Friday, July 19, 2019

Bald Eagles Thriving and Maintaining Island Balance for Island Foxes

Across the Channel Islands, 2019 has been the best year for bald eagle reproduction since recovery efforts began 35 years ago. This spring 24 bald eagle chicks successfully fledged from nests. (That means they survived to fly.)

According to a press release from Channel Islands National Park: "This year there were 19 breeding bald eagle pairs on the Channel Islands producing 24 chicks, including 10 on Santa Cruz Island, 9 on Santa Catalina Island, two each on Anacapa and San Clemente Islands, and one on Santa Rosa Island."


Orange wing-tags mark Catalina-hatched bald eagles
Bald eagles are a vital part of the Channel Island ecosystem. As fishing eagles, they prey primarily on fish and other birds, as well as consuming carrion. Bald eagles do not typically eat mammal prey and therefore are not usually a threat to island foxes.

On occasion island foxes climb up into bald eagle nests. For the most part the foxes act as a clean-up crew picking up tidbits of food left behind by eagle chicks. Eaglets are typically either protected by a parent when very young or too large for island foxes to prey upon.

blue wing-tags mark no. island eagles
Bald eagles therefore help transfer vital nutrients from the marine environment up onto the island. They help provide marine resources to island foxes, deer mice, and the island ecosystem. Nitrogen and calcium from fish are dropped on the land or eaten and deposited via scat. Marine resources can then help to fertilize island plants.  


Island foxes and bald eagles lived in balance on the Channel Islands for thousands of years. The oldest bald eagle fossils found in Southern California are 35,000 yrs old and from the La Brea Tar Pits. Bald eagles declined between 1945 and 1960 because of the insecticide DDT which had been introduced by people into the surrounding marine environment. DDT and bald eagle.



Bald eagles historically kept golden eagles from colonizing the Channel Islands and, in doing so, protected the island fox. Though they are both called "eagles," bald eagles (Haliaeetus leucocephalus) and golden eagles (Aquila chrysaetos) are not closely related. They come from two distinct evolutionary branches of predatory birds that separated and became competitors more than 12 million years ago. (By comparison, humans and chimpanzees diverged from a common ancestor just 7 million years ago.)

Golden eagles are mammal predators; they specialize in hunting small mammals about the size of a football (rabbits, ground squirrels, deer fawns, marmot, etc.) . Golden eagles hunt island foxes. They also eat carrion. Because both species will eat something that is already dead, they are known to take food from each other. There have been accounts of a bald eagle taking a dead island fox body from a golden eagle.


These two large birds have evolved to specialize in different food, but they compete for territory and nesting sites. Around the world fishing eagles and mammal-eating eagles are in competition with each other. You might think of them like dogs and cats–they share an ancestor, both are predators, but they have different specializations. They put up with each other at times, they will steal food from each, and in a confined space, like the islands, they just don't get along.

Though both bald and golden eagles are similar in size, resident bald eagles on the islands are frequently in mated pairs. Golden eagles encountering the islands are typically migrating individuals. This two-on-one situation gives bald eagles the upper hand.

When the Channel Islands' bald eagle population is thriving, there is no room for golden eagles and the habitat is safer for island foxes. Check out live bald eagle nest cams on the islands: http://www.iws.org/livecams.html

Friday, July 12, 2019

Foxes on Santa Cruz Island are Wearing FIF Collars


This island fox was captured and counted this week on Santa Cruz Island. 

She received a health check and her radio-tracking collar was replaced with a newly refurbished collar. Her old collar will come off and be eligible for refurbishing. 



Earlier this year, 20 radio collars from Santa Cruz Island were sent in for refurbishing and funded by FIF.

In just a few minutes this little fox was released back into the wild. Her refurbished radio collar has a battery that will last 2-3 years.


Her microchip enables biologists to identify her as a specific individual. If she is caught again this summer, the microchip reader will quickly identify her so that she can be released immediately without being handled.

Your donation of $220 would recycle her used radio collar to be placed on another island fox.

Saturday, July 06, 2019

Research Grant Deadline - July 12, 2019


The more we know about island foxes, the better we can play a positive role in their continued survival.

Friends of the Island Fox is accepting proposals for research projects that improve our scientific understanding of island foxes. Grant funding up to $5,000 is available.

The deadline for this year's applications is July 12, 2019.



Friends of the Island Fox Funded Research


Other Researchers:

We hope you are noticing that island fox research is filled with innovative women.


For other research regarding island foxes: 

Wednesday, July 03, 2019

Fox Foto Friday - Radio Collars Going On Island Foxes

photo courtesy of M. Navarro, CINP
Island foxes on Santa Cruz Island are receiving health checks and being fitted with newly refurbished radio tracking collars RIGHT NOW!

You refurbished these radio collars and today they are going on island foxes.