Friday, November 17, 2017

What Do Brown Boobies Have To Do With Island Foxes?

Have you heard that a seabird called the brown booby (Sula leucogaster) has recently been found nesting on Santa Barbara Island for the first time? 

brown booby beneath western gull; Santa Barbara Island, CA

If you did, you might not have connected this news to island foxes. Brown boobies have historically been residents of Baja and Mexican coastlines. They typically feed on fish species found in warmer waters and are considered a tropical and subtropical species. Channel Islands National Park reports that brown boobies have been gradually moving north since the 1990s. Their occurrence on the Channel Islands coincides with documentation of warmer ocean temperatures along California's coast. The fact that these southern birds are attempting to nest here for the first time is evidence of a healthy marine ecosystem, but also changing local climate. Similarly, our brown pelicans (Pelecanus occidentalis), which were previously only known to nest in California, have been ranging further north. They have attempted to nest along Washington's Columbia River and in the past few years have become summer regulars in southern British Columbia, Canada.

Strong-flying birds have the ability to relocate as temperatures change. Island foxes and the other terrestrial plants and animals of the Channel Islands do not have that option. They will have to adapt to changes in their environment to survive. There are some reports of island foxes breeding and having pups earlier on the southern Channel Islands then documented in the past. Lightening storms brought fire to Santa Cruz this summer and extended drought has challenged some island fox populations.

While the brown boobies are a native coastal species, they have only been occasional visitors to the Channel Islands in the past. Brown boobies are diving seabirds larger than our commonly seen western gull (Larus occidentalis). They are exciting to see, but will their northern movement have an impact on other native species? (video of brown boobies on Santa Barbara Island in 2015 via

Are there other, small and less observable species, that are also relocating to the Channel Islands? Will climate roamers bring beneficial diversity or new parasites and disease? 

In this time of global change, monitoring island foxes and their island ecosystem is vital to the species' long-term survival.