents north of San Francisco. I think that, in the 1800s, condors occupied a more or less continuous strip of habitat from the Sierra San Pedro Martir in Baja California, Mexico, north at least to the Columbia River in Oregon and Washington, maybe a little farther. Within this total range, subgroups of condors occurred where suitable nesting and foraging habitat existed together. Condors disappeared from the Pacific Northwest some time after 1900, as a result of human-caused mortality and not due to any failings of the habitat available then or now. I'll elaborate on this below, and discuss the other major "hypothesis," but first we need to look at the data available, its strengths and shortcomings.

The information on which I base my conclusions is summarized by region, and each reference is discussed separately. But not all references are created equal, and the milieu in which Nineteenth Century natural history records were accumulated needs to be understood.

When the explorers of the 18th and 19th centuries returned home with their fascinating stories of the American West, people in "the States," Great Britain, and Europe couldn't get enough of this new lore. Everyone who went West in the years following the Lewis and Clark expedition was urged to find out all that could be found out, and to get the word back as quickly as possible. Because of the time it took to travel around, no one person could see very much; consequently, many people took to padding their own accounts with "they say" information. This practice wasn't limited to explorers, fur trappers, gold seekers and pioneers, but was practiced by journalists, statesmen, politicians, and even the most respected scientists of the day. To this day, much of our knowledge of condors (and many other species) is tainted by the blend of fact and fiction contained in early accounts, that has been repeated (and often further corrupted) over and over again.

For example, much information included in the accounts of late 19th Century scientists (Baird, Henshaw, Ridgway, Cooper, Bendire) can be traced back to a series of articles that Alexander Taylor wrote between 1855 and 1860 for "Hutching's California Magazine," "California Farmer," and "Zoologist." Taylor had some condor experience, but very little, and he embroidered liberally to make a good story out of what he did know. Hubert Howe Bancroft, famed California historian, noted that Taylor "had a most unfortunate passion for working the results of his observations and study into what he regarded as a scientific form, the result being too often an absurd jumble of bad Spanish, worse Latin, and unintelligible affectations." Uncharitable as was Bancroft's observation, the bad writing is the least of the problems for the condor researcher. For example, Taylor's personal observations of a dead condor he examined are presented side-by-side with hearsay reports of a condor flying with a rabbit in its talons, and of a flock of condors completely devouring a cow, that had fallen out of a wagon, before the driver could stop and turn the wagon around! We can perhaps take his dead condor descriptions at face value, and can reject his rabbit-in-the-talons report. Anyone would probably excuse us for a certain level of disbelief for his cow falling out of the wagon tale. But what do we do with Taylor's hearsay reports of hundreds of condors in a flock (something reported by no one else), or of hundreds of condors succumbing to strychnine poisoning (also not reported by anyone else)? Unfortunately, many who came after Taylor repeated fact and hearsay as if both had equal validity.

The Pacific Northwest had its own "Alexander Taylors," in the persons of David Douglas and John Kirk Townsend. Perhaps the most famous of the condor "they say" stories involved David Douglas, a noted botanist who traveled early in Oregon Territory. He wrote an entertaining blend of fact and fiction for the prestigious British "Zoological Journal" in 1828 [Reference 22]. He saw condors himself; in fact, collected two specimens. His paper therefore starts out with meticulous data on weights, measurements, and plumage characteristics of the two birds he examined. He saw condors flying and feeding, and gave reasonable descriptions of these activities, but even here he padded his account with some local folklore: "Preceding hurricanes or thunder-storms they are seen most numerous and fly the highest." This one doesn't even pass a "weather test," since hurricanes are unknown in Oregon, and thunderstorms are uncommon in the areas known to have supported condors.
Douglas' "they say" story about condor nesting seems preposterous to us today, but nobody had any better information at the time: "They build their nests in the most secret and impenetrable parts of the pine forests, invariably selecting the loftiest trees that overhang precipices on the deepest and least accessible parts of the mountain vallies. The nest is large, composed of strong thorny twigs and grass, in every way similar to that of the eagle tribe, but more slovenly constructed... Eggs two, nearly spherical, about the size of those of a goose, jet black..".

Douglas also reported that condors "in the summer are seen in great numbers on the woody part of the Columbia, from the ocean to the mountains of Lewis and Clarke's River, four hundred miles in the interior" [Reference 23]. Fortunately, Douglas left a detailed journal of his 1825-1827 travels that includes specific information about the birds he saw, including condors. This statement was written in February 1827 and, from Douglas' journal, it is clear this was not his personal observation. All his observations from the Columbia River were from "the woody portions," as were those of the Lewis and Clark Expedition, a maximum of 150 miles from the Pacific Ocean.

Like David Douglas before him, John Kirk Townsend was a scientist, and he did see condors in Oregon. Unlike Douglas, nowhere in Townsend's writings is it clear where, when, and how many condors he personally saw. His formal journals fail to mention condors, except as a name on a list of birds "found in the Territory of the Oregon" [Reference 75]. A longer, annotated manuscript, "Description of the Birds of the Columbia River Region," doesn't even include the condor's name [Jobanek and Marshall, Northwestern Naturalist 73 (Spring 1992):1-14].

In an article published in 1848 [Reference 74], Townsend gave a much embellished account of his one successful attempt to kill a condor. That event took place in April 1835, and he said that this was the first time since he entered the Columbia Basin in August 1834 that he had seen a California condor. After that, he said "during the spring, I constantly saw the Vultures at all points where the Salmon were cast upon the shore." In a letter Townsend wrote to John James Audubon [before 1840; ca 1837?], he wrote that the condor "is most abundant in spring, at which season it feeds on the dead salmon that are thrown upon the shores in great numbers." Yet, farther along in the same letter, he wrote: "It (the condor) is seen on the Columbia only in summer, appearing about the first of June, and retiring, probably to the mountains, about the end of August. It is particularly attracted to the vicinity of cascades and falls, being attracted by the dead salmon which strew the shores of such places" [Reference 3].

In addition to being noteworthy for its confusing presentation about the seasonal status of condors, this 1848 publication contains the only first-hand account of condors feeding on salmon. Every other written reference is apparently a "they say" account, perhaps all having their source in Audubon's publication of Townsend's letter. Townsend's letter to Audubon also included the information that condors were found 500 miles from the mouth of the Columbia River, something he never saw personally, and that is not substantiated by any other information. [Before he came West, Townsend had access to some of David Douglas' information, and perhaps his "500 miles" is a re-telling of Douglas' "400 miles" hearsay report.]

I've taken this space to talk about the errors and confusions included in Douglas' and Townsend's reports because much of later speculation and "analysis" of condor status in the Northwest derived in part from the repetition of their misinformation. For the best understanding of where and when condors occurred in the Pacific Northwest, and the reasons for their disappearance, we need to keep clearly in mind what people actually saw, and what was just part of Nineteenth Century reporting styles.

[NOTE: This discussion is an adaptation of Chapter 33, "The Wilbur Line," from my book "Condor Tales: What I Learned in Twelve Years with the Big Birds" (Symbios 2004).]

Carl Koford [Reference 44] didn't think that condors found north of San Francisco Bay or south of the California border with Mexico were permanent residents there. It's clear from his writings, and from my personal discussions with him, that he believed all sightings of condors, no matter where or when they were made, were of birds that made their homes between San Francisco and the Mexican border. According to him, movements of birds out of this permanently occupied area were food related: either the condors moved because of food scarcity in their main range, or because they had knowledge that better food could be found in some distant area at certain times of the year.

Koford's idea made no sense to me. True, condors can fly great distances (they've been known to travel 100 miles in a day), and Carl and I both recognized that, at certain times of year, some condors in the population could be found at considerable distance from nesting areas. But there are no 20th Century records from California - at any season - of condors farther than 150 to 200 miles north of the closest known nest sites. (Data from a minor study of a few condors equipped with radio transmitters suggest that breeding condors rarely travel as much as fifty miles from the nest [Meretsky and Snyder (1992) Condor 94:313-335]. That distance is similar to what Koford estimated during his study. If much greater distances were being traveled in the early 1800s, why didn't the condors continue to make similar treks in the 1900s?

We know of two general types of "migration" in bird populations. One kind is the annual movement that occurs on schedule every year: perhaps north in spring, south again in the fall; or, up to the mountains in spring, down to the valleys in fall. These moves have become part of the fabric of the species. While they usually have an obvious utilitarian value (like moving birds from areas of severe seasonal weather to more temperate climes, or from diminishing food to potentially more dependable food), they have become so much a part of group behavior that they occur like clockwork regardless of yearly variations in weather or food supply. In other words, it doesn't matter if it's going to be an "early" winter or a "late" one; the birds are going to leave on about the same date every year.
Condors were not "migratory," in the usually accepted sense, but the population did have seasonal movements that were nearly identical each year. One can speculate on the values of these movements to the species (to move non-breeding birds out the nesting areas, so they don't interfere with breeding condors; or, to bring most of the unpaired birds together, with matrimony as the object). Whatever the original objective, or the then current need, the seasonal movements had become so much a part of the "tradition" of the species that they continued whether or not they were "best" for the condors. For example, I found in our supplemental feeding studies that we couldn't hold condors at a source of regular food when it was their customary time to "migrate," even if the food supply we were providing was much better than it was where they were going.

If condors lived in one big freely interchanging population, and were flying to northern California, Oregon, Washington (and occasionally even to British Columbia?) because of "tradition," there was no reason for these annual movements to have stopped. It seems pretty clear to me that "migration" from central California to the Columbia River and beyond was not the reason for condors being in the Northwest.

The second type of movement responds to an immediate need. Most years, snowy owls and gyrfalcons winter north of the "lower 48," but especially severe winters (with accompanying food shortages) may force them far southward. Annual variations in the seed crop in coniferous forests make for highly variable "migrations" of crossbills and other seed-eating birds dependent on the bounty of these forests. These variations may be somewhat predictable, particularly if the food supply (snowshoe hares or pine nuts) shows a cyclical pattern, but they are still irregular. From the 1930s through the 1970s, condors made some movements of this reactive type, particularly in response to local availability of food. None of these moves are known to have taken the condors beyond the limits of their "traditional" use areas. I think it would have taken a spectacular change to the condors' environment in central California to force a resident population to travel north of the Bay Area. If the condors were going north to a known food supply, then we might expect that a definite change had occurred in that food supply that made the condors quit their long distance traveling. But there were no significant food or habitat changes, north or south.

During the period that condors are known to have been regular in the Pacific Northwest (1805-1835), there were few pressures on condors in central California. Food availability was probably at post-Pleistocene peaks: pronghorn, tule elk and deer had not yet been decimated, and livestock numbered in the millions (Chapter 3 of "Condor Tales"). There was no reason for condors to make drastic reactive movements. No significant changes were occurring in the Northwest, either. Before 1840, there were a mere handful of people in the region. Salmon runs, often suggested (probably erroneously as the main reason for condors to head for the Columbia River, would not diminish for many, many years. In short, if all the birds were Native (Central and Southern) Californians, there was no reason for them to go north, and there was no reason for them to stop going north.

The alternative to condors visiting areas north of San Francisco Bay, either regularly or irregularly, is that they were there all the time. Koford's resistance to this idea was based on: (1) no prehistoric evidence of condors in the region; (2) lack of nesting records; and (3) lack of observations from certain seasons. In fact, condor remains have been found in Oregon that date from thousands of years ago, confirming that condors were in the Northwest for a long, long time. Carl also overlooked the rich tradition of condor interactions with Native Americans in northern California and parts of Oregon. And, although there weren't many records, I was able to find enough reports to add to Carl's list to show that condors were around somewhere north of San Francisco Bay all year. Neither I nor anybody else found a nesting record north of the San Francisco Bay area, but condors were gone from the Northwest before anybody did any serious looking. [I'll comment further on this, below.] Carl remained unconvinced, noting that (even with the additional records I had found) there still was no "proof" on residency. He was right, of course, but there was plenty of information on which to build a pretty good hypothesis.

Here's my view of how condor distribution looked from the end of the Pleistocene until the early 1800s. Condors were yearlong residents from the Sierra San Pedro Martir in Baja California, Mexico, north in the coastal mountains at least to the Columbia River, maybe a little farther. There were also condors resident in the hills east of the San Joaquin and Sacramento valleys, north to perhaps the latitude of Sacramento, and maybe to Marysville or Chico. Within this total range, subgroups of condors occurred where suitable nesting and foraging habitat existed together. Condors in each of these subgroups "homed" to their specific nesting areas, with their seasonal wandering taking them no more than 150 or 200 miles from "home base" (probably mostly less than 100 miles). No condor in Oregon ever met a condor from Mexico, but there was undoubtedly regular interchange between the nearest neighbor groups (probably in foraging areas seasonally populated by two or more groups, as occurred in the 20th Century). Tenacity to a home nesting habitat gave cohesiveness to the subgroup, and for much of the year isolated its members from other condors. However, the seasonal mixing of subgroups improved the chances of new pair formation, and likely helped maintain diversity in the gene pool of each group.

Although I am speculating about the operation and location of most subpopulations of condors (because most were gone before anybody had a chance to study them), subgroups have been identified in many species of birds. For example, common terns live in small colonies, each of which maintains its own membership, even though located only a few miles from other colonies [Austin (1951), Bird-banding 20:1-39]. Pink-footed geese "form closed groups occupying small, well-defined areas" in which "the scale of mixing is negligible" [Boyd (1972), pp. 251-262 in "Migratory Birds: a Symposium. U. S. Fish and Wildllife Service, Wildlife Research Report 2]. Ducks, crows, ravens, eagles, and peregrine falcons are other species that have been shown to have strong "homing" instincts to a particular area and particular group of companions [Brown (1972) Ibis 114:263-265; Hickey (1942) Auk 59:176-204; Sowls (1955) Prairie Ducks. Harrisburg, PA: Stackpole Co.]

This concept of subpopulations helps explain the disappearance of condors from various parts of their range. Because each group was isolated from other groups, there may not have been eligible birds to re-populate an area if the resident birds were lost. Even if there were other condors within 150 miles or so, their ties to their own area would have inhibited them from filling vacant habitat. To show how it might have worked, consider what is known about Canada geese. They're one of the most abundant and most successful species of waterfowl in the world. Yet, if a local population of geese is removed from a marsh (by overshooting, for example), that marsh may not be nested in by Canada geese for many years. Other members of the species from other subpopulations may fly over the area and see that suitable habitat still exists. Yet, their ties to their own home marshes are too strong for them to break, even for a marsh that might be much better than their own.

Actually, there are anecdotal records by Native Americans of condors nesting in the Columbia Gorge and in southwestern Oregon [58, 67A]. The reason that no specific sites have been identified can easily be explained - at least in the areas north of Marin and Napa counties in California -- by looking at where condors were seen, and by whom. Almost all of the written condor records in Oregon and Washington were made by explorers affiliated with fur trading companies or government expeditions. The great majority of these explorers' time was spent in the river valleys, which were the main travel routes through the region. Few of these people ventured far from the river banks. Not surprisingly, then, most condor observations were made in the river valleys, of birds flying or feeding, not associated with potential nests or roosts. The few scientists who made their way deeper into mountainous areas (for example, David Douglas and Titian Peale in the Umpqua area) merely passed through, with no time for pursuing birds away from their expeditions' established travel routes.

While Oregon and Washington had a number of government and fur company sponsored expeditions in the first half of the 19th Century (Lewis and Clark, Wilkes Expedition, Wyeth's party, the Railroad Surveys), northwestern California had only one such group (Jedediah Smith's party in 1828; he saw condors, but did not have time to look for nesting). In all the Pacific Northwest west of the Cascades and Sierra Nevada, the scientific surveys had ended by 1855, and for the next 50 years the sparse Caucasian population had little time for the pursuit of natural history. In contrast to central and southern California, where the climate and the cultural environment attracted many people with the time and interest to study wildlife, the Northwest was populated mainly by homesteaders and miners, and the city merchants needed to support them. Few of these people left any kind of systematic records, and almost none mentioned birds. I have found no publications on birds of northwestern California between 1828 and 1887, and only five significant papers on birds of that area between 1887 and 1906. For western Oregon, I found only six papers on birds between 1855 and 1895, and most of these were brief notes of birds seen near the Willamette Valley population centers. After 1855, the first bird reference I can find for southwestern Oregon was from 1892. In other words, for nearly fifty years almost no one was looking for birds (or birds' nests) in the Pacific Northwest.

In my 1973 evaluation of California condors in the Northwest [Reference 80], I followed Koford's lead in considering that condors had become very rare in the area by 1850, and that perhaps there had never been a population of more than two or three dozen condors in Oregon. Following further examination of the available information, I suspect that neither statement was true. Reports of condors decreased after 1850 but, as noted in the previous section, the lack of records might merely be the result of fewer people looking for condors. It wasn't just that there were few scientists and naturalists around; there were very few people in condor habitat, period. In 1860, northwestern California (Del Norte, Humboldt, Mendocino, Trinity and Siskiyou counties) had a total population of less than 25,000 people, most of whom were either miners or people living in the lowlands around Humboldt Bay. By 1900, the population of that area had climbed to about 60,000, but the great majority were living at Crescent City, around Humboldt Bay, and around Ukiah, leaving some 20,000 square miles of mountainous habitat essentially uninhabited. The total human population of Oregon in 1860 was only 52,000, and almost all of them lived in the Willamette Valley. [The combined population of Douglas, Coos and Curry counties-the Umpqua-Rogue mountains area -- in 1860 included less than 4000 people.] There were about 415,000 people in Oregon in 1900, but over 250,000 of them were in the Willamette Valley. [Douglas, Coos and Curry counties had a combined population of less than 25,000.]

The observations of California condors in Douglas County, Oregon in 1903-1904 are usually considered to represent birds that wandered into that area from somewhere far to the south, or a few remnant individuals holding on after the rest of the population disappeared years before. Considering the ruggedness and isolation of southwestern Oregon and northwestern California, and the sparse human population as late as the early 1900s, it seems to me equally likely that there was still a viable population of condors in the area until sometime early in the Twentieth Century. Although most observers agree that condor numbers decreased in the Sacramento Valley and the North Bay regions after about 1860, condors were still being regularly seen at a variety of locations in northern California into the 1880s and early 1890s, with some later records. Clearly, there were still one or more reservoirs of condors somewhere north of San Francisco Bay for many years after 1850.

Precisely why condors disappeared from the Pacific Northwest will never be known, but I suspect it occurred because of a combination of three factors:
(1) The Northwest condors were probably living at the margin of habitable range. I don't mean that the habitat was unsuitable in any way; after all, we know condors survived there for hundreds of years, and (as Lewis and Clark found) were not noticeably affected by the cloudy, rainy weather of Northwest winters. Nevertheless, it seems logical that a large scavenger like the condor would be better suited to the vast open grasslands of central California, populated (as they were through most of the 1800s) with hundreds of thousands of large wild and domesticated mammals, with many more clear days available for foraging. Comparing equal acreages of the Northwest and central California, the latter would almost certainly have a higher scavenger carrying capacity, and there would likely be more condors per unit of land than in the Northwest. Under pristine conditions, the difference in carrying capacity would not be a problem - the population size would adjust to the amount and quality of available habitat - but might be important as other factors came into play.

(2) The Northwest condor population sustained significant documented losses in the 1800s, and probably considerably more mortality than is documented. As I explain in my "Condor 101" lectures, the balance between condor reproductive potential and condor mortality is always tenuous, and it takes only a very small change in that balance to produce a very large effect. A condor population has almost no capacity to better its reproduction rate, so the effects are by definition harmful. From the rather sparse written records, I have found information on about 25 condors known killed north of San Francisco Bay between 1805 and 1900. All but perhaps one of these was shot, some in the name of science but mostly out of curiosity or specific intent. Almost every early journal mentioning condors also mentioned the frustrations of killing deer or elk to replenish often critically low larders, only to find that condors and other scavengers had consumed the carcasses before they could be brought into camp. It takes little imagination to add quite a bit of "frustration killing" to the documented condor losses.
No source of condor mortality other than shooting has been confirmed, but there were certainly other possibilities. For example, strychnine was used for killing wolves around Puget Sound as early as 1841, and the amount used probably increased markedly after the first big shipment reached the West Coast about 1848. Use of strychnine for predator control peaked in the United States between 1860 and 1885, but was still used in large quantities into the 1960s. No condor losses in the Northwest can be attributed to strychnine poisoning, but the potential was certainly there.
The important point to make is that there didn't have to be one big reason for the condors' disappearance. One particular impact may have been particularly important in upsetting the population balance (probably shooting, in the Northwest), then the combination of a number of lesser factors kept the population from stabilizing.

(3) As explained above, condors throughout their range appear to have existed in a number of semi-discrete subpopulations, that mixed with adjacent subpopulations at certain seasons but mostly had their own habitat. If a particular subpopulation vanished, or fell below some minimum level, it was unlikely that other condors would move into the vacated area. I think the known losses along the Columbia River could have been great enough to destabilize that subpopulation and lead to its eventual disappearance. Perhaps the losses of condors in Marin and Sonoma counties, or in the mountains surrounding the Sacramento Valley, prevented the infusion of new condors into northwestern California and southwestern Oregon, and those subpopulations were not large enough to sustain themselves over time.
Here are two examples of how the division of condors into subpopulations led to local extirpations.
(a) Carl Koford felt that condors had become very rare in what I'll call the "South Bay" area (Monterey, San Benito, Santa Clara and Santa Cruz counties in California) by 1890 or 1900. Between 1870 and 1900, I compiled records of 30 condors killed and 9 eggs collected in those counties. The mortality records are mostly of birds that ended up in museums; there were surely other condors that were wantonly shot or otherwise died, for which no records survive. This level of loss to a species that had no significant natural enemies, and which died mainly of old age or accidents, had to have a major impact. If, as I believe, there was little interchange between condor groups to the north and south, the losses would have been disastrous. In fact, although condors continued to be seen occasionally in these counties in later years, there were only a few nesting records after 1910. The area was within 100 miles or so of condors nesting to the south, but there was apparently little or no pioneering of new pairs into the "South Bay" area.

(b) A similar situation occurred in the region from the San Gabriel Mountains south to the Mexican border (Orange, Riverside, San Bernardino, San Diego counties, and southern parts of Los Angeles County). According to Koford, condors pretty much vanished from this area between 1900 and 1910. Losses I was able to confirm between 1870 and 1910 totaled 38 condors and 7 eggs. Again, this accounts for very little indiscriminate killing, so the numbers are surely minimal. Although condors were still "common" just to the north of the Los Angeles Basin for 60 more years, there are only a handful of condor records for this vast southern coastal area after 1910. Both nesting and feeding habitats were still available, but no birds emigrated to fill the vacant niche.