Listening For Marbled Murrelets

Imagine for a minute that you’re a marbled murrelet – a robin sized black and white sea bird found near the Pacific Ocean from Alaska to central California. From late March through September you’re busy with nesting season and will fly as far as 50 miles inland to build your nest high on the branches of old-growth trees.

Yes, you read that right.

Marbled murrelets are the only alcids (a bird of the family Alcidae) known to nest in trees – it’s very unique. Other birds in the alcid family include puffins and auks. And murrelets won’t nest in just any trees, they need big trees in old-growth forests. Old-growth forests have closed canopies and trees with big branches and deformities that support their eggs – they don’t actually build a nest rather they nestle their egg into moss or other debris.

Ok, back to our exercise.

Once you’ve laid your egg, you will spend the next 30 days or so, trading off with your mate incubating your egg round the clock, and then you spend the next 30 days traveling to and from from your nest site to the ocean in search of small fish to feed your chick. The chick needs to be fed constantly and so that means many trips back and forth, and since it’s safer to fly in the cover of darkness, you’ll make the commute mostly in the dawn and dusk hours.

Once large enough for flight, chicks usually fly straight to the sea, and might not return inland to nest until they reach about 3 years old and have attained sexual maturity. They are basically on their own as soon as they fly off. You and your mate will return again to the same nest the following year in early spring and start over. But as you might imagine given the challenge of it all, breeding success is low and chick mortality is quite high.

As if things weren’t hard enough for the marbled murrelet, they’ve lost more than 90 percent of their nesting habitat due to logging. It wasn’t until 1992 that these birds were listed under the Endangered Species Act by the U.S. Fish and Wildlife Service and were finally protected in Washington, Oregon, and California. This gave them a good shot at recovery and is when coordinated conservation efforts across the Pacific states were initiated to help the bird rebound.

It’s been challenging for scientists to monitor the populations of marbled murrelets and measure the success of our collective conservation efforts.

Finding a small bird, that nests high up in towering trees, and travels fast in low light hours, deep in the forest isn’t the easiest thing to do. The standard practice has been to have trained biologists visit old-growth stands during nesting season and listen and watch for the birds. But they’re notoriously elusive.

New technology, however, is making it easier to monitor the marbled murrelet. Researchers from the University of California Santa Cruz and the consulting firm Conservation Metrics have been experimenting with acoustic monitors as a listening tool for this rare bird.

They’re placing lunch-box size acoustic monitors in the forest and recording nearby sounds for months at a time. They then use pattern recognition software to analyze hundreds of hours of field recordings to isolate the sounds of marbled murrelets.

It’s the high-tech way of finding the needle in the haystack.

In the summer of 2013, they tested this acoustic survey equipment at the 8,532-acre POST-protected San Vicente Redwoods. This property has some of the last remaining old-growth redwood and Doug fir in the Santa Cruz Mountains and is prime nesting habitat for marbled murrelets at the southern end of their range. 

The study confirmed the presence of marbled murrelets at San Vicente Redwoods for the first time since 1914. Of the 6 survey sites they studied, murrelet calls were recorded at only one site in the Laguna Creek portion of the property. It is not clear at this time if the birds are nesting on the property, or if it Laguna Creek is on their commute route to nests elsewhere. You can listen to that audio recording above.

Acoustic monitoring is a really cool new technology, with lots of potential applications.

One of the concerns about marbled murrelets in the area are corvids (ravens, crows, jays). These noisy bird bullies prey on murrelet nests, and are sometimes attracted into forest areas by human activities, such as overflowing trash cans or trail litter that can accompany recreation. At San Vicente we want to make sure that public access does not have a negative impact on this endangered species. Long term we are interested in using acoustic monitoring to help us track murrelets and other birds in the forest, and how populations are changing over time.  Monitoring can help us evaluate our management, making sure that we are protecting species while providing opportunities for more people to enjoy this beautiful forest property.

This information all came from the fish and wildlife recovery plan which can be found here.

Banner image: Marbled Murrelet, U.S. Forest Service Martin Raphael, CC