The Cassin's Auklet is an ecosystem sentinel of the California Current; as a zooplanktivorous seabird feeding low in the marine food web, its demographic rates are closely tied to the oceanographic conditions that drive primary productivity along the west coast of North America. To understand how oceanographic variability shapes auklet demography across space, we used over 20 years of nest monitoring data from two offshore rocks in the California Channel Islands that are just 50 miles apart but subject to varying oceanographic conditions. Using Bayesian daily nest survival models, we found that warmer sea surface temperatures reduce nest survival, but that this relationship is stronger at one colony than the other, suggesting that not all colonies are equally vulnerable to ocean warming. Scaling up to the full population, an integrated population model revealed that both colonies are growing despite episodic reproductive failures, consistent with demographic buffering, though positive covariance between survival and fecundity suggests this resilience has limits. Understanding where vulnerability is greatest is necessary, but not sufficient, because with limited conservation resources, we also need to know where to act. To do so, we applied structured decision making and constructed value of information analysis to identify where targeted research and monitoring are most likely to improve conservation outcomes for auklets and co-occurring seabirds at Channel Islands National Park – because while we cannot stop a marine heatwave, we can make better decisions about where limited resources will be most effective.  

Speakers:

• Sarah Converse, Unit Leader, USGS Washington Cooperative Fish & Wildlife Research Unit
• Amelia DuVall, post-doc, USGS Washington Cooperative Fish & Wildlife Research Unit