Wednesday, May 12, 2010

Another new breeding species on the Farallones!

California Gull on the nest
Over the last few seasons we have seen an influx of new breeding species on the island (or at least a return of some species that had not bred here in a very long time). First were California Gulls, which suddenly started breeding on SEFI during 2008. This was not only a first for the island, but also a first record of this species breeding in the marine environment.

Then last year Peregrines nested for the first time in 100 years. Earlier this season we saw evidence that Common Ravens were nest building on Arch Rock. They last bred here in 1911. Though we haven't been able to get around to where we think the nest is, we are fairly certain that they are at least attempting to breed (we will post an update on that once we confirm the nest).

On May 7th, we found a new species that was somewhat unexpected. It is a species that has never before bred on the Farallones and would not typically be thought of as a species you find on an offshore island.

Now, before we tell you what it is (and no fair scrolling down!) we thought we would tell you about a little experiment first. You see, the biologists that work at PRBO are a pretty savvy bunch and certainly have a great wealth of knowledge about avian breeding biology. So we decided that we would let them weigh in on what species they thought could conceivably start breeding on the Farallones. This would not only be a fun test of their ability to predict species distributions (well fun for a geeky bunch of biologists like us anyway), but would also help us to generate a list of other species which are likely to breed on the island at some point in the future. Just to make it a little more interesting, the first person to name the new species wins a prize.

We received many entries from biologists across PRBO and had many good suggestions, often accompanied by detailed accounts of why that species might be found on the Farallones. From these we have generated this list of the top 10 theoretical breeders (listed in order of most votes received).

There were also two species – Rock Wren and European Starling – mentioned by several folks as likely breeders. These species have bred on the island in the past, so we will consider them the most likely to do so again.

These are all good guesses and there are a variety of reasons why each of these species might be expected to breed on SEFI. But none of them were correct. In fact only one person guessed the correct answer.




The Canada Goose!
Canada Goose sitting on its nest on the Marine Terrace

Canada Goose often pass over the island in the spring and fall as part of their annual migration and it is not unusual to see a pair hang around for a short while in the spring. But, they generally prefer marshes and open grasslands (or lawns at your local golf course) to rocky offshore islands. However, these geese have been spreading rapidly along the coast in the past decade and have been found breeding at several locations where they would not normally be expected. Although there are still abundant grasses this time of the year, they will dry out and disappear by mid-June, leaving the geese without a reliable food source when their chicks hatch.

Then again, it is likely that their chicks will just be gobbled up by the ravenous Western Gulls – as has happened for every California Gull chick hatched thus far on the island. But Canada Geese are big and can be very aggressive when defending their young. So maybe they will have a chance. We will keep you posted on their success as well as the next new species to breed on the Farallones. Will it be one of the species on the list above or will it be something totally unexpected? On the Farallones, anything is possible.



Oh, yeah. The winner? Tom Gardali – associate director of the Terrestrial Ecology Division. Congratulations Tom!

4 comments:

DJ said...

Maybe you guys can set up an exclusive hunting club on the island where the rich pay you to hunt. Cost: $10,000 per goose taken. $25,000 once the starlings return. It's a win-win situation. ; )

Humboldt Honeys said...

Crazy Canada Geese! Yeah, those cute fuzzy chicks sure don't last long on Alcatraz and the gulls there are probably not nearly as crazy as the fulls on SEFI. Gull food!

BourbonHawk said...

Posting from Alcatraz over here. We might actually have a Canada Goose fledge this year.
If you scroll toward the bottom of this post you can see our most recent pictures of him. He's certainly too big for gull food at this point.

Sweep Commander said...

Yeah, Alcatraz will finally fledge a goose this year. He's a bit of a celebrity now. We've been covering that at WWW.MAGANRORD.COM, our photo blog about birds on Alcatraz. I'm really enjoying reading about the Farallones. It has many things in common with our environment on Alcatraz, such as WEGUs, CAGUs, ravens, peregrines, and now Canada geese. It seems like a larger, more pristine, less trampled on version of our island, albeit one that is located in the pacific ocean. Amazing stuff.