Endless miles of bluffs and beaches shelter sleepy towns along the wild Pacific Coast of North America. The ocean spreads away from sand and rock in an implacable expanse. Birds float lazily beyond the breakers. Gulls wheel and scream overhead. Sandpipers and peeps dash about madly at surf’s edge, spinning in unison in the air. And, under cover of early-morning semi-darkness, marbled murrelets leave the ocean and fly to the trees.
The landscape is ruled by the stoic height and girth of trees. In the early morning fog, it is easy to miss a fast-flying bird the color of tree bark as it trades places on the nest with its partner and settles into its 24-hour egg-incubating shift.
Marbled murrelets forage for small fish in near-shore waters of the Pacific coast from Alaska to Central California. They nest in late seral forests (although a small percentage of more-northern birds nest on the ground) and, despite increased forest conservation over the last twenty years, their population continues to decline in some regions of their range.
The presumed equation: protected forest = thriving murrelets
In 2017, Oregon researchers began a telemetry study designed to learn more about marbled murrelets. They wanted to know where they feed, rest, breed, and nest. How do they use forest and ocean resources, and, by extension, how can humans better manage those resources for their continued survival? In 1994, the Northwest Forest Plan was implemented to protect coastal fir, hemlock, and cedar forests on federal lands as a means of protecting species while supporting local economic sustainability. The intent was to prevent further decline in protected species like the marbled murrelet, but just protecting the forest didn’t help these mystifying seabirds.
We rarely connect the salty realm of waves and wind with moss-muffled forests. But all seabirds must, at some point, leave their food source, and come to land to breed and raise young. Many hard-core pelagic birds, those who spend their lives on the wing over open ocean, nest in colonies on remote islands or inaccessible cliffs. Some nest in rock crevices or excavate burrows. Inexplicably, and defying all known logic of seabirds for generations of observers, marbled murrelets nest alone in the forest, laying their eggs in a mossy divot on a branch large enough to be its own old-growth tree. Partly due to this unexpected forest connection, they were the last North American bird species to have their nesting habits described – in 1974.
More than a decade after the first nest was recorded in California, Kim Nelson was the first person to find a marbled murrelet nest in Oregon. She was conducting species-specific murrelet surveys in the Oregon Coast Range for the Oregon Department of Fish and Wildlife (ODFW) and the U.S. Forest Service (USFS). Today, Nelson is a senior faculty research assistant at Oregon State University working with assistant professor Jim Rivers on the Oregon Marbled Murrelet Project, a multi-year telemetry project using radio transmitter tags to track murrelets along the Oregon coast. Working as an independent university research team, Nelson says the telemetry project focuses on increasing knowledge about murrelets in order to provide land managers with the information necessary to make sound management decisions that will help sustain the birds.
Capturing murrelets off the Oregon coast each spring, the team attaches VHF radio tags to the birds, tracking them through the breeding season. According to Nelson, VHF batteries last only about three months, so there is no winter data, and the murrelets’ small size prevents them from carrying heavier battery packs, solar or satellite tags. Rivers believes the work will provide useful information in the context of forest management. Knowledge gained through tagging birds helps to better understand the species’ needs for survival and helps us manage for those needs.
“Tagging birds at sea, they lead us inland and give unbiased data,” Rivers says, because the birds take the researchers to their nests and foraging grounds, wherever they may be. The murrelet team has not caught as many birds as their USFS research permit allows in any of the years of the study and never as many birds as they would like. Rivers states, a bit ruefully, that this embodies the species, “Not easy to work on, on the ocean or inland.”
The variables
A substantive lack of information about this unique species makes it both fascinating and frustrating. The Cornell Lab of Ornithology’s Birds of North America marbled murrelet species account, written by Nelson, reads like a confidential case profile, “no information,” “limited information,” ”few data,” “unknown.” Lacking fundamental knowledge makes management and protection difficult.
Meanwhile, Rivers reels off a rapid-fire list of facts. For example, because male and female murrelets have identical plumage, there is no reliable way to determine sex in the field, even with the bird in your hand–blood samples can later be analyzed in a lab for sex-specific genetic markers. Murrelets can’t be aged, but, he says, based on a relationship between body size and longevity in other auk family members, murrelets are estimated to live 15 to 20 years. There is also no data on their first-year survival rate–if a nest is successful and a chick fledges, how likely is it to survive through its first year and beyond? As with age, this can only be estimated based on other auks.
Able to fly up to 100 mph, and traveling as much as 50 miles inland to nest, marbled murrelets often approach the forest in low-light conditions, making detection challenging. Within a day or two of hatching, the chick is left alone while the parents go to sea, and unlike many birds, Rivers continues, they don’t regurgitate food for their young, rather, they carry whole fish from the ocean to the nest, one fish at a time. Adult birds will sit on the water in the dark, fish in bill, waiting until the light is right before venturing to the nest. Making several roundtrips each day–a discovery Nelson and other researchers made through detailed nest observations in earlier studies–the adults feed the chick until it leaves the nest and makes its first flight directly to the ocean, regardless of the distance. Some fledglings crash land on this inaugural flight, never reaching their destination.
All of this–breeding, nesting, feeding, commuting–requires a tremendous amount of energy. Long-lived birds with low reproductive rates, a murrelet pair lays only one egg each spring. A single egg that falls from a tree or falls prey to a predator may not be replaced. For a bird that weighs less than two-thirds of your morning 12-ounce latte, flying multiple roundtrips daily, with the fattest fish you can carry, to feed a chick that needs to go from egg to flight in a month takes a toll. The physical cost of breeding and raising a chick is high for murrelets. If ocean conditions do not allow for plentiful fish, an egg, and even a chick, will be abandoned; waiting a year for better conditions is a viable evolutionary strategy.
According to Nelson, earlier nest findings in Oregon not only showed that murrelets nest in old-growth as anticipated, but also in younger trees and those deformed by dwarf mistletoe, a parasitic plant commonly called witch’s brooms. And, unexpectedly, the current telemetry project found a murrelet nest in a big leaf maple. Among 400-some nests recorded throughout the murrelets’ range prior to this study, only two were found outside of the targeted coniferous tree species, and these were both in British Columbia. This new data implies that while murrelets rarely nest in deciduous trees, they are not restricted to conifers. This means both more potential nesting sites and possibly the need for conservation of more diverse forest habitat.
Rivers says data indicate murrelets are known to return to the same forest stands where they nested previously. They don’t nest in colonies as many seabirds do; however, where there is suitable habitat, they will nest in small groups, with more than one pair in a stand. Nelson adds that as the forest becomes fragmented by timber harvest and road building, being more tightly packed into stands could compromise their nesting strategy of staying hidden and secretive. This may make them increasingly vulnerable to predators, and could potentially affect nesting success. Being able to quantify where murrelets are nesting and how they are using the forest is a valuable benefit of tagging birds and could offer important information for forest managers determining what should be cut or conserved.
Filling in the unknowns
In 2018, a remote camera monitoring a tagged murrelet’s nest near the forest edge recorded nest predation by a red-tailed hawk, a bird more typically found in open country. Additionally, corvids, a family of birds including ravens, crows, and jays, are smart, keen observers, and relentless opportunists that commonly follow roads searching for easy food. In California, where suitable habitat is mostly limited to state and national parks, a campaign called Crumb Clean reminds human visitors to the forest to remove all food and trash to help prevent corvid populations from increasing and to deter predation.
Without tracking birds to their nests, researchers and resource managers would have little insight into the shifting dynamics of predator-prey interactions relative to the changing forest structure. Understanding how forest structure affects nesting success allows managers to plan for roads, harvest, and recreation with less impact.
Rivers hypothesizes that murrelets in California, Oregon, and the Pacific coast of Washington may be less likely to breed in any given year than other murrelet populations. He believes this is partly due to living on the open ocean rather than in resource-rich and protected bays. Adding another stress factor, like reduced habitat or increased predation risk, can potentially further decrease the likelihood of murrelet nesting success.
The numbers, as Nelson laid them out, are a bit staggering. In the first year of this study, just over 60 birds were tagged; none of them nested. The following year, 2018, nearly 80 birds were tagged, eight nested and five of these nests failed. While 2019 numbers are still being compiled, all indications are that marked birds on the Oregon coast did not initiate nests in the last three years. Rivers states that knowing there are some years when few or no birds nest is an important finding and helps support the idea that not breeding in a year with poor conditions was, historically, a viable survival strategy. Nelson wonders whether this will remain a viable strategy with the modern challenges of habitat loss, climate change, and changes in prey availability.
Solving for ‘x’
Although new data can create more questions than answers, according to Nelson, tracking tagged birds leads the murrelet team into the forest and to nests, providing new insight that chips away at the mystery a little more each season. “There are a limited number of seabirds that fly inland to nest and with this unique strategy of occurring in both the terrestrial and marine environment,” Nelson said.
Rivers takes a minute to look up the name of this strategy, “I want to make sure I get this right,” he says, “it’s called habitat split strategy” and it’s important to the murrelet issue. Habitat split strategy, he continues, is relatively common among birds. We see it in action annually—birds need nesting sites and ample food for breeding and rearing young, so they move to the nutrient-rich north for the breeding season. When northern resources are frozen or dormant, they find a more suitable seasonal home somewhere south of their breeding range. These split habitats are divided both spatially and temporally.
The difference for marbled murrelets is their need for forest and ocean simultaneously. For murrelet breeding to be successful, two significantly different habitats must align both spatially and temporally and solving for ‘x’ becomes a bit more complicated.
Tamara Enz is a writer, photographer, and biologist who aspires to create images of the world, both written and photographic, that draw people into the untrammeled spaces, where she hopes they leave tiny pieces of their hearts. Follow her on Twitter @TamaraEnz
Read More
Far from Land: The Mysterious Life of Seabirds by Michael Brooke
Status and Trend of Marbled Murrelet Populations and Nesting Habitat by Gary A. Falxa and Martin G. Raphael, technical coordinators
Flying Under the Radar by Nick Houtman
From Sea to Tree, Scientists Are Tracking Marbled Murrelets With Rising Precision by Juliet Grable
Rare Bird: Pursuing the Mystery of the Marbled Murrelet by Maria Ruth
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