Two baby northern spotted owls, perching side by side in a bishop pine, stared down at wildlife technician Taylor Ellis last Friday. Their heads bobbed and swooped and their breasts were still covered in soft white down. Too young to make the typical four-note hoot of the species, they let out occasional high-pitched whines.
“They’re just kind of hanging out and waiting for a delivery service,” joked Mr. Ellis, who works for the Point Reyes National Seashore and conducts most of the spotted owl surveys in Marin’s federal parklands. But if it sounds like life is easy for the young owls, think again: most chicks die in the first year.
In fact, life isn’t easy for most northern spotted owls, which have been designated endangered since 1991. But though the species is suffering from population declines across its range from British Columbia to Marin, this county is home to one of the densest and healthiest populations.
This year is even more important for the species in one key way: for the first time since 2002, monitoring efforts this nesting season uncovered no evidence in Marin of the barred owl, a problematic intruder to the birds’ habitat that researchers believe is contributing to declines.
“Marin is pretty much the last intact population of spotted owls ,” said Dave Press, a wildlife ecologist for the seashore.
The northern spotted owl, one of three subspecies of the spotted owl known for its alluring white-flecked coat, is a non-migratory bird that is deeply territorial. Once it establishes a home, it remains within a small area for a decade or so, warding off others with it hoots.
Often seen as an iconic species of old-growth forests, they live in a variety of forests in Marin: Bishop pine, Douglas fir, redwood, bay and oak. They tend to favor closed canopies with open ground easier to hunt for prey—in Marin, mice and wood rats, though they feed on flying squirrels in Oregon and Washington. When nesting season starts in March, they don’t build their own nest but instead lay their eggs in tree holes, raptor nests and even beds of poison oak.
During the nesting season, Mr. Ellis has a few options to find them during his surveys. He has a megaphone loaded with preprogrammed calls, although he prefers to mimic their calls himself. Occasionally, if he’s having a tough time, he might lay out bait. And although the calls provide the vocal confirmation he needs, he’s often also on the lookout for owl waste. Unlike many other birds, he said, the spotted owl’s poop or “whitewash” contains no discoloration. “It’s always pure white,” he said.
Luckily the owl tends to be on the curious side. “They don’t seem to be that scared of people,” he said while looking up at the two young ones he saw in the Limantour Wilderness last Friday—one of which was the first to fledge this year in the seashore.
Over the years, the average occupancy rate of northern spotted owls in Marin—meaning how many surveyed territories contained a known pair of spotted owls—has remained relatively stable, at 85 percent.
This year, early tabulations in federal parklands where 39 sites are monitored annually are somewhat lower, at 69 percent, or 27 pairs, but Mr. Press said they’re finding more pairs even this late in the monitoring season. And of the pairs they did find, the percent that nested is pretty typical.
Avian biologist Renée Cormier of Point Blue, which annually surveys roughly 40 sites on county-owned lands, said the nonprofit observed fairly typical nesting rates, but preliminary results found a higher than average rate of nest failure.
Both researchers suggested that late rains may have caused some of the lower numbers—if they hold true till the end of the season.
But for most northern spotted owls, unseasonal rains are the least of their worries. Across their range, the owl’s population has plummeted in recent decades due in large part to timber harvesting. According to the United States Fish and Wildlife Service, the owl has lost 60 percent of suitable habitat over the past two centuries.
And another threat looms large. Even where habitat exists, the northern spotted owl has suffered from competition with the barred owl.
The barred owl originated in the eastern part of the United States, probably unable to make its way west because of the emptiness of the Great Plains. But it started gaining ground in the late 1800s. As pioneers and European immigrants made their way across the country, they did not manage the land with fire like Native Americans did and, in fact, planted trees. Those changes in habitat probably facilitated the expansion, according to 2009 research by the Fish and Wildlife Service.
Researchers have blamed the barred owl for a playing a major part in the population decline of the northern spotted owl. The barred owl prefers the same habitat as the northern spotted; it’s also a bit bigger and gets aggressive with the endangered bird. Not only does it push it out of its territory and hamper its survival, but the cousin species also breeds with the northern spotted, resulting in hybrids.
Mr. Press noted that in places like Humboldt Redwoods State Park, areas considered to be “quintessential northern spotted owl habitat” haven’t seen a successful nest since 2010.
Marin hasn’t been completely spared, but a barred owl population boom has so far not come to pass. Here, the first barred owl was detected in 2002, in Muir Woods. A few years later, one pair successfully nested, and by 2011 local researchers estimated that Marin had between four and seven.
The presence of hybrids has never been confirmed, though a few local birders reportedly heard calls that sounded somewhere between the two owls’ signature hoots.
This year, neither the National Park Service nor Point Blue have spotted a barred owl.
“Most people would’ve expected that once a barred owl moves in, it would’ve been an exponential increase, but that’s not what we’ve observed at all,” Mr. Press said. He surmised that development and grassy ranchlands that separate Marin from Sonoma and Napa are probably slowing the barred owl’s expansion. That theory is bolstered by the fact that genetic testing conducted about 15 years ago found that this county’s northern spotted owls are genetically distinct from Napa and Sonoma’s, further supporting that it is difficult terrain to cross.
Mr. Press stressed that there is more spotted owl habitat than the park or Point Blue can monitor. He also suspected that, given the many birders in the county, he would have heard of other reports if barred owls were still around.
Yet it’s probably highly unlikely that Marin will be completely spared from the barred owl.
“Given the pattern throughout the rest of the range, I think there’s a high probability that they’ll eventually invade Marin,” Ms. Cormier said.
Dave Press will speak about the northern spotted owl population in Marin during the Inverness Association’s annual meeting at 7:30 p.m. on Saturday, July 9 at the Inverness Yacht Club. The meeting is open to existing and new members; for information, visit invernessassociation.org.