Hi Jackie, Do you think most, or all, of those birds on Bodega Rock are Cormorant species? And, do you know whether all of that white beneath the bird colony is simply their guano, or is it also partly a substrate of bleached algae? I encountered some algae, bleached that color, covering some rocks at the tideline in Mendocin county once, although it was limited to one small cove and there were no birds around. (Could be very common, but I'd never seen it before.) Thanks. Vishnu
Most of the birds in these photos are Brandt's Cormorants. If you look carefully, you'll also be able to find a few Common Murres -- they're smaller, with white bellies.
In this case, I'm guessing most of the paler colored areas are that color because of bird guano. There could be some bleached algae, but I think guano is the most likely cause.
Sometimes algae can be bleached if there's a low tide coinciding with very warm air temperatures. It can also be bleached by seal/sea lion excretions (which are very acidic). Recently we noticed a tidepool where the water level had dropped about 1 foot below the normal level. We think it's likely the drainage of the pool had changed somehow, but because of the water level change, much of the algae had been bleached in the newly exposed area.
3 comments:
Hi Jackie,
Do you think most, or all, of those birds on Bodega Rock are Cormorant species?
And, do you know whether all of that white beneath the bird colony is simply their guano, or is it also partly a substrate of bleached algae?
I encountered some algae, bleached that color, covering some rocks at the tideline
in Mendocin county once, although it was limited to one small cove and there were no birds around. (Could be very common, but I'd never seen it before.) Thanks.
Vishnu
Hi, Vishnu!
Most of the birds in these photos are Brandt's Cormorants. If you look carefully, you'll also be able to find a few Common Murres -- they're smaller, with white bellies.
In this case, I'm guessing most of the paler colored areas are that color because of bird guano. There could be some bleached algae, but I think guano is the most likely cause.
Sometimes algae can be bleached if there's a low tide coinciding with very warm air temperatures. It can also be bleached by seal/sea lion excretions (which are very acidic). Recently we noticed a tidepool where the water level had dropped about 1 foot below the normal level. We think it's likely the drainage of the pool had changed somehow, but because of the water level change, much of the algae had been bleached in the newly exposed area.
I hope this helps!
Jackie
Yes, thanks for the info. It's good to hear some varied explanations for algae bleaching. It had quite surprised me when I came upon it.
And if that's mostly seabird guanao, I would imagine boats always attempt passing on the upwind side of Bodega Rock :)
Vishnu
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