Common Murre Colony as Indicator

Explanation: This week we are on the coastal cliffs of Oregon, USA, overlooking the Pacific Ocean and these offshore stacks comprising the Yaquina Head Outstanding Natural Area. And here resides the largest and highly viewable breeding colonies of seabirds ... especially this massive congregation of Common Murres.

For some 27 years now, researchers have tracked, counted, and monitored these colonies at this site, at times the murre colony swelling to some 60,000 strong. Their work has revealed swings in their reproductive success and survivorship. For Common Murres, some threats include direct predation by Bald Eagles, secondary predation by gulls, ravens, and other small predators on eggs of exposed nests, and other factors.

The Yaquina Head site occurs within the Northern California Current System that itself varies over the years in timing and degree of upwelling, and that, in combination with variations in the Pacific Decadal Oscillation and the El Niño Southern Oscillation, affects marine prey abundance and availability. As influenced by all of these forces, the productivity of the Common Murre colony here, in particular, has varied significantly over time in response to secondary changes in predation and in their marine food sources.

The birds typically crowd together for optimal roosting sites, but the crowing also provides some individual degree of protection from aerial predators such as eagles.

And when threatened by an eagle, even as a "test" flyby, the murres commonly bolt from their rocky thrones and dash into the water by the hundreds:

What an incredible place to visit, this is, with such fine opportunities to study the behavior, ecology, and environmental factors and response to this marine-dwelling species! So, as a way, they serve as a vital ecological indicator of the health of the fuller coastal and marine ecosystem.

Information:
Signa, G., A. Mazzola, and S. Vizzini. 2021. Seabird influence on ecological processes in coastal marine ecosystems: An overlooked role? A critical review. Estuarine, Coastal and Shelf Science 250:107164. https://doi.org/10.1016/j.ecss.2020.107164

Note: My photos from this posting were were taken in March of 2024.

EPOW - Ecology Picture of the Week