JWM study: Low-quality marine habitat impacts murrelet

Dubbed “the enigma of the Pacific” until ornithologists finally tracked down its nest in the 1970s, the marbled murrelet (Brachyramphus marmoratus) is a seabird that forages by the coast and flies inland to lay a single egg in the old-growth canopy of the Pacific Northwest. A recent study suggests that in the state of Washington, where the species is threatened, its breeding success is low, and it’s traveling longer distances to forage and nest than populations elsewhere, possibly due to the poorer quality of marine and inland habitats.

“We’ve known for quite some time that we need to conserve breeding habitat on land, late successional forest,” said Teresa Lorenz, research wildlife biologist with the U.S. Forest Service at the Pacific Northwest Research Station and first author on the paper published this month in The Journal of Wildlife Management. “Our research highlights that we have to also look at the quality of foraging habitat in the marine environment if we want to sustain populations of this fish-eating bird.”

From 2004 to 2008, Martin Raphael, a co-author who is also a research wildlife biologist at the Pacific Northwest Research Station, and his colleagues followed over 150 radio-tagged murrelets to track their breeding and use of space. Whenever they could push through the remote, dense forest, the scientists also hiked to identified nests and set up cameras to monitor the birds. Analyzing the data collected, Lorenz found that the murrelets traveled much wider foraging ranges in the water and longer distances between the sea and nests than did much more abundant Alaskan populations of the bird.

In Washington, the research team found evidence of breeding in only 20 individuals, and the likelihood that a murrelet would attempt to breed was as low as 13 percent, about a third of the probability in the Alaskan population. What’s more, just four of the breeding Washington murrelets successfully fledged a chick.

“What we found were extremely low rates of breeding compared to other populations of murrelets,” Lorenz said.

Overall, the results indicate that improving marine habitats and providing terrestrial breeding habitat close to shore could help Washington’s murrelets, the researchers concluded, and align with previous research on the species in the region. Nesting habitat on most federal lands in the state is already protected, but nesting habitat on state and private lands will require extended protection to stop losses, they said.

Their findings suggest that enhancing the health of marine food webs in the Salish Sea and along the Pacific Coast would benefit the species, the biologists said. Without such measures, Washington’s murrelet population — which also faces threats from commercial logging, fire, climate change, oil spills and gillnets — could continue to decline because of poor reproduction rates.

For the past two decades, a collaborative group including the state, U.S. Fish and Wildlife Service and private consultants has monitored the murrelet quite extensively through at-sea surveys, but this is the first time scientists have used radio-tracking to follow such a large number of the birds in Washington.

The Washington Department of Fish and Wildlife has been conducting surveys of the fish the murrelets eat for at least a year now. Raphael and his team noted the need for additional research on the murrelet’s prey species, their distributions and abundance and its interactions with them throughout the study area, especially with respect to successfully breeding birds.

TWS members can log into the member portal to read this paper in the February issue of The Journal of Wildlife Management. Go to Publications and then The Journal of Wildlife Management.

Header Image: A marbled murrelet incubates an egg in the coniferous canopy of Washington state. ©Nick Hatch