Warmer Oceans Delay Marbled Murrelet Chicks by 25%

Marbled murrelet chicks spent 25% more time in their nests during years with poor ocean conditions, a finding that leaves the young birds exposed to predators like ravens and hawks. Oregon State University scientists documented this shift while tracking how the small, stocky seabirds feed their offspring.

The research team installed cameras to record 12,000 hours of video footage over four years. They used this data to monitor how changes in marine environments impacted feeding behavior. Warmer water temperatures, often tied to poor ocean conditions, reduced the supply of Pacific sand lance, the primary food source for the chicks.

During these warm periods, parents brought fewer fish to the nest each day. The reduced food intake meant chicks grew more slowly. This developmental delay forced them to remain in the nesting site for an extended period, increasing their chances of being eaten by predators.

Jim Rivers, an associate professor of wildlife ecology at OSU and director of the Forest Animal Ecology Lab, led the study. The marbled murrelet is listed as threatened in California, Oregon, and Washington under the Endangered Species Act. The new data suggests climate change is slowing the population recovery by intensifying El Niño events and warming marine temperatures.

The study also notes that climate change harms old-growth conifer forests, which provide the essential habitat where these birds nest. The combination of warmer oceans and shrinking forest cover creates a double threat to the species. The findings were detailed in a recent broadcast on OPB’s Think Out Loud program.